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Project Specific Discussions => Preamplifiers => Topic started by: gyraf on September 07, 2006, 02:05:43 AM

Title: The official G9 help thread
Post by: gyraf on September 07, 2006, 02:05:43 AM
This will be The official G9 help thread - there's too many loose threads out there.

Jakob E.
Title: The official G9 help thread
Post by: ChrioN on September 07, 2006, 08:32:33 AM
at last

I'll be back  :oops:
Title: The official G9 help thread
Post by: Kev on September 07, 2006, 05:05:28 PM
yep
good one
 :thumb:

strange how no-one prompted that earlier ?
Title: The official G9 help thread
Post by: tony dB on September 07, 2006, 05:29:11 PM
Big up for Jakob!  :thumb:
Title: The official G9 help thread
Post by: gregcs1 on September 12, 2006, 05:58:58 PM
No one is working on G9?
Title: The official G9 help thread
Post by: tony dB on September 12, 2006, 06:04:39 PM
no, they just don't need help, that's all  :green:
Title: The official G9 help thread
Post by: matta on September 12, 2006, 06:05:28 PM
HV scares people :shock:

Hah hah! I actaully am working on one, slowly, only cause I can't afford all the parts at once ;-) I'm sure in time the questions will come.

Cheers

Matt
Title: The official G9 help thread
Post by: enthalpystudios on September 12, 2006, 07:46:42 PM
i have all the resistors stuffed ;]

and diodes.

pcb sockets on mine wont fit.  and i need to reorder all the solen's i ordered from AES, because ups shipped my order back to them without telling me.  lost out on the cheap 12av7's too!

i got pcb sockets from apexjr for a really great price....  they may actually fit at some point, its only the center post thats having a tough time fitting.  i have drills for things like that

billy
Title: The official G9 help thread
Post by: gyraf on September 13, 2006, 02:53:04 AM
..the center post on tube sockets can usually be cut off - just don't cut too close to the joint, as this sometimes also holds the socket together..

Jakob E.
Title: The official G9 help thread
Post by: enthalpystudios on September 13, 2006, 05:37:55 AM
oh cool i'll try that out tomorrow.

right now its 5:33 am and i just spent an hour finding a prob on my (OT) gssl board...   the 100r output (load balancing?) resistors at the very very output had a solder bridge.  and that doesnt work well

thanks again jakob
Title: The official G9 help thread
Post by: tony dB on September 13, 2006, 05:44:25 AM
well, I will try to get my chest wet. Having a few close to complete stuffed G9-boards lying around, this thread will be of use when I try to get them working...
Title: The official G9 help thread
Post by: rotation on September 13, 2006, 09:20:34 AM
Hi!
I-m happy to see this. Another very helpful thing would be adding BOM for Americans and Europeans, because they are all around the forum and are difficult to find. So post them please.
Miha
Title: The official G9 help thread
Post by: tony dB on September 13, 2006, 09:47:14 AM
I think I found what I needed in the META, isn't it there? This thread is about debugging/roundup of the G9
Title: g9 project help
Post by: analogical on September 20, 2006, 10:27:02 PM
Howdy all. This is my second diy build and my largest to date, I want to thank all the people here for being so nice and guiding me into the uncharted waters of the g9.  I hope you all won't mind answering some boneheaded questions over the next few weeks as I try to build this up to a working pre. I'll post pictures of my progress outside of this meta once i feel I have something worth showing off.  :)  

And an extra thank you to Jacob for releasing this pre's design into the public domain!

Cheers,
Don
Title: G9 R38 location?
Post by: analogical on September 21, 2006, 08:14:07 PM
I have a question about a resistor R38 which is supposed to protect the T1. I can't find it on the board!?! Am I blind?
Title: The official G9 help thread
Post by: tony dB on September 22, 2006, 03:05:40 AM
I've got your PM Analogical, I remember I was looking for that myself but since my pcb's are already stuffed since over a year now I don't recall where it sits. Jakob? on the schematic its in between T1 collector and R40/D12
Title: The official G9 help thread
Post by: gyraf on September 22, 2006, 04:54:13 AM
R38 is a leftover from a previous revision.  :oops: sorry.

R39 is all we need here..

Parts list updated.

Jakob E.
Title: The official G9 help thread
Post by: tony dB on September 22, 2006, 04:55:15 AM
no Jakob, na apologies necessary...
 sorry and  :oops:  to me, now I remember that it's this what you told me last year...  :oops:
Title: R38
Post by: analogical on September 22, 2006, 05:55:52 PM
Thanks Guys!
Title: The official G9 help thread
Post by: dinesh on September 23, 2006, 01:21:43 AM
Hi there,
I am collecting parts for my G9. Is that Toroidal Transformers are must for G9? or can i use normal PSU transformers?
Regards
Dinesh
Title: The official G9 help thread
Post by: gyraf on September 23, 2006, 03:02:26 AM
Toroids are important, but not necessarily a must.

The thing is that a toroid have much lower electrical noise around it - and as we have audio transformers in the box, we like low electrical noise.

But it is possible - just not easy at all - to acheive good results with standard EL-core power transformers

Jakob E.
Title: The official G9 help thread
Post by: dinesh on September 23, 2006, 03:12:28 AM
Thanks Jakob.
Title: The official G9 help thread
Post by: dinesh on September 23, 2006, 05:21:21 AM
Hi there,
I have a couple of Sowter 9145 & 8751 Transformers. Can I use these in G9 or 1176?
Regards
Title: The official G9 help thread
Post by: ioaudio on September 23, 2006, 06:17:14 AM
Quote from: "dinesh"
Hi there,
I have a couple of Sowter 9145 & 8751 Transformers. Can I use these in G9 or 1176?


the 9145 with secondaries wired in series will make a 1:4 input transformer, should work in the g9 as input. the 8751 might work as ouput if you turn it around 1:1.5
Title: Lorin pot orientation
Post by: analogical on September 26, 2006, 12:44:30 AM
Hello all. I'm confused as to which way switches 1,3,4 should be positioned on the board. I looked at the shema but I don't see how identify the right way to mount them.  Are the lorin pots on the "L" shaped board all suposed to be pinned the same way, such that A & C (the two center pins) on sw1 would be null?


Thanks for your help,
Don
Title: Lorin pot orientation
Post by: analogical on September 26, 2006, 12:58:56 AM
Ok, I think I answered my own question. Looking at the Gyraf pictures I see how SW1 is rotated 90 degrees from the way sw3,4 are. Now the question is which way to turn it? Should the "from 12v" lead go to pin A or C on the switch?

Thanks again folks.
Title: The official G9 help thread
Post by: gregcs1 on October 11, 2006, 03:50:01 AM
Hello.

My G9 is almost complete, but I still have some questions. I soldered everything except ic's, xformers and tube sockets (because I can't find any)

What's that with spare psu pcb? It is actually not mounted in G9 isn't  it? I guess it's there just in case onboard psu die... Am I wrong?

I also have a question about ic's. Can they all be mounted on one larger heatsink and connected by wire, or must they be on separated heatsinks. I really don't want to mount heatsinks in pcb, because there is already a mess.  How can I totaly isolate IC when mounting on heatsink? (i understand how to isolate touching surface, but what about screw?) Do they need to be 100% isolated?

Are there any tests which can determine that everything is in order, before I actually put everything together? (psu test, voltages...)


This is for now... I think there will be more.  :wink:

Thanks guys
Title: The official G9 help thread
Post by: Black Dog on October 11, 2006, 04:28:52 AM
Quote from: "gregcs1"
Hello.

My G9 is almost complete


Nice one :thumb:

Quote from: "gregcs1"
What's that with spare psu pcb? It is actually not mounted in G9 isn't  it? I guess it's there just in case onboard psu die... Am I wrong?


It's a bonus - you won't need it for the G9, but you might find it usefull for a future project..

Quote from: "gregcs1"
I also have a question about ic's. Can they all be mounted on one larger heatsink and connected by wire, or must they be on separated heatsinks. I really don't want to mount heatsinks in pcb, because there is already a mess.  How can I totaly isolate IC when mounting on heatsink? (i understand how to isolate touching surface, but what about screw?) Do they need to be 100% isolated?


The best way is to mount them directly to the case, but they do need to be isolated.

You will need something like this:

(http://www.oselectronics.com/Images/pg_85/mkto220.jpg)

I'm sorry, but I don't know the english word for it :roll:

You will only need to heatsink the TL783 and 78S12 though, as the TIP121 won't get too hot..

Lars
Title: Can I test the G9 without the output trafo in place?
Post by: crazytooguy on October 11, 2006, 06:25:33 AM
This is kind of a dumb question, but I thought I'd toss it out anyway...

I've completed my G9 build, but haven't bought the Lundhal input and output trafos yet (saving my pennies...). Since the Instrument input bypasses the input trafo, I suppose that I can do without it for testing purposes. Can I add a load resistor on the output and test it safely? Or should I just be patient and wait on the trafos? My build uses my own design for the boards (channels are on separate boards, relays for inst, phase switching, VU meter drive circuit, etc.) so I'd like to find out if I have oscillation problems and such. Thanks!
Title: The official G9 help thread
Post by: gyraf on October 11, 2006, 07:21:18 AM
Yes, the Hi-Z input will work even without input transformer

Quote
Can I add a load resistor on the output and test it safely?


In theory, yes - as we're isolated from HT voltage by a 4u7/250V polyester cap. But watch what you're doing.

You probably won't get oscillation problems before mounting the transformers anyway, so there's little reason for trying out the construction without the transformers.

Good luck with the build..

Jakob E.
Title: The official G9 help thread
Post by: gregcs1 on October 11, 2006, 07:35:03 PM
Can be done like this?

(http://freeweb.siol.net/gregcs1/heatsink.jpg)


And one pic from "my favourite" collection  :wink:




(http://freeweb.siol.net/gregcs1/C103.jpg)
Title: The official G9 help thread
Post by: gyraf on October 12, 2006, 03:27:24 AM
Nice image..

gregcs1,

for mounting a to-220 housing IC isolated on a heatsink, you'll need an insulator slice (for the back of the IC) and an insulated "grommet" to isolate the mounting screw from the IC. This grommet thingy is plastic, and has a recess that kinda goes into the mounting hole of the IC, keeping sides of the screw from touching IC metal.

Any halfway decent electronics shop has these.

Jakob E.
Title: The official G9 help thread
Post by: ChrioN on October 19, 2006, 12:28:20 PM
Where did my post go? I asked a question yesterday I think, and Jacob you answered me. but its gone now?

Just read what happened.

Jacob do you remember what you said? hmm...something about checking the input wiring and see if signal reaches the instrument jumper or something.
Title: The official G9 help thread
Post by: gyraf on October 19, 2006, 12:40:47 PM
..exactly..
Title: The official G9 help thread
Post by: radiance on October 19, 2006, 03:04:38 PM
I have some Haufe transformers laying around and was wondering whether they could be used as input transformer for the G9.

Here the spex....(sorry, German only)

Haufe  RK531
Ubersetzungsverh.      0,5+0,5: 2,97
Quellwiderstand   200 Ohm
Lastwiderstand    10kOhm
Primärpegel       16dBu  V
Frequenzbereich   30 Hz  20kHz  +/-  0,3 dB  ref.  1 kHz
Klirrfaktor    <  0,3%  bei  40Hz
Symmetrie IRT   > 60dB  15 kHz
Impedanz   10 kOhm  1kHz  (+/- 30%)
Wicklungswiderstand  1-4 = 34 Ohm     5-6 = 200 Ohm  (+/- 10%)
Bemerkung:  ü last    16dB  :  25dB


Haufe T-5223-1
Ubersetzungsverh.   5 : 1
Quellwiderstand      40Ohm
Lastwiderstand       200Ohm
Primärpegel        23 dBu  V
Frequenzbereich      40Hz  15kHz   +/-  2dB  ref.   1kHz
Klirrfaktor     1%  bei  40Hz
Kurschlussausgangs-scheinwiderstand   50Ohm   1kHz
Impedanz    300kOhm  1kHz  (+/- 30%)  
Wicklungswiderstand   prim.   253Ohm    sek.  33Ohm

Thanks in advance......
Title: The official G9 help thread
Post by: needlz on October 19, 2006, 06:41:13 PM
Is the G9 supposed to be a low output pre? Only on incredibly hot signal sources (ie guitars / basses with preamps) do I get a healthy level to tape. On mic'd sources - vox, trumpet, cello, etc, I have to crank both the gain and output to get a nominal amount of level.
Title: The official G9 help thread
Post by: radiance on October 21, 2006, 08:08:03 AM
Where's the official G9 help?  :wink:
Title: The official G9 help thread
Post by: gregcs1 on October 24, 2006, 07:07:42 AM
Can all these connections (rounded with circles on picture) be connected with zero ohm resistors? (,25W, 5%)

(http://freeweb.siol.net/gregcs1/connections.jpg)
Title: The official G9 help thread
Post by: gyraf on October 24, 2006, 08:25:44 AM
Yes. these are wire links - use 0R resistors or cut-off from the other resistors.

If you're unsure, look at the schematic and compare to the pcb..!

Jakob E.
Title: The official G9 help thread
Post by: gregcs1 on October 24, 2006, 08:37:16 AM
It's ok. I've got that this are wire links. I just thaught something could go wrong if there are resistors instead of wire. (temperatures...)

Btw, G9 almost finished (only connectors to solder). Now I'm waiting case.
Title: The official G9 help thread
Post by: Godders on October 24, 2006, 01:58:23 PM
Nearly there! I'm frankly amazed I've got this far without having to bother the good folks of the Lab.

The pre is up and running and sounding pretty fantastic (with dynamic mics at least :? ).

With 48v engaged and a condensor mic plugged in the level was a bit low and there was a lot of hiss. I inspected the PS and noticed I had neglected to fit D6 (the 56v zener diode).

So after giving myself a slap and fitting the diode the hiss has gone but the level remians a bit low and there's a buzz at higher gain settings. Phantom power is measured at 31.7v (with the trimmer at max) so a bit on the weedy side there.

I'm not entirely sure what the function of D6 is? Did I damage something else like the 48v regulator by firing the unit up without D6 fitted?

Any help/suggestions appreciated. :thumb:

Cheers

Nick
Title: The official G9 help thread
Post by: needlz on October 24, 2006, 06:05:50 PM
My levels are also quite low but it sounds great with all mic types. I am just concerned that my output is much lower than it should be. My API312 kicks the living heyzeus out of it in terms of total output gain.
Title: The official G9 help thread
Post by: Godders on October 24, 2006, 06:58:39 PM
I haven't really run it through it's paces but with a dynamic (EV635a) I get a pretty decent level.

I believe the available gain should be in the region of 60dB which is plenty for most things.
Title: The official G9 help thread
Post by: needlz on October 24, 2006, 09:51:26 PM
I am definitely not getting 60db... If that's how much gain it is supposed to produce, something is definitely hosed. Any ideas of what to check for?
Title: The official G9 help thread
Post by: gyraf on October 25, 2006, 02:33:45 AM
Maxgain with Lundahl's is some 55-57dB. 60-62 with OEP input.
Title: The official G9 help thread
Post by: Godders on October 25, 2006, 04:56:17 AM
Maybe my post was a bit too rambly (must waffle less :green:).

What is the function of D6?

Could I damage other components by firing the G9 up with no D6 fitted?

As I said I'm getting a low level and some buzz with phantom power on (measured at 31.7v, trimmer at max).

I previously fired up with no D6 fitted.

No problems with dynamic mics and regualr mic input.

Cheers

Nick
Title: The official G9 help thread
Post by: gyraf on October 25, 2006, 05:08:25 AM
D6 is the zener reference for phantom (look at the schematic!!)

Prevents phantom from going over some 48V

You could have burned electrolytics downstream from the regulating transistor - from overvoltage.

Jakob E.
Title: The official G9 help thread
Post by: Godders on October 25, 2006, 05:25:51 AM
Thanks Jakob  :thumb:

I'm still at the very early stages of learning, I'm getting my head around schematics but there are still vast gaps in my knowledge.

I will check out those 'lytics.

Cheers

Nick
Title: The official G9 help thread
Post by: gregcs1 on October 25, 2006, 08:46:57 AM
What do you think about using IDE computer cables for front panel connectons?
Title: The official G9 help thread
Post by: gyraf on October 25, 2006, 10:14:15 AM
Hard to say. try it, and report back..
Title: The official G9 help thread
Post by: gregcs1 on October 26, 2006, 07:36:11 PM
This is the connection cable I made from floppy connection cable. Making it was real pain in the @ss. It took me almost a hour. It really isn't some piece of art, but I hope it will do the job.

step by step  :?
(http://freeweb.siol.net/gregcs1/conn.jpg)

finished, only 3 to go!  :roll:  :grin:
(http://freeweb.siol.net/gregcs1/finished%20con.jpg)

And some pics of (slowly) progressing G9

(http://freeweb.siol.net/gregcs1/G9_1.jpg)

(http://freeweb.siol.net/gregcs1/almost%20finished.jpg)

Jeah, I know, I screwed up connections (female is soldered on pcb instead of male) but who cares! It'll work anyway!  :wink:

The only thing left (on main PCB) are IC's and T1. I'm still looking around for an IC1 heatsink.

Beside that heatsink, the only thing that gives me a hard time are that god [email protected] lorlins on front panel pcb's. I still don't know how to connect them. Obviously I still have some reading to do.


@gyraf

There are some kind of marks (A, B, C, D) on the bottom of the switches (poles). I also found them on pcb. Are they correctly aligned? Can I just solder a to a, b to b and so on...?


Thanks to all for your answers!
Title: BOM
Post by: JerryPbury on October 26, 2006, 08:55:16 PM
Gregcs1,

Do you have a copy of your BOM in regards to your Capacitors (all) and connectors? I used the only one I could find here and it had a lot of wrong / bad (non-fitting, to large/small etc.) component choices.

Thanks,

Jerry
Title: The official G9 help thread
Post by: gregcs1 on October 27, 2006, 03:27:10 AM
I ordered (almost) everything from Farnell. I was really careful to order components with right spacing. (connectors - 2.54mm) etc... I printed PCB in 1:1 and then measured all crytical connections. Farnell has nice thing on their site - you can actually choose component by lead spacing. So I had no problems except with C21,22 because they were 100uF/100V instead of 63V and were too big to fit in. I changed them and now is ok.

order:

http://freeweb.siol.net/gregcs1/Order1.txt
Title: The official G9 help thread
Post by: JerryPbury on October 27, 2006, 10:21:18 PM
Thank You!

Jerry
Title: The official G9 help thread
Post by: Mailliw on October 28, 2006, 12:04:43 AM
Hello,

Recently, my G9's phantom power isn't enough to make the pattern/cut switches work on an AKG414. I measured 14 volts on the XLR pins! It was 48 volts last time I used it.

I had the case off for a second today to adjust the trimmer, but 18VDC was all it could muster. I verified that 16VAC is going into the phantom circuit, but thats all I had time for.

EDIT: The top of C26 (47uF/50V) is ruptured. 16.6VAC is going into the phantom circuit. Right now, the mains AC is 117 volts. Could it have simply been a faulty capacitor?

Thank you,
William
Title: The official G9 help thread
Post by: gregcs1 on October 28, 2006, 03:41:15 AM
C26 and C27 are 47uF, 63V. Maybe this is the cause...
Title: The official G9 help thread
Post by: Godders on October 28, 2006, 09:17:39 AM
Quote from: "gregcs1"
C26 and C27 are 47uF, 63V. Maybe this is the cause...
Hmmm, the board says 63v but the parts list and the schematic on the Gyraf website both say 50v for the 4 P48 triplers (C26-C29).

I bought my board already stuffed with resistors, diodes and 'lytics and I've noticed that C28 & C29 were 100uF, 35v instead of 47uf 50v (or 63v?).

I'm thinking this is probably the source of my phantom power problem but I'd like clarification on the correct voltage before I fit the correct capacitance values.

Cheers

Nick
Title: The official G9 help thread
Post by: gyraf on October 28, 2006, 10:11:24 AM
Go with 63V capacitors, that'll keep you on the safe side. and keep an eye on polarisation!!

Jakob E.
Title: The official G9 help thread
Post by: Godders on October 28, 2006, 10:15:22 AM
Thanks as always Jakob. :thumb:

Cheers

Nick
Title: The official G9 help thread
Post by: gregcs1 on October 28, 2006, 04:12:16 PM
Front panel question...

Shouldn't SW3 (phase switch) be 2 pos.? PCB marks says 3pos...  I understand input has 3 pos. (line, mic, 48V) and low cut sw (sw4) has 3 pos (off, low, high) but I don't understand why phase switch has 3 pos (in, out, ?)
Title: The official G9 help thread
Post by: gyraf on October 29, 2006, 01:35:15 AM
yes. pcb marking glitch, sorry.

Jakob E.
Title: The official G9 help thread
Post by: gregcs1 on October 29, 2006, 05:56:42 AM
I have another question about Input selection switch.

(http://freeweb.siol.net/gregcs1/lorlin.jpg)

so:

When switch is in it's first position I have connection between A and 1, and C and 7

When switch is in second position there is connection between A and 2, and C and 8

And finally with switch in it's third position I have connections between A and 3, and C and 9.

Is that ok?

I understand first and third position, when there is connection, but I don't see the point in second position where no connection is made. (maybe thats just the way it is  :grin:  :?:
Title: The official G9 help thread
Post by: AudioJunkie on October 29, 2006, 06:24:33 PM
Just curious.  Could one use the Lundajl 1530 as an input?  1:7 would give even a little more gain than the OEP 1:6.45.

I would much rather use Lundahls for the high bandwidth.  But also want the little bit of added gain from the OEP.  I'm torn between which one to go with.

Maybe OEP input and Lundahl output?

Daniel
Title: The official G9 help thread
Post by: gregcs1 on October 30, 2006, 03:10:01 AM
How about one channel Lundahl and one OEP?
Title: The official G9 help thread
Post by: radiance on October 30, 2006, 04:47:56 AM
Quote from: "gregcs1"
I have another question about Input selection switch.

(http://freeweb.siol.net/gregcs1/lorlin.jpg)

so:

When switch is in it's first position I have connection between A and 1, and C and 7

When switch is in second position there is connection between A and 2, and C and 8

And finally with switch in it's third position I have connections between A and 3, and C and 9.

Is that ok?

I understand first and third position, when there is connection, but I don't see the point in second position where no connection is made. (maybe thats just the way it is  :grin:  :?:


Yes, it's ok. Just take a look at the schematic.
First position switches 48v on (mic in + 48v), second position (no conection) switches the 48v off (still mic in.), third position switches to line input with a relay.
Really, when I first saw your question with the pic and all I was wondering my self how this was suppose to work but a look at the schematic made it clear....
Title: The official G9 help thread
Post by: gregcs1 on October 30, 2006, 06:30:46 AM
Nice. Thanx

So my thaugts were right!

Does anybody know how to check if gain switch is switching or none switching? (switch is already soldered)
Title: The official G9 help thread
Post by: AudioJunkie on October 30, 2006, 10:50:25 AM
Quote from: "gregcs1"
How about one channel Lundahl and one OEP?


That wouldn't work for me as I do stereo location recording and having a stereo pair of mics running through mis-matched preamp wouldn't sound too good.   :thumb:

Daniel
Title: input trannies?
Post by: nielsk on November 01, 2006, 08:35:54 AM
I would like to try different mic input transformers on my G9, does anyone know the impeadance this circuit wants to see on the load side? Most tube mic pre's want to see a pretty high impeadance, and get the gain as well, but this one seems different. What are the impeadances of the OEP's? I only see them listed as ratios....
Title: The official G9 help thread
Post by: ChrioN on November 02, 2006, 11:54:10 AM
From sheet:

Source Impedance: 150/600ohms
Optimum Load Impendance: 6.25k/25kohms
Title: The official G9 help thread
Post by: ChrioN on November 05, 2006, 06:14:43 AM
Quote from: "ChrioN"

Jacob do you remember what you said? hmm...something about checking the input wiring and see if signal reaches the instrument jumper or something.


The signal doesn't reach the instrument jumper. I read 0v AC jumper->ground.
Title: The official G9 help thread
Post by: gyraf on November 05, 2006, 06:54:51 AM
Then trace the circuit - referring to the schematic - to that point....

Jakob E.
Title: The official G9 help thread
Post by: ChrioN on November 05, 2006, 07:10:06 AM
Okey, thanks. Im still learning.

I feed the preamp with a 1.76vac signal, and I get 0.4vac after C2. Is this good or bad?

Also, it appears as I have 0.43vac on the input xlrs (pin 2 & 3 to ground) with nothing connected.
Title: Impeadance
Post by: nielsk on November 06, 2006, 11:54:00 AM
So as the schematic shows the input transformer coils wired in series, then the input is set up as 600  to 25K...whay 600 instead of 150 for a mic input?
Title: The official G9 help thread
Post by: gyraf on November 06, 2006, 12:13:58 PM
Quote
whay 600 instead of 150 for a mic input?


To get primary inductance up - for better low-end..

Jakob E.
Title: The official G9 help thread
Post by: enthalpystudios on November 07, 2006, 03:01:09 AM
working on my g9 all night, I've got lundahl 1538's fitted at the input and ll1517's fitted on the out.

the ll1517s on the out have a daughterboard on stripboard, and it gets the point across without too much ugliness, as nice i could anyway.

the ll1538 solution i found is actually decent, maybe there's a more clever way of doing it.... since the pinout is different, i got by nicely with 2 jumpers, 2 cuts, and one wire.

dont have a camera available at the moment, but figured i'd post in case anyone else has 1538's they'd like to use for this.

getting exciting over here!  4 countries are on board, solen, nos rca, lundahl, and nichicon pw!  its a new world order mic pre.
Title: input trannies
Post by: nielsk on November 07, 2006, 11:19:42 AM
I think I'll try an A-26 I have, it is 50/125/200/33/500 to 30K...
Title: The official G9 help thread
Post by: analogical on November 21, 2006, 12:09:39 AM
On R34, 100k 2w, is it ok to use a 5% instead of a 1%?
Title: The official G9 help thread
Post by: caps on November 21, 2006, 01:29:25 AM
What exactly is a "switched" jack, as specified for the G9 DI inputs?

The jacks Ive used only have two connection points PLUS a ground, that goes to the PCB.

Im having some noise/buzz issues on higher gain settings when using the DI input, and Im looking into what I might have done wrong...
Title: The official G9 help thread
Post by: gyraf on November 21, 2006, 04:12:21 AM
Quote from: "analogical"
On R34, 100k 2w, is it ok to use a 5% instead of a 1%?


Definitely ok, yes. 2W/1% are not easy to find at all, and not neded at all here (look at the schematic - this resistor sets working voltage)

Jakob E.
Title: The official G9 help thread
Post by: radiance on November 24, 2006, 07:21:55 PM
Finished my G9 today. It seems to be working OK except for some 90Hz hum on both channels. I suspect it might be something with the TL783 regulator.
I meassure 248V on cap #14 (before regulator) and 236V on cap #15 (after reg.) This seems a bit low.....should I replace the TL783 regulator?
Or maybe increase cap #14/15? (they are now 220uF BTW)

Also, ripple is 166mV on cap #14 and 3mV on cap #15......
Title: The official G9 help thread
Post by: gyraf on November 25, 2006, 08:01:01 AM
Rad,

If you look earlier in this thread, you'll find that your HT voltage is too low, and what to do.

Jakob E.
Title: The official G9 help thread
Post by: radiance on November 25, 2006, 10:19:12 AM
:oops: looked everywhere except for this thread....

Thanks!
Title: The official G9 help thread
Post by: radiance on November 25, 2006, 10:33:51 AM
I feel like an idiot but I can't find it in this thread.... :?
Title: The official G9 help thread
Post by: Black Dog on November 25, 2006, 11:15:39 AM
I think your problem is that the HT voltage is not high enough to make the TL783 regulate.
You will likely need to replace the 2nd(=stepup) transformer to something like 2x12V .
That should make your HT voltage higher so the TL783 can regulate..

220uF is cool  :thumb:

Lars
Title: The official G9 help thread
Post by: radiance on November 25, 2006, 11:30:45 AM
Thanks Lars!
Title: The official G9 help thread
Post by: enthalpystudios on November 27, 2006, 05:28:12 PM
Getting there, just a few more components and the interconnects!

(http://i110.photobucket.com/albums/n91/enthalpystudios/img009.jpg)
Title: The official G9 help thread
Post by: radiance on November 28, 2006, 03:49:43 PM
Quote from: "Black Dog"
I think your problem is that the HT voltage is not high enough to make the TL783 regulate.
You will likely need to replace the 2nd(=stepup) transformer to something like 2x12V .
That should make your HT voltage higher so the TL783 can regulate..

220uF is cool  :thumb:

Lars


Got my new 2X12 tranny today and it works like a charm.
311V before and 246V after the regulator.
Still some hum I've got to sort out.
We are getting there slowly  :grin:
Title: The official G9 help thread
Post by: radiance on December 01, 2006, 06:06:16 AM
Ok, heater voltage is ok now but I still got some 100Hz hum (with both in and output on lowest setting ).
I have a ripple of 1,7 mV on both the 12V and the 245V heater.
I even upped the (c14 and c15) caps from 220 to 330uF but that did not make any difference.

Is it normall to have a small amount of hum in a OK working G9?
Title: The official G9 help thread
Post by: radiance on December 01, 2006, 10:29:37 AM
Quote from: "radiance"

Is it normall to have a small amount of hum in a OK working G9?


Small amount beeing -85,00 dB.

I just connected the G9 to the in's and out's from my audio interface and read the meters in Logic (DAW). I guess it's not very acurate... :?
Title: The official G9 help thread
Post by: gyraf on December 01, 2006, 10:42:31 AM
Quote
Small amount beeing -85,00 dB.


..good enough..
Title: The official G9 help thread
Post by: radiance on December 01, 2006, 10:51:45 AM
Ok, it's a rap then  :cool:
Title: The official G9 help thread
Post by: dissonantstring on December 16, 2006, 05:12:09 PM
hello everybody,
i've read through the G9 threads on the meta, but still need some help on this one.  i'm really close to finishing my G9 build, but i've run into a problem.
i was able to rid my oscillation on the higher gain settings with axel's oscillation fix (thanks for that one axel! :thumb: ).
i'm getting good gain out of both channels and all front panel controls work properly.  i'm getting my "click-ity-click" from my relays when switching "line" on/off.  both mic and DI sound very good so far, but...
i have 48V PP on both pin 2 and 3 of both channel input XLRs at the main board input jumpers.  I've checked for shorts and cannot find any on both main and control pcbs, nor any shorts in my wiring (XLR in, 10-pin, 5-pin, etc).  Without control boards and XLRs connected to main board I still get 48V on both pins 2 & 3 on the main board input jumpers (so the problem has to be on the main board).
I'm at a loss after about 3 hours of looking at schems, pcb traces and pads. :?  Why would I get PP on both pins?  
Any suggestions or help would be greatly appreciated.
thanks
-grant
Title: The official G9 help thread
Post by: gyraf on December 17, 2006, 05:29:31 AM
I'm not sure what your problem is - you should have 48V phantom at input XLRs pins 2+3 - when phantom power is engaged.

Phantom power is switched by the input selector - look at the layout .PDF's on the G9 webpage - it switches from the "from 48V" to the "P48" points on each channel.

Use an ohmmeter to verify switching and connection/disconnection from phantom supply.

Jakob E.
Title: The official G9 help thread
Post by: dissonantstring on December 18, 2006, 12:33:31 PM
hi jakob,
thank you for the info.  
i looked at all the information on the G9 page at your site before, during and after my build and did notice that both pins 2 & 3 are connected to PP.  
my connection/disconnect via 48V/mic/line switch does turn on and off the PP
as verified with my DMM.
the reason i thought something might be wrong initially was that when i connected a condensor mic to the mic input there was a voltage drop after a minute or two from 48V to about 39V.  this seemed strange and i thought possibly that there was something wrong in my PP circuit.  i'm using a TIP 122 (instead of the 121) for regulation.  i'll have to do more tests to see if i can find anything i might have done wrong and overlooked.
thanks for your help.  very much appreciated.
regards,
grant
Title: The official G9 help thread
Post by: radiance on December 24, 2006, 07:44:59 PM
Having used my g9 for I couple of weeks now I have to say that it sound wonderfull.
When I use it on an insert of my mix bus I notice a slight low end roll off, in other words, it's lacking some bottom end. When using it as a mic pre I had not noticed this though.
Is this normall?  I have no good way of meassuring this but I do hear it.

A wild guess....Could I've mixed up the in and output transformers? (I'm using Oep's), or would that have been way more obvious than a slight lack of bottom end? I mean, the unit is working as it should (low cut works fine..).

Ok, and if I did wire the trannies right, where should I be looking first?

Also, I'm using rather thin microphone (2 wires and a shield) cable to and from the XLR's (and to the frontpanel jack). Could it have something to do with that?

Thanks and Merry Christmas to whoever reads it at this time.....
Title: The official G9 help thread
Post by: radiance on December 26, 2006, 10:39:36 AM
Ok, I did some meassurments and although they're not really acurate I think they will give an idea of the lack of low-end I'm talking about.

G9 inserted

Hz____dB
10___-14,3
16___-10,2
21___-7,3
26___-5,5
32___-4,4
37___-4,0
43___-3,8
48___-3,5
53___-4,3
59___-3,5
64___-4,8
69___-4,4

G9 Bypassed
Hz_____dB
10___-2,5
16___-2,4
21___-2,5
26___-2,4
32___-2,6
37___-2,5
43___-2,6
48___-2,6
53___-3,7
59___-2,8
64___-4,2
69___-4,4

It's all done with a sine sweep recorded through the G9 into my DAW...
Maybe it's just the frequentie characteristics of the Oep transformers I've used.
Title: The official G9 help thread
Post by: laiben on December 28, 2006, 02:30:26 AM
Hi,

I got the board of G9 and start to collecting parts for the project.

I wonder if anyone chassis-mount the pots and switches rather than using the PCB? If I do it in this way should all the componet on the control pcb  be directly soldered on the swtiches/pot? I am asking because when I built guitar amp some componet should be as close as possible to avoid oscillation.
Also I am thinking to use pots or 24-stepped attenuator to replace the 12-position switch so that I can have more control on gain. What do u think?


laiben
Title: The official G9 help thread
Post by: dissonantstring on December 28, 2006, 05:30:21 PM
hi laiben,
i do not think you'll gain anything by not mounting the switches to the control pcb directly.  flying leads to all those switches seems like it's more trouble than it's worth.  jakob has a very well thought out control pcb layout.

the oscillation problems that occur in some of the G9 builds (including mine) are due to the rather long traces from the DI jack to the input xfrmr and related cap (C2 and C102) or lack of shielding on the in/out xfrmrs.  look in the G9 meta for the oscillation fix thread.

as for a 24 position gain switch, the G9 does have an output trim pot which allows for various levels of gain control even with the 12 position switch.  once again, i'm not sure you'll gain anything from trying to apply a 24 position switch, but this is DIY and you're welcome to try.
regards,
grant
Title: The official G9 help thread
Post by: laiben on December 28, 2006, 08:32:13 PM
Thanks dissonantstring. I think i will just follow the PCB strictly for the first build. I will report to all of you if I did any other mod to G9. Yeah right this is a DIY! But you know... we have too many projects and too much things to try and too little time!
Title: The official G9 help thread
Post by: laiben on January 02, 2007, 09:15:44 PM
Another Power Transformer question...

If I use 50VA transformer instead of 30VA transformer, what that generate much more heat? I am asking because I always feel that more 'headroom' is safer. Also look at the guts of those Hi-end audiophile equipment their transformer are always ridiculously big!


laiben
Title: The official G9 help thread
Post by: tony dB on January 03, 2007, 05:30:53 AM
Quote from: "laiben"

...
Also look at the guts of those Hi-end audiophile equipment their transformer are always ridiculously big!

laiben


those Hi-end audiophile equipment is usually ridiculously expensive  :green: , if you get big cash selling it, why not spend a little of it on expensive looking components?

IMHO you would have less heat buildup
Title: hum hum hum....
Post by: nielsk on January 03, 2007, 09:57:14 PM
on my second G9 now, 1st one works perfectly, 2nd built identically, & has a hum I can't find the cure to. They both have outboard supplies, using 1 tranny for B+ and heaters & (rated [email protected] / 15.3v @ 1 a) and one 15v for the phantom. Other than that built strictly to the scematic, the bridges and res caps are in the remote supply w/ a 100K 2w bleeder resistor to ground on the post cap side of the B+ and 48V.
The B+ measures 356v DC & around 1v AC before the reg, and 258DC / .1v AC after.
(I am seeing 1.5v AC on my scope, a very distinct triangle waveform, when I measure on the fluke, it reads around 20 volts to begin with, and rapidly drops to stabilize around .5v...is this normal?)
I see the same "ripple" on all voltages.
I have rotated & moved everything every which way, not inductive as far as I can tell.
I have replaced all caps, bridges, regulators, no change.
I have tried every ground scheme I can think of, no improvement (I can make things worse!)
When the AC mains is removed & it runs off the caps, it is as clean as can be. Would this rule out a bad tube?
I did the DI bypass, works great (I am waiting on parts to try a relay switch DI mod, using a 113 style 1/4 jack to switch the 12v to a  relay at the input tranny when the jack is inserted)

I am using an EMI filter AC input.....
maybe a choke?

any ideas?????
Title: The official G9 help thread
Post by: gyraf on January 04, 2007, 03:55:17 AM
Quote
I am using an EMI filter AC input.....


That is probably the problem. These are fine for digital/switchmode stuff, but often problematic in linear. Try with a standard ac input without filter.

Jakob E.
Title: The official G9 help thread
Post by: Greg on January 04, 2007, 09:10:54 AM
Don't those AC inlets with filters dump a bunch of hash into ground?
Title: The official G9 help thread
Post by: gyraf on January 04, 2007, 09:29:30 AM
yes - that is the problem with'em..
Title: EMI gone, hum remains
Post by: nielsk on January 04, 2007, 10:36:08 AM
with much anticipation for my salvation, I removed the EMI AC inlet, & tried it wired direct......
No change

Is the "sawtooth" shaped waveform what I should expect to see out of the bridges?

any other ideas?
Title: The official G9 help thread
Post by: INDI03 on January 08, 2007, 05:15:44 AM
G9 newbie question ;) - where is the 0V connected to the Chasis ? thx IA
Title: The official G9 help thread
Post by: gyraf on January 08, 2007, 05:20:52 AM
Quote from: "INDI03"
G9 newbie question ;) - where is the 0V connected to the Chasis ? thx IA


As always - at the input XLR, and only there. Connect XLRpin1 to XLR ground tab. In case of more than one input XLR, then the first one.

Jakob E.
Title: The official G9 help thread
Post by: INDI03 on January 08, 2007, 07:05:13 AM
thx for quick reply :)
Title: The official G9 help thread
Post by: INDI03 on January 09, 2007, 05:48:24 PM
another question on cases - yesterday I got an aluminum case from a friend - is this ok or does it have to be an ordinary steel case to have optimal shielding ? and 2nd I wanted to know how the airslots on the case effect the shielding ? no slots will probably heat up the case too much ?! - thx IA :)
Title: The official G9 help thread
Post by: INDI03 on January 10, 2007, 08:49:29 AM
one more thing - can I use JJ ECC802S tubes for the G9 ?
Title: The official G9 help thread
Post by: dissonantstring on January 10, 2007, 11:14:40 AM
hi indi03,
check here for some chassis discussion:
chassis discussion (http://www.groupdiy.com/index.php?topic=12373&highlight=shielding+steel+chassis)
i simply did a search and came up with this, so please make sure you do the same.  i know sometimes i like to have answers quickly, but doing a search will often give you the same answer quickly.
as to your tube question, the ECC802S is listed as a premium 12AU7/ECC82.  
i'm not expert so double check the data sheets for specs and pinout config.
hope this helps.
-grant
Title: The official G9 help thread
Post by: INDI03 on January 10, 2007, 05:41:37 PM
thx for reply - its not the way that I didnt use the search function but on most things I get 20 threads with 100 posts - it would take 10 days to find an answere for 1 question - well on some I found easy :)
Title: Hum solved
Post by: nielsk on January 18, 2007, 04:02:33 PM
I just solved the hum problem, I was able to look at the 1st one I built and found I ran the secondary B+ cap ground to the HV in ground point and the input Ground to the secondary cap ground point (I used single 100/350 caps mounted off board instead of a multicap, WAY cheaper). switching this on the second unit made it totaly clean...kind of odd, the ground path connects all the way through.  The remote supply is great, extremely clean. I used high voltage cable and AMP circular plastic connectors, female pins on the cable end. I placed the bridges and primary caps in the supply, & jumpered out these parts on the main board. All B- and grounds tied to power ground in the supply, and a seperate chassis and p/s ground run from there to the unit. The trick is to connect the p/s ground to the secondary B+ cap ground point.
I also tried using a P&B shielded 12v relay for the DI input, switched by the 1/4 jack (Switchcraft #113). I was able to fit the relays right next to the input transformers, it works fabulously. This would make a good revision to the board.
Title: hum too but with internal PSU
Post by: Wolferl on February 07, 2007, 07:05:57 AM
About six months after finishing my G9 I found the time to reanimate my "old" problem with this preamp:

http://www.groupdiy.com/index.php?topic=15513&highlight=

In a few weeks I have a recording session and I want to use the G9 for Vocals because it sounds sweet. But I have still some hum at the outputs - stable without any gain - left. It is a bit 50Hz hum and a lot of 100Hz, both good audible on both channels (right channel has got more 50Hz hum). I changed / adapted / increased /measured capacitors, regulator, diodes, resistors, ... I even used a additional 10H Choke for B+.

No improvement.

I checked ground lines for loops, earth, shielded all cables, ....

No improvement.

I turn the power-transfomers outside the housing - no improvement.

In the next step, I will change the HV-power-transformer

Any ideas left? I invested so much time in this project and hope to find finally the solution for a clean output signal...  :?  :roll:  :roll:

Thanks a lot!
Title: I give it up...
Post by: Wolferl on February 08, 2007, 05:09:16 AM
yesterday I changed as a last action the HV-tranny. No improvement. So I close this chapter of DIY and try to be satisfied with about [email protected] noise. It's not really bad but I expected a bit less hum.
Title: Re: I give it up...
Post by: laiben on February 08, 2007, 08:11:07 PM
Quote from: "Wolferl"
yesterday I changed as a last action the HV-tranny. No improvement. So I close this chapter of DIY and try to be satisfied with about [email protected] noise. It's not really bad but I expected a bit less hum.


Hi,

I am going to make a G9.. hopefully all the parts will be here by March.

Just some thought, what is the filter cap value you are using? if you are using 100uF as suggested in the schematic, you may try to use 220uf?
Title: Another improvment
Post by: nielsk on February 08, 2007, 09:15:32 PM
BTW, I also added a Line + 48V position just by making the switch 4 position and jumpering the 48V to that pos, actually very useful. It just so happens that I mostly need the pad on phantom powered mics......
you should try changing the ground point for the off board caps to cure your ground noise, it worked for me, any line freq noise is so far under the hiss that it is not a problem.
Title: The official G9 help thread
Post by: radiance on February 10, 2007, 09:46:06 AM
I'm using my G9 on the insert of a group/bus of my mixing console and I'm noticing a low end roll off starting at 60Hz. It seems like the G9 is lacking bottom end. Could this be because of an impedance mismatch?
(inserts are fully balanced with separate xlr's for send and return and they're spitting out line level)
When I connect my G9 between the in and outputs of my RME Adi 8 pro soundcard there's still a lack of low end.

I've checked my G9 very thorough and could not find any fault. It's working like it should, low cut works fine. I realy don't know where to look further....
Also, if I use the instrument input there's still a low end roll of so I guess I don't have to look for faults at the input tranny. I build my G9 with Oep's.
I even replaced the output Oep for a Lundahl but that did not solve the lack of low end.
The G9 should deliver a solid bottom right?

Could it be the JJ tubes I've used?
Title: The official G9 help thread
Post by: waldorfcave on February 10, 2007, 10:17:44 AM
Hi Radiance,

i will also build a G9. For my synths and mostly line signals, going into my
rme fireface audiointerface.

The your lost of the low end, worries me :?

I hope you will find out why.
g. Lars
Title: The official G9 help thread
Post by: radiance on February 16, 2007, 08:33:31 PM
Bump.. :roll:
Title: The official G9 help thread
Post by: clintrubber on February 16, 2007, 08:38:54 PM
Quote from: "radiance"
Bump.. :roll:

We gaan hier om half drie 's nachts toch niet zitten bumpen, right ?
Ook net uit de kroeg gevallen ?  :wink:
Title: The official G9 help thread
Post by: radiance on February 17, 2007, 08:40:47 AM
Quote from: "clintrubber"
Quote from: "radiance"
Bump.. :roll:

We gaan hier om half drie 's nachts toch niet zitten bumpen, right ?
Ook net uit de kroeg gevallen ?  :wink:


 :oops: Nee, moest er nog heen..... :sam:  :guinness:  :sam:
Title: The official G9 help thread
Post by: clintrubber on February 17, 2007, 09:13:04 AM
Quote from: "radiance"
Quote from: "clintrubber"
Quote from: "radiance"
Bump.. :roll:

We gaan hier om half drie 's nachts toch niet zitten bumpen, right ?
Ook net uit de kroeg gevallen ?  :wink:


 :oops: Nee, moest er nog heen..... :sam:  :guinness:  :sam:

JIJ BEEST !  :green:  :green:  :green:
Title: The official G9 help thread
Post by: gyraf on February 19, 2007, 05:16:07 AM
Quote
I'm noticing a low end roll off starting at 60Hz


Depends on your source impedance, and the primary inductance of the input transformer used. As standard, Lundahl, and 200 Ohms source impedance, we go below 30Hz

Jakob E.
Title: The official G9 help thread
Post by: radiance on February 19, 2007, 05:46:29 AM
Quote from: "gyraf"
Quote
I'm noticing a low end roll off starting at 60Hz


Depends on your source impedance, and the primary inductance of the input transformer used. As standard, Lundahl, and 200 Ohms source impedance, we go below 30Hz

Jakob E.


Ok thanks. I was  testing this by inserting the G9 between the in and outputs of my RME ADi8 pro soundcard. Input impedance from the ADI is 10K and output impedance is 47R. Forgive me but I'm a total noob when it comes to understanding impedance. Could this be an impedance mismatch?

EDIT: Oh, and BTW I 've used OEP in and output trannies...
Title: voltage problem
Post by: INDI03 on February 24, 2007, 06:37:16 PM
hi there - Im nearly done but I got some strange voltage problem - I get 370 volt output after the TL 783 - shouldn`t there be just 245 ? couldn`t find anything at the forums about that - well first when I turned on the amp I havent put the tubes inside to do some measuring without them - after 10 to 20 seconds I heart 5 little explosions ? maybe some condensers said goodbye ? lol - well I put the tubes in and tested it again - still 370 volt after 5 seconds I turned it off not to ruin the tubes - I did a test by building a save switch with 2 resistors and suddenly it went down to 235 volt. when I turn it off it goes back to 370 - hm - any help would be nice - sorry for my bad english I hope you understand what I mean ...

well here a photo of the preamp :) - thx to everybody for making this possible

(http://i25.photobucket.com/albums/c84/radiolife03/IMG_3236.jpg)[/img]
Title: The official G9 help thread
Post by: gyraf on February 25, 2007, 07:30:42 AM
If your regulated HT voltage is more than 250V (with tubes in!), you have a problem in the regulation section.
Title: The official G9 help thread
Post by: INDI03 on February 25, 2007, 12:20:16 PM
just figured out that the TL 783 needs 15m-amber to start working - hm but Im not sure why it doesent get it. any experience on that ?
Title: The official G9 help thread
Post by: maxime on February 26, 2007, 08:22:44 AM
a blown 12volts regulator can lead your preamp to that behaviour (no mA drawn from B+). it happens readily as  the 78s12 is not  sufficiently cooled...
best
maxime
Title: The official G9 help thread
Post by: INDI03 on February 26, 2007, 12:01:20 PM
will check that thx :)
Title: Low gain problem
Post by: MrShhh on February 28, 2007, 09:24:01 AM
Hi there,

Having cut my teeth on Jakob's awesome 1176 and Pultec clones I decided to make the G9 and have just finished putting it together.

Just one tiny problem, there is way too little gain on both channels and no bottom end. I have to crank it up to 11 with full output to get any meaningful signal (having cut traces etc. to cure the oscillation problem). This is the same for line or mic inputs.

I thought it might be the HT supply as the 783 is regulating from 270V down to 238V with all 4 valves in place (<245V)

However, I see people are running with as little as 208V HT with no problems and that there should be barely any audible difference until the HT voltage drops as low 150.

I've read almost every thread on the meta and sweated over the schematic for hours but my knowledge of what to do next just isn't there. I tried changing the 783 but it made no difference at all to voltage readings or the lack of gain.

Can anyone suggest what I should check next?

Thanks in advance :grin:

Mark

PS. 12v and P48 are both ok
      I'm using 30VA  2 x 15V transformers
Title: The official G9 help thread
Post by: radiance on February 28, 2007, 11:33:15 AM
Did you mount the transformers correct? For example when using OEP's the in and output trannies look almost the same except for the text on top. When canned it's hard to tell the difference...
Title: The official G9 help thread
Post by: INDI03 on February 28, 2007, 12:03:38 PM
I think I got mine running now - thx for help - btw when turning the G9 on the voltage jumps over 300v until the tubes get warm - therefor I made a small automatic saveswitch so the voltage never goes over 245v and automatically turns itself off when the tubes got warm ( its called "schmitt - trigger" ) - also I have made a "star" ground system so there can be no groundloops at all - works like a charm - next thing is I think we figured out some "errors" on the original thats why we designed the whole new schematics in AutoCAD - if anybody needs it I can send it :)

cheerz , INDI
Title: The official G9 help thread
Post by: idylldon on February 28, 2007, 12:15:30 PM
Just finished mine and it sounds fantastic!  In my never-ending quest to find old enclosures and breathe new life into them, I put a new front panel on this one and haven't had the time to get it to the laser engravers yet.  

(http://home.mindspring.com/~idyll/G9front.jpg)

(http://home.mindspring.com/~idyll/G9inside.jpg)

Cheers,
--
Don
Title: The official G9 help thread
Post by: MrShhh on February 28, 2007, 02:01:36 PM
Quote from: "radiance"
Did you mount the transformers correct? For example when using OEP's the in and output trannies look almost the same except for the text on top. When canned it's hard to tell the difference...


I'm using OEP A262A3E input and Llundahl LL5402 output transformers. I read somewhere it was ok to do this. No real reason, I just had the LL5402's spare and the OEP's were cheaper.
Title: The official G9 help thread
Post by: radiance on February 28, 2007, 02:24:04 PM
Quote from: "MrShhh"
Quote from: "radiance"
Did you mount the transformers correct? For example when using OEP's the in and output trannies look almost the same except for the text on top. When canned it's hard to tell the difference...


I'm using OEP A262A3E input and Llundahl LL5402 output transformers. I read somewhere it was ok to do this. No real reason, I just had the LL5402's spare and the OEP's were cheaper.


Nah, you will not mix those up....
Title: The official G9 help thread
Post by: INDI03 on February 28, 2007, 02:24:36 PM
@Mrshhh

maybe this could help you - check the R34 , R35 , R36

Vo ("245") = Vref ( 1+ 100Kohm/470ohm+47ohm ) means the same like Vo ("245") = Vref ( 1+ R34/R35+R36 )

Texas instruments TL783 says that Vref = typical 1,27v ( min. 1,2v , max. 1,3v )

I think you know that the TL783 needs a minimum load of 15milliamber to start regulating ?!

cheerz , INDI
Title: The official G9 help thread
Post by: laiben on March 01, 2007, 04:12:35 AM
I am buying the heat sink. A quick question:

Among the  TL783 and 7812, which one is hotter?

Thanks
laiben
Title: The official G9 help thread
Post by: gyraf on March 01, 2007, 04:25:24 AM
78S12 is by far running the hottest of the two

Jakob E.
Title: The official G9 help thread
Post by: dinesh on March 01, 2007, 05:40:49 AM
HI,

Can I use 7812 instead of 78S12??
Title: The official G9 help thread
Post by: gyraf on March 01, 2007, 06:11:43 AM
I'd prefer 78S12 - that's why it is specified in stead of the easier-to-get 7812.

Jakob E.
Title: The official G9 help thread
Post by: MrShhh on March 01, 2007, 08:14:12 AM
Quote from: "INDI03"
@Mrshhh

maybe this could help you - check the R34 , R35 , R36


Cheers, Indi03, I've checked they are the correct values. I also checked some voltages:

783:
Vin = 264
Vout = 243
Vadj = 239

272V from the rectifier
242V at the zeners

R33:
Vin = 272
Vout = 264

R34 239V

R35 243V

R36 243V

R37:
Vin = 243
Vout = 235

Vc14 = 264
Vc15 = 235

Should I be losing that much voltage across R33 & R37? I will check the current going through the 783 if that helps...
Title: The official G9 help thread
Post by: Soeren_DK on March 01, 2007, 04:22:08 PM
Hey Foks.
I just put a G9 preamp together and it sounds so great. Thanks again Jakob for a great project.

The next is:
There is a little hum but not like a grounding problem. I have tried that a lot and this is a little different.

I can only hear the hum when I set the volume on my mixer yo max and its stays when all knobs on the G9 is in 0 position.. Weird. I discovered when I put my ear to the 12v trafo I can hear that same hum is comming from this.
Could there be a connection?

Soeren Sailor
Title: The official G9 help thread
Post by: MrShhh on March 01, 2007, 07:03:42 PM
I think I've found the source of the low gain problem I spoke of earlier.

I have 16.6mA HT current which is in the 15-20mA range, but only 157mA heater current (should be around 600mA).

No heater = no sound right?

I will try to work out where the problem originates with the 12V supply.
Title: The official G9 help thread
Post by: MrShhh on March 01, 2007, 08:16:20 PM
There's 610mA at the output pin of the 78S12 so I'm not sure how it's falling to 157mA when measured at the +12V bridging wire just above C24.

Could it be the valves? Or the valve sockets?

Looking at the schematic, the 12V supply circuit is very simple, The only other components I can see after the output pin of the 78S12 are C19, C24 and the light.

I've ruled out the light so far.

Just a thought, is it correct to assume that the heater current should be the same through all four valves? In other words does it drop lower after each valve? I know squat about valves, but if the heater is acting as the cathode and emitting electrons, would that then explain the current loss?? 157 is curiously approx. 600 / 4 and where I measured the heater current, it had yet to pass through 1 valve. Am I just babbling nonsense? Please advise, this is fascinating stuff!

Thanks again
Title: The official G9 help thread
Post by: laiben on March 02, 2007, 01:57:14 AM
Hi,

I am still building the G9 but my experience of DIYing a guitar tube amp tell me that the heater current should be very close if not the same  through out the four tubes. Is the tube lighting up normal when you power on? I think if there is only 1xxmA current you can't see the tube light up, or it may be very dim.

How do you measure the heater current? with the tube all in sockets? desolder some parts? measuring current should be put the meter in series with the component.

laiben
Title: The official G9 help thread
Post by: MrShhh on March 02, 2007, 04:39:02 AM
Quote from: "laiben"
Is the tube lighting up normal when you power on? I think if there is only 1xxmA current you can't see the tube light up, or it may be very dim.


Hi laiben, thanks for getting back :grin: All 4 tubes do light up, not very brightly however, but uniformly bright.

Quote from: "laiben"
How do you measure the heater current? with the tube all in sockets? desolder some parts? measuring current should be put the meter in series with the component.laiben


I measured the current (with all tubes in place) by cutting the long 12V bridge wire just above C24 and then placing the multimeter in series with the two cut ends of the wire.

I also measured the current at the output pin of the 78S12 by cutting the pin in half and attaching crocodile clip probes across the 2 halves being very careful not to short anything with the clips.

If the heater current should be the same through all 4 valves then that gives me something to work on.

I've checked for shorts on the main board but found none. I noticed that 12V goes to the switch boards as well so maybe there is a problem there.
Title: The official G9 help thread
Post by: gyraf on March 02, 2007, 05:31:29 AM
Measure voltages, not currents - that makes many things easier.

If the tube gets the needed 12V for the heater, it'll draw the right current (providing it's functional, and the right type).
Title: The official G9 help thread
Post by: MrShhh on March 02, 2007, 10:34:19 AM
Quote from: "gyraf"
Measure voltages, not currents - that makes many things easier.


Thanks Jakob, I started off down this route thinking it was the "easy" cheats way of doing things :!:  

There is 11.73 heater voltage which is down to the 78S12. Some of them seem to like putting out around 11.7V. There is 19V at the input pin so I'm fairly sure the 78S12 is working correctly.

The tubes are 2 x Amperex and 2 x Valvo ECC82. The dealer claims they are in very good condition but I can't know for sure without a tester.

Would it be a good idea to check the voltages at the valve pins?
Title: The official G9 help thread
Post by: enthalpystudios on March 08, 2007, 07:50:27 PM
if i want to use a standard tube power transformer for my build, what should i be looking at?

I'm thinking that a 250-0-250 at 250ma each winding, with a 2A 12.6v winding.  

Will each of those ac voltages be enough, after rectification, to properly keep the regulators working?
Title: The official G9 help thread
Post by: dinesh on March 20, 2007, 08:16:08 AM
Hi,

I am not able to get 78s12 in India. Can I use LM317?

or any other equivalent??

Regards
Dinesh
Title: The official G9 help thread
Post by: gyraf on March 20, 2007, 10:19:24 AM
You should be able to find 78S12 nearly anywhere - it is not rare at all. TL783 is much, much more hard to find...

Jakob E.
Title: The official G9 help thread
Post by: dinesh on March 20, 2007, 10:25:14 AM
Hi Jakob,

I have searched these in my 400km area without any success. some comman parts are not easily available in India, & I am from a very small town. I got 783 as Samples. Thanks to TI for samples
Title: The official G9 help thread
Post by: gyraf on March 20, 2007, 10:59:41 AM
Hi Dinesh,

In that case you may want to try with a standard 7812 regulator - but make sure that it has very good heatsinking.

What part of India are you in? I lived most of my childhood in Orissa, India..

Jakob E.
Title: The official G9 help thread
Post by: dinesh on March 20, 2007, 11:03:29 AM
WOW Jakob,

Thats great :grin:  What was you doing there??

I am in North (Punjab), I am going to delhi in couple of days in search of

some parts.

Thanks for your help

Regards
Dinesh
Title: The official G9 help thread
Post by: gyraf on March 20, 2007, 11:32:16 AM
Quote
What was you doing there??


In fact, very little.

My father was a lone doctor on a far-out countryside hospital in Bissamcuttack, Rayagada district, for six or seven years - he was sent there by some help organization to start up a hospital from scratch.

But for me there was very little to do - almost no technology around  :razz: - one telephone in the village (in the post office) - absolutely no mains power until 1972 (and we lived there from '66 or so), no tv, no libraries... Oh yes, we had a battery-driven transistor radio that would occasionally pick up something other than static noise... ..but not often..

We spoke the Orya dialect locally - but sadly I've forgotten most of it because of no use the latest 30 years..

Nice to see someone from that part of the world in this forum!

Jakob E.
Title: heaters
Post by: nielsk on March 20, 2007, 09:47:57 PM
I wound up seperating the heater supply from channel 1 & 2, and running them off seperate regulators. Even with the "s" series, & lots of heat sinking, they get very hot. This approach seems to be holding strong
Title: The official G9 help thread
Post by: dinesh on March 21, 2007, 04:36:16 AM
Hi nielsk,

Thanks I was thinking of same. I am going to use two 7612 for testing.

Regards
Dinesh
Title: The official G9 help thread
Post by: madreza on April 11, 2007, 08:33:41 AM
Hi everyone

I built A G9 1 year ago
It perfectly worked.
I wanted to change a few things and now I only have 1 channel working

My question is :
How do I have to troubleshoot the problem ???
( what to begin with, how to test ....... )

Thanks
Title: The official G9 help thread
Post by: gyraf on April 11, 2007, 03:27:05 PM
supply voltages. signal-through..
Title: The official G9 help thread
Post by: laiben on April 16, 2007, 11:53:30 AM
I am building the G9 and all the wiring is done. My B+ without tube is 285VDC (the schematic said 245V), is that too high? I am using two 330uF/450V cap instead of the suggested 100uf cap in the schematic, will it cause any problem?

Thanks
laiben
Title: The official G9 help thread
Post by: maxime on April 16, 2007, 12:07:34 PM
the caps size won't affect the tension value up to that point. I think you should try to measure tension before and after the regulator to see if it's properly working. are your filaments glowing ? if not the problem may be a overheating 12 volts regulator (78s12)... this one really needs sufficient cooling.
the 783  needs current passing through it to start regulating. if the filament don't warm the cathode, no current through the tube...


maxime
Title: The official G9 help thread
Post by: laiben on April 16, 2007, 09:32:39 PM
Quote from: "maxime"
the caps size won't affect the tension value up to that point. I think you should try to measure tension before and after the regulator to see if it's properly working. are your filaments glowing ? if not the problem may be a overheating 12 volts regulator (78s12)... this one really needs sufficient cooling.
the 783  needs current passing through it to start regulating. if the filament don't warm the cathode, no current through the tube...


maxime


Thanks for the reply maxime. I measure the 285V at the 1K/2W resistor (R31 if I remember correctly), without tubes.
I already have a big heatsink with the 78S12, I will post a picture when I back home.

I will also report all the voltage in and out of each regulator. Thanks!

laiben
Title: The official G9 help thread
Post by: maxime on April 17, 2007, 03:31:38 AM
without tubes, the regulator (because no current flows through it) won't bring your high tension (285V) to a lower 240V regulated output.
put your tubes on the board for testing  :green:
best regards

maxime
Title: The official G9 help thread
Post by: laiben on April 18, 2007, 02:40:36 AM
Thanks maxime. I put 4 12AX7 in there and the HT is now 250V, it's less than 2 % difference from the schematic so I think it is okay. Next step will be go out to buy some 12AU7..

laiben
Title: The official G9 help thread
Post by: laiben on April 26, 2007, 11:57:13 AM
well I just finished my G9, and it hums  :sad:

Here is the clip of the hum when there is no input, turning the gain knob will not make the hum loud, turning the output knob will increase the hum.

http://www.mediamax.com/laiben/Hosted/G9%20hum.mp3

chopstick makes no difference, any suggestion?

some pics:
(http://i4.photobucket.com/albums/y136/laiben/G9%20preamp/RIMG0505.jpg)
(http://i4.photobucket.com/albums/y136/laiben/G9%20preamp/RIMG0506.jpg)
(http://i4.photobucket.com/albums/y136/laiben/G9%20preamp/RIMG0507.jpg)

laiben
Title: The official G9 help thread
Post by: ChrioN on April 27, 2007, 02:40:38 AM
chopsticks? Try moving the wires and transformers around a bit.
Title: The official G9 help thread
Post by: jdr on April 27, 2007, 03:08:16 AM
From the pictures, it looks like you haven't put your star ground at the input XLRs. From gyraf's g9 diy page (http://www.gyraf.dk/gy_pd/g9/g9pd.htm):

"- Connect 0V/Gnd to chassis at one - and only one - point: At the input XLR's.

- Connect the power ground from the power inlet to the ground at the input XLR's also."

Also, on the same page, Jakob recommends keeping the power transformer far away from the front panel because " the 'output gain' is somewhat highohmic and hence sensitive"

Hope that helps. Good Luck!

John
Title: The official G9 help thread
Post by: laiben on April 27, 2007, 12:20:01 PM
Thanks JDR!! I can't believe I read all the meta but forget to look at Jakob's page!! Now I connect the pin1 of the one of the XLR to the chassis and now the G9 is slient as hell!

Now the channel 1 is good, but the channel 2 is very quiet :evil: No gain at all. Swapping tubes did no help, I am gonna check the wiring but if you have an idea please give me some insight.

laiben


Quote from: "jdr"
From the pictures, it looks like you haven't put your star ground at the input XLRs. From gyraf's g9 diy page (http://www.gyraf.dk/gy_pd/g9/g9pd.htm):

"- Connect 0V/Gnd to chassis at one - and only one - point: At the input XLR's.

- Connect the power ground from the power inlet to the ground at the input XLR's also."

Also, on the same page, Jakob recommends keeping the power transformer far away from the front panel because " the 'output gain' is somewhat highohmic and hence sensitive"

Hope that helps. Good Luck!

John
Title: Hum on one of the instrument input
Post by: ubxf on April 30, 2007, 12:17:50 AM
After dealing with oscilation and cutting the traces and connecting directly
with shielded wire. The result is that the first instrument input is dead quiet
the second one does'nt oscilate any more but has a hum, btw that same channel is quiet thru the microphone input. Any help would be greatly appreciated.
francois
Title: The official G9 help thread
Post by: gyraf on April 30, 2007, 06:21:39 AM
Try with a electrostatic shield (a grounded metal plate or foil of some kind) between the transformers and the pcb/frontpanel-pcb..

Jakob E.
Title: The official G9 help thread
Post by: AudioJunkie on May 05, 2007, 02:14:02 AM
Before I try and power up my G9 on Saturday, I had a couple questions about wiring the power transformers.  Just want to be sure before I do anything to blow up this expensive project.

1:  I'm using Amveco's.  But the diagram only tells which Primary wire is 0 and which is 115V.  

0 - Yellow   ====== Green
                      |
110 - Black ====== Red

0 - Red       ====== Brown
                       |
110 - Violet ====== Blue

So is Brown and Green on the secondaries the Ov and Red/Blue the 15V?


2:  Assuming I have that part right.  Here's how I have them wired now.
1st transformer:

IEC + to Black/Violet
IEC - to Red/Yellow

Red and Green will go to 15V/1Amp next to the 280 jack.
Blue and Brown will go to 15V on the right of the board and Trans. 2

Then coming off of the Blue and Brown from Trans 1, Trans. 2 will be Green/Brown to the Ov Brown and Red/Blue to the 15V Blue?

Then Black/Red combined and Yellow will be Ov and Violet will be 220V or whatever?

3: And finally when hooking to the board.  Which of each pairs is the Ov and which is other?


Hope this makes sense.
Daniel
Title: The official G9 help thread
Post by: madreza on May 05, 2007, 12:37:47 PM
Hi

My G9 still doesn't work
after spending some time fixing it , I'm here to ask for HELP.

Tubes don't light up. At first I thought it was the HT
checked the HT and I get 300 V  :shock:
after a while I noticed that the 12V LED doesn't light up either
then I came to check the 12V, and even changed the regulator
didn't work
I have 230V, 17V and 300V HT
I don't have anything between the pin 2 ( Ground )of the regulator and pin 1 or 3

any ideas ?
THX
Title: The official G9 help thread
Post by: gyraf on May 05, 2007, 01:22:16 PM
Check that you get a correct DC voltage to the input of the 78S12 heater-regulator - you should at least have some 14-15V DC here. If you don't, check why - look at the schematic and follow the layout. some AC>rectifier>electrolytics>regulator. not complicated at all.

If you have DC at the input, but not at the output, of the 78S12, look for stuff shorting the heater supplies somewhere on the PCB.

As it has been mentioned several times in this thread before, the HT will be high until the tubes have heated - which they won't if the 12V is missing..

Take care - when heaters are down, there's nothing to discharge the HT voltage!!

Jakob E.
Title: The official G9 help thread
Post by: madreza on May 05, 2007, 01:51:43 PM
Great and Fast as Usual  :razz:

Thanks Jakob


 :sam:  :sam:  :sam:
Title: The official G9 help thread
Post by: madreza on May 06, 2007, 08:04:06 AM
Hi  , me again !  :grin:

Solved my problem ! It was a bad soldered point !

Now, I have 226V and 211 V on the HT

I used 2 2*15V Txformer. I saw on your schematic that I should use 1 2*15 and 1 2*12 V !!!!
Can this help rising the HT ? ( I guess so, you'd get more than 230  AC )

what about rising the values of R34 and R35+36 ?
( Ok, I guess I have the answer to my question : it won't help because TL783 doesn't have enough voltage to regulate !? )
Title: The official G9 help thread
Post by: gyraf on May 06, 2007, 10:44:23 AM
Quote
Can this help rising the HT ?


yes, that is the idea.
Title: The official G9 help thread
Post by: Godders on May 07, 2007, 12:56:39 PM
Quote from: "madreza"
Hi  , me again !  :grin:

Solved my problem ! It was a bad soldered point !

Now, I have 226V and 211 V on the HT

I used 2 2*15V Txformer. I saw on your schematic that I should use 1 2*15 and 1 2*12 V !!!!
Can this help rising the HT ? ( I guess so, you'd get more than 230  AC )

what about rising the values of R34 and R35+36 ?
( Ok, I guess I have the answer to my question : it won't help because TL783 doesn't have enough voltage to regulate !? )
Some good stuff here on getting the HT right:

http://www.groupdiy.com/index.php?topic=11347

Cheers

Nick
Title: c3 and c103 unsure bout value in the g9,
Post by: nashkato on May 07, 2007, 04:17:22 PM
sorry :oops: i posted this question in the lab too,until i saw this official thread for the g9,
i´m gonna delete it there.
on the pcb is a value of 220n given for C3 and C103.
in the parts list with 470n
whats the right one.?
thanx in advance.
Title: The official G9 help thread
Post by: Godders on May 07, 2007, 04:20:52 PM
There's a thread in the G9 meta. I believe 470n is the correct value although either will work.

Cheers

Nick
Title: The official G9 help thread
Post by: ubxf on May 10, 2007, 09:56:13 AM
Quote
Try with a electrostatic shield (a grounded metal plate or foil of some kind) between the transformers and the pcb/frontpanel-pcb..

Thanks Jakob everything works as it should. thank you for sharing and supporting this design
francois
Title: The official G9 help thread
Post by: gyraf on May 10, 2007, 09:59:40 AM
:thumb:
Title: g9 nearly ready
Post by: nashkato on May 15, 2007, 06:45:43 AM
hello,
i´ve just finished the work on a g9.
how to get some pictures in here??
my questions before i get the missin output potis and turn the lights on.:
---???----i used 230volt trafos ,couldn´t get other,how will this affect the     currents on anode?(245V)
----????----- the heatercurrent can´t be adjusted.wouldn´t it be more lifelasting to the tubes to set it to 12,6V?[img]
Title: The official G9 help thread
Post by: gyraf on May 15, 2007, 12:41:04 PM
..the 12V for the heater is well within the specified +/-10% range for heater voltage, and will not influence tube life for the worse...

Jakob E.
Title: The official G9 help thread
Post by: veermaster on May 17, 2007, 02:36:00 PM
Dear members,
I just finished a G9 but I´m having serious trouble with the output trannies. You might wanna follow this link here since I posted this problem also in the Lab, but I don´t have a solution yet:

http://www.groupdiy.com/index.php?topic=22602

Thank you in advance, Emre
Title: The official G9 help thread
Post by: laiben on May 19, 2007, 09:13:57 AM
Hi,

I am having problem with the channal 2 of my G9, the output volume of channel 2 is very low. Channel 1 is fine.
On my crappy scope, I can see that on the grid of V2A is signal is very week,
but on the grid of V2B is signal is still strong on both channel. I suspect it is
the bad tube but I swap both tube the problem still exists. I suspect it is the bad tube socket so I move the tube while my mp3 player is plugged in the preamp it still does not help.

I measure the DC voltage of the V2 on both channel and the reading is similar.. so I really have no idea what else I can do, could someone give me an insight?

The DC readings of the V2 is shown in the pic.


(http://i4.photobucket.com/albums/y136/laiben/G9%20preamp/weaksignal-1.gif)

Thanks
laiben
Title: The official G9 help thread
Post by: gyraf on May 19, 2007, 01:23:23 PM
DC points arenot that bad off - Maybe a short at the transformer solderings?
Title: The official G9 help thread
Post by: laiben on May 19, 2007, 07:18:48 PM
Quote from: "gyraf"
DC points arenot that bad off - Maybe a short at the transformer solderings?


It is very hard to desolder the transformer from the PCB to check.. hope not the solder goes into the shield when I put the mu-metal sheild on the OEP... will report the result.
Title: The official G9 help thread
Post by: maxime on May 20, 2007, 10:37:30 AM
you can check for shorts with a ohm meter instead of desoldering...
Title: g9 ready,not working
Post by: nashkato on May 20, 2007, 06:39:27 PM
hi,
got just ready ,and got no signal on the scope.wether mic nor instr.-input
heat is exactly 245V,ff is 11,9V
tubes are new, all connections to the scope checked.
maybe i got something wrong with those lorlins?(haven´t used them till now)
anyone got an idea?
Title: The official G9 help thread
Post by: gyraf on May 21, 2007, 02:38:38 AM
There is no way to guess what your problem might be.

Any of the usual suspects..

Try tracing signal through the unit, following the schematic and looking at the pcb layout. And read the function description at the gyraf page.

Use an continuity/ohmmeter to check if the switches do as you would want them to.

Jakob E.
Title: Re: g9 ready,not working
Post by: laiben on May 21, 2007, 09:49:20 AM
Quote from: "nashkato"
hi,
got just ready ,and got no signal on the scope.wether mic nor instr.-input
heat is exactly 245V,ff is 11,9V
tubes are new, all connections to the scope checked.
maybe i got something wrong with those lorlins?(haven´t used them till now)
anyone got an idea?


just my guess: if a lorlin is bad you will only have problem in one channel..
do u see any signal going into the transformers?
Title: The official G9 help thread
Post by: nashkato on May 22, 2007, 02:49:29 PM
ok, now,
you can´t imagine how stupid one can be, not seeing the wood cause all of the trees.
( i didn´t  solder the 10pin connections ,they fit that good)

now it´s so far that i got a really good sinus on the scope until i turn up the gain to setting 6,7, or 8,i guess.

then it gets weird: this must be some kind of very high frequency and the sinus is gone. on both channels the same.
didn´t hear it right now,thats what i saw on the scope.
Title: The official G9 help thread
Post by: maxime on May 23, 2007, 06:48:11 PM
hello happy G9 users,
it's been a while I'm using the preamp with great pleasure. I just have one little annoying bit with it. mine have some crosstalk from channel 1 to 2 (but not the other way around).
I checked many details upon its wiring, and every step seems to have been executed in the nice manner.
so I followed the crosstalk on channel 2 from a 10khz sine signal on ch.1.
and:
1. bleed source on channel 1 lies after the output pot (as output pot gives no bleed when down)
2. ch. 2 attenuation (gain pos1-4) affects crosstalk, but not gain (gainpos5-11)

I really suspect some bleed from output circuit of channel 1 to the input circuit of channel 2.
so I  grounded temporally some parts of the circuit to locate the bleed source. the source of bleed lies in the output section between the first grid (after r45)
and before the output capacitor (c13). (disconnecting the tube gives no crosstalk, disconnecting one end of c13 gives bleed)

do you think of one factor connecting to my problem? experiences of this type?

capacitor size (some of mine are rated 400V, instead of 250); capacitor type and orientation tube shields? pcb traces?

to get the idea:
-40dB /fullgain on channel 1 at 10kHz gives -17dB on channel 2

thanks
Maxime
Title: The official G9 help thread
Post by: maxime on May 28, 2007, 05:18:52 AM
do you think capacitor geometry/ shape can affect the crosstalk in this circuit?
would other caps (scr or or solen) give me different results?

best
Maxime
Title: The official G9 help thread
Post by: josh on May 28, 2007, 10:40:43 PM
I am nearly finished with this bad boy and I have just a few questions.

-The BOM I used calls for 10mf 500V caps at C25 & C125, the pcb asks for 250V caps.  Can I use the ones I have?  I ordered the 250's and they'll be here in a few days anyway.

-The BOM I have also crosses out C7 & C107, but another one does not.  What's going on with that?  I also have these arriving soon anyway.

-The instrument jacks I bought have 4 pins on the bottom, 2 fore and 2 aft.  The pcb has 3 positions, from to and ground.  Which goes where?

-Underneath the psu section I see a "to light 12V/50mA" with F+ and F-. Is this for the power on/off LED?
Title: The official G9 help thread
Post by: maxime on May 29, 2007, 05:09:30 AM
the 12V is for the LED. make sure you are using a properly  rated lamp or LED with series resistor. 500V ratings for the caps are ok.
the jacks meant to be used are of the mono type but with a "normalizing pin". it should be wired so that when nothing is plugged in, the signal comes from the pcb ("to") and gets back to it ("from") . the tip is connected to "from" on the face pcb.
best
maxime
Title: The official G9 help thread
Post by: gyraf on May 29, 2007, 06:28:14 AM
..and 250V is also fine for the caps - remember to take a look at the description at the gyraf/diy page..
Title: The official G9 help thread
Post by: josh on May 31, 2007, 08:13:04 AM
One more question while I'm waiting for D06 to arrive.

I know where the power grounding comes in, but where is this point?

"Connect 0V/Gnd to chassis at one ..."
Title: The official G9 help thread
Post by: ilikeit on June 01, 2007, 02:35:00 AM
Hello has all I have a probleme with my g9
 when I am in line level and when I return by the xlr everything is well
but when I connect a dynamic or static microphone I tres only little sound
my transformer is ope
the selection of entree works because j manages well to have my 48 volt somebody
 would have he an idee??
Title: The official G9 help thread
Post by: maxime on June 01, 2007, 09:05:16 AM
did you try the instrument input ?
what are the results?

best
maxime
Title: The official G9 help thread
Post by: josh on June 02, 2007, 02:49:48 AM
So I finished wiring up the G9 tonight.  Plugged it in, powered it up, turned it on....  it made a weird clicking noise when I flipped the switch.  I left it to warm up.  Nothing blew up or smelled funny at all, but the tubes didn't warm up either.
So I turned it off for a few minutes, then back on.  The tubes glowed brightly for a few seconds then dimmed.  So I passed some audio though the mic section.  The left channel worked for about 45 seconds before it faded out.
What's odd is that when I turn it off for a minute then back on the tubes glow briefly then fade out.
Any suggestions on where to start looking for mistakes?
Title: The official G9 help thread
Post by: ilikeit on June 02, 2007, 06:59:43 AM
OK first test
for example I bring in first input by l xlr (i have removed input hiZ) with sine of 1Khz has a level of 200mV in level line on the condo C2 I meet myself with a level of 50 mV it is normal???
 In level microphone on the other hand in the same place i have almost 1V and those on 2 channel
is my transfo checks???
Title: The official G9 help thread
Post by: jdr on June 03, 2007, 03:10:56 PM
Quote
What's odd is that when I turn it off for a minute then back on the tubes glow briefly then fade out.


That sounds like maybe the 12V regulator is going into thermal shutdown shortly after being powered on.

First, make sure you are using the correct version of the 7812 regulator. The "S" version (78S12) or it's equivalent: something capable of supplying 1.5A of current is specified for this part. Check the datasheet for the manufacturer of your regulator to make sure it can deliver the needed current.

Second, make sure the regulator is adequately heatsinked. On his G9 DIY page at Gyraf (http://www.gyraf.dk/), Jacob says the regulator will dissipate about 5W of heat, and suggests mounting it (electrically isolated) on a big heatsink, preferably with thermal contact to the chassis.

Hope that helps,
John
 :guinness:
Title: The official G9 help thread
Post by: rascalseven on June 06, 2007, 08:05:57 PM
I just powered up my G9 for the first time, and it sounds great, however I do have a noise issue.  I looked through this entire thread and don't see it, so I'm posting it:

Firstly, I have, indeed, hooked the chassis and power supply ground together in only one spot -- at one input XLR.  I have verified this with my meter.

The problem is buzz in the signal except when the output fader is just above halfway.  There is a spot just above half the throw where it is totally silent.  On the two lowest gain settings there is also another spot almost all the way up the throw of the pot (almost wide open) where it also gets dead silent, but on the 3rd gain position and higher this second, higher, 'quiet spot' disappears.  The midway 'quiet spot' is consistent for all gain settings.

Both channels have this problem.

This noise is independent of the input transformers as it is present in the DI signal as well, which effectively bypasses the input transformers.  

FWIW the output level pots are 50k log, not 47k, though I doubt this has anything to do with the noise.

Help??

 :?:  :?:

BTW, when testing in the 'quiet spots' I must say I am floored by the sound of this thing.  I'm using Cinemag 75101's (wired 1:5) on the inputs and Edcor XS1100's on the outputs.  Fantastic sound!!

Thanks!

JC
Title: The official G9 help thread
Post by: rascalseven on June 07, 2007, 12:21:09 PM
Bump??

:sad:

JC
Title: The official G9 help thread
Post by: Godders on June 07, 2007, 12:56:40 PM
Here's how I grounded my G9, all XLR pin 1's go to star ground point (same place as safety ground). Jakob's design takes care of the rest.

http://img.photobucket.com/albums/v518/godders1/DSC02254.jpg

http://img.photobucket.com/albums/v518/godders1/DSC02257.jpg

http://img.photobucket.com/albums/v518/godders1/DSC02252.jpg

Quiet as you like. :thumb:

Cheers

Nick
Title: The official G9 help thread
Post by: rascalseven on June 07, 2007, 03:44:54 PM
Thank you, Nick!!

:thumb:

I copied your grounding scheme exactly (would you consider leaving those pics up for others?  They're the perfect visual for showing how to ground this thing!).

It's now as quiet as can be.... sounds amazing as well!  I'm going to enjoy putting it to use at the studio.

:green:

Peace to all,

JC
Title: The official G9 help thread
Post by: Godders on June 07, 2007, 04:06:47 PM
Cool, glad it helped, now you can enjoy your G9! :thumb:

Yeah the pics will stay.

Cheers
Title: The official G9 help thread
Post by: MrZpliff on June 08, 2007, 05:54:42 AM
Quote from: "rascalseven"
Thank you, Nick!!

:thumb:

I copied your grounding scheme exactly (would you consider leaving those pics up for others?  They're the perfect visual for showing how to ground this thing!).

It's now as quiet as can be.... sounds amazing as well!  I'm going to enjoy putting it to use at the studio.

:green:

Peace to all,

JC


Does anyone of you guys have any (audible) oscillation ?
 I've done the mod where you cut the tracks to the instrument input, but I still have some (VERY little) oscillation at some gain-settings. Going for perfection here  :razz:  I'll try this grounding scheme. Mine's a little different...
Title: The official G9 help thread
Post by: Godders on June 08, 2007, 07:12:43 AM
Well, I didn't use the DI ins on mine. If you look at the pics a couple of posts back you'll see I jumpered the board with shielded cable. Suffice it to say, no oscillation. :green:

Cheers

Nick
Title: The official G9 help thread
Post by: MrZpliff on June 08, 2007, 08:03:19 AM
Quote from: "Godders"
Well, I didn't use the DI ins on mine. If you look at the pics a couple of posts back you'll see I jumpered the board with shielded cable. Suffice it to say, no oscillation. :green:

Cheers

Nick


Ok ! Thank's ... I use mine as a DI very often and I love the sound  :grin:
so I won't try that one......
Title: g9 240 v transformers
Post by: objectx on June 19, 2007, 01:16:21 AM
Hi there, I'm a newbie here but I've been lurking for a while :grin: , I'm thinking of embarking on a g9 diy venture after doing a few guitar amps. I have some questions re: transformers... being an Australian resident we're on 240v mains power here, will I be able to sub the 220v transformers for 240v versions (specifically the 12v-220v second TF on the schem) or will it be neccessary for me to source a 220v version?

Here's a page with the tfs I'm looking at:

http://www.altronics.com.au/index.asp?area=prod&grp=354
Title: The official G9 help thread
Post by: gyraf on June 19, 2007, 04:40:08 AM
240V-versions should work fine as direct-subs for 220V-versions...

Jakob E.
Title: The official G9 help thread
Post by: objectx on June 19, 2007, 08:02:06 PM
thanks jakob, much appreciated  :grin:
Title: G9 assembled- 120Hz Hum
Post by: analogical on June 20, 2007, 04:23:10 AM
Hya folks!

After a few clean SCA builds with no issues, I thought I would try my hand at a G9, and alas, it has humbled me. :)

Here are some picts of the build. If you see anything out of whack, please, school me!

Freq analyzer gives me a nasty 63Hz hum 120Hz, both channels.

Voltages from torridals seem within tolerances.

Checked for shorts. The board seems to be ok.

The hum was present before, and now after, the unbal mod/trace cut.

The noise exists regardless of gain settings, mic/line switch- any knob turning on the front panel does not attenuate the hum.

Any advice? Presently I'm working on godders grounding scheme.  Thanks in advance for your help!


-Don
(http://img517.imageshack.us/img517/7646/pic0028gu2.jpg) (http://imageshack.us)
(http://img524.imageshack.us/img524/404/pic0031qm8.jpg) (http://imageshack.us)
(http://img353.imageshack.us/img353/475/pic0037jg5.jpg) (http://imageshack.us)
(http://img201.imageshack.us/img201/3272/pic0038sc1.jpg) (http://imageshack.us)
(http://img201.imageshack.us/img201/9004/pic0041kh7.jpg) (http://imageshack.us)
Title: The official G9 help thread
Post by: gyraf on June 20, 2007, 11:25:14 AM
Are you sure you have ground present at output xlr's? Usually we make a link bar across all XLR pin1's...

Jakob E.
Title: The official G9 help thread
Post by: madreza on June 22, 2007, 02:09:04 PM
I was troubleshooting a friend's G9 and noticed that he had mismatched the Xformers :  all input Xformers on 1 channel and Outputs on the other one !
I was wondering if this could damage anything ?

I still have a problem : I have a very low output signal ( maybe 40 db less than my G9 ) on both channels !!!

his HT voltage was very low , i changed a Xformer for a 12V to raise the HT but the pb is still the same !
Title: The official G9 help thread
Post by: madreza on June 24, 2007, 05:30:10 AM
UP
Title: The official G9 help thread
Post by: madreza on June 28, 2007, 04:19:58 PM
Quote
I was troubleshooting a friend's G9 and noticed that he had mismatched the Xformers : all input Xformers on 1 channel and Outputs on the other one !
I was wondering if this could damage anything ?

I still have a problem : I have a very low output signal ( maybe 40 db less than my G9 ) on both channels !!!

his HT voltage was very low , i changed a Xformer for a 12V to raise the HT but the pb is still the same !



UP AGAIN
Noone can help me ???
Title: The official G9 help thread
Post by: gyraf on June 29, 2007, 06:28:21 AM
Quote
I was wondering if this could damage anything ?


No, not likely.

For error tracing, try comparing signal levels and working voltages between working and non-working units.

Jakob E.
Title: The official G9 help thread
Post by: JimiH on July 06, 2007, 12:48:52 PM
My G9 is almost complete. All it needs is some xlr connectors, some tubes and some power transformers. Quick question, can I get away with 20VA torroids? There is a local supplier but they only do 20VA. Will I scrape through? I am assuming that I will have to go 15+15 and 12+12 if it will even work at all...
Title: The official G9 help thread
Post by: Godders on July 06, 2007, 01:01:26 PM
Quote from: "JimiH"
My G9 is almost complete. All it needs is some xlr connectors, some tubes and some power transformers. Quick question, can I get away with 20VA torroids? There is a local supplier but they only do 20VA. Will I scrape through? I am assuming that I will have to go 15+15 and 12+12 if it will even work at all...
I had problems (and so did others) with low HT voltage with 30VA torroids, I got some 50VA and now everything is dandy.

I think different brands behave differently when used in this way but I don't fancy your chances with 20VA.

Cheers

Nick
Title: The official G9 help thread
Post by: kazper on July 06, 2007, 03:16:01 PM
JimiH If your in the states contact Avel sales department

http://www.avellindberg.com/

There transformers are very inexpensive and there price point breaks at 2 transformers.
I got 8 transformers for a little over $110 shipped for my 1176's and some other projects.
Title: The official G9 help thread
Post by: JimiH on July 06, 2007, 10:34:06 PM
Ok sweet! Thanks everybody.
Title: The official G9 help thread
Post by: maxime on July 14, 2007, 03:11:25 PM
hello all

I had spare time to get into my crosstalk problem on channel 2 my g9. it looks like the  C2 (first cap right after the transformer) is likely to pick signal from channel 1. I had 10 dB less crosstalk with the cap soldered under the pcb and laid out parallel to it !
i suspect the channel 1 output tube to act as a source of matter.
do anyone of you think that the tube sockets can have an influence? (mine are ceramic and 3/4 inch high) maybe geometry and layout plays a role in here?


best

maxime
Title: The official G9 help thread
Post by: JimiH on July 15, 2007, 10:59:50 PM
Well my G9 is almost complete. Just need 2 more tubes (well, 4 more, all have is 2 of these damn 40 year old mullards...) and to hook up the outputs and test it fully. I solved my transformer problem (I could only find 20VA units) by using 3 transformers, and it seems to have done the trick rather well, except for phantom. The most I can squeeze out of that is around 27 volts. All my caps seem fine and I'm going nuts trying to find the source of the problem. There is 15V AC before the regulation too. Anyone hazard a guess?
Title: The official G9 help thread
Post by: maxime on July 16, 2007, 07:25:33 AM
did you check diodes and their orientation?
Title: The official G9 help thread
Post by: JimiH on July 16, 2007, 08:05:08 AM
Maxime, you are a genius. I was about to post a reply telling you that I had obviously already done that, but I just ahd another look thanks to you as I thought, ehh, can't hurt, and there you go. D6 is around the wrong way. I haven't changed it yet, but I'll let you know how it goes, as I am sure you are dying to know...
Title: The official G9 help thread
Post by: maxime on July 16, 2007, 08:40:53 AM
glad to hear that!
Title: The official G9 help thread
Post by: JimiH on July 16, 2007, 08:58:09 AM
I meant to say D9 and by the way, it's fixed!!! Thanks a billion!
Title: The official G9 help thread
Post by: JimiH on July 17, 2007, 01:29:51 AM
Well it's all done (I still have only 2 really really old and crusty mullard ecc82's) and after testing it one channel at a time I can say with all honesty and conviction, "holy crap."

I am really inpressed at the smoothness of this preamp. All other tube preamps I have had experience with have all been a bit harsher than expected. This one is as creamy as. Thank to everyone who has helped. I am glad I underwent this endeavour. Even though I coudln't really afford it, it was worth every cent so far. On top of all this I have no issues (except for that one diode - see above) and I didn't even have the high gain oscillation on channel 2... well not yet anyway. This new toy is oh so much fun!
Title: The official G9 help thread
Post by: gyraf on July 17, 2007, 04:36:12 AM
:razz:  :thumb:
Title: The official G9 help thread
Post by: CurtZHP on August 03, 2007, 12:52:26 PM
Not sure if this was covered before....

I'd like to use an LED instead of a lamp for the "ON" light.  I'm assuming I'll need a current limiting resistor in series with the anode of the LED.  Can you recommend a correct value for that resistor?

Thanks!
Title: The official G9 help thread
Post by: gyraf on August 04, 2007, 09:08:53 AM
For a LED fed from 12V, something like 1K or 2K2 / 1W
Title: The official G9 help thread
Post by: CurtZHP on August 07, 2007, 05:17:52 PM
Thanks.  Now another question....

I think I screwed up the installation of the phase switch.  I have it installed with the "Lorlin" label on the right side (facing the switch), which is how the Gain and Pad switches are installed.  Its two positions are 12 o'clock and one click to the right.

Now I'm taking a closer look at the front panel graphics on your website and what I saw made me panic a little.  On the site, the phase switch is shown with the "in-phase" position at 12 o'clock and the "invert" position one click to the LEFT.  Ooops!!!

When I check the schematic, my understanding is that the switch is rotated clockwise to invert the phase of the output.

Help!!
Title: The official G9 help thread
Post by: CurtZHP on August 09, 2007, 11:16:14 AM
This might be the answer to my previous question.....


Does the output transformer on the G9 invert the phase of the signal?

If that's the case, that would mean that a clockwise rotation of the phase switch would put the output IN PHASE, rather than OUT OF PHASE.

How am I doing so far??   :grin:
Title: The official G9 help thread
Post by: gyraf on August 10, 2007, 01:54:59 AM
..it's easy to reverse the two wires going to the out xlr, if polarity dosen't fit at first..
Title: The official G9 help thread
Post by: CurtZHP on August 10, 2007, 11:25:20 AM
I also realized that it's just as easy (probably easier) to simply reorient the knob on the switch shaft.

 :oops:


How does one say "Duh!" in Danish?
Title: The official G9 help thread
Post by: Godders on August 10, 2007, 12:57:02 PM
Quote from: "CurtZHP"
How does one say "Duh!" in Danish?

Düh?

 :green:

Cheers

Nick
Title: The official G9 help thread
Post by: CurtZHP on August 15, 2007, 01:20:50 PM
I've got a few pictures of my G9 construction on my website.  Check them out and tell me what you think!

http://www.zerrohouseproductions.com/

Go to the preamps page.
Title: Startup
Post by: Sandersonic on August 19, 2007, 06:50:39 AM
Hi Everyone,
I've decided to build a G9 and have been slowly working my way through this thread to avoid asking any redundant questions. I've allowed myself the shortcut of ordereing pre-made PCB's from Gustav and will begin buying components soon. One question I wanted to ask is if anyone has modified the design to allow for toggle switches instead of rotary switches for the Input, Phase and Lowcut switches? It looks feasable when I look at the schematic, but when I look at the control board layout it seems a bit more complicated.

Thanks!
Title: The official G9 help thread
Post by: laiben on August 22, 2007, 12:17:41 AM
Hi,

Sorry to report so late. I swapped two OEP output transformer and then the other channel got the same problem, so I concluded that one of the output tranny was dead. I ordered another tranny from Farnell and last night I put the new tranny to the dead channel now it works! The only problem is I got the oscillation when the gain is at MAX. I chopstick it and the oscillation change when I move the cable to the direct jack socket (I already used the "cut-the-trace" approach to avoid the oscillation, but I didn't cut the trace on the pcb. I don't want to damage the pcb just because I can always "fall-back")

Tonight I will try to re-solder the jumper cable to the jack socket to see if it helps.

BTW, what can I do with the dead output transformer? I don't think Farnell will give warranty on the used transformer...


laiben

Quote from: "laiben"
Quote from: "gyraf"
DC points arenot that bad off - Maybe a short at the transformer solderings?


It is very hard to desolder the transformer from the PCB to check.. hope not the solder goes into the shield when I put the mu-metal sheild on the OEP... will report the result.
Title: The official G9 help thread
Post by: jdr on August 22, 2007, 08:01:31 PM
Quote
last night I put the new tranny to the dead channel now it works!

 :thumb:

Quote
the oscillation change when I move the cable to the direct jack socket (I already used the "cut-the-trace" approach to avoid the oscillation, but I didn't cut the trace on the pcb...)


From the pictures that you posted a few pages back, it looks like you aren't using shielded cable to connect the intrument jack to the transformer and cap. Try using shielded cable instead (ground the shield at one end only). If that doesn't work by itself, then cut the traces (http://fast-cars.de/G9/g9_pcbs_mod.jpg). I think that even if you have connected wires to bypass the PCB traces, that the uncut traces will still be able to induce oscillations in the circuit...(?)...

Hope that helps,
John
Title: The official G9 help thread
Post by: laiben on August 22, 2007, 10:25:48 PM
Thanks for the tips John. Actually I already replace the jumper wire with shield cable, the problem still exists. Tonight I will cut the trace!!!


laiben


Quote from: "jdr"
Quote
last night I put the new tranny to the dead channel now it works!

 :thumb:

Quote
the oscillation change when I move the cable to the direct jack socket (I already used the "cut-the-trace" approach to avoid the oscillation, but I didn't cut the trace on the pcb...)


From the pictures that you posted a few pages back, it looks like you aren't using shielded cable to connect the intrument jack to the transformer and cap. Try using shielded cable instead (ground the shield at one end only). If that doesn't work by itself, then cut the traces (http://fast-cars.de/G9/g9_pcbs_mod.jpg). I think that even if you have connected wires to bypass the PCB traces, that the uncut traces will still be able to induce oscillations in the circuit...(?)...

Hope that helps,
John
Title: The official G9 help thread
Post by: laiben on August 23, 2007, 11:27:27 AM
I cut the trace on the pcb, now the oscillation is gone!

However when I test the noise level of the preamp, when both gain and volume is at MAX and no mic is connected. Though my ear hear nothing from it, it gives around -85db (ch.1) and -90db (ch.2) of noise in my Tracktion.
Screen capture is here. The peak frequency is about 40hz. Is that normal?

(http://i4.photobucket.com/albums/y136/laiben/G9%20preamp/G9max2.jpg)
Title: The official G9 help thread
Post by: laiben on August 26, 2007, 10:30:30 PM
I remove the direct jack jumper cable and short it directly on the pcb, the noise still exists. So I can conclude that the noise is not introduced by the jumper cable. Also I notice that when the phantom power is on the noise is a bit louder (on the DAW, my ear still cannot hear the noise).

So, am I done now?
Title: Voltage is too high before Darlington
Post by: Ilya on September 12, 2007, 03:56:40 PM
I'm not sure if this is an issue... I've just built a PSU for G9 (no other components on the board yet), and everything seems to be fine except one detail. I'm seeing a suspiciously high voltage after the tripler and befor the collector of TIP121. It measures in the 80-85V range. After the regulation it's 48 though. Now, my concern is that those lythics are specd for 63V and 85 is much more than that. And I can't get it how 15 (ok, 16.5 'cause the PSU is unloaded) turns into 85 which is almost 6 times more. Is this because I have no load connected? Or have I screwed something?
Title: The official G9 help thread
Post by: originalmusician on September 15, 2007, 01:59:40 PM
Could someone straighten me out on Skylar's G9 wiring diagram? The primaries of the first transformer are connected in parallel (i.e. 115v). Power then flows across the to the secondaries. Now BLK and ORG are 0v and Red and Yel are 15v. Is this correct so far?

If so, The Yel 15v wire connects to the board and then to the Blk/Org secondary of Transformer 2. Keeping in mind that Blk and Org are 0v on transformer 1, wouldn't we want to connect the 15v yellow wire to Red/Yel of transformer 2 instead of Blk/Org?

(http://www.bombproofsoftware.com/electronics/G9Toroidconnections.jpg)
Title: The official G9 help thread
Post by: josh on September 15, 2007, 03:56:12 PM
I can tell you that mine is hooked up exactly like that and is working good.
Title: The official G9 help thread
Post by: originalmusician on September 15, 2007, 04:25:27 PM
Okay, thanks for replying. The more I look at it, the more correct it seems. It makes sense that I would want the 110 on top and bottom of primary of transformer 2 as opposed to the middle. It took me a while to get that. I'll hook it up as shown.  :grin:

edit: And thanks to Skylar for making this diagram. It has been extremely helpful.
Title: The official G9 help thread
Post by: originalmusician on September 16, 2007, 12:03:15 AM
Well, I managed to slam the thing together, but it turns out I don't have the correct length 1amp fuse to fire it and see if it smokes. I'll have to go to radio rip tomorrow and pick some up. The waiting is killing me, but at least I managed to get this far. This pre is a heavy solid piece of hardware and is more impressive looking when built than I was expecting. I can't wait to see how it sounds. :grin:

(http://www.bombproofsoftware.com/electronics/g9.jpg)
Title: The official G9 help thread
Post by: originalmusician on September 16, 2007, 07:59:49 PM
Progress update: I got the fuse and fired the G9 up. The good news is nothing smoked. But I do have a few problems. The right channel oscillates on the last two gain setting when in mic mode. I think I read when this happens to cut the traces and wire the line ins directly?

The left channel works fine up until the 4th or 5th gain click, and then the gain knob has no affect from there until the top of the range. I'm guessing the problem originates from the switch or its card as the tone of the pre is not affected. The switch just stops increasing the gain after the 5th click. I guess the best way to find out is to swap the gain cards and see if the problem reverses channels.

Despite these problems, both channels sound excellent. This pre has a very strong tube flavor on both the mic input and line input. Obviously that's because it's a tube pre, but I guess I'm saying that the sound is very flavorful, classy, and distinctive. This is an excellent project, and I am really grateful to Jakob for providing us DIY guys with the opportunity to build a piece of studio equipment of this caliber. To put it mildly, I love this thing!  :grin:  :guinness:  :sam:  :thumb:  :green:
Title: The official G9 help thread
Post by: laiben on September 16, 2007, 09:25:54 PM
Use "cut-the-trace" method, it works on mine.


Quote from: "originalmusician"
Progress update: I got the fuse and fired the G9 up. The good news is nothing smoked. But I do have a few problems. The right channel oscillates on the last two gain setting when in mic mode. I think I read when this happens to cut the traces and wire the line ins directly?

The left channel works fine up until the 4th or 5th gain click, and then the gain knob has no affect from there until the top of the range. I'm guessing the problem originates from the switch or its card as the tone of the pre is not affected. The switch just stops increasing the gain after the 5th click. I guess the best way to find out is to swap the gain cards and see if the problem reverses channels.

Despite these problems, both channels sound excellent. This pre has a very strong tube flavor on both the mic input and line input. Obviously that's because it's a tube pre, but I guess I'm saying that the sound is very flavorful, classy, and distinctive. This is an excellent project, and I am really grateful to Jakob for providing us DIY guys with the opportunity to build a piece of studio equipment of this caliber. To put it mildly, I love this thing!  :grin:  :guinness:  :sam:  :thumb:  :green:
Title: The official G9 help thread
Post by: originalmusician on September 17, 2007, 11:33:05 PM
Thanks, I used the cut-trace method, and it solved the oscillation problem completely!

Interestingly, switching the Lorlin cards did not change the problem with the gain maxing out at position four of the left channel. Up till position 4, the gain is actually a little louder than the right channel, but after that, it does not increase. Switching front panel cards had no effect. I'm currently at a loss.

Also, when I cut the traces and put things together, I lost ground to the main board. If I run a ground wire from the power Cap ground to chassis ground, things get extremely quiet. But otherwise, the board is floating free of ground. This one seems easier to diagnose than the left channel gain problem, so maybe I stand a chance of figuring it out.

It looks like I have a lot of work to do. I'm not real good when it comes to electronics, so I appreciate any advice or feedback.  :thumb:

edit:

Gain problem plan of action: Next I'll check the wires between the front panel card and the main board. If that doesn't work, It looks like I'll be getting really familiar with the schematic and begging for info  :grin:
Title: The official G9 help thread
Post by: gyraf on September 18, 2007, 03:48:13 AM
Quote
Up till position 4, the gain is actually a little louder than the right channel, but after that, it does not increase.


Look at the schematic of what the gain switch does. It depends on a voltage divider - the feedback resistor (R10 - 47K) and then the variable resistor to ground.

If this divider dosen't work (i.e. wrong/missing/shorted parts), then you only have the first four "attenuating" gain steps to work with.

Jakob E.
Title: The official G9 help thread
Post by: originalmusician on September 20, 2007, 01:28:42 AM
Quote from: "gyraf"
Quote
Up till position 4, the gain is actually a little louder than the right channel, but after that, it does not increase.


Look at the schematic of what the gain switch does. It depends on a voltage divider - the feedback resistor (R10 - 47K) and then the variable resistor to ground.

If this divider dosen't work (i.e. wrong/missing/shorted parts), then you only have the first four "attenuating" gain steps to work with.

Jakob E.


Hi Jakob:

Your post was very helpful. I think I've traced the problem to either a bad C7 or a bad solder joint at C7. I was going to pick up a couple of new caps anyways as the ones I am using are too big to fit the board. I don't think I can get Wima's but Digikey should have something that will work.

Interestingly, my meter reads 75v feeding the C7 caps. I'm using 100v rated caps right now but the schematic lists these at 63v. Do you think my high reading is problem with my circuit?  Should I stick with 100v caps or should I try to bring the voltage down that is feeding the caps?

Thanks! :grin:


Edit: I had an extra Wima 100v cap for C7 laying around, so I soldered it in, and it fixed the gain problem. I think I'll pass on buying new caps that fit the board better and call this good. The pre sounds fantastic!
Title: The official G9 help thread
Post by: Stagefright13 on September 21, 2007, 10:16:12 PM
Hey have a look at my new G9! Tell me what ya think and be honest. I can take it...

(http://www.stagefrightrecords.com/G9.jpg)

But seriously any tips? I think I am gonna cut the traces from the get go. But other than that any advice would be welcome. And thanks in advance everyone. I am VERY excited about this one! Something about tubes and trannys just gets me psyched! And thanks Gyraf for making something like this available for everyone. You Rule!
 :thumb:
Title: The official G9 help thread
Post by: originalmusician on September 22, 2007, 11:59:57 AM
Quote from: "Stagefright13"
But seriously any tips? I think I am gonna cut the traces from the get go. But other than that any advice would be welcome. And thanks in advance everyone. I am VERY excited about this one! Something about tubes and trannys just gets me psyched! And thanks Gyraf for making something like this available for everyone. You Rule!
 :thumb:


Good idea to cut the traces from the start. I thought I had the noise out of my line ins, but when I finally got my studio back together, I discovered I still have a problem even after cutting the traces. So I still have a little work to do there.

The sound of this thing with a guitar plugged in is excellent (OEP trannies). It has a very sweet flavor to it that inspires a playing style that is distinct from any of my guitar amps. It is mellow, sweet, tube flavored, and compressed.

Plugging my 5 string bass in doesn't produce as good of result as my Groove Tubes Brick. The upper strings sound great, but the lower two strings are muddier than the Brick. Perhaps this is a problem with my G9 and doesn't show up on others? I'll have to try my 4 string bass and see if this changes my opinion.

As far as mics go, my g9 is very saturated. The sound is excellent, but it is  characteristically tube distorted even at the lower settings. This could be a problem with my particular build, but right now I'm thinking, if it is broken, don't fix it. IOW, it sounds cooler than [email protected] :cool:

I picked up Purusha's case for this thing, and I'm really glad I did that. Not only does it take a lot of work out of the assembly, when you are done, you have a high quality looking unit.

Take your time when you solder the boards up. Upstream care will save a lot of downstream headaches. Truthfully, there is enough info already posted to put this thing together without too much agony as a lot of people have already done most of the work for us. The only hitch is going to be if you solder something incorrectly. Then you are in an entire new ballpark where instead of paint-by-numbers, you have to understand why things work the way they do. But depending on how familiar you are with electronics, that can actually be a good thing. Just be careful with the high voltages. My caps drain down pretty fast once the thing is shut off, but you definitely want to check them with a meter before tinkering. Be extra careful when the unit is actually turned on and you start tinkering around inside measuring voltages etc. Okay, I have to admit, I only got shocked by this thing one time--so far :guinness:  :sam:

I'm aware that you probably are a lot more familiar with electronics than I am. I'm pretty much just putting the voltage shock stuff and other basic stuff here just as a general warning to others.

One thing I'm unsure of is that my big power caps (c14, c15) don't measure evenly. I have 240v on one and 270v on the other. Does anyone know if this represents a problem?

Good luck, this is a really super cool piece of gear! :grin:
Title: The official G9 help thread
Post by: Stagefright13 on September 22, 2007, 12:48:55 PM
thanks originalmusician! Some inspiring words are always welcome. I am hoping it will compliment my UA pres. But if it replaces them that is cool too! It just looks like such a fantastic project I couldn't resist it. The circuit boards may be here in a matter of hours :) I keep checking mailbox lol!

I have read this entire thread AND all the metas about the G9. I like to be prepared. :) But someone like you obviouslly has more experience with the unit than any amout of reading can afford.

And yes I have a Tat Purusha case on the way. I have no way of silk screening graphics and such...

I did test my power transformers and have 240 volts coming out of the step up one. Is that enough?

And thank you!
Title: The official G9 help thread
Post by: Stagefright13 on September 22, 2007, 01:24:51 PM
I would think both HT caps should read the same. However the schematic only shows one channel. Possibly excessive current used by one side that is dropping the voltage? Short or wrong component on one side only? Just guessing. I would thoroughly check the components on the side with less voltage. 30 volts is a big difference. And try swapping tubes from one side to another.
Title: The official G9 help thread
Post by: jdr on September 22, 2007, 01:49:48 PM
Quote
One thing I'm unsure of is that my big power caps (c14, c15) don't measure evenly. I have 240v on one and 270v on the other. Does anyone know if this represents a problem?


C14 is before the voltage regulator, so it should have a higher voltage across it than C15. C15, after the TL783 regulator is the HT reservoir cap for the circuit, so something like 245VDC is just what you want.

Quote
I did test my power transformers and have 240 volts coming out of the step up one. Is that enough?


The schematic shows 220VAC loaded by the rest of the circuit, so 240VAC unloaded is in the right ballpark.

Enjoy the build!

John
Title: The official G9 help thread
Post by: Stagefright13 on September 22, 2007, 02:43:51 PM
oops! your right C-14 IS on the schematic! My bad! And thanks I will be assembling it hopefully Monday if the pc boards come. :)
Title: The official G9 help thread
Post by: originalmusician on September 22, 2007, 05:57:53 PM
Thanks you guys! I have finally got the grounding scheme correct on this thing, and it runs quiet. I can put it in the rack and actually start using it! Sometimes with these DIY projects, I start to feel like I'm never going to get a piece of gear quite finished, but this baby is done.

Now my mic pre arsenal consists of GT brick, vintage Neve 1272, G9, and Green Pre. I have the stuff around to make a 1290 and a Great River, but seriously, I have to lay off this pre building...and start making some microphones. Ever since I discovered this forum, my girlfriend thinks I'm crazy. Just how many of these strange looking gadgets does a guy really need? But she says as long as it makes me happy, that's the important part. In return, I keep my mouth shut every time she buys a new pair of shoes, which is quite often IMO. LOL :grin:
Title: The official G9 help thread
Post by: originalmusician on September 23, 2007, 11:59:23 AM
Quote from: "Stagefright13"
thanks originalmusician! Some inspiring words are always welcome. I am hoping it will compliment my UA pres. But if it replaces them that is cool too!


I think the G9 will be a nice compliment to the UA pres and will add variety to your arsenal.

You know, the first project I built here was the Green pre using PTownKid's kits (but I replaced the caps with Wima). As inexpensive and straightforward as that project was, I continue to be impressed with the pres. They have such a nice big clear sound to them. In order to take these away from me, first you would have to kill me.

I feel the same way about the G9 as it relates to its unique characteristics. When I say the G9 is distorted and saturated, I should point out that this is actually rather subtle. I recall one builder saying that the G9 is clean and without saturation and distortion. From my experience, the pre has obvious high-quality tube amp characteristics. I think using the transformers you used you can expect a fairly clean sound with classic tube amp characteristics embedded into it. You might not prefer it on all sources, but when you do prefer it, you will get a real feeling of accomplishment from it. :grin:
Title: The official G9 help thread
Post by: Stagefright13 on October 02, 2007, 09:04:13 PM
Well looky here is my New G-9! :

(http://www.stagefrightrecords.com/g91.jpg)
(http://www.stagefrightrecords.com/g92.jpg)
Coming along great. May have it done tomorrow if my missing Wima's come. I ran out of parts and brain cells so taking a break lol. Been working on it all day. Let me know if ya see something goofy in there.

But I would like to say this is my most personally rewarding project yet. I spent weeks reading the threads on here while I was waiting on parts etc.
Thanks so much Gyraf!!!! Having great fun.

 :green:

Originalmusician: Tell her as many boxes as these 2 five Foot ten inch racks can hold. And as long as the floor can support them. Well that's what I tell my girlfriend anyway! ;)
Title: The official G9 help thread
Post by: originalmusician on October 02, 2007, 09:40:48 PM
You are moving fast! Where did you get those cool looking heatsinks?  :cool:

And where are you getting the last of your Wima's from and what values are they? I had trouble finding Wimas that fit.
Title: The official G9 help thread
Post by: Stagefright13 on October 02, 2007, 09:51:19 PM
Hey when your computer power supply blows up don't forget to rape it for parts. :)

If something blows up here I even keep the wire sometimes lol. I like to recycle stuff. If it breaks make sure ya open it up and see what will fit in the scrap bin. You may be surprised. As I was. I have a "Vintage" collection of heatsinks now.

Getting the Wima's from Mouser. They frequently upgrade my orders now to 2nd day air for free so I stickin' with them. Just type in Wima in their search. If ya do that in Digikey NOTHING comes up. Hopefully all will be well tomorrow I am close and anxious...

For some reason I never got the .22uf's and the 2 10 uf's. The BOM I used was off by quite alot but not too far. I had some spare parts to get this far.

 :green:  :thumb:
Title: The official G9 help thread
Post by: Stagefright13 on October 04, 2007, 02:40:46 AM
WOW It works perfect! I think my heart rate went up a bit when I powered it on... :roll: But it passed the smoke test and the voltages looked good so I plugged a mic in and OMG sounds great!! I haven't tested it in the studio yet. BUT at first sample I believe it may crush my Universal audio 610's. I'll do a shootout tomorrow.
Pics are here:

(http://www.stagefrightrecords.com/g95.jpg)
(http://www.stagefrightrecords.com/g96.jpg)
(http://www.stagefrightrecords.com/g97.jpg)
Thanks again for everyone's help. It is as always greatly appreciated!
Title: The official G9 help thread
Post by: MATTI on October 09, 2007, 12:06:16 PM
Considering making this but for more gain I
would put 1:10 input transformers instead of OEP´s, possible?

Matti
Title: The official G9 help thread
Post by: gyraf on October 09, 2007, 12:51:23 PM
Yes, possible.

But you could run into too-much-gain, i.e. overloading of the input stage with loud mics.

It's all a balance in these simple designs.

Jakob E.
Title: The official G9 help thread
Post by: MATTI on October 09, 2007, 01:51:20 PM
I´m quite amatourish but if I skipped the "line in" and
used different resistor values for use it as a mic pad, say
-15db or make an separate switchable t-pad input attenautor pefore the pcb. ( now that I looked at the schem. )
Just speculating at this stage...

Thanks

Matti
Title: The official G9 help thread
Post by: Stagefright13 on October 09, 2007, 08:02:01 PM
It has plenty of gain as is. With an SM7 shure mic and a fairly powerful singer I had the knobs like 70 input and 60 output.
Title: The official G9 help thread
Post by: MATTI on October 09, 2007, 09:54:55 PM
Ribbons, VO work?

Matti
Title: The official G9 help thread
Post by: originalmusician on October 09, 2007, 11:21:38 PM
The OEP transformers are inexpensive and result in 60+db of gain. By contrast the Groove Tubes Brick  only has 50db of gain and is still considered usable.

A G9 with OEP's might need more gain when using certain classic ribbon mics (I've heard that some require 70db of gain, but I do not own any such beasts). My experience is that the G9 has plenty of gain when using my voice as a source for my cheap Chinese Apex 210 ribbon mics. The Groove Tubes Brick is a gain wimp in comparison, thus I only use it on certain sources.
Title: The official G9 help thread
Post by: Stagefright13 on October 10, 2007, 02:22:36 AM
If using a modern DAW as your input it has Mucho gain. It will bury your VU in Protools. (If that is what you are using) AND your external converters. I find in my motu and Logic the same thing is true. I really can't see why anyone would ever want 70db gain! You would have to attenuate that to get a good sound.

It sounds great as is and the commercial version I am sure is STELLAR!

And I do 78% VO and will be using it for that on Thursday...

But I don't use ribbons and if you need massive gain for quiet sources and insist on a ribbon it may not be for you. And why in God's name would you use a ribbon for VO??? Weak output and terribly flat. Not the kinda thing a good announcer would want when he says "Come one Come All, Smoking Hibachi Burnouts! It's Atco Raceway!!!"

And if you ever heard that don't tell anyone it was me. :oops:
Title: The official G9 help thread
Post by: MATTI on October 10, 2007, 03:22:06 AM
Easy, easy my friends!
I just cannot see any harm from some extra gain...
As a former film sound recordist I´m used to have
70-80 db of gain -if needed.
My main mic for the moment Is a Chinese tube mic
heavyly modified and with a sweet Dale "M7" capsule,
no extra gain needed for that.

Regards
Matti
Title: The official G9 help thread
Post by: Stagefright13 on October 10, 2007, 04:02:29 AM
Sorry I got off track. :) You will find it useful for VO and other things. But if your time is Valuable you would be better of buying a real one from Gyraf. Honestly. It is expensive for parts and the time involved is quite high. Buying a unit from Gyraf may be more cost effective. And it will be the Premium one!

Sure gain is ok until you have ridiculous amounts like you are suggesting and then you need more cables and an atty to get the mic amp in the nice balance of working some.

You recording to tape or DAW I have at least 1 of each?

Good God 80 db of gain? What is that useful for lol. Just kidding ya maybe someone needs a HUGE noise floor. :)

And you may very well know what that gain is needed for. I am just goofing with ya.

And I kinda pissed one of my monitors went south. Hard to mix without the 2 screens... Maybe I was taking it out on you if so I am very sorry!
Title: The official G9 help thread
Post by: MATTI on October 10, 2007, 04:46:51 AM
I was thinking of some 5 extra db´s with a different input transformer,
nothing insane (this time).
The other alternative could be New York Dave´s Mila or...

Cheers ;-)
Matti

P.S. I could have your Eisen rack as a compliment ,-)
Title: The official G9 help thread
Post by: Stagefright13 on October 10, 2007, 05:22:37 AM
I would think with my limited knowledge that you would need a higher ratio output transformer. Otherwise you would saturate the input tubes. For ass kicking gain I would change the output trannie. And keep the circuit as is.

But you may be surprised how good it is stock and leave it alone. However the 2 toroids create a HUGE field. So you may need to MU them from internal and external gear.
Title: The official G9 help thread
Post by: Stagefright13 on October 10, 2007, 08:14:38 PM
OUCH! My G9 just fried! One of the rectifier diodes D19 just caught on fire. Melted the circuit board and everything. I replaced all 4 of them and it works perfect again. And the rectifiers don't even get warm now. Is it possible it just went south after 72 hours use?? Maybe the diode was bad? It's a 1 amp 4007. Do I need a higher amp one?
Title: The official G9 help thread
Post by: gyraf on October 11, 2007, 06:17:52 AM
1N4007 is what's needed - either it was bad from start, or was overloaded by a casual short...

Jakob E.
Title: The official G9 help thread
Post by: crazytooguy on November 24, 2007, 05:55:41 PM
Hello! I just completed my G9 and while I thought I had adequate heatsinking for the 12V regulator, I apparently did not and it gave up the ghost after half an hour. I'm going to mount the new 12V regulator to the chassis, but would it help to substitute a 78T12 for the 78S12, since the 78T12 has a 3A capacity? Seems like an easy extra measure of insurance. Thanks!
Title: The official G9 help thread
Post by: gyraf on November 25, 2007, 04:37:13 AM
The heaters in the G9 only draw 600mA of total current, so a 78s12 is plenty. They vrey rarely fail, because they have safe-area temperature shutdown - power off and wait, and they'll come around again. Easiest way too heatsink is to mount (isolated!!) on chassis baseplate.

Jakob E.
Title: The official G9 help thread
Post by: steppenwolf on November 25, 2007, 08:16:16 AM
I think you'll have 100mA extra on the heaters when using 5814 Tubes as they draw 175mA @ 12,6V per tube (700mA total), just a little higher than the ECC82...
relays and light(s) aren't mentioned, though...
With appropriate heat sinking should be no problem...

Greets,
Stefan
Title: The official G9 help thread
Post by: crazytooguy on November 25, 2007, 12:57:22 PM
My G9 is a bit of a modded one - I layed out my own PCBs, and added a relay on each channel for the Instrument input, high brightness LEDs for phantom and power indicators, as well as a VU meter circuit and small cooling fan. You wouldn't think those would add that much current draw, but I did manage to kill the 78S12 - it wouldn't come back on. I will heatsink its replacement to the chassis, though. Even though the heatsink I had for the regulator was fairly large, it got quite hot. I think it just wasn't enough.
Title: The official G9 help thread
Post by: steppenwolf on November 26, 2007, 08:32:55 AM
Hi!

I was thinking to use a VU meter, too.
My problem with this:
Where should I put it. Directly on the output?
That would be possible, but as the circuit uses an output pot, it can only measure the output but I could have distortion before the pot...
I would like to put an additional switch to be able to look at the level
1) Before the output pot and
2) directly on the output and calibrate those two settings with a resistor attached to the aforementioned switch.  

Is this possible?
What is the impedance around the output pot? I don't want to drop the signal when loading it with the VU meter circuit.
That shouldn't be a problem with the 600Ohm output, right?

Thanks!
Stefan
Title: The official G9 help thread
Post by: Stagefright13 on November 27, 2007, 02:29:19 AM
I just use my ears for sound. The VU may be nice to look at but your DAW or Tape deck will give you the level. Trust me VU is NOT something you need on this project. It is perfect the way it is. It's already as full featured as my commercial UA 610's less the ground lift. And of course that is an easy add.

Preamps as far as I am concerned don't need VU cause before they start clipping your next chain (Recording media) will be buried LONG before. :)

Especially A true tube pre such as this. I never saw a led meter or VU on a Marshall before. Use your ears and sidestep the extra stage. Just my opinion.
Title: The official G9 help thread
Post by: steppenwolf on November 27, 2007, 03:35:08 AM
Right, but the output pot is there to attenuate the signal in case you drive the previous stage hard so you won't overload the ad converter for example. But I would like to monitor, how much I'm overloading that stage...
Title: The official G9 help thread
Post by: Stagefright13 on November 27, 2007, 03:56:44 AM
You can hear the overload trust me. :) Gentle overload has a nice smoothness to it. Great with an LDC. Smooths the brittleness of a cheap mic. Makes a good mic sound fantastic. Or just look at the knobs! Low input settings are very clean with moderate output settings. Just like a tube guitar amp. think of it that way. It is a tube amp for a mic. Use your ears and trust me you will enjoy it. But is not an easy project! At least for me I am not like the Super Pro's.

 :green:

You speak great English from Germany!! My Family is from there. You are right the output is  there to attenuate the signal to your DAW. It is there to allow the the input pot to be turned to the level of saturation or no saturation you desire. The output pot is there to give the desired output to your compressor or converters. And does a great job! Gyraf did his homework. :)

Your DAW or tape deck will see the levels of the output so no meter will be necessary. And I believe you need a meter buffer such as the one on the Purple 1176 so you won't add distortion. But I am an amateur experimenter so don't go by me.
Title: The official G9 help thread
Post by: steppenwolf on November 27, 2007, 10:02:37 AM
Quote
You can hear the overload trust me. :) Gentle overload has a nice smoothness to it. Great with an LDC. Smooths the brittleness of a cheap mic. Makes a good mic sound fantastic. Or just look at the knobs! Low input settings are very clean with moderate output settings. Just like a tube guitar amp. think of it that way. It is a tube amp for a mic. Use your ears and trust me you will enjoy it. But is not an easy project! At least for me I am not like the Super Pro's.



 :grin: You mean, crank the gain and listen...

Of course you are right, but those VUs look so nice... :wink:

Quote
You speak great English from Germany!! My Family is from there. You are right the output is there to attenuate the signal to your DAW. It is there to allow the the input pot to be turned to the level of saturation or no saturation you desire. The output pot is there to give the desired output to your compressor or converters. And does a great job! Gyraf did his homework. :)


Thanks, I can't even think of how many hours I spent in english speaking forums. I think I have had a good education especially languages. Is it weird that I'm studying electronic engineering... :wink:
Where do your parents come from?

Have a nice day!
Stefan
Title: The official G9 help thread
Post by: crazytooguy on November 27, 2007, 02:39:41 PM
Yeah, the VU meters I added are basically eye candy. I did, though, calibrate them so that 0VU = +4 dBu so I have some idea of how much signal I'm hitting my A-D converter with. The circuit I installed has a selector switch to choose between VU indication and Peak Program Meter indication, which is more useful. Still, you don't really need it. I have to admit to liking dancing needles. :wink:

I take the signal for the meter circuitry off off the SRPP output stage, at the hot lead connected to the primary of the output transformer. It has a 47k resistor on it to prevent loading the output stage.  The meter drive circuitry has an FET opamp buffer at the input, so there's no distortion of the signal it's monitoring. Stagefright's got it right, though: Set the gain by ear.  That's what's great about the design; you can dial in controlled amounts of fat tubey goodness by gently overloading the stages. Or get nice shimmery clarity by not overloading them. Or go for that crunchy Lenny Kravitz "American Woman" vocal sound by cranking it. Best to set this by ear, though. Meter readings might be useful for a few times, but you'll stop paying attention to them after a few trys. Meters on a Marshall would be useless, but it'd look cool!
Title: The official G9 help thread
Post by: Stagefright13 on November 27, 2007, 08:01:39 PM
My family is from Erlangen. Hope I spelled it right :)

The faceplate on my G9 is pretty busy I wouldn't even know where I could put a meter if I even wanted one.
Title: The official G9 help thread
Post by: matta on December 05, 2007, 08:03:49 AM
Ok, spent the last 2 hours reading all 20 pages of this thread... great to be able to afford some time for DIY again!

I'm in the process of building my G9 (abandoned the first one because of insufficient funds which became Godder's) and I have a couple questions.

For the 2 offboard filter caps C15-15 (100-220UF/350VDC min) I noticed that lot of guys are using these SERIOUS JJ Tesla ones, no doubt springing from Sklyar's G9 parts list... but it seems overkill...

Could one not just use a 'snap in' type, I'm looking at the Rubycon CE series, as shown below (ironically in the same value, series and voltage I'd be looking at) and try and find a mounting clip or mount them on perfboard? Anyone see a problem with that?

(http://www.73.com/a/me681.gif)

Th other thing is that with the power transformers, I have mine wound and was wondering if it is feasible to not just wind a single transformer with multiple taps rather than using 2 transformers, or is this a big no-no?

Thanks in advance!

Matt
Title: The official G9 help thread
Post by: gyraf on December 05, 2007, 08:40:20 AM
Quote
Could one not just use a 'snap in' type, I'm looking at the Rubycon CE series, as shown below (ironically in the same value, series and voltage I'd be looking at) and try and find a mounting clip or mount them on perfboard? Anyone see a problem with that?


No problem

Quote
Th other thing is that with the power transformers, I have mine wound and was wondering if it is feasible to not just wind a single transformer with multiple taps rather than using 2 transformers, or is this a big no-no?


No problem
Title: The official G9 help thread
Post by: matta on December 05, 2007, 05:26:41 PM
Thanks Jakob,

A man of few words, LOL!

On the transformer am I right in thinking the specs would be as follows:

Primary 1 = 230VAC
Primary 2 = 230VAC
Secondary 1 = 15+15VAC
Secondary 2 = 15+15VAC

Each Primary/Secondary pair being a MIN of 30VA, from the sounds of it it is better to go with 50VA.

Cheers

Matt
Title: The official G9 help thread
Post by: Stagefright13 on December 09, 2007, 03:12:33 PM
One transformer is 230 to 15. The other is a step up to 220 volts. Here's a pic:

http://www.groupdiy.com/index.php?topic=16168

Obviously the pic is wired for 110 mains. But you get the idea. Only 1 transformer is connected to the mains.
Title: The official G9 help thread
Post by: Stagefright13 on December 10, 2007, 10:17:35 AM
Oh and just for the record I found out why my rectifier diode fried. The power switch/iec/fuseholder was arcing. It must of had a defective switch. Sometimes when I turned it on the power light would flicker and I could hear a nasty high voltage sound. I hear arcing can increase voltage. New switch and all is fine.

I did notice after using this alot that the output pot on channel #2 will hum somewhat at over 80% volume. Didn't notice at first. But I have a bunch of mu metal and will try that around the transformers after my ebay tin snips arrive. :)

Probably going with higher rated transformers would be a good idea. Less load on them would probably tame the noise some. My 1176 has about 5 times the transformer needed lol. But Is quiet as a mouse.

But this is an exceptionally great sounding preamp. WELL worth the time and cost to build it. Thanks again Gyraf! It's without a doubt my favorite project I have built so far.

Oh and one more thing. Anyone that put a VU meter on their G9 could you show a pic? I can't even imagine where it would fit. I am obviously a big G9 fan and would like to see others creations!
Title: The official G9 help thread
Post by: Godders on December 10, 2007, 11:05:28 AM
I just built a second G9 and have a small concern. I used a different brand for the power transformers and they’re rated at 80VA (my original had 30VA and then 50VA because of low HT voltage). They are also stacked one on top of the other (they were mounted side by side in my first build).

When I power up, the transformers make a brief humming noise for about 2-3 seconds. After that all is well and the pre works fine.

I’m not overly concerned about it as I’ve left the unit powered up for around 24 hours without any problems but then I’ve built a few DIY units using torroidal transformers, including another G9 like I said and have never witnessed this before. So I’d like some reassurance that this isn’t abnormal and isn’t indicative of anything untoward or dangerous?  :?

Cheers

Nick
Title: The official G9 help thread
Post by: Stagefright13 on December 10, 2007, 11:51:59 AM
The transformers hum or does the audio hum?

BTW here is the G9 in action:

http://www.stagefrightrecords.com/Mike.mp3

It was performed by Mike Masse. http://mikemasse.com/

Samples are always good. Drip LA2 2.0 also in there...
Title: The official G9 help thread
Post by: Godders on December 10, 2007, 12:03:58 PM
Yeah, it's the transformers themselves that buzz, momentarily.

Nice sounding sample!  :thumb:

Cheers

Nick
Title: The official G9 help thread
Post by: Stagefright13 on December 10, 2007, 12:05:19 PM
I wouldn't worry about it then personally. I had a bad power switch. And thanks the G9 is very silky :)
Title: The official G9 help thread
Post by: Godders on December 10, 2007, 12:05:55 PM
Cool, thanks.

Cheers

Nick
Title: The official G9 help thread
Post by: matta on December 10, 2007, 12:13:26 PM
Nick,

Awesome to see you are on G9 #2! I'm finally getting together fund to build my own after I sold you the last one, which Cannikin sold to me... go figure! Quite excited about it, hope to be done in Feb (waiting on parts and what not).

Stagefright, RE the transfomers I'm considering having a SINGLE torrid wound with multiple taps, instead of 2 seperate transformers that most are using, it will look neater.

Cheers

Matt
Title: The official G9 help thread
Post by: Stagefright13 on December 10, 2007, 12:18:36 PM
Yeah a single transformer would be so much neater! Just make sure ya hook it up right. ;) I see you get custom wound ones. Nice job! I may be on G9 #2 myself. Altho I need more preamps like I need a hole in the head. I have 2 NYD Mila's in the build process right now. One as a Christmas present for my son. Trying to hurry on it tho cause he frequently comes over early to exchange gifts.

What I really need is 4 more compressors...
Title: The official G9 help thread
Post by: Godders on December 10, 2007, 01:17:51 PM
I reckon you'll find it was worth the wait Matt.  :thumb:

The G9 is my fave mic pre, every home should have one! :green:

Cheers

Nick
Title: The official G9 help thread
Post by: Stagefright13 on December 10, 2007, 01:28:38 PM
No Child should be born without one!!  Matt will be in for a pleasant surprise.



quote="Godders"]I reckon you'll find it was worth the wait Matt.  :thumb:

The G9 is my fave mic pre, every home should have one! :green:

Cheers
Title: G9 humming
Post by: rockinrudeingo on December 24, 2007, 03:50:20 PM
Hi there !

i've just finished my G9! It was working right on from first power on, besides some oscillation (that now is solved) and the sound i just amazing.
Only one problem i can't solve at all is a 100 Hz Hum, not very loud but noticable, i've read through the whole thread, used the SEARCH-function like crazy, but never found any solution to this problem... this hum i'm speaking of is stable, with all pots GAIN and OUTPUT down it is there and doesn't change. I've tried allready
changing the TL 783,
changing the 78S12,
changing filtercaps to 220/400V,
moving around the Mains-TX (even out of the box didn't make any difference),
lifting ground. I've read that Wolferl and radiance had the same problem, but i never read any solution...
I've measured 294 V on Cap#14 and 246,4 V on Cap#15
or ist this just normal? thanks for you answers

Ingo
Title: The official G9 help thread
Post by: gyraf on December 25, 2007, 02:53:26 AM
Have you used screening cans for the transformers (in case of OEP)?

Try rotating your power transformer to find the spot with least hum induced into audio transformers, and lock it there..

Jakob E.
Title: The official G9 help thread
Post by: rockinrudeingo on December 25, 2007, 06:26:09 AM
Hi Jakob,

thanks for your quick reply,
yes i used screening cans on all the OEPs and i rotated the transformers in every way i could think of, but the 100 Hz Hum doesn't change in any way.(http://foto.arcor-online.net/palb/alben/54/84754/400_3261366539656532.jpg)(http://foto.arcor-online.net/palb/alben/54/84754/400_6530626239643938.jpg)(http://foto.arcor-online.net/palb/alben/54/84754/400_6162363864313966.jpg)

By the way maybe you can see that theres something wrong?

best wishes Ingo
Title: G9 hum issues
Post by: analogical on December 25, 2007, 06:29:11 PM
Happy Holidays,

I'd like to bump rockinrudeingo's comment. I myself am having the same hum issues. Might a mu-metal shield around the trannys help, as found in Jacob's original version?
Title: The official G9 help thread
Post by: Godders on December 26, 2007, 07:00:40 PM
What about grounding? Are all your XLR pin 1s wired to star ground?

I posted some pics a few pages back of how I grounded my (quiet) G9.

Cheers

Nick
Title: G9 hum issues
Post by: rockinrudeingo on December 27, 2007, 04:38:02 AM
Hi Godders,
i don't think it's a grounding issue, cos it's there even if i lift ground completely, anyway heres my grounding, i know it's hard to see, but there's the green/yellow-wire coming from the IEC-Inlet to pin 1 on the XLR-F from there a black wire to chassis ground and one to  pin 1 XLR-F (channel 2) from there a black wire to pin 1 XLR-M (channel 2) and one from pin 1 XLR-F (channel 1) to pin 1 XLR-M (Channel 1). From the XLR-F 's ground goes to Mainboard. the XLR-M (output) don't go on the board yust shielding the wire...

thanks ev'ryone
tschau Ingo

 (http://foto.arcor-online.net/palb/alben/54/84754/1280_3031393439363933.jpg)
Title: The official G9 help thread
Post by: Axelerator on January 04, 2008, 07:45:40 AM
after finishing my studium i now have some lucky time to spent
in Diy again!
-just want to ask if it would be possible to do a only stereo version
of the G9 just for stereo tracking&colouring  as i do no microphone works
and just 2 knobs would be more nice then handling 4...
so if i use all L/R matched components (means expensive stereo pot ,
I know ) is there a chance to get the levels matched also ?
Title: The official G9 help thread
Post by: gec on January 12, 2008, 09:22:25 AM
Hi, I tried to use the G9 like buss insert on master in a DAW, but I'm having the same problem Radiance stated here: (http://www.groupdiy.com/index.php?topic=17980&postdays=0&postorder=asc&start=120) a roll off on bass frequencies
I've used OEPs for in & out, I wonder if changing Oep for Lundahl will solve this problem. I'm using it with Apogee DA&AD 16X
Thanks, Gec
Title: The official G9 help thread
Post by: steppenwolf on January 23, 2008, 04:43:44 PM
Hi Guys!
I'm thinking about building a G9. I already have an G7 mic and I'm VERY happy with it!
I'm just wondering if there will be any problems when connectin the G7 to the G9. Somewhere I read that the G9 has 1k input impedance but the G7 has 600Ohms...
I was told that the impedance of the mic pre should be much higher than the mic's impedance.

Any problems arising?
Thank you!
Stefan
Title: The official G9 help thread
Post by: Stagefright13 on January 23, 2008, 04:46:05 PM
I have tried at least 10 different mics with my G9 and they all sound fine. If that means anything. :)
Title: The official G9 help thread
Post by: steppenwolf on January 23, 2008, 05:01:29 PM
Right, but most Mics I came across had impedances in the 200 Ohms region...
But wouldn't it be strange if Gyraf designed a mic and a pre that aren't compatible...
Somewhere I read that tubed mics like to see higher impedance loads.
And most pres are around 2k, right?
regards,
Stefan
Title: The official G9 help thread
Post by: Stagefright13 on January 23, 2008, 05:18:38 PM
If it means anything my Cad M9 tube mic sounds fantastic with the G9...
Title: The official G9 help thread
Post by: steppenwolf on January 24, 2008, 09:02:34 AM
I just looked up the specs for the M9 and it says it has 200Ohms output impedance and is a transformer less design so it should be pretty different than the G7...
Anyone has already tried to run a G7 through a G9?
Title: The official G9 help thread
Post by: gyraf on January 24, 2008, 10:21:00 AM
Quote
Anyone has already tried to run a G7 through a G9?


Yes. And it ain't no problem  :grin:

Jakob E.
Title: The official G9 help thread
Post by: steppenwolf on January 24, 2008, 10:30:07 AM
Great! Thanks!
Title: Noisy G9 power supply
Post by: crazytooguy on January 30, 2008, 07:42:17 PM
Hi all. my G9 has a lot of buzz and hum in the output, and I think it's coming from the power supply. I have all the grounds starred through the channel one input XLR. Here's a scope pic of the output at max gain

(http://i177.photobucket.com/albums/w224/crazytooguy/channelOut.jpg)

And here's the heater 12V. The HT 245V looks very similar.

(http://i177.photobucket.com/albums/w224/crazytooguy/postreg12Va.jpg)

Just in case it's useful, here's the input to the 12V regulator

(http://i177.photobucket.com/albums/w224/crazytooguy/prereg12V.jpg)

When I first hooked everything up, there was a short to ground in the heater circuit and it trashed the regulator. It's been replaced, but is it possible that the diodes or the smoothing caps are wrecked as well?  Is it just easier to replace them and see if it helps? Thanks!!

Pat
Title: The official G9 help thread
Post by: tony dB on January 31, 2008, 06:18:04 AM
To add to the mic choice ...
this preamp is killer with all mics I've tried so far. AKG 461 with omni capsule sound very close in room and spaceyness as compared my Neum 149 (tru another -UA-! preamp).

Have also a very little hum on 50 and 100 hz (seen on analyzer - hooked up my G9's are dead silent!) what I need to sort out, but I believe this issue came up already so many times, that the solution is to be found in this thread.
Title: The official G9 help thread
Post by: steppenwolf on February 07, 2008, 06:42:55 AM
Hi guys!

My g9 is close to be finished but there are some problems with the transformers.
I'm using one 2x15V 50VA toroid and an 2x12V toroid at 50VA.
I hooked up the first 15V transformers to the mains and connected one pair to the ECC82 heater terminal and the other pair to the 48V terminal.
Everything works fine. I'm getting 12V on the heaters and 48V phantom.

But as soon as I connect the secondary of the second trafo to the 15V of the previous it begins to hum and it draws around 650mA with nothing connected???
I tried to connect just one pair of the secondary of the second tranny in case I messed up the phase but I'm still having the same problems.

I thought I could have a defective transformer but when I connect the second transformer straight at the mains it works fine an puts out around 14V idle so it can't be the transformer...
Has anybody an idea what the problem could be?

Thanks!
Stefan
Title: The official G9 help thread
Post by: steppenwolf on February 15, 2008, 11:55:01 AM
Hi guys!

The transformers problem is gone. I inserted a 4 Ohm resistor between the secondary of the first tranny going into the primary(secondary) of the second. That lowers the voltage down a bit and everything settles fine.

But I observed two problems and they make me a bit nervous:

1)

The voltage rating of the 10uF cap just after the 1k in the 245V line is 250V.
When I turn on the G9 the voltage rises up to around 280V AFTER the regulator until the tubes heat up a bit and begin to consume some mA and than settle around 245V. I'm afraid that this overshoot will kill the cap...
What do you think?

2) Phantom power:
I feed the phantom power circuitry with around 16,5VAC and I get more than 80VDC after the last diode. The cap attached to it rates 63V like in the schematic. That's again too much.
Same behavior on your G9?

Would be nice to here from you!
Best,
Stefan
Title: The official G9 help thread
Post by: steppenwolf on March 29, 2008, 07:44:55 AM
Hallo!
I finished my G9 a few weeks ago and I'm really happy with the outcome!
(PICS soon)
The only little issue I have is the following:
With both the Gain and the Volume Knob cranked and nothing connected to the inputs I get a tiny bit of white noise on one channel (that is perfectly accepteble) but on the other channel I'm getting some random crackling noises and I can hear voices sometimes so I think it's RF interference...
Both input and output trannies are shielded as well as the wires.
Do you have any suggestions on how to improve that or should I keep it as it is? It's defenitly not bothering me as it is low in level...

Thanks,
Stefan
Title: The official G9 help thread
Post by: maxime on April 06, 2008, 03:38:38 PM
hello,
I may be wrong but I don't understand the reason (except a ground loop) for the ground (0V) jumpers on the pcb. the ground path is already complete without these.
anyone knows the reason behind the existence of these two jumpers?
(one jumper is right aside the r26 resistor, the other aside the r31)
best
maxime
Title: The official G9 help thread
Post by: ognam2 on May 08, 2008, 05:42:40 AM
Hello....
I ordered a custom trafo for my g9 like this:

Prim: 230V - Sek: 220V(60mA) / 15V(1A) / 15V(10mA) toroid
(do you think the values are OK?)

so I will have one instead of two....
My question is, if it would make sense to place it outside of the chassis....
Maybe to prevent hum?
Would be no problem because it is molded in a plastic can and can be mounted easily with one screw....
what do you think?

Jonas
Title: The official G9 help thread
Post by: gyraf on May 08, 2008, 06:55:41 AM
15V/10mA makes no sense.

You'd want something like 50V/30mA for the 48V phantom power (and change the phantom power circuit accordingly)

Jakob E.
Title: The official G9 help thread
Post by: ognam2 on May 08, 2008, 01:13:58 PM
You think pahntom power needs more than 10mA?
I just thought about to take some kind of a "plug and play" Trafo for the circuit that you made... (one of the custon one cost the same like two standards) because I bought the pcb from gustav and can´t change the pcb design anymore to have a new phantom circuit.
I know that there other possibilitys, but is there any reason why it is not good  just to feed your circuit with 15V?

so maybe 15V/30mA for this?

cheers Jonas
Title: The official G9 help thread
Post by: ognam2 on May 09, 2008, 06:50:48 PM
or is there an easy way to modify the circuit. what is wrong with the way that I thought about?

thanks!

Jonas
Title: The official G9 help thread
Post by: ognam2 on May 12, 2008, 03:12:28 PM
I´m a little bit confused now...
What is the right value for the phantom circuit trafo?
Title: The official G9 help thread
Post by: gyraf on May 13, 2008, 03:52:12 AM
I have not tried to calculate the needed current of the 15V-winding driving the P48 voltage-tripler.

To play it safe, just use another 15V/1A winding - the cost probably will be the same or cheaper than a low-current winding.

Jakob E.
Title: The official G9 help thread
Post by: ognam2 on May 13, 2008, 09:02:44 PM
1A for Phantom?  I guess thats really "safe"... ;-)
I thought that it would be more expensive if the winding is made for more current.... well I will ask the trafo guy....

thanks

Jonas
Title: The official G9 help thread
Post by: JimiH on June 06, 2008, 10:24:25 AM
Ok I have a new problem.

I was using my G9 with a small condensor mic and happened to notice the oscillation problem in both channels with the gain up high. I decided to fix this in the usual way and it worked a charm for channel 1. Now channel 2, only a distored signal was being passed (same mic) so I decided to open 'er back up and see what all the fuss was about. I had the lid off and I was making a few measurements when I noticed that the temperature of the 12 volt regulator was shooting sky high and smelling funny (it was either that or the diodes before it, they were also getting rather hot) and that it was also touching the case, as in the insulating washer had slipped out and past my observation when I was screwing it all back up.

So anyway the 12 volts cut out once the regulator reached about 140 degrees C (yes I know, I let it go all the way up without turning it off, shame on me) and the audio subsequently also cutout. I know that the 12 volts cut out as my power indicator and heaters turned off suddenly. Before this happened however there was a humming like a ground loop coming out of the speakers, the cheap speakers that I was not worried about ruining if there was a massive pop by the way.

So my question to you out there, whoever you may be, is this: can a dodgy heater voltage regulator be the culprit in my hum issue? Does no heater voltage = no sound? I would assume this to be the case as there would probably be no heaters in thermionic tubes if they weren't needed. Can loss of heaters cut the sound this quickly? I guess my G9 needs a new 12 volt regulator...

As a side note I should probably mention the fact that once I had everything open and "jiggled" about a bit channel 2 seemed to work as well as channel one did, albeit with the hum and loss of sound once the 12 volt regulator cutout...
Title: The official G9 help thread
Post by: steppenwolf on June 06, 2008, 11:08:57 AM
I would suggest to solve one problem after the other. maybe the shutting down regulator causes the trouble, maybe not.
You might need a bigger heatsink.
I used an old CPU sink that is pretty big. After a few hours on, it's still gets really warm. BIG heatsink needed here...
Cheers,
Stefan
Title: The official G9 help thread
Post by: JimiH on June 06, 2008, 11:15:23 AM
Yep yep. I have it bolted to the case which seemed to work fine before this little incident. It used to be on for up to 6 hours a day, no trouble. Thanks though. I might try a different heatsink anyway.
Title: The official G9 help thread
Post by: JimiH on June 08, 2008, 04:34:31 AM
Hey everybody, again.

My G9 has a new problem. I fixed the regulator and it no longer cuts out, but now it humslike a little *****. It never used to do that. but here is the funny thing. Both channels hum the same, but with the output volume all the way down, there is no hum... Anybody experienced this yet? I am at a loss as to where this could be coming from, especially considering that it didn't do this before I burned out the heater regulator.
Title: The official G9 help thread
Post by: steppenwolf on June 08, 2008, 06:11:41 AM
When the hum is gone when you turn down the vol knob, the problem should be before that stage. You might have a problem somewhere around the first gain stage. What's your B+ voltage AFTER the regulator? If you use 10uF 250V filter caps on the board, you might want to check them. I noticed that the voltage rises up to around 280V before the tubes gets heated properly, so the regulator can't regulate(it needs a few mA to do that), as a cold tube has nearly infinite resitance...
It should go down to 250V pretty fast, though. I included a stand-by switch because of that.
Maybe the regulator shuttet down, there was no heater voltage, but you B+ was still up high. In that case, the regulator couldn't clamp down the B+ to 250V and the cap got higher voltage for too long?
What rating do they have in your circuit?
Title: The official G9 help thread
Post by: JimiH on June 08, 2008, 06:23:45 AM
On the board I have 10uF 250V capacitors. If the HT regulator has crapped itself would I be expecting the hum to be there regardless of the output volume? I guess I had better check anyway...
Title: The official G9 help thread
Post by: JimiH on June 16, 2008, 10:12:11 PM
For those of you who care, and i hope that there are some of you out there, my problem was grounding. For some strange reason my G9 decided it wanted the ground connection redone after I did the oscillation fix. So anyway, it has nice new high voltage rated filter caps on the board, a nice new 78S12 and it is grounded properly. I can't get over how low the noise coming from this thing is. I'm not sure I can even hear it through the noise from everything else! I wish I had means to measure it. Anyway, my G9 is going down well with everyone and sounds great and we all lived happily ever after.
Title: The official G9 help thread
Post by: gyraf on June 17, 2008, 04:47:29 AM
:thumb:
Title: The official G9 help thread
Post by: maxheadroom on June 17, 2008, 06:51:00 AM
Jimi, nice to hear that good news  :grin:

pics would be nice too  :thumb:
Title: The official G9 help thread
Post by: maxheadroom on June 17, 2008, 03:26:18 PM
i have some questions about the G9. for the power supply, i wired the
two toroids (230V/1x15 and 12V/230V) without the PCB and the second
toroid began to hum. i replaced the second toroid with another two (30VA and 50VA) and the hum is not away.
while reading the PSU schematic the question why is 15VAC is in use came out.
for the 12VDC heater voltage i think its enough the supply the regulator with 12VAC. for this, the power loss is lower.

Is that a idea?

the next question is about the external mounted caps C14/C15.
i got two from RS with a M8 srew to mount it on the backsidebanel of the
housing. after measuring the connections and the mounting screw i found
out the the screw is connected with the negative pole of the cap.
so, when i mount the two caps on the chassis, i connect the GND/0V with the chassis. is this ok for the further grounding connections?
Title: The official G9 help thread
Post by: steppenwolf on June 17, 2008, 03:43:48 PM
Hi!

I used two toroids, too and the second one hummed, too.
I measured and the second one took 600mA of current with no load!
I solved the problem with a resistor between the secondary of the first and the secondary of the second one...

Greets,
Stefan
Title: The official G9 help thread
Post by: fucanay on June 18, 2008, 09:52:29 PM
Ok Stupid question time.

Has anyone used D Shaft Lorlin switches on the G9? I'm having a hard time finding  the right ones in PCB mount and .25 inch. 6mm is no problem, but knobs are a pain in the ass to find in 6mm locally.

But I'm concerned about knobs not lining up right with the D Shaft.

Now if someone had some not to expensive knobs that are 6mm and fit with Purushas G9 case, I'd be fine with the 6mm ones.

Ok, too much coffee and I'm rambling.

Thanks

Matt
Title: The official G9 help thread
Post by: JimiH on June 18, 2008, 10:54:31 PM
My G9 has D shaft lorlins. And no, they aren't all oriented the right way. But it hasn't made any difference, all the knobs are still centred and don't rotate all funky like.
Title: The official G9 help thread
Post by: fucanay on June 19, 2008, 03:25:13 AM
Quote from: "JimiH"
My G9 has D shaft lorlins. And no, they aren't all oriented the right way. But it hasn't made any difference, all the knobs are still centred and don't rotate all funky like.


Yeah, The orientation is important when you have printing on the front panel though, right? Otherwise the knobs won't point to the right place. That's kind of what I was fearing. I guess I'm going to pick knobs and pots at the same time and get all 6mm stuff. Bah.

Matt
Title: The official G9 help thread
Post by: maxheadroom on June 20, 2008, 10:16:12 AM
so, yesteday and today i completed my G9 with the 230V / 2x12V and
12V / 230V toroids.
the hum on the toroids was away.
with all the tubes i measured:

HT: 240VDC
Heater: 11,98VDC
Phantom: 48,1VDC

the power dissipation on the 7812 is lower, so my (big) heatsink is still warm, not hot.
Title: The official G9 help thread
Post by: JimiH on June 20, 2008, 10:56:09 AM
Quote from: "fucanay"
Quote from: "JimiH"
My G9 has D shaft lorlins. And no, they aren't all oriented the right way. But it hasn't made any difference, all the knobs are still centred and don't rotate all funky like.


Yeah, The orientation is important when you have printing on the front panel though, right? Otherwise the knobs won't point to the right place. That's kind of what I was fearing. I guess I'm going to pick knobs and pots at the same time and get all 6mm stuff. Bah.

Matt


Yeah that's what I was getting at. I thought it would matter, but if you just rotate the knobs and they have a little screw in the side (I guess I should have mentioned that) it just means it tightens on the round bit, not the flat bit of the shaft. It still works rather well. If it means anything I am using a purusha case and the flats on my rotary switches didn't line up, but my knobs are still pointing to the right places thanks to the screws.
Title: The official G9 help thread
Post by: fucanay on June 20, 2008, 09:07:26 PM
Quote from: "JimiH"
Quote from: "fucanay"
Quote from: "JimiH"
My G9 has D shaft lorlins. And no, they aren't all oriented the right way. But it hasn't made any difference, all the knobs are still centred and don't rotate all funky like.


Yeah, The orientation is important when you have printing on the front panel though, right? Otherwise the knobs won't point to the right place. That's kind of what I was fearing. I guess I'm going to pick knobs and pots at the same time and get all 6mm stuff. Bah.

Matt


Yeah that's what I was getting at. I thought it would matter, but if you just rotate the knobs and they have a little screw in the side (I guess I should have mentioned that) it just means it tightens on the round bit, not the flat bit of the shaft. It still works rather well. If it means anything I am using a purusha case and the flats on my rotary switches didn't line up, but my knobs are still pointing to the right places thanks to the screws.


Thanks man. I went ahead and ordered the 6MM ones because I found some knobs that I really like that come in either size. Knobs are too expensive though, bah.

Matt
Title: The official G9 help thread
Post by: fucanay on June 20, 2008, 09:10:26 PM
Ok, another question, that shows my newbieness.

I still need to order the C14/C15 Caps. Does this cap do both at one time?

http://www.tubedepot.com/cp-jj-100x2-500v.html

I don't understand the whole 100 x 100 thing and I couldn't find anything about them anywhere.

Cheers

Matt
Title: The official G9 help thread
Post by: Stagefright13 on June 20, 2008, 11:06:27 PM
I used 2 JJ 50/50 caps from Triode. Work fine. But I don't think something that big is necessary. I like the guitar amp look... You need 2 100 caps with an appropriate voltage rating. And the big caps need clamps to mount them. So don't forget the mounts if you go that way. Each cap is a dual 50 so 100 when chained.

Caps needed 2: 5050clampmount
Clamps needed 2: clamp-1-38

At http://store.triodestore.com/

Hope I helped somewhat. :) You can get smaller cheaper caps but I don't know wich others will definitely work besides these. I'm just an amateur experimenter!
Title: The official G9 help thread
Post by: fucanay on June 21, 2008, 01:00:19 AM
Well, I have two smaller ones of the correct rating, but they look nowhere near as cool as the big one and I like the idea of the clamp mount for structural integrity. But if I need two of the big ones, I'll just make due with what I have. No need to spend $20 or so for things that I won't see after I close the case, I guess.
Title: The official G9 help thread
Post by: maxheadroom on June 23, 2008, 02:51:44 PM
what SNR @ 200 Ohm (EIN) is for a G9 normal?
i want to measure my G9, but at the moment i can't do it at home with my soundcard, because its a bad one and i will measure false.
is there a option with a good fluke?
Title: The official G9 help thread
Post by: maxheadroom on June 29, 2008, 07:20:06 AM
has anybody measured the crosstalk from CH1 to CH2?
Title: The official G9 help thread
Post by: kazper on June 29, 2008, 11:56:02 AM
For the C1/C15 caps I used a pair or Radial caps and secured them to a 2x2 PCB from Radioshack.
Title: The official G9 help thread
Post by: flintan on June 29, 2008, 06:17:08 PM
Do the heater and the phantom PSU's need to be isolated from each other or can i use a single secondary 15V transformer?

I'm asking only because i have a bunch of 1x15V transformers lying around..


Quote from: "steppenwolf"
Hi!

I used two toroids, too and the second one hummed, too.
I measured and the second one took 600mA of current with no load!
I solved the problem with a resistor between the secondary of the first and the secondary of the second one...

Greets,
Stefan


Why is this? Could it be if the transformer has different DCR/voltages between the two parallelled windings? I've been trying to understand this and found some interesting reading here: http://sound.westhost.com/xfmr2.htm#8.series-parallel

If this is the case, wouldn't it be better then to use a single 12V winding for the second transformer?
Title: The official G9 help thread
Post by: ognam2 on July 02, 2008, 04:08:05 AM
Does it make sense to mount the power trafo to the case from the outside?
I mean to prevent Hum Problems....

Jonas
Title: The official G9 help thread
Post by: steppenwolf on July 02, 2008, 05:20:32 AM
I really don't understand, why you are so concerned about hum and noise.
I have two toroids inside the case and even on full gain no hum. A little bit of white noise but every high gain preamp does that. The G9 is a really quiet device.
Of course, if you analyse it with spectralab you'll notice some 50 and 100hz hum, but who cares if it is down -75dB?
Even my AD converter has 50hz hum, but at -120dB.
If I can't hear it on full gain, I don't care much.
By the way:
I have a little bit of hum, too, when I have a XLR cable connected without a mic attached. If you connect a mic, you have an impedance of only 200ohms on the primary, a lot less than without the mic.
Try to short Pin 2 and 3 of the XLR to ground and listen again. Is the hum gone?
Best,
Stefan
Title: The official G9 help thread
Post by: ognam2 on July 02, 2008, 06:55:12 PM
well... I just thought "why not" ... because some people seems to have problems with hum and Jakob E. describes this method to search for the right place for the toroid...
So why not place it outside of the chassis?
I just want to know if there is any reason not to place it there....

Thanks Jonas
Title: The official G9 help thread
Post by: steppenwolf on July 03, 2008, 05:26:04 AM
If your toroid isn't potted, there are flying leads coming out of it that need to be routed through the chassis. I think, taht could be a bit vulnerable but I can't see any electrical reason not to do so. But I would use a potted one...
Title: The official G9 help thread
Post by: ognam2 on July 03, 2008, 06:16:35 AM
it is in a black plastic pott and the cables are isolated....
to cut a small hole in the chassis to put the cables to the inside is not the problem.
Do you think this is a stupid idea?
Title: The official G9 help thread
Post by: steppenwolf on July 03, 2008, 11:45:58 AM
Well, I don't think it's a stupid idea, but I wonder, if it will be much better hum wise.
I would try that, if I run into problems using it inside the chassis, but I don't think that toroids radiate that much...
I just think that it is more rugged having a piece of ewuipment all in one box with no trannies or tubes on the outside, rack depth might cause problems, too. Are you thinking of bolting it on top or behind it (LA2A style)?
Title: The official G9 help thread
Post by: ognam2 on July 03, 2008, 07:19:29 PM
in behind.
It fits perfectly to the size of the chassis.
Maybe I try....
Title: Gain switch trouble
Post by: jarlehal on July 09, 2008, 12:07:56 PM
Hello DIYers

I'm putting together a G9 - and ran into trouble. I'm quite unexperienced - so how deep I do not know yet :wink:

Well, I thought I'd ask here to see if any of you had run into this:

Using mic-input, when I turn the gain switch to the 11th and final step I seem to lose almost all gain (as I was back to 1st pos)!! Then when I plug in my SG and switch to DI/LINE, it works normally all the way up. This is true for both channels and both my control boards. Same mistake twice?? Arghh.. Haven't found any shorts or wiring mix-ups, but I might have overlooked something.

Any clues?

I thought I'd fix this one before I go further dealing with hum, osc and a really loud buzzing toroid. Speaking of that, Im using a 12V 50VA (step-up) and a 15V 30VA. Are you guys able to reach the required (regulated) HT with 2x 15V 30VAs?

And I read steppenwolf is using a resistor to somewhat limit the source for the step-up, and cured the buzz. Good idea?!? I'm a little afraid of messing with the toroids here..

EDIT: Cut the traces and connected the instrument-jack using shielded cable, now my gain switches are cured!!
Title: Resistor values for R26/126
Post by: riggler on July 16, 2008, 05:12:19 PM
Hi,

Can I use 31k resistors for R26 and R126 instead of 47k?

THANKS!
Title: bump -- resistor values
Post by: riggler on July 18, 2008, 11:58:47 PM
bump.... see my previous post in this thread please.
Title: The official G9 help thread
Post by: CurtZHP on July 22, 2008, 04:16:29 PM
Well, gentlemen, it's been a long time, but I finally have everything I need for the final assembly of my G9.  The OEP iron showed up this week, and I might be ready for a smoke test by Friday if I don't lose my nerve.

Here's a question:
How critical is the spacing between the PCB and the large 2W and 1W resistors in the HT supply?  I've seen no mention of that here, and I was wondering if I needed to worry about leaving a bit of space under the resistors to prevent them heating up the PCB.  Any thoughts?

Once I have completed the final assembly, I'll be sure to post detailed pictures before the smoke test.  I want several more pairs of eyes on this before I let the smoke out!
Title: Re: Resistor values for R26/126
Post by: flintan on July 23, 2008, 10:24:36 AM
Quote from: "riggler"
Hi,

Can I use 31k resistors for R26 and R126 instead of 47k?

THANKS!


Why not just stick with 47k? It's not a very uncommon value...
Title: The official G9 help thread
Post by: CurtZHP on July 23, 2008, 04:11:58 PM
One more question regarding the 78S12 regulator.  I'm bolting it to the chassis for heatsinking purposes.  Since the backplate of the 78S12 is basically its ground (same as pin 2), do I still need to bother with electrically isolating it from the chassis; or can I just put some heatsink grease under it, bolt it down, and call it a day?
Title: The official G9 help thread
Post by: Harpo on July 23, 2008, 04:29:09 PM
Quote from: "CurtZHP"
One more question regarding the 78S12 regulator.  I'm bolting it to the chassis for heatsinking purposes.  Since the backplate of the 78S12 is basically its ground (same as pin 2), do I still need to bother with electrically isolating it from the chassis; or can I just put some heatsink grease under it, bolt it down, and call it a day?

Doing so without isolation might give you a ground loop. just my 2ct.
Title: The official G9 help thread
Post by: CurtZHP on July 25, 2008, 06:31:23 PM
Here it is!  My finished G9!

(http://www.zerrohouseproductions.com/G9front.jpg)

(http://www.zerrohouseproductions.com/G9wide1.jpg)

(http://www.zerrohouseproductions.com/G9wide2.jpg)

(http://www.zerrohouseproductions.com/G9mainpcb1.jpg)


To see more pics:
http://www.zerrohouseproductions/preamps.html

I'd like to get everyone's $0.02 before I fire it up.

[/img]
Title: The official G9 help thread
Post by: Deeply Silent on July 28, 2008, 08:41:20 AM
Hi everyone, firstly thanks for all the valuable info to be found on this forum.
I have nearly finished building the G9 and have a question about adding 1/4 inch jack inputs and outputs.
Iv found a thread about this but the answer wasnt too clear - http://www.groupdiy.com/index.php?topic=13127&highlight=xlr+jack+cable
So with the output I can connect ground to the jack sleeve and the tip to P2 (hot) on the xlr? That would give me unbalanced out right? Now what if i connected the out to balanced TRS setup and then a mono jack was inserted would it be a problem if P3 (cold) on the xlr are shorted out?

Similarly with the input can i connect the xlrs P1 to the jack sleeve, P2 to the tip and P3 to the ring? Again would inserting a mono jack and shorting the ground to P3 (cold) be bad, I'm guessing so with the phantom power??
If not, could I connect the inputs in an unbalanced way for line in - ground to sleeve an hot to tip?

Sorry for the lengthy post and if the answers are obvious..
Title: SUCCESS!!!
Post by: CurtZHP on July 29, 2008, 10:48:41 PM
It's DONE!!

I finally got up the nerve to fire up my G9.  I plugged it in, flipped the switch, and immediately the fuse blew.   :?

After a bit of head scratching and rechecking my work, I found the problem.  Next to the main PCB I put a small two position solder terminal strip to facilitate the wiring for the main power transformers.  It appears that I failed to notice that one of the terminals was same piece of metal that formed the mounting bracket for the strip.  So I was basically connecting one side of the transformer's secondary to the chassis.  Talk about an "Amateur Hour" mistake!   :oops:   I cut all the wires loose, soldered them together without the terminal strip (covering the joints with wire nuts), and prayed that I hadn't cooked the transformer.

Flip the switch.  IT'S ALIVE!!   :grin:

I let it burn in for a few minutes and then started checking supply rails.  The 245V rail was showing 235V.  I assume this is within tolerance.  The 12V rail was showing 11.72V, and the 48V rail was showing 49.2V.  After letting it idle for a while, I connected a tone generator to the left input and a small powered speaker to the output.  Good tone.  Exercised the controls.  All good.  Switched everything to the right channel.  No audio.   :?

Careful examination of the right channel control PCB revealed the problem.  I had neglected to solder the center pins for the "phase" switch, so no audio was passing through it.  Another "Amateur Hour" mistake.   :oops:   A quick touch-up with the soldering iron, and the right channel is in business.

Tried it with a Shure SM-58 just to make sure it worked, then with an Audio Technica AT4040(?) to check the phantom power.  I also connected the tone generator via the instrument inputs.  All is well!  No hum, no oscillations, no weird noises, no smoke.

So it looks like I'm the latest proud new owner of a Gyraf G9 tube mic preamp!   :cool:

A HUGE "TAK" to Jakob and all the rest at Gyraf.  Thanks to all the guys here on the forum for your help as well.  I'd also like to thank the Academy.... (Oops!  Wrong speech!)

I can't wait to put this thing in action.

 :guinness:
Title: The official G9 help thread
Post by: gyraf on July 30, 2008, 08:01:06 AM
Congrats!

Now go make some great music...!!  :razz:

Jakob E.
Title: Mains transformer question
Post by: riggler on July 30, 2008, 10:17:42 PM
My G9 is almost done and I'm about to order power transformers. I'm going to get Avel Y236103 30VA toroids. I'm in the U.S. and I've read elsewhere in the forums here that some people got 50VA toroids instead of 30.

Why is this necessary for some, but not others? Is this just a preference for more stable voltages / cooler running?

My bottom line question is: Should I stick with 30 or get 50VA transformers?
I can't find the thread mentioning 50VA transformers now, but I do remember reading it!

THANKS GYRAF FOR THIS ROCKIN DESIGN! :green:
Title: The official G9 help thread
Post by: CurtZHP on July 30, 2008, 11:28:44 PM
I used the Amveco toroids from Digikey.  The model number is 62073, and they are 30VA.

In my initial tests, they seem to run pretty cool and all my supply rails are within tolerance and don't seem to fluctuate at all.

Somewhere on this thread (or elsewhere on the site) someone was kind enough to provide a detailed diagram of how to wire them to the main PCB, complete with color codes.


BTW, where in Pennsylvania are you?
Title: The official G9 help thread
Post by: riggler on July 31, 2008, 07:32:24 AM
Hey, Allentown is right in my backyard, I'm in Bethlehem! Shoot me a PM if you want.

Anyway, I did see the diagrams (which are great). I'll go with the Amveco's since you've had no issue.

Am I correct in thinking that you only need a current-limiting resistor when using an LED for the front panel indicator?
Title: The official G9 help thread
Post by: CurtZHP on July 31, 2008, 09:58:47 AM
Quote from: "riggler"

Am I correct in thinking that you only need a current-limiting resistor when using an LED for the front panel indicator?



Yes, a 1K or 2.2K rated at 1W should do it.  I don't have the unit in front of me right now, but I think I used a 1K.

Just attach it in series with the anode.  There's a detailed picture of what I did on my site.

http://www.zerrohouseproductions.com/preamps.html
Title: The official G9 help thread
Post by: riggler on July 31, 2008, 10:17:13 AM
Thanks!  :sam:

Let's have an A-B-E meeting of the G9's. Mine should be done in a few weeks.

BTW -- your link should be zhppreamps, not preamps, in case anyone else is ineterested in seeing Curt's build.

-Damian
Title: The official G9 help thread
Post by: CurtZHP on July 31, 2008, 06:00:10 PM
Oops!
Title: The official G9 help thread
Post by: gyraf on August 01, 2008, 06:18:59 AM
Quote from: "CurtZHP"
Oops!


Take care. Remember that the G9 circuit is dangerous when powered..! Very little room for Oops'es..


Jakob E.
Title: The official G9 help thread
Post by: CurtZHP on August 01, 2008, 09:53:11 AM
Quote from: "gyraf"
Quote from: "CurtZHP"
Oops!


Take care. Remember that the G9 circuit is dangerous when powered..! Very little room for Oops'es..


Jakob E.



Yes, but my website has yet to kill anyone.   :wink:
Title: The official G9 help thread
Post by: Leffe111 on August 08, 2008, 01:01:56 PM
Hi
So the world has seen yet another G9 preamp, or half of it anyway.
Channel 1 is dead. Channel 2 sounds and works wonderfully, with and without 48v (and DI) and is deadquiet. Got 245V at the rail, and a lot of other values wich I won´t bother you with now.
Here´s the thing: The output pot only shows 5Kohm??? when soldered but when desolvered it shows as should around 50 Kohm. Got 48 V at the input as well on channel 1. Any suggestions?
Thanks Jakob for a wonderful preamp...recorded some acoustic guitar with AKG c1000s today and it sounds soooo good, really.
best regards
Leif
Title: The official G9 help thread
Post by: CurtZHP on August 08, 2008, 01:24:17 PM
It sounds like your supply rails are healthy, and that's half the battle.  Can you try it with another 50K pot?  It could be that you have a bad one.  Also check for solder bridges on the control PCB for that channel.  One other thing....
Check back a few posts on this thread to read about my misadventures when firing mine up for the first time.  I had a very similar problem, with one channel being dead, and it turned out I forgot to completely solder in the phase switch.

Take heart.  If one channel works great, and it didn't burst into flames on you, it'll be something simple.
Title: The official G9 help thread
Post by: flintan on August 08, 2008, 03:17:39 PM
Quote from: "Leffe111"

Here´s the thing: The output pot only shows 5Kohm??? when soldered but when desolvered it shows as should around 50 Kohm. Got 48 V at the input as well on channel 1. Any suggestions?


I haven't finished mine yet but.. I don't think the pot is broken. Does it "change" resistance when you turn the 12 pos gain switch? Lock at the schematic. Could it be that you had the lo cut filter in when you measured on the other channel? (Assuming the working channel showed 50K on the pot..)
Title: The official G9 help thread
Post by: matta on August 13, 2008, 12:22:46 PM
Hi Guys,

I'm finally getting back to my G9 which I started a year and half ago! Not much time for DIY these days  :sad:

I had a custom trafo wound with 15V, 220V and 48VAC secondary windings. The 220VAC unloaded is putting out 245VAC, which I hope will be ok once rectified.

The questions now is the 48V (unloaded putting out 47.5VAC) winding. Rather than get a another 15VAC winding and use the voltage tripler I thought I could just use a 48VAC rail to power the +48V rail.

It is safe to assume the only 'mod' I would have to do is omit some of the diodes/caps? Looking at the schematic we are wanting to hit around 60VAC before rectification. What would be the safest/best way to do this?

(http://www.matt-allison.com/diy/G9/g9_psu.gif)

Jakob mentioned this a few pages back:

Quote
You'd want something like 50V/30mA for the 48V phantom power (and change the phantom power circuit accordingly)

Jakob E.


But we didn't get into details of how/what should be done, so at least this will clear it up for future builders.

Thanks in advance!

Matt
Title: The official G9 help thread
Post by: riggler on August 13, 2008, 09:02:55 PM
Matt,

I think that you're going to have to build a bridge rectifier to replace the voltage tripler. I think that you could get away with copying the 220V bridge rectifier seen in the schematic right above the 15V tripler.

But you're going to have to filter it picking the schematic back up around zener diode D6. Definitely will still need T1. I'm not the guy to best answer this, but from what I can see this is a good starting point.

Kudos on getting your G9 going, I'm in the same boat, took quite a while to get moving. :green:

BTW -- another question. I had some old Sprague Atoms to use for C14 and C15. Well, they're too old and I don't trust them. So I bought from Mouser 2 Nichicon 150uF 350V UPB2V151MHD. (Low Impedance Aluminum Electrolytic Capacitors - 105 Degree 350V 150uF 18X40 20%Tol 7.5LS 105Deg)

They're a LOT smaller than the Atoms I had... they going to be okay?

 :?:
Title: The official G9 help thread
Post by: matta on August 14, 2008, 03:20:29 AM
Ok,

So here it is, the updated power supply for the G9 using a 42V winding in place of the 15V if you are going to use a single custom wound trafo.

(http://www.matt-allison.com/diy/G9/G9_modded_psu.gif)

Note when compared to the original schematic parts D8 - D12, C26 - C29 are omitted and C20-22 need to have their voltage rating upped to 100V as 42V full wave rectified is doing to push you over the 63V tolerance.

You can cleanly do this with a bridge rectifier. I used a W02, but an 01 would have worked as well and then moved the legs around and lined it up on the PCB to make a neat fix. I added heatshrink on the - leg which goes to ground just incase it shorted with one of the AC junctions.

The results look like this:

(http://www.matt-allison.com/diy/G9/G9_48V_Mod_Comp.jpg)

Not in order to do this I needed to cut a trace under the board because one of the AC connections was also on the ground trace, I did like this:

(http://www.matt-allison.com/diy/G9/G9_48V_Mod_Traces.jpg)

Just for the record these are the specs of the torrid I had wound:

Prim1 : 230v
Sec 1: 220v @ 75mA
Sec 2: 15v @ 1.5A
Sec 3: 42v @ 50mA

Come to 42VA, but I just had them make up a 50VA.


While on useful info and since I had my camera handy, here is another tidbit:

DI/INSTRUMENT MOD:

This has been brought up in the past but a couple builders have experienced problems with oscillation at the highest gain settings and forum user AXEL offered a solution to the problem that seems to cure it here: http://www.groupdiy.com/index.php?topic=114787

Jakob has a detailed drawing of this on his site here: http://www.gyraf.dk/gy_pd/g9/G9-EDIT.GIF

But I thought it might be nice to shoot a of the mod done so you can see it on the actual PCB.

(http://www.matt-allison.com/diy/G9/G9_DI_Mod.jpg)

You can see where the traces have been cut, I used a small cutting wheel with my Dremel drill and it did the job just fine.

Riggler,

RE your caps, they should be fine. If you look a few pages back you will see that I have shown the Rubycon brand version of your Nichicon. Jakob confirmed they will be fine and I think Godders used the same ones in his circuit... caps have come done in size over the years as have many other components.

Cheers

Matt
Title: The official G9 help thread
Post by: riggler on August 14, 2008, 09:30:30 PM
That looks about right Matt! Nice drawing!

 :cool:

And thanks for answering my cap question. Now I just found the slickest little meters that fit exactly into the open area above the line/mic & phase switches.

The AL15 is 1.4" square, vintage look, and is a perfect fit! A cool TV guy I worked with pointed these out to me and I thought I'd pass it along. I wonder if Jakob planned for this when laying out the front panel PCBs.

http://www.sifammeters.com/Audio_Level/AL15_Retro.htm

I am not going to add these to my G9, but maybe in the future. My DAW gives me a good reading, so I really don't need them.
Title: The official G9 help thread
Post by: matta on August 15, 2008, 09:42:49 AM
Post updated!
Title: The official G9 help thread
Post by: Soeren_DK on September 29, 2008, 03:13:48 PM
I have some problems with my G9.

It has been running a whole year without problems but suddenly the 48v powersupply roasted and after 3 month the 15v trafo died. I took it apart and replaced everything in the 48v powersupply, the roested trafo and now it works okay. The trafo I replaced it with is only a 25VA and now it gets really hot.

My question is: Is the new trafo undersized? and could there be some problems in the circuit that also would have roasted the old one?

Best regards
Soeren - Denmark
Title: The official G9 help thread
Post by: CurtZHP on September 29, 2008, 03:49:32 PM
If I had to take a wild guess, I'd say that maybe the original 48V supply had either a shorted diode, or maybe the regulator (TIP121) went bad.  The resulting excessive current could have sufficiently damaged the transformer to the point that it died when it did.  

You could certainly stand a bigger transformer in terms of VA.  It certainly wouldn't hurt.
Title: The official G9 help thread
Post by: riggler on September 29, 2008, 04:16:00 PM
How's the voltage regulator? Not just the phantom, but also B+?
Are their heatsinks getting very hot?

If your power transformer is getting hot, then you are asking too much of it, so it is either undersized (G9 calls for 30va I believe), or a fault is drawing too much.

Have you checked voltages? On the PCB, there are several handy spots for this, just be careful.

Also, I would carefully look at caps, especially C14 and C15. They bulging, oozing, or anything?
Title: The official G9 help thread
Post by: Soeren_DK on September 29, 2008, 04:46:35 PM
Quote from: "riggler"
How's the voltage regulator? Not just the phantom, but also B+?
Are their heatsinks getting very hot?

If your power transformer is getting hot, then you are asking too much of it, so it is either undersized (G9 calls for 30va I believe), or a fault is drawing too much.

Have you checked voltages? On the PCB, there are several handy spots for this, just be careful.

Also, I would carefully look at caps, especially C14 and C15. They bulging, oozing, or anything?

I thought the same with the 30VA.
I have asked around and no one have ever heard about a trafo could die just that so have a suspicion maybe some other thing could be wrong.

I checked my voltages:
C14: 361v
C15: 239,3v
Heater: 11,55v

The trafo with 220vac gives 286vac and the 15vac is instead 17,65vac.

Is there other voltages I should check.
Also the caps looks just fine. Nothing that shows any problems.

The 12v regulator is mounted on the surface on the bottom plate electric separate. It get very hot,
The 245+ HT is mounted with a heatsink and also gets very hot.

Best regards
Soeren - Denmark
Title: The official G9 help thread
Post by: ognam2 on October 08, 2008, 10:40:39 PM
why does my g9 loose all the gain at the 12 Position of the Gain Switch?
Thanx Jonas
Title: The official G9 help thread
Post by: Emperor Tomato Ketchup on October 08, 2008, 11:41:17 PM
Quote from: "ognam2"
why does my g9 loose all the gain at the 12 Position of the Gain Switch?
Thanx Jonas


It's oscillating.  Search here for more info.

-Chris
Title: The official G9 help thread
Post by: gyraf on October 09, 2008, 01:49:48 AM
No - there is no 12'th position on the gain switch. The switch must be limited to 11 positions by the "programming pin" under the lock nut.

Jakob E.
Title: The official G9 help thread
Post by: ognam2 on October 09, 2008, 05:53:36 AM
haha.... what a stupid fault....  :-)
Thanxs!
But there is another problem. At the 11 Step of the right channel There comes something out of the box that I can´t hear but see at the meterbridge of my mixer. seems to be very lout, but I can´t hear it. Is that an oscillation issue? It is only there if a microphone is connected. With a condenser it is also at the 10 position.

Oscillation?

Thanx Jonas
Title: The official G9 help thread
Post by: gyraf on October 09, 2008, 06:52:11 AM
Quote
is that an oscillation issue


It might be - but it should not only occur with a mic connected. Maybe ultrasonic feedback? Does it still do this with mixer full-muted?

Jakob E.
Title: The official G9 help thread
Post by: ognam2 on October 09, 2008, 07:56:48 PM
I fixed the issue with alex´method... cut the trace and use a shielded cable instead. This thing is working fine now... sounds very sweet!
Only one question:
I trimed the phantom to exactly 48V, but when I connect a Mic it goes down to 35V. Is this normal?
Thanx Jonas
Title: The official G9 help thread
Post by: gyraf on October 10, 2008, 03:36:05 AM
Quote
I trimed the phantom to exactly 48V, but when I connect a Mic it goes down to 35V.


Measured where?

The voltage after the 6K8 resistors is supposed to drop when loaded with a mic..

Jakob E.
Title: The official G9 help thread
Post by: ognam2 on October 10, 2008, 05:42:30 AM
measured at the xlr´s ... so it´s normal right?
Thank you for this awsome project!

:-)

Jonas
Title: The official G9 help thread
Post by: gyraf on October 10, 2008, 06:39:07 AM
:thumb: :razz:
Title: The official G9 help thread
Post by: ognam2 on October 29, 2008, 05:21:48 PM
finally the knobs arrived....

(http://www.kokicker.com/jonas/Myspace/G9front.jpg)
(http://www.kokicker.com/jonas/Myspace/G9oben.jpg)
(http://www.kokicker.com/jonas/Myspace/G9rack.jpg)
Title: The official G9 help thread
Post by: gyraf on October 30, 2008, 12:03:02 AM
Nice!  :thumb:

Jakob E.
Title: PSU Transformator
Post by: microc on November 25, 2008, 02:26:37 AM
Hi
Got a bit of an issue. I wonder what PSU transformator to choose. I looket at an  Avel Lindberg Toroid transformator P/N Y236003, the I go from 230/ 15+15. but I also need to go 15/230. Could I just use a 1:1 transformator parallell with the other one? then I get 15+15+230. Any better ideas?
Or two of 9531785 (Nr in Farnell, basic 50VA 230/15+15)

And also for the voltage regulators. I've bought a regulator for the 12V but I'm not sure what to do with the 245V and 48V

Thank you for Your time!
Best Regards
Jens, Norway.
 :)
Title: Re: The official G9 help thread
Post by: CurtZHP on November 25, 2008, 11:17:39 AM
Can you go with the Amveco transformers in Norway?  They make exactly what you need for this.
Title: Re: The official G9 help thread
Post by: microc on November 26, 2008, 04:49:35 AM
Can you go with the Amveco transformers in Norway?  They make exactly what you need for this.


Thanx. Do you have any product name else then Amveco ? Or do you order a custom design. Then I could order a two in one transformator.

I'm a bit nuuubie. lol

Title: Re: The official G9 help thread
Post by: CurtZHP on November 26, 2008, 09:48:21 AM
If you've got the time to look at this entire thread, there is another product name that some here have used.  I don't recall what it is.

I ordered the Amveco transformers through a US company called Digikey.  I'm sure they handle international orders.  Or you could e-mail the company (www.amveco.com) and see if they have a European distributor.

Title: Re: The official G9 help thread
Post by: microc on November 28, 2008, 11:50:34 AM
Allright, Thank You CurtZHP   8)
This is really cool!
Title: Re: The official G9 help thread
Post by: Stagefright13 on December 27, 2008, 10:30:41 PM
I know it's not just me but everything sounds WAY bigger thru the G9. I use it in line mode during mixing alot. I pipe it in using a protools insert at the front of the track. Of course everything can't be big lol. But this has a special sound and use it tons.

Thanks so much Gyraf!!

I know this is a little late but Holy Cow ognam2 that's a nice looking G9!!
Title: Re: The official G9 help thread
Post by: gyraf on December 29, 2008, 06:26:09 AM
 :)
Title: Re: The official G9 help thread
Post by: Stagefright13 on January 04, 2009, 12:53:44 AM
Pic of my G9 after MU mod :

(http://www.stagefrightrecords.com/p1010196.jpg)

From http://www.lessemf.com/mag-shld.html (http://www.lessemf.com/mag-shld.html) Cheap and virtually silent! Giving away my secrets. But I was actually copying Jakob! The G9 was pretty quiet except a small amount of noise on the right channel. But it interfered with equipment bolted next to it. No longer any problem. And I have enough MU metal left to isolate alot of other projects if need be... It's a "Mac Daddy" pre or line amp!
Title: Re: The official G9 help thread
Post by: caseyc on January 06, 2009, 11:37:47 AM
Hi people!

Have been building pro audio gear for a long time (build a lot of ssl clones and all the other great gyraf stuff, EXCEPT the G9).... until now! Had some parts over and put one together.

It works fine, nu hum what so ever. BUT, ok i have read this thread and cant access oscillation problem thread for some reason....but on the the three last gain settings it both channels it totally goes too high...screaming/distorsion. I just wanted to ask here about the oscillation issue before making the cuts on the board?

/regards



Btw, if you have hum in a DIY project and you have checked every soldering etcetc and properly grounded it but still got a 100 hz hum....measure the resistance between to points on the pcb (example from one side to antoher) when its off (should be zero) if the value changes when powering it up (lets say above 1 ohm) well then your pcb tracks are so thin that they have become a resistance. Just a tip from me.
Title: Re: The official G9 help thread
Post by: gyraf on January 07, 2009, 01:04:51 AM
If you have the oscillation problem, you need to cut the traces just beside the input transformer:

http://www.gyraf.dk/gy_pd/g9/G9-EDIT.GIF

1) Cut the two traces that comes from the input transformers and goes to the instrument jack.

2) Cut the two traces that goes to the 220nF input capacitors from the instrument jack.

3) Mount four shielded cables to/from the instrument jack, wireing directly to the transformer and to the input capacitor, using shield-ground from the transformer ground that is found close by your cuts.

..good tip about finding high-res ground loop problems..!

Jakob E.
Title: Re: The official G9 help thread
Post by: caseyc on January 07, 2009, 10:04:08 AM
If you have the oscillation problem, you need to cut the traces just beside the input transformer:

http://www.gyraf.dk/gy_pd/g9/G9-EDIT.GIF

1) Cut the two traces that comes from the input transformers and goes to the instrument jack.

2) Cut the two traces that goes to the 220nF input capacitors from the instrument jack.

3) Mount four shielded cables to/from the instrument jack, wireing directly to the transformer and to the input capacitor, using shield-ground from the transformer ground that is found close by your cuts.

..good tip about finding high-res ground loop problems..!

Jakob E.

Hi Jakob, Did this modification right now, problem solved  :) Thanks a lot! It sounds veryvery good :)

And many thanks for sharing these really great DIY projects

/C
Title: Re: The official G9 help thread
Post by: stitch-o on January 07, 2009, 04:56:43 PM
BUT, ok i have read this thread and cant access oscillation problem thread for some reason....but on the the three last gain settings it both channels it totally goes too high...

I've been trouble shooting a similar problem but I have high freq osc only on the right channel (closest to the PT) with the last 3 gain settings...I would imagine this the same issue that needs traces cut but only on problem channel?
Edit: I'll answer my own question and say yes, the DI mod helps tremendously.
I just performed the mod and it ended any HF oscillations in the furthest gain settings.


Also, I've been researching ground schemes for the G9 design and have found that there are many seemingly successful grounding schemes - pin1 inputs strapped, inputs and outputs strapped, 1 input strapped directly to IEC, starground to chassis : which is the best?

Heres mine BTW, and other than the oscillation, its pretty quiet..:

Edit: I think I'm going to pull the output grounds and just tie input and IECplug to a star ground at chassis.The pres are pretty quiet untill they are full out then have just a trace of crackling and hum. I'm trying for ultra-quiet..

(http://img145.imageshack.us/img145/6860/g9groundzu9.th.jpg) (http://img145.imageshack.us/my.php?image=g9groundzu9.jpg)
Title: Re: The official G9 help thread
Post by: pstcho on January 10, 2009, 03:15:07 PM
hi, i made a lot of g9 and i love it
i have 8 channels in my studio using OEP and 4 channels using Lundal transformers

i would like to do a dual channel without transformer (with op amp or something else)

somebody as an idea about that?

thank you

David
Title: Re: The official G9 help thread
Post by: audiophreak on January 10, 2009, 07:13:00 PM
  Hi,

 A little help please  ;D

   I am getting together a parts order list for a G9 and have a few newbie questions..sorry.. ;D

I think I'm good with the resistors

Output Level pot - 47kb (log) 6mm - any suggestions ?

10k Trimmer 5x10mm or 5x2.5mm  - any suggestions ?

C6,106 - 68p 50v ceramic, is this one correct?
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=BC1011TR-ND

Need voltages for, C8,108 - C9,109

D3,D4,D5, - ZD39 - any suggestions ?

D6 - is this correct?
http://www.mouser.com/Search/ProductDetail.aspx?qs=rsHPD1Ud3U45bB7MnDGbLQ%3d%3d

TL783 - is this one correct?
http://www.newark.com/texas-instruments/tl783ckcse3/linear-regulators/dp/10M0615

78S12 - is this one correct ?
http://www.newark.com/stmicroelectronics/l78s12cv/voltage-regulator-ic/dp/89K0776?_requestid=243966

TIP121 - is this one correct ?
http://www.newark.com/jsp/search/browse.jsp?N=500003+1001808&Ntk=gensearch_001&Ntt=TIP121&Ntx=

  and the lorlin switch's - use silver, Gold plated or Gold Flash ?

  Any and all help greatly appreciated,

                Thanks ,
                          Chip


Title: Re: The official G9 help thread
Post by: Stagefright13 on January 10, 2009, 10:53:20 PM
This isn't a bom for the G-9. But here is the Mouser order I made back when I built my G-9. It should have all the parts I needed from Mouser for my G9. But probably has a few items for other projects also. But not many. Maybe it can answer a couple of your questions.

I did also order some parts from Farnell, triode, and digikey etc. tho...

www.stagefrightrecords.com/G9.rtf (http://www.stagefrightrecords.com/G9.rtf)

And Gyraf has the parts list on www.gyraf.dk (http://www.gyraf.dk) It lists the voltages for the caps.

Hope it was some help. Hope you have a great build!!

John
Title: Re: The official G9 help thread
Post by: audiophreak on January 10, 2009, 11:41:20 PM

 Hi John,

      Thanks so much, that answered a lot of them. ;)

 I am going by Gyrafs list, but am having difficulties finding the right values for some of the parts listed, and also because of my Newbie-ness   ;D

  Output Level pot  -  47k (Log) pot - logarithmic/inverse/linear - carbon/conductive plastic - there's so many different types

  Need voltages for, C8,108 - C9,109 - there is no listed voltages on Gyrafs list

  D3,D4,D5, - ZD39 - any suggestions ? - link to the only .5w mouser lists - not sure if the voltage is correct
http://www.mouser.com/Search/ProductDetail.aspx?qs=DHPsj9PSUngBff3BfOGZhA%3d%3d

  Thanks again,
                  Chip


 


   

 

 
Title: Re: The official G9 help thread
Post by: Stagefright13 on January 11, 2009, 05:17:53 AM
I'll try to help ya best I can If ya can gimme a little to check parts orders. And BE VERY SAFE. There are HIGH voltages in there when ya get done. Best to have 2 meters. 1 on the high tension line. So you can see when it is safe and one meter to check other stuff like heaters or phantom etc. Leave the high one on ALL the time. Be back in a bit lemme look... The bom I used went down. And wasn't correct anyway. The diodes are listed in my Mouser order somewhere... Type zd39 into mouser search engine... For cross reference.

Think the diodes are this  526-NTE5086A. And the c8/108 and c9/109 are for the high pass filter. Get anything. I think I used wimas for accuracy. But totally unnecessary. Don't think voltage is much a problem on them...  But I may be corrected soon. LOL
Title: Re: The official G9 help thread
Post by: Stagefright13 on January 11, 2009, 05:53:43 AM
Digikey and Farnell suck at histories sorry that is all I got. :(

You can buy a 47k log pot anywhere. And try not to be a newbie with tubes! Just be careful.
Title: Re: The official G9 help thread
Post by: audiophreak on January 11, 2009, 12:53:37 PM


 Hi,

   John,
           Thanks so much for the help and advice, I've read it in hear many time - " One hand in the pocket"
 
  I think I am all set for now, will post back on progress,

                                                                      Thanks again,
                                                                                        Chip
Title: Re: The official G9 help thread
Post by: keithcamilleri on January 15, 2009, 07:20:56 AM
hey guys,

i am experimenting a bit with psu ...i have a toroid which is putting in 287 volts across the 470r is this too much for the tl783 to handle? my 470r keeps blowing up.

cheers
keith
Title: Re: The official G9 help thread
Post by: gyraf on January 16, 2009, 03:30:42 AM
resistors should not burn no matter what.

If you read through the circuit description, you'll notice that the in/out voltage difference for the TL783 voltage regulator circuit must be kept below 120V - so at 245V out, it should accept some 255 to 360V DC (but around 260 to 280 is ideal).

Remember - as mentioned several times earlier in this thread - that you can only measure voltages with tubes in-circuit and heated up.

Jakob E.
Title: Re: The official G9 help thread
Post by: thelabyrinth on January 16, 2009, 03:51:02 PM
First post. My tech and I are about to embark on this project. We plan on doing 4 channels, 2 separate power supplies, VU meters and vintage knobs. For those of you who built this, what brand of tubes are you using and why? I was looking on tubedepot.com and they have a lot of ECC82's to choose from so any suggestions would be great.
Title: Re: The official G9 help thread
Post by: ognam2 on January 16, 2009, 05:55:27 PM
I used JJ´s in mine... sounds just great
Title: Re: The official G9 help thread
Post by: Mbira on January 16, 2009, 08:33:45 PM
I have some old Jan specs-love them.
Title: Re: The official G9 help thread
Post by: audiophreak on January 17, 2009, 12:33:33 AM


 Hi All,

    A Little confused  :o
 

  On the Gyraf site it says:
                                      "For 110V mains, you'll need two 110+110:15+15V (30VA or larger) toroid transformers. The two first primaries - for mains input - should be coupled in parallel, for 110V. The two primaries of the second transformer should be connected in series, to bring voltage up to around 220Vac."

  but in the shoppig list it says:

                                   "OR - if you're in a 110V mains area:
First:     110+110:15+15V/ 30VA TOROID       PSU 220V mains to 15VAC
First:     110+110:12+12V/ 30VA TOROID       PSU 15VAC to 220VAC *note:updated!

   So.... which one is it?
                               Two 15v or one 15v and one 12v   ?


    I haven't read ALL the Metas, but I think I've read enough, and haven't read anything on this? 

  Sorry for,the Newbie-ness

                        Chip

Title: Re: The official G9 help thread
Post by: gyraf on January 17, 2009, 12:58:42 AM
where it says *note:updated! - we changed from two 15V transformers to a 15V and a 12V - to get voltages closer to what we want.

Jakob E.
Title: Re: The official G9 help thread
Post by: audiophreak on January 17, 2009, 02:06:45 AM


 Hi,
    Jakob, Thanks so much, and Thanks for Designing such an awesome project. I'm learning, and having a blast !

            Chip     ;D
Title: Re: The official G9 help thread
Post by: Stagefright13 on January 17, 2009, 03:31:37 AM
I used NOS GE's Vintage mid 60's on mine from tubeworld.com and am very happy. They were also reasonably priced. I have also gotten other tubes from there for other projects and they all tested great on my tester and sounded just perfect. I think he listens to them if you tell him it is for a preamp. Nice guy.

audiophreak when you get this done and start using it you will say holy crap can't believe I built this. It's worth it and best of luck to you! My G9 is on right now. ;) In use once again...

John
Title: Re: The official G9 help thread
Post by: keithcamilleri on January 18, 2009, 03:11:26 PM
hi jakob ,
thanks for your reply , i am not even coming close to measure voltages as soon as i hit the switch on the 470r immediately burn out...im so confused ... i've checked all components ....do you have an idea what could cause this?

thanks

keith

edit : could it be the capacitors ? i am trying to test them but i do not have a propr capacitance meter...
Title: Re: The official G9 help thread
Post by: Mbira on January 18, 2009, 03:45:26 PM
Hmmm...
Never noticed that now we are using a 15v and 12 v transformer.  I just ordered two 15v torroids.  Does that just make the 78s12 run hotter?  I remember having problems with that before and having to get a really big heatsink, but all runs fine now after a few years with the two 15v torroids...

Cruious to know.
Thanks,
joel
Title: Re: The official G9 help thread
Post by: audiophreak on January 20, 2009, 05:42:58 PM

 Hi,
   
   Need some advice, I've noticed in pics of others G9s that the
  C3-103
  C4-104
  C5-105
  C7-107
  C10-110
  C13-113
 
  Polys were WIMAs, or what looks like Hovland Musicaps, or others I dont know the manufacturer of.

    Do these make a huge difference in the sound, I know that's very subjective, but am in the middle of the build and want to use the best components,

I have been looking at:

  TRT Dynamicaps/Wondercap, Hovland Musicap,Solen/Axon, and Jupiter beeswax and paper caps


  any advice or preferences appreciated,
      Thanks,
               Chip
Title: Re: The official G9 help thread
Post by: gyraf on January 20, 2009, 11:54:18 PM
Hmmm...
Never noticed that now we are using a 15v and 12 v transformer.  I just ordered two 15v torroids.  Does that just make the 78s12 run hotter? 

No - it's mainly for getting the HT voltage more within a good range...

----
Quote
Audiophreak
- you can use any type of capacitor you like, as long as it fits the needed specs. I like Wima's, but any type will do fine as well. 99% of the "sound" is in the tubes and transformers anyway.

Jakob E.
Title: Re: The official G9 help thread
Post by: audiophreak on January 21, 2009, 03:45:53 PM

  Thanks Jacob,
     
               another question... the input/phaze/high pass switches, I looked at the circuit board and looks like the "A" pole of a 4 pole switch goes to the upper right, looking at the pcb from the printed side, then noticed that the register pin was in the 12 O'clock position. is this correct positioning ?
             also I noticed that there are two pads marked " to light 12v 50mA" is this "DC" ?

  Thanks,
            Chip
Title: Re: The official G9 help thread
Post by: Didierterrific on January 21, 2009, 04:54:17 PM
Hi,
I have just bought G9 at second hand. and the input jack does not work.
Do you have any idea ?
thank you
didier
Title: Re: The official G9 help thread
Post by: RAM on January 21, 2009, 05:43:48 PM
               another question... the input/phaze/high pass switches, I looked at the circuit board and looks like the "A" pole of a 4 pole switch goes to the upper right, looking at the pcb from the printed side, then noticed that the register pin was in the 12 O'clock position. is this correct positioning ?
             also I noticed that there are two pads marked " to light 12v 50mA" is this "DC" ?


I can't remember the way the switch goes. If you have a meter then simply use it to make sure it is switching the connections properly. The 12V to the lamp is DC.


I have just bought G9 at second hand. and the input jack does not work.


Do you mean the DI input isn't working? Does it work when you hook up a mic to the same channel?
Rob


Title: Re: The official G9 help thread
Post by: audiophreak on January 21, 2009, 06:07:50 PM

  Jakob and Rob,

        Thanks so much, I'm sure I'll have more questions as the build continues.  ;D

   Thanks again,
                           Chip
Title: Re: The official G9 help thread
Post by: Didierterrific on January 22, 2009, 02:11:10 AM
To Ram

Yes the mic input is ok but the DI input doesn't work...
Title: Re: The official G9 help thread
Post by: Mbira on January 22, 2009, 02:53:30 AM
The 4 pole rotaries can go any direction-it's all the same.  didierterrific, If I were in your shoes I'd open it up and see if there is something obviously wrong with the jack-otherwise, you are going to need to trace the signal.
Title: Re: The official G9 help thread
Post by: Didierterrific on January 22, 2009, 03:34:16 AM
the switching jack is soldered in points From To and Ground ...
i'm a newbie in DIY !!!
haow can i trace the signal .
thank you
Title: Re: The official G9 help thread
Post by: RAM on January 22, 2009, 06:19:12 AM
In the G9 the mic signal goes through the jack and since the mic input is working it could be a problem with the way the jack is wired. Or, seeing as you bought it second hand, the previous owner may not use the DI so he could have cut the connection to it to avoid the oscillation at high gain. Given the fact that the mic input is working, whatever the problem is it's probably easy enough to fix.

A picture or two of the inside of the unit would help us understand what problem you're having.

Rob
Title: Re: The official G9 help thread
Post by: audiophreak on January 22, 2009, 05:39:42 PM

  Hi,
  Its me again...
         I read in a thread here somewhere that a Carbon Pot with DC voltage will deteriorate over time, and to use cermet or conductive plastic, but cant find any with a Log tapper as well as 47k

     Can I use a Linear tapper instead of a Log ?
     Can I use a 50k instead of a 47k

  or is carbon fine.

  Thanks,
           Chip

       
Title: Re: The official G9 help thread
Post by: Mbira on January 22, 2009, 06:14:22 PM
Just use a 50K log carbon pot or pay more for another kind.  log is important, type-not so much.  In 30 years when it goes bad, you can replace it.
Title: Re: The official G9 help thread
Post by: audiophreak on January 22, 2009, 11:21:55 PM
 Thanks Mbira !  :)
Title: Re: The official G9 help thread
Post by: Didierterrific on January 24, 2009, 09:38:22 AM
To Ram :
sorry for the late reply. I was in London to see Kings'X ... aaaaaaaaaaaahhhhhhhhh!!!!!!!!!!
So! yes the previous owner didn't use the DI...
i tried to connect a switching jack on the channel 1 but no sound.

I go back to my home this evening... i take pictures and send them to you.

thank you
Didier
Title: Re: The official G9 help thread
Post by: audiophreak on January 24, 2009, 05:26:30 PM
  Hi,
   Not sure where I lifted this image from, but is this the corrected way to hook up the power transfos ?
(http://<table style="width:194px;"><tr><td align="center" style="height:194px;background:url(http://picasaweb.google.com/f/img/transparent_album_background.gif) no-repeat left"><a href="http://picasaweb.google.com/audiophreeek/G9TransforHookup?feat=embedwebsite"><img src="http://lh4.ggpht.com/_VoN7bQ_xa2Y/SXuQ7IYtQlE/AAAAAAAAAOc/N-tRKCJ9XH8/s160-c/G9TransforHookup.jpg" width="160" height="160" style="margin:1px 0 0 4px;"></a></td></tr><tr><td style="text-align:center;font-family:arial,sans-serif;font-size:11px"><a href="http://picasaweb.google.com/audiophreeek/G9TransforHookup?feat=embedwebsite" style="color:#4D4D4D;font-weight:bold;text-decoration:none;">G9 transfor hookup</a></td></tr></table>)

Thanks,
          Chip
Title: Re: The official G9 help thread
Post by: Didierterrific on January 24, 2009, 06:07:01 PM
To Ram :
#1
Title: Re: The official G9 help thread
Post by: Didierterrific on January 24, 2009, 06:09:55 PM
#2
Title: Re: The official G9 help thread
Post by: Didierterrific on January 24, 2009, 06:11:16 PM
I hope it can help you ...
#3
Title: Re: The official G9 help thread
Post by: Mbira on January 24, 2009, 06:39:42 PM
please reduce the size of those images.
Title: Re: The official G9 help thread
Post by: Didierterrific on January 24, 2009, 07:34:00 PM
Like That ?
Title: Re: The official G9 help thread
Post by: Mbira on January 24, 2009, 07:49:14 PM
Yep.
OK.  Does the jack work on either channel?
Silly question, but are you sure you switched the rotary to "line" when you tested it?
Title: Re: The official G9 help thread
Post by: Didierterrific on January 25, 2009, 03:00:26 AM
The 2 DI inputs don't work.
yes, the rotary was switched to line when i tested it.
Title: Re: The official G9 help thread
Post by: RAM on January 25, 2009, 02:54:03 PM
I could be wrong but are those jacks switching jacks? Since the mic inputs are working: it seems like the jacks just aren't disconnecting the mic input if you plug in a jack connector to the DI input. I don't think there is really much that could be wrong.


Even if they are switching jacks it could be that it has just been wired wrong. The wires that should go to "from" and "to" may have been reversed.

Basically the switching jack should just be stopping signal coming from the mic/ line input. This obviously isn't happening. Or maybe it is, plug a line level signal into the line input, hook up th output from the G( so you can monitor the sound. Does the sound from the G9 disappear if you insert a lead into the DI input?

Here's a suggestion: with the unit off(and left for awhile to discharge) open it up and insert a lead into the DI input. Have a look at the DI connector. Part of the metal strip that the guitar lead connects to should be lifting up. Does this happen? which side of the metal strip on the DI jack does the wire from the "from" connection on the PCB go to? is it the longer part of the strip that lifts up when you insert a guitar lead into the DI jack?

Do you have a multimeter?

Rob
Title: Re: The official G9 help thread
Post by: Mbira on January 25, 2009, 03:01:09 PM
Like Rob said-first test.  Plug in a jack and retest mic input.  Does mic input work now?

Title: Re: The official G9 help thread
Post by: RAM on January 25, 2009, 03:11:12 PM
Sorry, as Mbira made clear, it wouldn't actually be necessary to use a line signal. Just hook up a mic, making sure you can monitor the signal. Tap it or talk into it, then insert a jack into the DI input. does the sound the mic is picking up disappear?

Rob
Title: Re: The official G9 help thread
Post by: Didierterrific on January 25, 2009, 03:39:53 PM
Yes the mic input is ok...
and when i insert a jack, the signal doesn't disappear
I tried to reverse the To and From but it's the same
Title: Re: The official G9 help thread
Post by: RAM on January 25, 2009, 04:26:07 PM
It may not be a switching jack then. If you have a multimeter: plug a lead into the DI, then check for continuity between "to" and "from".

Judging by your pictures, one of the channels doesn't have a DI attached at the moment. Is this the one you are working on? However what I'm thinking of may not matter seeing as you said both DI's aren't working.

I have one really stupid suggestion which I'm sorry for making: It looks like you're using TRS sockets as opposed to TS. It's fine because of the way you wired them: but make sure that the guitar lead is fully in. If it isn't inserted properly it won't cut off the connection from the mic input. (Sorry, it's an obvious one but could potentially be the cause of the problem)

Rob
Title: Re: The official G9 help thread
Post by: Didierterrific on January 25, 2009, 05:51:45 PM
So,
yes the second channel is not attached and i'm trying the first one.
and yes it's a TRS jack... then, it could be the problem !!!
i'm in Marrakech until thursday, I check back at home
i hope it's that !

thank you for your assistance & sorry for my english ...

Title: Re: The official G9 help thread
Post by: Mbira on January 25, 2009, 07:44:35 PM
Yes, as stated, if the jacks are actually hooked up correctly, when you physically put in a guitar cable, it should cut out the signal from the mic input.  You can safely assume that the jacks are either the wrong type or hooked up wrong.
Title: Re: The official G9 help thread
Post by: Didierterrific on January 30, 2009, 08:04:20 AM
Hi,
i came back !!!
I just soldered a TS switching jack and the problem is the same :
The signal from the mic input is not cutted when i insert a guitar cable in the DI
And no signal in the DI position
!!!


Title: Re: The official G9 help thread
Post by: RAM on January 30, 2009, 06:29:46 PM
Well you'll need to use a multimeter to check for continuity along the line from the input transformer to the jack. It's possible that whoever built the unit decided to eliminate the connections to the DI to prevent oscillation at high gains.

It's a simple enough problem and will be easy enough to find.


And no signal in the DI position


What exactly do you mean by this? ( I realise you aren't a native english speaker but please explain it as best you can). Do you mean that you just aren't getting input from a DI'd instrument? As the G9 doesn't technically have a DI "position" as there isn't a switch you turn to activate the DI (like you do for the line, Mic and +48).

Were the DI jacks wired up when you got the unit?

Rob
Title: Re: The official G9 help thread
Post by: Harpo on January 30, 2009, 07:58:47 PM
from your G9-Did-3-.jpg, exchanging the blue with the white wire at the tip of your TRS-plug (or at the from/to inst.jack spot at the pcb) might do the trick.
Title: Re: The official G9 help thread
Post by: Didierterrific on January 31, 2009, 02:53:08 AM
I have already tried to invert the white wire and the blue wire, it's the same.

when i bought the G9 there were not Jack inputs...
i soldered wires with TS switching jack on channel 1, but with a guitar cable insert in the jack input (the one i have soldered) and the rotary in line position. i have no signal.

i go to try to check for continuity along the line from the input transformer to the jack. I really don't know how to make that, but i'm gonna try.
Title: Re: The official G9 help thread
Post by: RAM on January 31, 2009, 09:59:13 AM
Since there were no jacks on it when you bought it, it would lead me to believe that whoever built it disconnected the wires or PCB traces,to prevent oscillation at high gains.

You could visually inspect the unit. But be extremely careful. Since you don't have a meter you won't know if the unit is fully discharged or not.Leave it plugged in, but turned off for 20 minutes or more. The G9 discharges quite fast but seeing as you don't have a meter you will want to give it a lot of time.

Then plug the unit out from your AC wall source.

You'll need to disconnect all the wires from the board that can be disconnected (no des-soldering required). Remove the tubes and screw that hold the PCB down. Lift the PCB to check if any of the traces from the input transformers, or others around that point, have been cut. Also see if there any additional wires on the underside of the PCB, that are bridging certain traces.

Obviously a multimeter might make this easier and would allow you to track down the problem faster. But it may be possible to solve the problem without one.

Rob
Title: Re: The official G9 help thread
Post by: Mbira on January 31, 2009, 03:00:54 PM
You know guys, we are talking about 245+ volts of DC.  Didleteriffic doesn't even have a multimeter, so I STRONGLY RECOMMEND that he just get someone with a little experience to take a look at the unit.  The G9 is a hard first build, and troubleshooting is always harder than building.  It should take a tech les than one hour to fix the unit.  THat is my recommendation.  Didlerterrific, this isn't meant as an insult or anything like that, just that inn\f you're into DIY, probably the best thing would be to start with somethingthat can't kill you easily.  Maybe you can evel look over the shoulder of the tech and learn what was wrong at the same time!

Good luck!
Joel

Title: Re: The official G9 help thread
Post by: Didierterrific on January 31, 2009, 06:43:16 PM
Don't worry !!!
i have got a multimeter. I know how to solder.I have build and wired my studio.
I am not electronics engineer. i'm a newbie in DIY but I have already modified small equipments as microphones or pedales.
I think have understood how to check the PCB.
tomorrow i 'll try to trace the signal and i'll inform you.
Thank you for your advices and your patience.
Title: Re: The official G9 help thread
Post by: RAM on January 31, 2009, 07:16:09 PM
Yeah I was a bit hesitant to suggest a visual inspection unless you have experience.There's no need for pride on this forum: we're all here to learn and share! The most important thing is to just be safe.

Be extremely careful when doin anything inside the unit. As Mbira said the G9 as a very high B+.

Just use your meter very carefully (with your unit switched off, no need for it to be on with what you need to check). Do you know how to check if the G9 is discharged? It's an important one to know, and best to learn it early on.

Good luck with finding the problem. And be safe! The G9 sounds awesome (thanks again Jakob!) you'll love this unit.

Rob
Title: Re: The official G9 help thread
Post by: tommypiper on January 31, 2009, 09:05:42 PM
I borrowed a friend's G9 to try it out.  Sounded great, very musical. 

But for acoustic music, I had to turn both channels and their output to full gain the whole time using an AKG 414 and a tube mic on a bashing acoustic guitar.  This seemed like very low gain for a relatively loud acoustic instrument and two hot microphones.

I'm interested in building one, but I'm concerned about the lack of gain.  It would never work with a ribbon mic on an acoustic source, for example. 

How much gain does the G9 officially have?  Is there a way to increase it?

thanks.
Title: Re: The official G9 help thread
Post by: gyraf on February 01, 2009, 03:35:12 AM
Officially, there's some 60dB available - which should cover most situations..?
Title: Re: The official G9 help thread
Post by: Mbira on February 01, 2009, 03:46:43 AM
I use a 414 here and I'd never need to crank it up all the way to get the gain needed for an acoustic.  There must be something wrong on that build...
Title: Re: The official G9 help thread
Post by: Didierterrific on February 01, 2009, 08:10:53 AM
To Ram and Mbira
Yes some traces have been cut and there are any additional wires on the underside of the PCB,  certain traces are bridging.

Here is a very bad photo of the pcb... it's a picture from my phone !

i found a mod on the Gyraf audio G9 page... i understood the problem.
I must remove the bridges of traces and running a length of shielded cable directly to/from the jack as explain in the mod.

can you confirm this?

thank you
Title: Re: The official G9 help thread
Post by: Didierterrific on February 01, 2009, 08:50:56 AM
yeah !!!! it's good... i think the problem is solved.
strange noises appear sometimes... like used tube in a guitar amplifier !!!

Title: Re: The official G9 help thread
Post by: RAM on February 01, 2009, 09:47:06 AM
That's exactly what I expected you would find.

Glad you got it sorted out! You should try DI'ing some bass through it. It sounds great.

What are the strange noises?

Oh and welcome to the wonderful world of DIY audio. You will be completely hooked from here on in!

Rob
Title: Re: The official G9 help thread
Post by: Didierterrific on February 01, 2009, 09:54:04 AM
Strange noises...
a high-pitched noise which hold and disappears...
Title: Re: The official G9 help thread
Post by: Mbira on February 01, 2009, 11:38:20 AM
That's probably oscilation-which is why the person did that mod...
Title: Re: The official G9 help thread
Post by: Didierterrific on February 01, 2009, 11:47:15 AM
what can i do ?
i have not oscillator ...
Title: Re: The official G9 help thread
Post by: Didierterrific on February 02, 2009, 11:52:57 AM
Hi,
 i closed the box. All is ok !!!
but i have always this noise... a little like a whistle
when I pat the box,a noise appears. And disappears in the same way.

can be that the tubes start to vibrate ?

i don't know
Title: Re: The official G9 help thread
Post by: junkmaster on February 16, 2009, 02:58:48 PM
hi everybody...i started a topic in the lab by mistake...so here i am where i belong.....but it  should be said that thanks to everyone's help, i'm hopefully very close to fiishing my g9 (minus a nice faceplate, though)....i was having some grounding issues, now solved! :)
i'm having another interesting little problem now....pretty sure it's not related to the main pcb or power supply, but maybe a wiring problem...specifically the switch pcbs....i will post pics tonight hopefully....i've tried swapping my switch panels out and have discovered that channel one is significantly louder than ch.2....along with that,the 'good' channel's line/mic/48v switch operates in reverse! the 'bad' quieter channel 2 operates just fine, except for the lower gain...channel one sounds amazing! (thank you jakob!)....but whether i put ch1 into ch2 of the main pcb or vice versa ch1 card is louder, sounds great and is backwards! i think the line input may always be on as well....
i haven't done the hf osc mod yet, so both channels top out at about notch 9 or 10 on the lorlins before the squeal, but that doesn't really bother me....i may not even do the mod just so i can use these lovely things....but....could the lack of the hf osc mod be somehow affecting the gain in ch2 and the backwards switching? or have i just soldered a switch in backwards? i've checked w/ my meter and it seems to be fine....
one caveat to this is that i have all the switches wired w/ the front tab at 6 o'clock, except for the line/mic/48 switches....but why would one work fine and the other backwards?!! ???
i think that's it for now and any advice is appreciated.....sorry to babble on....pics on their way soon...cheers, alex
Title: Re: The official G9 help thread
Post by: junkmaster on February 16, 2009, 04:05:02 PM
hopefully these pics load...
Title: Re: The official G9 help thread
Post by: junkmaster on February 16, 2009, 04:06:39 PM
more g9...
Title: Re: The official G9 help thread
Post by: Stagefright13 on February 17, 2009, 11:30:57 PM
Been a while since I built mine. But I cut the traces and ran shielded cable to the direct inputs from the get go. Using it on a project now and the drummer is flipping out cause he can hear his ride like a clock and his hat even over my wide guitar effect. Mine was set to track from LDC's at 50% gain and 27% Output. For drum overheads. And hit about -5 in Protools wich may be a bit high but ok for me.

So you swapped the front panel boards from left to right and you saw a change? Pull both front boards and compare them maybe you did something differently between the 2?

Your pics loaded fine

Check the resistor colors and orientation of the lorin switches. Hopefully I am getting what you are saying. The left channel works fine but when you switch the front panel boards your problem follows that board. I'll do my best but am an amateur...
Title: Re: The official G9 help thread
Post by: Stagefright13 on February 17, 2009, 11:40:53 PM
And Be Careful and stay away from the high voltage stuff!!
Title: Re: The official G9 help thread
Post by: gyraf on February 18, 2009, 12:27:26 AM
junkmaster,

Specially check that your input select switches are "programmed" right - that is, that the switch is turned completely counterclockwize before inserting the stopper pin washer.

Also double-check the sequence of cables between boards!!

Jakob E.
Title: Re: The official G9 help thread
Post by: gyraf on February 18, 2009, 12:27:45 AM
junkmaster,

Specially check that your input select switches are "programmed" right - that is, that the switch is turned completely counterclockwize before inserting the stopper pin washer at the needed position.

Also double-check the sequence of cables between boards!!

Jakob E.
Title: Re: The official G9 help thread
Post by: junkmaster on February 18, 2009, 10:44:27 AM
thanks for the insights folks...i will first try the pin-stop....i have been going through the resistors and everything seems ok....thought about just taking the harness apart and starting over completely on one or both cards....but the simplest way is usually best so i will report back after i get off work and havea chance to puzzle over it again....many thanks...alex
Title: Re: The official G9 help thread
Post by: junkmaster on February 18, 2009, 11:49:09 PM
hi all ......did the pin-stop thing and it fixed the gain discrepency.....brilliant simpicity thanks jakob....still channel one is backwards except for the gain knob...so close yet so so far..... i might just rewire ch 1 from scratch and see if that fixes it....it sounds great otherwise....just don't want to make a faceplate w/ one channel reversed! ill report back when i have time to go throug it again...thanks again, alex
Title: Re: The official G9 help thread
Post by: junkmaster on February 21, 2009, 01:55:29 PM
hi all....just ran through it again ....same issues...ready to re-assemble except for the mysterious line/mic/48v reversal....it's gotta be some thing simple....i desoldered the switch and tried it in different orientations and still the reversal.....checked and double-checked wiring harness continuity etc.....checked pcb w/ my loup over and over but don't see any bridging....checked resistors against other board ....should i just take it apart and rewire it again??.....so close........any thoughts appreciated....cheers, alex
Title: sigh, more g9 mysteries!
Post by: junkmaster on March 04, 2009, 03:52:16 PM
hi all...i did the oscillation mod which cleared up the feedback problem....also turns out i had a faulty lorlin switch which after rigging it so it would stop where it should seems to work fine..no more reversed line/mic48v problem.....but ch1 seems to be about 30% quieter than ch2...once again i swapped the switch pcbs, tried swapping input/output molex connectors,etc....ch1 still always quieter ???...ch2 sounds amazing tho! any ideas where i could measure voltages,etc and compare the two channels? i'd like to think this is a simple wirig problem but maybe i've blown something up w/ all my messing around....any thoughts much appreciated! cheers, alex
Title: Re: The official G9 help thread
Post by: audiophreak on March 04, 2009, 08:00:49 PM
Hi,

   I am at the point in my G9 build to cross my fingers and flip the switch. I admit I have not poured over the thread recently so if I have missed it I apologize. Is there a set of test procedures and test points to check voltages, I mean, I know the 245 and 15 and 12, but how about heater,cathode, plate and such? Also, I don't have a scope, but I do have a signal generator, are there test procedures to check high pass, noise floor etc.

   Thanks in advance,
                              Chip
Title: Re: The official G9 help thread
Post by: audiophreak on March 07, 2009, 12:34:24 AM

O.K.      so now I have spent the last 3 1/2 hours reading the G9 META and this G9 help thread and have found some test points and readings to check when I flip the switch.
 
  HOWEVER, I have not found ( or I have not comprehended correctly) the Info on hooking up the power transformers - I find this very confusing with the corrected transformers of one being 15vac and the other 12vac. Here is a graphic that I found.

    Here is how I interpret this :

    One 15vac secondary from T1 MAINS to 15vac on PCB next to 220va, the other 15vac to back feed T2 connected to 12vac secondary, Primary on T2 to 220vac on PCB.
   
       What feeds the 12vac on PCB - ( Black Arrow )
   
        Do I combine 15vac AND 12vac together at Black Arrow as sugested by the lines indicated by the RED arrows ?


   I apologize for my Newbeeness, but my head hurts  ???


   Please .... some one take pity on me.... :-[


    Thanks in advance


                              Chip(http://)

   
Title: Re: The official G9 help thread
Post by: audiophreak on March 07, 2009, 08:05:47 AM
Now that I've had some sleep, maybe I should give clearer Info   :-[

   T1 is 110 + 110/ 15 + 15,  and T2 is 110 + 110/ 12 + 12.  - the Black arrow indicates where the PCB is labeled 12vac.  I understand the " back feeding " or feeding T2 " the other way around " as in the G7 PSU, but then that wouldn't leave anything to feed the 12vac at Black arrow.

 OR  am I supposed to combine one 15vac form T1 and the 12vac from T2 at the 12vac point on PCB ( black arrow) as the graphic indicates?
Title: Re: The official G9 help thread
Post by: CurtZHP on March 07, 2009, 11:07:33 AM
If you go to the preamp page on my website (www.zerrohouseproductions.com) you can see the pictures of my G9 build.  There are a couple pictures showing how the power transformers are connected.  I used Amveco toroidials.

Basically, I took the secondary of the mains transformer (115V Pri -15V Sec) and attached the wires to two solder lugs located OFF the PCB.  At those solder lugs, I also attached wires to each of the points on the PCB that call for 15VAC.  Finally, I attached the 15V secondary of the tube plate transformer (15V - 220V).  If you don't have any solder lugs handy, you could just attach all the wires off board with wire nuts.

Basically, you're just taking the 15V secondary of the mains transformer and splitting it off to three different places:  the two points on the PCB, and the secondary of the plate transformer.

Note: If you use solder lugs, make sure they are COMPLETELY isolated from the chassis.  In my initial build, I made the mistake of using one that wasn't, resulting in the mains secondary being connected directly to ground.  An Amateur Hour mistake that fortunately only cost me a fuse.  Better yet, just use wire nuts. 
Title: Re: The official G9 help thread
Post by: audiophreak on March 07, 2009, 07:09:07 PM

  Thanks so much CurtZHP,

    But I am still confused, I'll explain....  If both transformers were still 15vac secondaries, I would not be confused and everything makes seance. But Gyraf changed transformers to one 15vac and one 12vac, and in the graphic I posted the 15vac that the black arrow indicates is now 12vac - Thats whats confusing me , do I use the other 15vac from T1 to backfeed T2 12vac  for 220 on T2? will I get 12vac from the other secondary on T2 to feed the 12vac indicated by the Black arrow?

anyone? :(
Title: Re: The official G9 help thread
Post by: Harpo on March 07, 2009, 10:51:22 PM
actually your black arrow is pointing to the left side. Draw this arrow pointing to the right side to see in what direction your T2 is fed.
The paralleled secondaries of your T2 connect to the feeding 15VAC secondary of T1 and get a 1:18.33 step up transformation as this transformer is connected backwards. This is not 12VAC in this spot, but a 12VAC:220VAC has a higher ratio than a 15VAC:220VAC transformer to get the increased target voltage.
Title: Re: The official G9 help thread
Post by: audiophreak on March 08, 2009, 04:42:40 PM

  Thanks so much Harpo,

     I think I have it now..  after reading you post and looking closer at the schematic. I think what was throwing me off ( besides the Newbeeness ) is that the PCB is printed 12vac at the black arrow so I thought that I needed to "Feed" 12vac TO there.

   So let me see if I have this right:

    One 15vac secondary from T1 FEEDS 15vac TO PCB near the 220vac on PCB
     The other 15vac secondary from T1 FEEDS the other 15vac at the Black arrow in the Graphic AND is Tapped to FEED the paralleled secondaries of T2 and the Primary of   T2 FEEDS the 220vac on the PCB.

   This makes sence to me.... is this correct?

    ;D
Title: Re: The official G9 help thread
Post by: Harpo on March 08, 2009, 04:50:52 PM
yes  :)
Title: Re: The official G9 help thread
Post by: audiophreak on March 08, 2009, 07:05:03 PM

  YIPPEEEE  !!!!!    ;D ;D ;D ;D

    Thanks Harpo and CurtZHP for taking the time.

       My G9 is done except for this and a nice face plate,  so tomorrow I will wire this up and flip the switch  ;)

  Thanks again,
                       Chip   ;D

 
Title: Re: The official G9 help thread
Post by: audiophreak on March 09, 2009, 03:28:31 PM

  Well.... I hooked it up.. I used a terminal strip and parralleled the secondaries of T1 to the terminal strip the branched out to both 15vac inputs on PCB and input to secondary of T2.
    flipped the switch and blew the fuse  >:(  , replaced fuse with correct value, flipped the switch, smoked D15 and blew the fuse  >:(

  checked the schematic and saw that D15 is traced directly to the power input for channel two supply from the 15vac on PCB, so I replaced D15 and the fuse and disconnected that 15vac to the PCB, flipped the switch..... no smoke .... did some checking and got:

  119.2 incoming AC
  16.8vac from T1 secondaries
  270.8vac from T2
  12.29 from indicator light feed
  240.8vdc from C14
  309.8vdc from C15

   I think these reading are all within spec. so I think my problem is isolated to channel two power supply

  ... any ideas/thoughts/suggestions ?

   





Title: Re: The official G9 help thread
Post by: Harpo on March 09, 2009, 04:04:12 PM
.. and parralleled the secondaries of T1 to the terminal strip the branched out to both 15vac inputs on PCB ..
there is a reason for dual secondaries. Why don't you wire this transformer as already described in your previous post?
Quote
One 15vac secondary from T1 FEEDS 15vac TO PCB near the 220vac on PCB
The other 15vac secondary from T1 FEEDS the other 15vac at the Black arrow in the Graphic
Title: Re: The official G9 help thread
Post by: audiophreak on March 09, 2009, 04:08:41 PM

I will do that tomorrow --  Thanks  ;D
Title: Re: The official G9 help thread
Post by: audiophreak on March 10, 2009, 07:17:44 PM

  O.K. ...... I think I fell out of the Newbie tree and hit every branch on the way down ...   ;D

  I finely got the power transformers hooked up correctly and all voltages look good, set the 48v with trimmer, no audio  :'(  forgot what color leads I used for the input and output jacks on the starquad shielded cable, fixed that,

  Channel two up and running, no occiation , no noise, all switches work correctly and sounds great !  ;D

   No audio on channel one  >:( 

  I think it maybe the input or output cables, I soldered them directly to the PCB, makes troubleshooting a pain, so I'm gonna order the Mollex connectors to make that neater and better for removing the PCB.

  I'm sure I will have more questions and I will try to be more thorrow before asking, so thanks for putting up with me.

 

 
Title: Re: The official G9 help thread
Post by: CurtZHP on March 10, 2009, 08:16:58 PM
Check and make sure you've soldered all the pins on the rotary switches, paying particular attention to the center pins.  When I first fired mine up, I had no audio on one channel and discovered that one of the center pins of the phase switch was never soldered.  Oops!

Relax.  If the thing worked perfectly on the first try, it would just make you paranoid.

 ;)
Title: Re: The official G9 help thread
Post by: audiophreak on March 10, 2009, 10:48:25 PM

  Ha Ha Ha... Thanks CurtZHP,  :D

   I think I did solder them all but i will defiantly check.

     Thanks
Title: Re: The official G9 help thread
Post by: junkmaster on March 11, 2009, 10:33:44 AM
audiophreak...i recently had a similar problem that left me puzzled for hour/days....i'm a newbie here too...and it turned out that my DI jack wasn't making contact on the shorting tongues...i clamped them together and bingo! just replaced the jack....just a thought...easy to try it...cheers, alex
Title: Re: The official G9 help thread
Post by: audiophreak on March 11, 2009, 01:52:12 PM

 
 Hi junkmaster ,

   Thanks for the tip, I didn't get a chance to check the DI inputs yesterday, so I did today and BOTH channels work !   :)

  so I guess my problem with Channel 1 is on the XLR input side, need a break for a few days anyway

 Question, I did the trace cut fix for oscillation and noise, so I just want to verify that with the trace cut fix, it doesn't matter what position the input selector switch is in because the " switching jack" takes care of that - correct?

  - also I read earlier in this thread about the relays making a clicking sound  when 1/4" jack inserted, mine do not, is that also a result of the trace cutting?

    all other switches work correctly, that 78s12 IC does get very HOT, I have a good large heat sink on it but the case top above the heat sink gets VERY warm, the case is vented top and bottom though.


  Thanks so much,
                        Chip

 p.s.  - CurtZHP  - that was " I'll Definitely check on that " - my spelling sucks  :o






 
Title: Re: The official G9 help thread
Post by: audiophreak on March 11, 2009, 05:44:45 PM
 
 O.K. ... you didn't think I could keep my OCD ass away from this for a couple of days ... did ya?

   after finding out the instrument jack worked on Ch.1, I knew it had to be on the input cable to PCB. I found that the insulation on the + lead had melted and shorted to ground, as well as, I broke the 0v trace to the relays trying to make sure there was no solder bridge between the XLR pads.   >:(

   So I scrapped off some trace mask and made a little jumper, then soldered the Input cable directly on the ground trace-0v,(+)-R3,(-)-R2-R4.

  It Lives!!   :D  and all works, Inst. w/relays, Mic, Mic +48,  Phase, Low Cut, Both Channels  !!! :D :D :D ;D ;D ;D


   I havent had a chance to put it through ALL the paces and let it burn in, but I did notice that with no input plugged in and the output to a crown D-75 to some old Marantz 3ways, there in a Humm with the Gain in any position, and the Output pot full Counter Clockwise, as I move the Output pot it gets quieter up to the Twelve O'clock position, then gets louder to Full Clockwise and as it passes from 12 O'clock to full Clockwise it changes to a Buzz instead of a hum ...

   Any Ideas ?   


  Thanks in Advance ,  I gotta get some sleep now




   
Title: Re: The official G9 help thread
Post by: junkmaster on March 11, 2009, 11:07:25 PM
audiophreak that's great ....seems we had similar problems w/ jacks and cable connections...i had to rewire my molex connectors a couple of times before i got the hang f it....in my very limited experience it seems to be mechanical faults that cause the most problems....i'll wait for someone better informed to offer you advice on the switches and the hum...good luck! alex
Title: Re: The official G9 help thread
Post by: gyraf on March 12, 2009, 04:50:06 AM
Quote
   I havent had a chance to put it through ALL the paces and let it burn in, but I did notice that with no input plugged in and the output to a crown D-75 to some old Marantz 3ways, there in a Humm with the Gain in any position, and the Output pot full Counter Clockwise, as I move the Output pot it gets quieter up to the Twelve O'clock position, then gets louder to Full Clockwise and as it passes from 12 O'clock to full Clockwise it changes to a Buzz instead of a hum ...

   Any Ideas ? 

Don't test with no input connected - at least plug in a shorted 1/4" jack to the front.

For noise/hum tests, also make sure that you de-balance correctly when going into unbalanced equipment.

Last - you need to know and relate to the levels you are working at: you can always have a lot of noise if you use high enough gain. The real test is if it's usable in your studio setup - and how it behaves there.

Jakob E.
Title: Re: The official G9 help thread
Post by: audiophreak on March 12, 2009, 09:08:01 AM

 Hi Jakob,

    Thanks for the insight !  and Thanks for making such a great piece of gear available to the community. I've only done a few Royer Tube Mods prior, although I have read that the G9 would not be a good first large project, I think I did pretty well, I had a ton of fun over the last few months and learned a LOT. also learned I have a lot to learn.  ;D
  Thanks to all that helped and all that post with their own experiences with their builds, it helped tremendously with avoiding some of the more common pitfalls.
   
           Photos to follow...


       Thanks again to all,
                                Chip
Title: Re: The official G9 help thread
Post by: sjekkih on March 13, 2009, 05:57:56 PM
Hi,

Would it be easy to make just one channel out of this? I still need all the tubes, or is the "B"-tubes channel 2 in a way? I don't understand how the signal from each channel don't get mixed :p The tubes seems common for both channels, but everything else is separated?

Hope anyone can fill me in, or anyone knows about a DIY 1 channel tube preamp. Thanks :)

Best Regards,
Vegard
Title: Re: The official G9 help thread
Post by: audiophreak on March 13, 2009, 11:26:56 PM
Hi All,
   
       My new G9 is AWESOME !!!!!!!!! :) :) :) :)

    I haven't recorded with it yet,..so I can not comment on this low frequency roll off stuff,but strait to an amp and speakers, this thing shakes the walls, plenty of smooth low end. I have a modest collection of Vintage tube and Diy'ed tube microphones and just the mics, through G9 to crown D-75 to old Marantz three-ways, the G9 ROCKs !

   Very very quiet, and the adjustability between the gain and output is very cool , you can " Dial In " some pretty cool tone, or Very Clean, or in between. The case gets VERY warm from the 78S12 heat sink - is it supposed to get this warm ?  I have let it Burn In over the last 36 hours or so, so no thermal shut down, but it does get very warm.

the only thing I need now is the nice face plate.

   Here is a link to pics of my build, my first large project.

     https://goo.gl/photos/dpxSrUpnvGHRzyhH9

 comments/questions welcome

    Thanks Jacob/Gyraf  Audio, Harpo ,CurtZHP,junkmaster, and everyone for helping me complete this very cool project.
                                                                                                                                                                         ;D ;D
Title: Re: The official G9 help thread
Post by: Stagefright13 on March 14, 2009, 03:05:52 AM
Don't worry about people trying to test it on analyzers. All the drum overheads on the CD I am making now are G9. And the drummer is freaking out. He said he never sounded that good. And he is understating that LOL. There is a pre for everything. But the G9 is on it's own. Use it where it belongs and it makes everything BIG. :)

BTW I didn't use any EQ on those tracks just 2 compressors...

And Congrats on your build!!!

John
Title: Re: The official G9 help thread
Post by: Stagefright13 on March 14, 2009, 03:13:59 AM
Wow that's one of the nicest builds I have ever seen! Great job!
Title: Re: The official G9 help thread
Post by: bpucekov on March 14, 2009, 04:01:02 PM
wooow that looks nice
Title: Re: The official G9 help thread
Post by: audiophreak on March 15, 2009, 12:26:32 AM
Thanks !    ;D

  I'm sure some of you can see, I was inspired by others who have posted pics of their builds, Thanks to all.

 I really love the way this thing sounds, and I had a lot of fun. I'll be tracking an acoustic Bass next week..DI and mic....I can't wait... ;) 
Title: Re: The official G9 help thread
Post by: 1954U1 on March 15, 2009, 02:12:16 AM
Congrats..
super-accurate building!

About the bass roll-off..

- I've verified that with OEP input transformers [thats not your case, you've Lundahl]:
50 Ohm input impedance is ok,
but if the impedance increase, there is a noticeable bass roll-off, starting at 200-300 Hz, using Mic/Line inputs.
With 600 Ohm input impedance, this roll-off is very big.

Other people are trying to improve the bass response focusing on output stage.

I for now I'm trying to better understand this issue, because I love so much the sound of the G9 [yes, its HUGE!],
and dont want to have bad impedance-related surprises in future,.

 
Title: Re: The official G9 help thread
Post by: audiophreak on March 15, 2009, 10:04:18 AM

Thanks !

Quote
I for now I'm trying to better understand this issue, because I love so much the sound of the G9 [yes, its HUGE!],
and dont want to have bad impedance-related surprises in future,.

 I too am watching this closely, I purchaced two G9 sets from Gustav and when buying the componants I got two sets of verything except case,audio and power transformers, so this outcome will influence the second build.

       Big Props to all those guys over there figuring this stuff out,

   Thanks again,
                       Chip
Title: Re: The official G9 help thread
Post by: mihailojocic on March 26, 2009, 08:11:50 PM
Hello,

my name is Mihailo. First of all I want to thank everyone in this forum, specially to you Jakob!!! I spend hours and hours building this beautiful thing and this evening I finished my first G9. Until now i never heard any TRUE TUBE mic preamp, so you can imagine how much I'm happy. My home studio is know almost complete. Just few more things. ;-) Lots of parts has been hard to find, but there is a good people in all parts of the world. Also I had all kind of HUM, BUZZ an..., but thanks to this forum and all of you, my troubles is gone now. I have one quiet TRUE TUBE preamp. WOW!!! :-) I would post my pictures but firs I must do some cosmetic stuff. :)

greetings from Serbia
Title: Re: The official G9 help thread
Post by: mihailojocic on March 27, 2009, 04:23:19 AM
And now question. :)

whether the quality of some parts, if exclude tubes and transformers, can directly affect the quality of sound?
Title: Re: The official G9 help thread
Post by: gyraf on March 27, 2009, 05:57:20 AM
whether the quality of some parts, if exclude tubes and transformers, can directly affect the quality of sound?

The other components, polyester capacitors and resistors can off course affect sound quality, but in real-life not by very much. The reason is that we use only polyester-type capacitors in the signal path, and these are order of magnitude better than electrolytics when it comes to variation in sound.

The electrolytics are only in powersupply - with the execption of the cathode DC bias bypass capacitor at the output tube stage. But at this point, it's influence on the units sound is marginal - even with it completely removed, there is just a slight change in the units' sound, which is why we think it's allright having it there, although it's technically part of the audio path.

Jakob E.
Title: Re: The official G9 help thread
Post by: mihailojocic on March 27, 2009, 10:44:52 AM
Thanks again Jakob,

I asked this because the capacitors that I used is from unknown manufacturer. Prior to soldering I checked all parts values and it was in the limits of tolerance. I used metal film resistors (1-5%). I am very setisfied but I wonder what the difference in sound would be that I used paper capacitors as audiophreak (I think this is the paper) or that I used a polyester blocks from trusted manufacturer (that is in my country hard to find) :-(

one more qouestion:

fantom power is on 48V, but when I plug microphone voltage drop to 42V. Is this normal?
Title: Re: The official G9 help thread
Post by: gyraf on March 28, 2009, 02:04:56 AM
yes, phantom is meant to drop with mic in - that's why the two 6K8's are there.

Title: Re: The official G9 help thread
Post by: Stagefright13 on March 28, 2009, 06:42:57 PM
Here's a sample of the G-9. All the drum overheads are G9. With no paralleled compression on drum buss yet. And no EQ on the G9. And also the bass guitar is G9 with a gentle plugin eq. Almost done mixing this. Hasn't been mastered yet and is just a low mp3 version...

Oh almost forgot it is Lundahls and Wimas and Gyraf!. And the Bass guitar went DI. Also I don't record with anything I am unsure of. After I screw around with a project I may use it or more frequently just wait 'till I know if or when it can or not go somewhere. G9 is a weapon. And I thank Gyraf again! He rocks.

John

www.stagefrightrecords.com/No Doubt.mp3 (http://www.stagefrightrecords.com/No Doubt.mp3)

Sorry it's not disco or classical. I don't go that way. At least at normal pricing LOL.
Title: Re: The official G9 help thread
Post by: mihailojocic on March 28, 2009, 10:10:50 PM
there is cheap but good toroid transformers here in Serbia

30VA is about 10 euro

http://www.trafco.co.yu/torusni.htm

if you have language problems just let me know :-)
Title: Re: The official G9 help thread
Post by: audiophreak on March 29, 2009, 12:56:06 PM

 
Quote
G9 is a weapon. And I thank Gyraf again! He rocks.

   I totally agree with Stagefright13, the G9 is awesome, I'm hearing detail and textures I haven't heard before. Mind you that I am VERY new to DIY and recording, I'm a live guy by trade.

Quote
I wonder what the difference in sound would be that I used paper capacitors as audiophreak (I think this is the paper)
     
   The Dynamicap,Auricaps, and Sonicaps I used are metalized polypropylene constructions, and put them in the areas I thought they would have the most influence,  I searched and searched, ( in all the wrong places )  for the corect values in WIMA, but couldn't find a source in the USA, in searching I found this article http://www.humblehomemadehifi.com/Cap.html and found that these caps rated the same or a little better than the WIMAs and  the cost was not that much more.
  Now I don't want to spark a discussion about caps, but I just got tired of trying to find the correct WIMA type,value and voltage rating, I figured that if I was going to spend all this time finding these caps, I might as well try some mildly exotics. when I checked into the other brands, the values and Voltage ratings were right there so I bought them.
   I have recently ordered a bunch of PCBs from Gustav, and am getting a couple more G9 sets, I now found THE WIMA site so I will build an all WIMA G9, as Jacob and Gyraf endorse, then I will have both flavors.

   Thanks again for the kind words guys, I hope one day to be able to contribute to this wonderful community, this is a great experience and I'm hooked for good now.    ;D


 
Title: Re: The official G9 help thread
Post by: flavio on April 04, 2009, 10:07:21 AM
Hello I have just finish to build my g9 pre, i have some little problem, the first is that I need the screening cans for the oep 262 trafo, and the other, more serious is that the channel 1 works lower than channel n. 2, I have try to change the position of the tube from channel one to two... but the problem remain... what I can do?

Thanks for all!!!

Flavio :-D

Title: Re: The official G9 help thread
Post by: mihailojocic on April 05, 2009, 05:38:06 PM
Hello I have just finish to build my g9 pre, i have some little problem, the first is that I need the screening cans for the oep 262 trafo, and the other, more serious is that the channel 1 works lower than channel n. 2, I have try to change the position of the tube from channel one to two... but the problem remain... what I can do?

Thanks for all!!!

Flavio :-D



Are you sure that all parts is in the good place? Check your OEP-s position than GAIN resistors on small PCB.
Title: Re: The official G9 help thread
Post by: Mike D on April 11, 2009, 07:26:47 AM
Here's a sample of the G-9

I like this track a lot. Thanks for posting it!
What were you using on bassdrum?
Title: Re: The official G9 help thread
Post by: mihailojocic on April 11, 2009, 09:30:34 AM
Some pictures of my first G9
Title: Re: The official G9 help thread
Post by: mihailojocic on April 11, 2009, 09:31:26 AM
one more
Title: Re: The official G9 help thread
Post by: mihailojocic on April 11, 2009, 09:32:10 AM
another  :)
Title: Re: The official G9 help thread
Post by: mihailojocic on April 11, 2009, 09:32:45 AM
and finally
Title: Re: The official G9 help thread
Post by: Stagefright13 on April 11, 2009, 11:09:57 AM
Excellent job!! Congrats!! What kinda caps are the blue ones?


Off topic but... Mike the kick is an Eisen 512 clone to a Drip La2a. The real mix has a sidechain on the bass compressor to bring it out better. Obviously the entire drum kit went thru the G9 in the overheads. And the band agreed to use NO samples so that's what they sound like... Bunch of great guys too. They recorded 14 song in total but can't upload a final mix. For obvious reasons.

John
Title: Re: The official G9 help thread
Post by: pstcho on April 13, 2009, 01:38:07 PM
hello, do someone have a solution to ad a second output on a g9?

completly separated, to be able to use the 2 output at the same time (1 for recording 1 for monitoring)

thank you very mutch for you help
Title: Re: The official G9 help thread
Post by: keefaz on April 13, 2009, 01:48:43 PM
I use a Y cable (one input, two outputs) for monitoring, it works just well :)
Title: Re: The official G9 help thread
Post by: pstcho on April 13, 2009, 01:52:16 PM
maybe i will loose a bit in quality no??

i will go to a A/D converter and to a old Dynamix Mixer
Title: Re: The official G9 help thread
Post by: keefaz on April 13, 2009, 01:56:32 PM
Why do you think that ? A wire has no sound, no distorsion, so you don't loose quality
Quote
i will go to a A/D converter and to a old Dynamix Mixer
So you will connect G9 output to 2 high impedance inputs, so no loss of bass either, try the Y cable :)
Title: Re: The official G9 help thread
Post by: pstcho on April 13, 2009, 02:01:44 PM
with an explanation it's credible  ;) then i'll try

thank you very mutch

but if someone one day have an electronic solution (transformer or op amp) it can be good

tomorow i'll record by this way

thank you
Title: Re: The official G9 help thread
Post by: mihailojocic on April 13, 2009, 03:32:34 PM
Excellent job!! Congrats!! What kinda caps are the blue ones?

Thanks! Blue caps are Siemens.
Title: Re: The official G9 help thread
Post by: audiophreak on April 13, 2009, 03:55:27 PM
 
 
Quote
Some pictures of my first G9

    Looks great !!  Congratulations !!
Title: Re: The official G9 help thread
Post by: mihailojocic on April 13, 2009, 06:08:22 PM
 
 
Quote
Some pictures of my first G9

    Looks great !!  Congratulations !!

Thanks, but it's nothing compares to yours!  :o
Title: Re: The official G9 help thread
Post by: Svart on May 01, 2009, 12:18:54 PM
I have another question about Input selection switch.

(http://freeweb.siol.net/gregcs1/lorlin.jpg)

so:

When switch is in it's first position I have connection between A and 1, and C and 7

When switch is in second position there is connection between A and 2, and C and 8

And finally with switch in it's third position I have connections between A and 3, and C and 9.

Is that ok?

I understand first and third position, when there is connection, but I don't see the point in second position where no connection is made. (maybe thats just the way it is  :grin:  :?:


I think I see this as a problem too.  Using a 2x6 lorlin, you don't get the right combination of switching. 
Title: Re: The official G9 help thread
Post by: Harpo on May 01, 2009, 02:02:33 PM
Pos. A-1 / C-7 = phantom engaged, line pad out of circuit
Pos. A-2 / C-8 = phantom off, line pad out of circuit
Pos. A-3 / C-9 = phantom off, line pad relay engaged.
A 2*6 lorlin does the same, just place the end-stop-washer to pos.3.
Title: Re: The official G9 help thread
Post by: dinesh on May 20, 2009, 10:45:03 AM
Hi,


I have a couple of OEP A262A1E transformers. Can I use these as Input Transformers in G9 Mic preamp, If I use these in reverse?

Title: Re: The official G9 help thread
Post by: fucanay on May 22, 2009, 04:08:43 PM
I'm using Purusha's G9 case and it has no place for a Mains switch on the front panel. I would like to find a decent illuminated push button switch that would work well on that panel. Does anyone have any ideas? And what would be the specs for this kind of switch to work with the G9?

I suppose I could just use an IEC power connector with a switch in it on the back, and then just put a light on the front panel. But switching the power on from the rear would be kind of lame.

Matt
Title: Re: The official G9 help thread
Post by: Stagefright13 on May 22, 2009, 11:24:03 PM
I try to switch all the power on the back with an IEC. Some things I don't have that option on. But If I can that's what I do. You can probably get away with running mains to the front panel. I just don't do it on purpose. I don't like to experiment alot on stuff like that. I like it to work and sound good.

My racks are powered by surge protectors. When I turn them on each rack lights up. Don't use the power buttons much on individual rack gear.

John
Title: Re: The official G9 help thread
Post by: fucanay on May 23, 2009, 03:19:06 PM
Very good point. I'll look into an IEC receptacle that has a switch and a fuse.
Title: Re: The official G9 help thread
Post by: microc on May 27, 2009, 08:54:36 AM
Hi guys,
I' soon ready to fire up my first G9 with a microphone, but I've got a problem:
The 245V is 296V over C15 and 289V over c14. I've checked all the components and tried to different TL783s'. Only one thing that I haven't tried: At one drawing D2 is a 1N4004, but in another drawing D2 is 1N4007. I use a 1N4007, could this course the high voltage?

thanks
Jens
Title: Re: The official G9 help thread
Post by: keefaz on May 27, 2009, 09:06:33 AM
Did you take voltage measurements with the tubes plugged in ?
Title: Re: The official G9 help thread
Post by: microc on May 31, 2009, 12:29:23 PM
I have changed R35 and R36 and the voltage is now finaly at 245V :D
I've tried the G9 on a mixer and it did hum alot with no gain or output, just like a guitar amp with a cable with no guitar :(. So I tried switch the gain switch, when it arrives at pos. 3 the G9 generates a sinus around 15kHz I guess, haven't checked with the scope.
ps both channels!  ???

thanks
Title: Re: The official G9 help thread
Post by: fucanay on June 03, 2009, 07:12:57 PM
I'm a little confused about the grounding scheme used on the G9 and want to make sure I have it right.

The way I understand it is that I need to have it connected to the chassis in one place, the input of channel 1 and that I should bridge pin 1 on the channel one input XLR to the little solder tab on the same XLR and that creates a chassis ground point. And then I also wire the Mains ground on the IEC to this point also. And because I'm visual I made this little diagram.
(http://fucanay.fischerworks.com/diy/g9_grounding.gif)


Does this look right? Jakob?

Matt

Title: Re: The official G9 help thread
Post by: fucanay on June 05, 2009, 02:05:12 AM
Ok, so no one is interested in G9 grounding. Well, other than the fact that I have the inputs in the wrong order on the board, I've determined that it is correct.

And other than putting in the tubes and getting a freaking fuse, I'm ready to turn this sucker on and hope for no sparks. Anyway, here are some pics.

http://fucanay.fischerworks.com/diy/G9/G9_1.jpg
http://fucanay.fischerworks.com/diy/G9/G9_2.jpg
http://fucanay.fischerworks.com/diy/G9/G9_3.jpg
http://fucanay.fischerworks.com/diy/G9/G9_4.jpg

I'll fix the diagram and leave it up once I've confirmed it works. well.

Matt

Title: Re: The official G9 help thread
Post by: PRR on June 05, 2009, 02:50:22 AM
> the little solder tab on the same XLR  ... wire the Mains ground on the IEC to this point also

Uh, not really.

Wall-power ground goes directly to chassis, shortest way, dedicated bonding point.
(http://i44.tinypic.com/vwy1pt.gif)

Look inside any Bee-ringer, PC power supply, etc. The IEC ground goes to a chassis stud a few inches away, and nothing else (maybe other chassis bonds) lands here.
(http://www.net-audio.co.uk/jpgs/303iec.jpg)

What you done will work. In fact I might not fix it. But in some moderately unlikely but possible situations, there may be a Safety Hazard.

As an unlikely case: if a fully-live 120V HOT wire hit the mike jack, the 200++Amp fault current could blow-up the mikejack lugs and mike cable, leaving the chassis fully hot.

What to do with pin 1 is controversial. Partly because many variations work most of the time. Since your PCB clearly expects pin 1 to arrive at the PCB, the way you did it (one pin-1 tied to nearest chassis lug) seems logical, and won't give trouble except in severe cases of interference or ground-loop, situations that small studios rarely run into.
Title: Re: The official G9 help thread
Post by: fucanay on June 05, 2009, 03:22:10 AM
Thanks PRR. I'm really trying to do everything right before I flip this thing on. The reason I did it the way I did was because Gyraf's site says:

- Connect 0V/Gnd to chassis at one - and only one - point: At the input XLR's.

- Connect the power ground from the power inlet to the ground at the input XLS's also.

I interpreted this as I have it drawn there. Now if this is not right, then I not only don't mind changing it, I'd be happy to. I am terrible at wiring and this is the best job I've done yet. So I want it to all be right, and neat. This is my first tube anything and I'm kind of afraid of it, especially the big caps. So the less messing around with it after power on the better.

Matt
Title: Re: The official G9 help thread
Post by: Kingston on June 05, 2009, 06:54:39 AM
fucanay,

in my G9 build, which has zero pin1 problem and no pin1 related hum obviously, I connected it like this image from PRR:

(http://www.net-audio.co.uk/jpgs/303iec.jpg)

Then connect one of the XLR input pin1 to that point in chassis also.


I have now used the same idea with another p2p two channel tube preamp and it works there as well. But in there due to very different p2p grounding layout, I connected both XLR input pin1 to that same chassis point.

[edit]


The above scheme isn't the only one, but the IEC connector chassis point always applies. In order to understand some of the rules on ground loops and current flow, there have been many threads in the past, but here is a more recent one with several quite enlightened points made.

http://www.groupdiy.com/index.php?topic=33819.0
Title: Re: The official G9 help thread
Post by: fucanay on June 05, 2009, 12:30:40 PM
Ok, so I will have two ground points. One for the mains ground, close to IEC jack. And one for the XLR pin 1 where it just bridges to the little solder tab on the shell of the XLR and therefor connects to the chassis. That should cover it. I see what PRR was talking about in terms of safety, so I see this as the best way to do it now.

On another topic, am I right that I should be using a 1 amp slow blow fuse on this thing? I am real close to firing this thing up and getting pretty excited about it. Probably early next week.

Matt
Title: Re: The official G9 help thread
Post by: fucanay on June 09, 2009, 01:31:18 AM
How bright are the tubes supposed to be when powered on? Even in the dark they are pretty dim. I have all the right voltages. I haven't actually tried any audio tests, so maybe I'm just worrying for no reason. Guess I'll go plug it in.

Matt
Title: Re: The official G9 help thread
Post by: fucanay on June 09, 2009, 04:15:17 AM
I guess I'm all done. Sounds amazing. No hum, no oscillation. Just pure wonderful sound.

Jakob,you are the man. Thanks to all who asked questions and figured out problems before I even started.

Matt
Title: Re: The official G9 help thread
Post by: fucanay on June 11, 2009, 01:43:51 PM
I have had only one actual problem on this whole build. The phase switch on channel 1 doesn't work right. In the "In" position, it doesn't do anything, but it works in the "Out" position. I haven't looked into it yet. but this part of the circuit is super simple, so it should be a quick fix.

I brought this thing to our rehearsal space last night and had my singer sing through it and it was amazing. Next time I'm going to feed it into some Pico compressors and it should be our go to vocal pre from now on. Still need to try it on snare and kick drums, but I love this thing so far. Much more than the fetboys I built.

Matt
Title: Re: The official G9 help thread
Post by: geetar_king on June 11, 2009, 02:31:55 PM
I have had only one actual problem on this whole build. The phase switch on channel 1 doesn't work right. In the "In" position, it doesn't do anything, but it works in the "Out" position.

I haven't built a G9 yet but it sounds like you could have your phase switch wired up backwards. Or maybe its an OFF-ON switch instead of ON-OFF? dunno.
Title: Re: The official G9 help thread
Post by: fucanay on June 11, 2009, 02:39:39 PM
I don't think it's possible to really put this thing in backwards, or at least I recall reading that. My guess, without having investigated it, is that I either have the Lorlin stop set wrong or I have a bad connection somewhere. I'll have it back open in a few days and see which it is. Either way, it should be a really easy fix.

Matt
Title: Re: The official G9 help thread
Post by: fucanay on June 12, 2009, 10:36:58 AM
Yeah, stupid me. I have to move the lorlin stop. I thought I had done them all, but I guess I missed one. 
 :-X
Title: Re: The official G9 help thread
Post by: as on June 15, 2009, 05:14:19 AM
Gyraf, Thanks for the circuit and for advice(councils). A fantastic sound!
(http://img-fotki.yandex.ru/get/3601/as-05.0/0_add2_efe49c54_L.jpg)

(http://img-fotki.yandex.ru/get/3500/as-05.0/0_add7_9dedcd61_L.jpg)

(http://img-fotki.yandex.ru/get/3601/as-05.0/0_add3_4a14f802_L.jpg)

(http://img-fotki.yandex.ru/get/3604/as-05.0/0_add5_c735f15f_L.jpg)

(http://img-fotki.yandex.ru/get/3503/as-05.0/0_adf4_109938be_L.jpg)
Title: Re: The official G9 help thread
Post by: Janou on June 20, 2009, 09:43:49 AM
Ok, so no one is interested in G9 grounding. Well, other than the fact that I have the inputs in the wrong order on the board, I've determined that it is correct.

 ;D Il really interested because i check the "best" method to do this with my Gyraf. I need to read the "point to point post"  :)

(http://fucanay.fischerworks.com/diy/g9_grounding.gif)
I think your color wiring is not the good one. Maybe i am wrong. Input in PCB is left to right : IN-,IN+,GND

XLR
1    Chassis ground (cable shield)
2    positive polarity terminal ("hot")
3    return terminal[2] ("cold")

(http://basstock.free.fr/tofs/gyraf/123.jpg)

... Can't wait to finish it  :-X
Title: Re: The official G9 help thread
Post by: fucanay on June 20, 2009, 12:19:17 PM
You are totally right. I need to fix that graphic all around.  I haven't revisited it because it all worked with now hum or oscilation on first power up. I'll try to do the final version soon.

Matt
Title: Re: The official G9 help thread
Post by: Janou on June 21, 2009, 02:29:07 PM
Just to be sure, no way to use a input instrument stereo switchcraft for the oscillation Mod ?

(http://www.guitarpartsonline.com/images/electronics/switchcraft_jack_1_4_stereo_b29644.jpg)

(http://basstock.free.fr/tofs/gyraf/120.jpg)
Other query is about jack output. I see a lot of standard cable ( XLR to jack ) with ground and - together. Do i need to add a switch to do this and select if i need to connect theses wiring to use jack ? I have no idea about this...
Thanks
Title: Re: The official G9 help thread
Post by: thelabyrinth on June 25, 2009, 05:16:50 PM
Hey guys...Having a tough time with rotary switches here. Anyone have a part number available from Digikey or Allied or any other distributer? Thanks.
Title: Re: The official G9 help thread
Post by: gregcs1 on June 27, 2009, 08:48:19 AM
Hi guys!

I'm having problems with power transformers. When they're connected, the first one (220V from the mains) runs very hot, and g9 doesn't turn on.

This are my transformers.

http://picasaweb.google.si/lh/photo/uwhU56v35SUBTYX4wjLK1A?authkey=Gv1sRgCNjc_I2Z1oDtvQE&feat=directlink
http://picasaweb.google.si/lh/photo/lH6EHiE767gR_nlkrIizww?authkey=Gv1sRgCNjc_I2Z1oDtvQE&feat=directlink

trasnlation of marks on toroid picture:

Prim: Črna-Black

Sec: Rdeča-Red
       Bela-White (it was white and conected together, then i took off white isolation and stripped the wires, so now they are raw copper (laquered)


I connected them (trafos itself) to 220V, and this is what i get:

15V on 3&4
15V on 5&6

There is no voltage between 3&5 or 4&6

If i get it all right, then (in my case) 3&6 and 4&5 of T2 must be connected togetger and they run to 15V connector (3&6 to one pin, and 4&5 to another) when there is also connection from one of secundars of T1? When i did that, i get some sort of shortage, and transformer got very hot.
Title: Re: The official G9 help thread
Post by: rodabod on June 27, 2009, 08:55:10 AM
Other query is about jack output. I see a lot of standard cable ( XLR to jack ) with ground and - together. Do i need to add a switch to do this and select if i need to connect theses wiring to use jack ? I have no idea about this...

Do you want an unbalanced output? If so, just use a mono jack socket with cold tied to ground. If you want balanced, use a stereo jack socket. If you want both, use a stereo jack socket, and when you want it to be unbalanced, use a mono (TS) jack in the socket at the G9 to cause the cold to be shorted to ground.
Title: Re: The official G9 help thread
Post by: gregcs1 on June 27, 2009, 09:45:42 AM
Forget about my previus post. It's working! I was watching audiophreak's trafo wiring picture, and it's wrong! I hook'd it another way and it's working. There is connection between those secundars leads which in normal mode doesn't produce 15v.
But i have another question. How much must tubes glow? I thaught they will glow like christmas tree, but they produce very little ammount of light. (pics later)
And another thing: Can someone please give me a summary of voltage measure points (and maybe advisable values) . Everywhere i read, there is always written: "measure voltage here, measure voltage there"), but where is other (minus) point of measuring? Ground?

Thanx, and greetings.
Title: Re: The official G9 help thread
Post by: idylldon on June 27, 2009, 12:02:44 PM
How much must tubes glow? I thaught they will glow like christmas tree, but they produce very little ammount of light. (pics later)

The heater glow is just a mellow kind of orange light.  It's not bright like a Christmas tree. 

Quote
Ground?

Yes.  All voltage measurements are in relation to ground unless you're measuring something like voltage drop across a resistor.  What you're looking for, though, is voltage between the test point and ground.

Cheers,
--
Don
Title: Re: The official G9 help thread
Post by: audiophreak on June 27, 2009, 12:04:48 PM
  Hi gregcs1

   Sorry for the confusion, I was trying to figure out the wiring myself, copied someone else s  diagram and and modified it cus I couldn't wrap my head around the 15v and 12v thing  , not realizing that the 12v was only for the HT the other way round.  ::)

   I,m not sure how or if I can remove it from this post as to not confuse anyone else, but I will try.

 
Title: Re: The official G9 help thread
Post by: gregcs1 on June 27, 2009, 06:35:53 PM
There is no need to remove pics. They're very helpfull. Just twist the wires of one secundar on T2. Then it will be ok.
Title: Re: The official G9 help thread
Post by: gregcs1 on June 27, 2009, 10:19:41 PM
OK. I had a little of spare time, and connected my Sansa Clip (actually is wife's  :) ) and played some music through both channels. It plays like heaven (even on my Truth B2031A  ::) ). The only thing that bothers me, is some kind of electric hum (buzz), which is present all of the time. It is quite noticable/disturbing when nothing plays. Changing gain and output levels is effectless on volume of this buzz (ok, on last three highest gain positions and output level crancked to max, new buzz/hum/hiss appears - is that normal?) But that electric buzz stays the same. It stops only when i disconnect G9 (so it's not behringer fault) I moved everything that is movable (trafos, in/out wires...) but buzzing remains and it doesn't change a bit, when i'm moving things around. The only thing i can't move are HT reservoir caps, and IC2 (which is mounted on heatsink on the back plate and connected with 2inch long wires - could that be a problem?).
Title: Re: The official G9 help thread
Post by: gregcs1 on June 28, 2009, 06:56:08 PM
I figured out, this might be some sort of a ground problem. I connected both direct ins, and mic on channel two. With no signal,  and gain&out on max settings, there is buzz on both channels, which is quieter if i touch the case or mic. Any thoughts?

pics for help:

http://picasaweb.google.si/lh/photo/5vxOHB9wRp1IEMCENcZZ1A?authkey=Gv1sRgCNjc_I2Z1oDtvQE&feat=directlink

http://picasaweb.google.si/lh/photo/ZWPJeMwGupKx2hxE7NsVRQ?authkey=Gv1sRgCNjc_I2Z1oDtvQE&feat=directlink

http://picasaweb.google.si/lh/photo/NMKhVn_kuoVClGSK4iwDYw?authkey=Gv1sRgCNjc_I2Z1oDtvQE&feat=directlink

http://picasaweb.google.si/lh/photo/tv_37CLJby3xZqOXWIc5pQ?authkey=Gv1sRgCNjc_I2Z1oDtvQE&feat=directlink

http://picasaweb.google.si/lh/photo/XHCQpJAi7aDZCn7g3bI90g?authkey=Gv1sRgCNjc_I2Z1oDtvQE&feat=directlink

http://picasaweb.google.si/lh/photo/e0mm1FJRt-5tc9KXtWQGaQ?authkey=Gv1sRgCNjc_I2Z1oDtvQE&feat=directlink

http://picasaweb.google.si/lh/photo/gQbIutg0L_oaG20xvLYeog?authkey=Gv1sRgCNjc_I2Z1oDtvQE&feat=directlink

http://picasaweb.google.si/lh/photo/p0gCA9DkZ3XNYyIyatXJZQ?authkey=Gv1sRgCNjc_I2Z1oDtvQE&feat=directlink

Title: Re: The official G9 help thread
Post by: idylldon on June 28, 2009, 08:04:38 PM
I figured out, this might be some sort of a ground problem.

Double check to make sure you followed the recommended grounding scheme.

BTW, I would put some heatshrink tubing on the legs of the regulator attached to the large heatsink on the back panel.  While I understand that the camera angle might be exaggerating how close they are to the heatsink, it might be good to have them insulated just in case you bump into them while probing around.

Cheers,
--
Don
Title: Re: The official G9 help thread
Post by: sethyrish on June 28, 2009, 10:02:37 PM
It looks like you have all your XLR grounds connected. My understanding is only pin one to board input of first channel is connected by it's grounding tag, then through case to fixed ground connection. See page 29. That's what Ive done and it's quiet. Let me know if I'm wrong.
Title: Re: The official G9 help thread
Post by: gregcs1 on June 29, 2009, 12:36:32 AM
BTW, I would put some heatshrink tubing on the legs of the regulator...

Angle is really exaggerated, and legs are even bent away from the heatsink, so bythemself they can never touch it. But just in case, I will heatshrinked them. You never know...  :)

It looks like you have all your XLR grounds connected. My understanding is only pin one to board input of first channel is connected by it's grounding tag...

I'll try that as soon as i get home from work. Should I scrape the paint away at the place where ground is attached?
Title: Jensen trafo
Post by: crystal on June 29, 2009, 04:47:36 AM
After reading all the positive stories about this pre-amp I decided to start building one. There is one thing though. I have two jensen transformers that I have spare from another project.

Output Trafo:
JT-10k61-1M
http://www.jensen-transformers.com/datashts/10k611m.pdf

Input Trafo:
JT-115K-E
http://www.jensen-transformers.com/datashts/115ke.pdf

Can these be used in this design? I know they won't fit the PCB, but thats not a problem since I am designing a new PCB myself.
Title: Re: The official G9 help thread
Post by: sethyrish on June 29, 2009, 10:42:13 AM
I finally finished my G9. I’m so pleased with my new found hobby that I went out and bought a new Hakko soldering station to celebrate its completion…..damn.  So thanks Jakob and Gustav and everyone else on this forum that made it possible for someone with limited experience to put something like this together. I’m sure people can see some of their own handy work such as audiofreaks recycled CPU heat sink and matta’s single toroid adaption so thanks for the input and great photos. The last thing I did before firing it up was to remove the solid core lightning bolt earthing system I had arranged. After reading the posts by fucanay and PRR.  Hopefully I’ve added something to the forum with some basic info on etching your own face plates.
http://www.groupdiy.com/index.php?topic=33056.0
(http://members.iinet.net.au/~tinasime/pro/IMG_G9.jpg)
Title: Re: The official G9 help thread
Post by: gregcs1 on June 29, 2009, 03:48:04 PM
WOW! Very neat! Congratulations.

Back to my problems with hum. Done some more testing with ground connections (btw - idylldon, i fixed that regulator legs isolation). I removed ground connections from all xlr's because this removed hi-gain hum. I tryed all variations of connecting ground, but sound is much clearer without ground. However, that electric buzz remain. Then i connected G9 to my Motu 828 mkII, and buzz disappeared! Now explain that!
Title: Re: The official G9 help thread
Post by: idylldon on June 29, 2009, 08:21:27 PM
WOW! Very neat! Congratulations.(btw - idylldon, i fixed that regulator legs isolation).

Excellent!  I've learned this lesson the hard way.  ;D

Quote
I removed ground connections from all xlr's because this removed hi-gain hum. I tryed all variations of connecting ground, but sound is much clearer without ground. However, that electric buzz remain. Then i connected G9 to my Motu 828 mkII, and buzz disappeared! Now explain that!

Have you followed the exact grounding instructions mentioned earlier in this thread?  Also, you mentioned:

Quote
Should I scrape the paint away at the place where ground is attached?

I see your grounding point is a long machine screw that also holds your caps in place, right?  Is this screw making a good connection to the case; that is, have you scraped the paint under the head of this screw?  You've checked continuity on all your ground with an ohmmeter?  

Cheers,
--
Don
Title: Re: The official G9 help thread
Post by: sethyrish on June 29, 2009, 10:03:40 PM
Have you tried this yet? Also, I think I read if the leads to 78S12 are to long it can cause problems. Other than that I'm not sure.
(http://members.iinet.net.au/~tinasime/pro/vwy1pt2.jpg)
Title: Re: The official G9 help thread
Post by: riggler on June 30, 2009, 08:00:59 AM
In regards to the Jensen JT-115-KE, it should work, but looking at the schematic I'd add ~150K 1/4w resistor from the ground rail to the top side of the secondary to provide proper loading for it. Should sound great and I am planning on trying these instead of the Lundahl's I have in mine.

For Line out, go ahead and try the JT-10K-61-1M. Increase C13, maybe to 20-30uF. Please let me know if you do these, if it sounds wonderful I will try them too. I like my Lundahls but want a little more color. I am also going to get some Mullards...
Title: Re: The official G9 help thread
Post by: RAM on June 30, 2009, 08:19:26 AM
With my G9 I grounded all of the pin ones as soon as possible. Straight to the chassis with wires about 2-5 cm or a little more and it's extremely quiet. If you haven't already tried it: try turning the toroid to remove some of the hum.

Rob
Title: Re: The official G9 help thread
Post by: gregcs1 on June 30, 2009, 09:06:02 AM
One of the hums disappeard when I removed ground from inputs/outputs. There is still that brum when it's working in standalone mode (out to monitors) which totally disappear when G9 is connected to Motu 828mkII, and one barely noticable buzz on channel two, related to longer direct in cable, which runs too close to psu part. I will fix that in future (problem is only on highest gain&volume). As said, buzz is there only in standalone mode, recordings are clear as they should be. Could go something wrong if there is no ground on input?

btw... observation on brum: when i turn the unit on, it's silent, then (about 10s) it gets louder (but not disturbing in any way)
Title: Re: The official G9 help thread
Post by: audiophreak on June 30, 2009, 10:43:42 AM

 .. sethyrish..  WOW.. :o :o

  That's one beautiful G9 !  That face plate is absolutely stunning, clean work, you should be very proud.  Thanks for the shout-out on the CPU heat sink, so happy to have inspired someone, as I have been inspired by so many in this forum.

... after finishing such a great piece of gear..... watchya gonna build next !!!   

   
Title: Re: The official G9 help thread
Post by: fucanay on July 01, 2009, 12:44:49 AM
Have you tried this yet? Also, I think I read if the leads to 78S12 are to long it can cause problems. Other than that I'm not sure.
(http://members.iinet.net.au/~tinasime/pro/vwy1pt2.jpg)

Other than the fact the the color coding for the wires is wrong in that drawing, yes, that is how I grounded mine. I also did the oscillation mod for the DI jack before I fired it up. This thing is dead quiet. The leads from my 78S12 isn't short either probably 5 inches to reach the head sink that is mounted to the rear panel.

Matt
Title: Re: The official G9 help thread
Post by: sethyrish on July 01, 2009, 03:47:05 AM
Thank's audiophreak. I've almost got all the stuff for mnats ver A 1176. How about you?
Title: Re: The official G9 help thread
Post by: Stagefright13 on July 01, 2009, 04:12:25 AM
I have a thoroughly busted in Mnats Rev A. And is top Class! But this is the G9 forum. I heard the CD after I sent it for mastering and the drummer is freaking out. I used the G9 for overheads. No samples of that not even on my site...
Title: Re: The official G9 help thread
Post by: audiophreak on July 01, 2009, 06:44:25 AM

    sethyrish .... I have been working on a pair of G7's for about 10 months now, it slowed down because I had to out source some  tasks ('cus I just dont posses thoughs skills ) so started  a pair of GSSL's, and about 1/2 way into another G9 with the ecc88 output stage and different output Trans. - yeah......I fell hard in to DIY  ;D

  Stagefright13 ... if you don't mind sharing.... what mics were used as the overheads?
Title: Re: The official G9 help thread
Post by: audiophreak on July 01, 2009, 07:04:33 AM
  and just to be clear, no matter the outcome of the second G9, the first one stays " AS IS "     'cus it sounds feak'n  fantastic !
Title: Re: The official G9 help thread
Post by: Janou on July 08, 2009, 02:12:07 PM
Thanks for all informations, and thanks Jakob and Gustav  ;)

It work great, only think i'm not sure at 100% is the wirring below. I use mono jack with this...
(http://basstock.free.fr/tofs/gyraf/142.jpg)

Other pictures now, it's normaly finished  ;D

(http://basstock.free.fr/tofs/gyraf/164.jpg)
(http://basstock.free.fr/tofs/gyraf/171.jpg)
(http://basstock.free.fr/tofs/gyraf/178.jpg)
(http://basstock.free.fr/tofs/gyraf/177.jpg)
Title: Re: The official G9 help thread
Post by: Morrow on July 08, 2009, 06:03:24 PM
I've been going through the thread and searching, but I can't find an answer to this (though I hope I didn't just miss it):

At Position 11 (highest gain) on ONE of the channels, the gain actually decreases, and there is a pop. Both channels seem to function perfectly and identically up until that point.

I replaced the switch, measured R11-R14, and swapped the tubes as well as C7, but no change. Any ideas?

Thanks, I love the sound of this guy!
Chris
Title: Re: The official G9 help thread
Post by: Morrow on July 08, 2009, 06:35:05 PM
Oh, also I checked the continuity of the wire going from C7 to R12 and it was good. While I was in there, I reheated a bunch of the joints in that neighborhood with the iron in case of cold solder joints. Still no fix.
Title: Re: The official G9 help thread
Post by: audiophreak on July 24, 2009, 06:07:32 PM
Hi All,
        Sorry to butt in, I finished my G9 6 months ago and am extremely happy with it. Just today I was listening to a CD thrugh it and at some point the low end on the right channel dropped out  :o  there was no indication of something wrong, no noise or pop, just I noticed that there was something missing, and when I checked it out, no bottom end on the right channel, signal was coming out, just no bottom end  :'(   swapped outputs and it followed, so its not the amp or speakers.

   The unit is and has been in a rack, so I don't think anything got jostled.

   any thoughts on were I might start to trouble shoot this ?


    Thanks in advance,
                               Chip
Title: Re: The official G9 help thread
Post by: 1954U1 on July 24, 2009, 07:20:39 PM
Have you tried with the DI?
If using the DI there is bottom end, and your input is an OEP, maybe your transformer has been magnetized by some DC [coming from the CD player?].
It happened to me with a 1176's input OEP feeded by dirty synths.
[edit]to demagnetize it: 0-3V 3V-0 sine at 30Hz[/edit]

I'd try also to swap tubes.
Title: Re: The official G9 help thread
Post by: audiophreak on July 24, 2009, 09:52:30 PM

     Thanks ... 1954U1 ..

        I was leaving my office when I noticed this, had no time to start digging in, I will definitely check out the DI input and I was also thinking about the tubes. I wont get back till Monday, I'll report back what I find.

    Thanks again,
                       Chip
Title: Re: The official G9 help thread
Post by: sjekkih on July 25, 2009, 08:47:47 AM
Hi! I have a question about the sound of the G9. I finished mine a couple a days ago and was hoping to get the tube sound like on old rap vocal recordings (mid 90's, NAS, Jay-Z). I know they have a tubepreamp (maybe alsp a tube mic) and set the gain so high that the tube clips and unlike transistors it creates a warm distortion sound, rather than the clipping sound in transistor preamps.

Anyways I can't get my G9 to make this distorition. I have a condenser mic, not a tube mic, will I need that too? Is the gain on the G9 to low, or must it be a class A micpre? This DIY preamp says it can create a distortion when driven hard, and is class A. (http://www.soundskulptor.com/uk/mp66.html) (http://www.soundskulptor.com/uk/mp66.html (http://www.soundskulptor.com/uk/mp66.html))

I would like to color my recordings a lot, harmonics, distiortion etc. can I do this with my G9? Change som resistors or something?

Best regards,
Vegard
Title: Re: The official G9 help thread
Post by: flintan on July 25, 2009, 11:24:18 AM
Have you tried cranking the first gain up high with the second set low?

You could  build a pad to put after the out transformer. http://www.csgnetwork.com/decibelattenuatecalc.html

Or maybe you could put another pot before the transformer, after C13. I have not finished my G9 yet so i can't say what is the best or how it would sound.
Title: Re: The official G9 help thread
Post by: 1954U1 on July 25, 2009, 12:37:50 PM
The G9 isnt made for big saturation effects, its always clean.
It seems like you want some real distortion.. so you can try a design without NFB loop.
See this thread:
Preamp that saturates vocals/Instrument on loud passages (http://www.groupdiy.com/index.php?topic=34649.0)
Btw the MP66 SoundSkulptor pre is based on the circuits that you can see on this thread, e.g. the Gates and the NYD one-bottle pre no-feedback versions.
Note that you must be logged to see the attached schematics of NYD 1bottle versions.

Back to the G9.. quickly looking at the schematic, dont know if I'm saying total BS, but I'd try to increase the R10's value, maybe that will lower the NFB loop, thus increasing THD.
If that works, you can add a pot in series to R10.
Title: Re: The official G9 help thread
Post by: sjekkih on July 26, 2009, 04:53:06 PM
Yes I tried setting the gain at max and the out low, but the G9 is too clean :p

I will try changing R10. I understand the NFB loop consept now, but what is this talk about pads and pots at the output transformer?

BTW, is there a big difference between a tube mic and a regular condenser one?

Thanks for the guidance ;)
Title: Re: The official G9 help thread
Post by: stanz on July 26, 2009, 06:36:59 PM
Noise issues with new input transformers.    >:(

In trying to improve the low end for my G9, I swapped out my input transformers from an OEP to an Edcor XSM600/15k. Before, it sounded great with no noise problems at all. I simply mounted the transformers to the side of the chassis nearest the previous loctation of the input transformers on the PCB. First I patched it in with a twisted pair, then went to a shielded cable, but both yield a very noisy pre amp. I have pretty much narrowed it down to the transformers. Unplugged the input cable from the board, but it is still noisy. As soon as I plug a cable into the inst jack, it is silent as one could hope, and plays a bass fine, as one would expect. The only thing between these two pints in the circuit is the relay for the line/mic/48v sw, and the transformer. Ther cable run from the circuit board to the transformers ar about two inches. I did not connect the shield to anything, but I did hook them up to a clip to try and see if grounding them would help. No luck.

The transformer is a center tap on both Pri and Sec, so I just hooked up the outer leads (1&4 5&8) to the + & - side of the respective pri and sec holes on the PCB. The transformers are a lot bigger than the OEP. Not sure if that is an issue or not.

Transformer specs.
http://www.edcorusa.com/Products/ShowProduct.aspx?ID=329 (http://www.edcorusa.com/Products/ShowProduct.aspx?ID=329)

Any ideas what I might have missed.
Title: Re: The official G9 help thread
Post by: audiophreak on July 27, 2009, 09:46:58 PM
Hi All,
         I started to troubleshoot my G9 today, sent CD audio in thru front directs and everything sounded fine, then for the hell of it, I went thru a pair of IMPs and the xlr inputs as before, and it also sounded fine ...after letting it play for an hour or so, the low end must have dropped slowly out of the right channel again.  >:(

    I swapped output tubes and both channels sounded fine again, let it play for 3 more hours, still sounds fine. ::)

  I'm thinking it might be the right ( now left)  output tube as the low end just kind of slips away but not sure, could I be loosing a cap? I guess I'll have to wait till it does this again, and I hope it does, because I cant stand not being able to find the problem, and the unit not reliable.

  anyone have any ideas?

    Thanks,
               Chip
Title: Re: The official G9 help thread
Post by: stanz on July 28, 2009, 12:24:53 PM
So, in doing some digging around, is the edcor XSM a suitable input transformer? Is this transformer susceptible to noise due to lack of shielding?
Title: Re: The official G9 help thread
Post by: 1954U1 on July 28, 2009, 01:15:51 PM
Hi All,
         I started to troubleshoot my G9 today, sent CD audio in thru front directs and everything sounded fine, then for the hell of it, I went thru a pair of IMPs and the xlr inputs as before, and it also sounded fine ...after letting it play for an hour or so, the low end must have dropped slowly out of the right channel again.  >:(

    I swapped output tubes and both channels sounded fine again, let it play for 3 more hours, still sounds fine. ::)

  I'm thinking it might be the right ( now left)  output tube as the low end just kind of slips away but not sure, could I be loosing a cap? I guess I'll have to wait till it does this again, and I hope it does, because I cant stand not being able to find the problem, and the unit not reliable.

  anyone have any ideas?

    Thanks,
               Chip

Thats weird.. erratic malfunctions are the worst.
if its still the same ch also after swapping tubes, maybe its a leaking cap  C2/C3/C4/C5/C10/C13..
At this point, if I were you I'd start desoldering the caps, both channels, searching for differences [leaking?],
then resolder all of them with inverted channels.
So at least you'll know if its a cap.

Keep us informed!

Title: Re: The official G9 help thread
Post by: shabtek on July 28, 2009, 02:10:40 PM
@stanz, xsm are  rated 2.5 watt (line level) but may still be usable . edcor does offer mic input transformers; mx series. I have no experience using either as a mic input transformer. shielding may be an issue, try different positioning.
Title: Re: The official G9 help thread
Post by: gemini86 on July 28, 2009, 04:03:20 PM
I've been thinking about using edcor iron as well, shielding them with some diy moly sheet cans. Anyone tried them in the g9 yet? I'm going for a budget build here and the price is about right... :D
Title: Re: The official G9 help thread
Post by: audiophreak on July 30, 2009, 06:40:53 PM
Hi All,
    Well..... it happened again, no low end on the right channel, so I swapped input tubes this time, was o.k. for awhile, then no low end on the right channel again  >:(
I noticed that when I power down the unit for a minute then fire it up again, the low end comes back, so I listened to the right channel only to see if I could hear exactly when and how the low end goes away, it did after an hour or so, and it just kind of faded away over a couple of seconds. Twice I shut it down with the CD still playing and power amp still on,  and when I flipped the switch off on the G9 the low end came back instantly and stayed that way until the G9 faded out ( caps draining ? ) .

 Anyone have any Ideas, if not I think I'll start with what 1954U1 suggested. I'm still such a newbie.. ;D

   
Title: Re: The official G9 help thread
Post by: Matthew Jacobs on July 30, 2009, 08:06:12 PM
Audiophreak, I'm sorry to hear you are having these strange bass drop outs with your unit.

I hope you get to sort it out.

Best of Luck

Keep us updated.

J
Title: Re: The official G9 help thread
Post by: 1954U1 on July 31, 2009, 12:09:06 AM
Hi All,
    Well..... it happened again, no low end on the right channel, so I swapped input tubes this time, was o.k. for awhile, then no low end on the right channel again  >:(
I noticed that when I power down the unit for a minute then fire it up again, the low end comes back, so I listened to the right channel only to see if I could hear exactly when and how the low end goes away, it did after an hour or so, and it just kind of faded away over a couple of seconds. Twice I shut it down with the CD still playing and power amp still on,  and when I flipped the switch off on the G9 the low end came back instantly and stayed that way until the G9 faded out ( caps draining ? ) .

 Anyone have any Ideas, if not I think I'll start with what 1954U1 suggested. I'm still such a newbie.. ;D



Ah, so, being maybe power supply related,
I'd try first to swap C25 and C125.
Title: Re: The official G9 help thread
Post by: audiophreak on July 31, 2009, 12:53:27 AM
Quote
  from 1954U1
Ah, so, being maybe power supply related,
I'd try first to swap C25 and C125.

  in the G9 parts list, C25/C125 are called "HT NOISE FILTER"  my newbiness... I don't know what that does  :-[

   But at this point, its as good a starting point as any. I think instead of swapping caps, I know so far, that this is confined to the right channel, so I think I'll replace one component at a time, maybe stare at the schemo for a few  hours and try to follow the right channel audio path :D

 Thanks so much for the insight,
                                           Chip

 
Title: Re: The official G9 help thread
Post by: gemini86 on July 31, 2009, 02:11:28 AM
the schematic only shows one channel, so you'll just need to go by the component numbers, eg- C4 = C104 on the second channel, so once you establish which channel you have wired as you 'right' channel you can figure out where stuff is.
Title: Re: The official G9 help thread
Post by: microc on August 02, 2009, 04:37:52 AM
Hi Guys,
I have almost completed my G9. The one thing remaining is getting it to work! When I fire it up I get a bit of hum, and a oscillation (at aprox. 8kHz, not sure, my oscilloscope is old) when the gain switch reach maximum.   ???
I’ve had some problems: I used wrong resistans (R34), so the 245V vas 20V. I changed the R34 to a correct value, and I change the TL783 and R33-37 aswell incase of any damage. I also checked C14 and C15. C14 and C15 is at 100uF/350V  Low Impedance Aluminum Electrolytic Capacitors (http://no.mouser.com/Search/ProductDetail.aspx?R=UCS2V101MHDvirtualkey64700000virtualkey647-UCS2V101MHD ). Could this have any influence at the system, should I change to big oil caps instead?
Now,all the primary voltage are correct. I also had some earth problems, but after reading all the post about earth, I’ve got it sorted out.
After reading all the posts about connection to XLR, I’m pretty sure that’s correct too.

So I guess I have to start unsolder all my components to check them (would be frustrating! :-\) if anyone of you don’t have a clue. ???

Thanks for your help and tips  ;D
Best Regards
Jens
Title: Re: The official G9 help thread
Post by: flintan on August 02, 2009, 05:28:36 PM
So, in doing some digging around, is the edcor XSM a suitable input transformer? Is this transformer susceptible to noise due to lack of shielding?

Using an unshielded transformer for mic input does not sound like a good idea to me. Will most likely result in hum, noise and/or oscillations..
Title: Re: The official G9 help thread
Post by: flintan on August 02, 2009, 05:58:40 PM
Another input transformer question.. I have some old Lundahl LL3815 (yes 3815, not 1538..). There is no data sheet for it but its turns ratio is 1+1 : 5 and each primary measures 5Ω DCR, the secondary measures 70Ω DCR.

I'm about to finish a G9 and need som input iron for it but i have a feeling these are too low Z for a tube pre. Anyone have a clue if it's worth trying them? Maybe it's better to save these for something like a JE-990 based pre instead..
Title: Re: The official G9 help thread
Post by: gemini86 on August 02, 2009, 08:32:11 PM
On the gyraf site there is a link to Kev's g9 build, (don't know who kev is...but anyway) He used OEP inputs and outputs, with NO shield cans, resulting in, well not much difference, to I don't think the non shielded cans will present TOO many problems that can't be sorted out with proper power transformer placement. Also, the most common cause for the HF oscillation is the long wiring/track for the instrument input jack, it's almost a foot long all together.

Quote
08. Jan. 2007: If you run into problems with oscillation on the highest gain settings, try running the connections to/from the front panel High-Z jack connector "directly" from the relevant points on the PCB - by cutting the PCB traces, and running a length of shielded cable directly to/from the jack. See this image for reference!! http://www.gyraf.dk/gy_pd/g9/G9-EDIT.GIF
Title: Re: The official G9 help thread
Post by: audiophreak on August 02, 2009, 09:18:24 PM
Hi,
  Quote from Gyraf's G9 page :

 "Note that OEP's HAS to be in screening cans, including the output trafos (that are not canned on the pictures, sorry). Without it, I've had oscillation problems because of the high gains and bandwidths involved."

 ...hope this helps,
                    Chip
Title: Re: The official G9 help thread
Post by: microc on August 03, 2009, 01:01:09 AM
Thank you gemini86 and audiophreak !
My wiring from the instrument input jack is about 1/2inch, I will try to cut the trace on the board then. I use Lundhal trans, not OEP, my bad not telling :)
I had forgot kev's projects, I will check it out again. Anywho, thanks, I check in later =)

EDIT: I was just slightly afraid that I had blowed some tubes...

EDIT 2: After reading kevs page again, I notised that he got oscillation problem, and he knew wich wire who caused it. I use very thin wires, with very little isolation around. I will try to replace them with quality wires.

EDIT 3: (I'm the edit-guy from downstairs) I changed C14 and C15 from 2x100uF to 2x330uF and it's now working like a preamp :D Still a bit noisy. I'm reading this http://www.groupdiy.com/index.php?topic=15513.0 (http://www.groupdiy.com/index.php?topic=15513.0), hoping to solve the problem xD
Thanks guys :D

EDIT 4: I got ridd of "all" the hum of 50Hz. Only abit hizz/hush left, but I think it will go away with better wires.
Title: Re: The official G9 help thread
Post by: guitarguy12387 on August 03, 2009, 06:44:04 AM
Just out of curiosity, has anyone tried replacing the output pot with a stepped attenuator? What do ya think? I may have to make one anyway, figured while i'm at it, may as well try it if it will make an improvement...
Title: Re: The official G9 help thread
Post by: stanz on August 03, 2009, 11:13:01 AM
In regards to using an Edcor XSM for input transformers, and them making noise, I am going to chalk this one up to lesson learned. After unmounting them and moving them around, position was crucial, but at best, I could only get it to a barely tolerable hum. Obviously, the input is very sensitive and these are not shielded enough. The position where the least noise is, it is not possible to mount. I am going to get some Cinemag mic input transformers, as they are clearly the correct part. I know, getting something cheaper is not always cheaper.
Title: Re: The official G9 help thread
Post by: Kir_For_Pleasure on August 16, 2009, 04:43:46 PM
Built my first G9  8)
Fired it up tonight and absolutely nothing happend ?? i have done some measuring and my conclusion so far is that toroidal 1 15v got 230vac and the secondaries have 15vac, one of them to each insert of 15v of the pcb, i have measure at the links of the card with no current as result ??
First tip besides quit buiding ??
Title: Re: The official G9 help thread
Post by: gemini86 on August 16, 2009, 09:28:23 PM
Built my first G9  8)
Fired it up tonight and absolutely nothing happend ?? i have done some measuring and my conclusion so far is that toroidal 1 15v got 230vac and the secondaries have 15vac, one of them to each insert of 15v of the pcb, i have measure at the links of the card with no current as result ??
First tip besides quit buiding ??

Are you getting 15v? 230v? a picture of your wiring would maybe help make things clearer?
Title: Re: The official G9 help thread
Post by: audiophreak on August 16, 2009, 11:17:53 PM
Hi,

  The G9 was my first large project and have since completed a GSSL. The power trans configuration and hook-up was ( and still is ) confusing to me. I found this link that was plain enough for me to understand, so I'm sure it will help you and others. 

  On the G9, T1,the primaries are configured for your mains voltage to dual isolated secondaries ( top middle diagram ) connect one secondary to the 15v that is next to the HT 220v, then split the second secondary, one split to the 15v that's next to the LED feed and the second split feeding the T2 the other way round into paralleled secondaries ( lower right diagram ) then take the primary of T2 connected in series ( second in from lower left diagram ) to the 220v on PCB. This is how I connected mine and its been working flawlessly for the last 6 months, and it sounds AWESOME ! 

  hope this helps,
                       Chip

http://www.diyfactory.com/data/transformer_connections.gif

  ps, I printed this diagram out and pinned it to the wall in my shop  and have referenced it MANY times  ;D

Title: Re: The official G9 help thread
Post by: Kir_For_Pleasure on August 17, 2009, 03:29:40 AM
My connection

Title: Re: The official G9 help thread
Post by: Kir_For_Pleasure on August 17, 2009, 10:01:21 AM
the primary on the T1 have to be in serial !! trying again !
Title: Re: The official G9 help thread
Post by: peterc on August 17, 2009, 10:17:45 AM
Check the second transformer, should be black/orange together & yellow/red together.....
Title: Re: The official G9 help thread
Post by: Kir_For_Pleasure on August 17, 2009, 11:13:41 AM
yes i had that wrong on the sketch *sorry*
played my bass throu it know for a hour and its sounds really nice =)
Title: Re: The official G9 help thread
Post by: audiophreak on August 24, 2009, 09:54:52 PM
Hi All,

   A little embarrassed, but I found that the cause of the low end loss in the right or #2 channel of my G9 was a poor connection at the CD player RCA connector  :-[
Thankfully I found it before tearing out and replacing components... just some of whats left of my hair  ;D  been running it for last week or so just to make sure and all is well.

 Thanks for all the suggestions and support,
                                                            Chip
Title: Re: The official G9 help thread
Post by: sjekkih on September 02, 2009, 04:39:11 PM
Yes I tried setting the gain at max and the out low, but the G9 is too clean :p

I will try changing R10. I understand the NFB loop consept now, but what is this talk about pads and pots at the output transformer?

BTW, is there a big difference between a tube mic and a regular condenser one?

Thanks for the guidance ;)

Hi, I tried changing R10 to get more distortion in the gain stage, I doubled R10, without any significant difference in the audio signal. Any other ideas to mod the G9 for a dirtyer, tubier sound? Or should I go for a new  preamp without NFB loop.

Anyone know anything about sound diffrence tube mics vs regular condenser, when you want some warm distortion?
Title: Re: The official G9 help thread
Post by: SaMpLeGoD on September 10, 2009, 10:33:18 PM
Hello! I'm have some questions about the G9... hop you can help me:

1) Could someone post again the fix for the high frequency oscilation? the JPG links aren't working :(
2) Anyone used flat cables to connect between the main PCB and the Front Panel one without problems?
3) I'm planning to use the OEP for output and the VTB9045 for inputs, is this help to get rid of the low cut problem with OEPs in and out?

Thanks a lot everyone!!

Eddie :)
Title: Re: The official G9 help thread
Post by: Kingston on September 11, 2009, 04:29:27 AM
1) Could someone post again the fix for the high frequency oscilation? the JPG links aren't working :(
2) Anyone used flat cables to connect between the main PCB and the Front Panel one without problems?
3) I'm planning to use the OEP for output and the VTB9045 for inputs, is this help to get rid of the low cut problem with OEPs in and out?

1) http://www.gyraf.dk/gy_pd/g9/G9-EDIT.GIF

2) I would not use flat cables. You might get lucky and not have problems, since most of it is just for the phase switch balanced audio, relay 12V and 48V. But there's the somewhat critical high impedance area: gain pot. You might even want an extra shield around those wires.

3) forget all OEP's if you want the low end. They simply aren't cut out for the task. Get a big 2:1 or 4:1 output transformer from edcor instead. same price, much better sound and it won't "duck and cover" when trying to reproduce bass.
Title: Re: The official G9 help thread
Post by: bpucekov on September 11, 2009, 08:32:30 AM
i used flat cable for connecting main pcb with front pcb whitout any problems
no any noticable hum or buz
puc
Title: Re: The official G9 help thread
Post by: flintan on September 11, 2009, 05:41:04 PM
Which is the correct connection for Edcor XS1100 in a G9? I believe the primaries should be in series and the secondary in parallell but I find two different schematics of the pins phase designation:
http://edcorusa.com/Products/ShowProduct.aspx?ID=547 (http://edcorusa.com/Products/ShowProduct.aspx?ID=547)
http://purusha.smokinggunrecording.com/MEQ5/XS1100%20Specification%20sheet.pdf (http://purusha.smokinggunrecording.com/MEQ5/XS1100%20Specification%20sheet.pdf)

Which is the correct connection? (I know the drawings/schematics don't show primaries in series but look at the phasing information.)
Title: Re: The official G9 help thread
Post by: flintan on September 11, 2009, 07:33:28 PM
Ok. This picture (http://purusha.smokinggunrecording.com/MEQ5/Edcor%20PCB.jpg) in comparision to LL5402 data sheet does not correspond with the picture at the end of this page (http://edcorusa.com/Products/ShowProduct.aspx?ID=547) but is the same as this one (http://purusha.smokinggunrecording.com/MEQ5/XS1100%20Specification%20sheet.pdf).

Am i wrong or is the phasing info on edcor's site wrong?? Or have they changed the pinout of XS1100 recently?  ???
Title: Re: The official G9 help thread
Post by: Kingston on September 11, 2009, 08:35:05 PM
Don't bother with the XS1100. It's physically too small to handle G9 output. So is the LL5402 actually.

A much better fitting transformer is XSM2.4K/600, or for even better drive capability but slightly lesser gain, the 4:1 ratio WSM10K/600 (would be my pick) or XSM10K/600.
Title: Re: The official G9 help thread
Post by: shabtek on September 12, 2009, 01:46:44 AM
I somewhat agree w/kingston regarding core size.; there have been many pleased builders using the suggested xfmrs though. I've built 2 of these. best with DI bass has a heavy 600:600:600 wired 2:1 opt. The circuit is useful with any transfmrs, even oeps but maybe not always for solid lowend-- there is a difference. I've a shelved board with the XS1100...I was not real confident in this trans so it went back in line (never heard it). otoh people seem to like it it in that gyraf passive eq. I don't think you'll go wrong with an xsm in the out. And I would not say to forget the 1100 either.
Title: Re: The official G9 help thread
Post by: flintan on September 12, 2009, 07:33:14 AM
Ok. I will try XS1100 first, think i've got it wired correct now.. Although i also have some XSM 10k/600 to try later if the XS is too weak..
Title: Re: The official G9 help thread
Post by: Kingston on September 12, 2009, 09:02:50 AM
otoh people seem to like it it in that gyraf passive eq.

That's because there is no impedance mismatch problem with the E88CC tube in SRPP configuration. It can happily drive lesser transformers.

Not so with the 12AU7 in SRPP. You'll have a constant bass roll off with it.

A worthy upgrade to boost G9 capabilities is to simply take the gyraf pultec SRPP, and slap it as the G9 last gain stage. Then change all heater wiring and PSU to handle 6,3V filaments.

Call it G9 mkII.
Title: Re: The official G9 help thread
Post by: Kir_For_Pleasure on September 14, 2009, 05:49:38 PM
I have problems with the phantom power, xlr out pin 2&3 just measures 8,2v ! At the Emitter of the tip 121 i measure 12v should it constantly be 48v there ?
Title: Re: The official G9 help thread
Post by: flintan on September 15, 2009, 05:21:30 PM
Yes you should have 48V at the emitter of TIP121. If you have trimmed it to that voltage? Measure voltage from the power transformer and forward trough the phantom power psu and you shall find where the problem is.
Title: Re: The official G9 help thread
Post by: Kir_For_Pleasure on September 15, 2009, 05:31:44 PM
something is seriously wrong flintan ! nothing happend when i turn the trimmer ?? ok must go in deeper in troubleshooting !!
Title: Re: The official G9 help thread
Post by: flintan on September 15, 2009, 07:14:00 PM
Just measure AC V at transformer, then DC after the diodes D8-D12 etc and compare to the schematic.
Title: Re: The official G9 help thread
Post by: guitarguy12387 on September 15, 2009, 07:48:49 PM
Hey everyone! My turn to play the troubleshooting game. Well i just fired up my first G9 the other day. It passes signal well, but i have some hum/buzz. Before tackling that, i'm also having an issue with my phase switch. When off (ccw) it passes signal fine (save the aforementioned hum/buzz...). When i switch the phase switch on (CW), the signal disappears (as does the hum, actually). Anyone have any ideas? Thanks in advance.
Title: Re: The official G9 help thread
Post by: Harpo on September 16, 2009, 04:00:43 AM
Maybe end-stop washer placed to pos.2 before turning the rotary switch full ccw, now switching between pos.2 and 3 instead?
Title: Re: The official G9 help thread
Post by: guitarguy12387 on September 16, 2009, 09:43:40 PM
Aaah yup hah! Forgot to adjust the washer. Thanks! AND took a closer look at my ground scheme and fixed it which solved the hum! Thanks!
Title: Re: The official G9 help thread
Post by: microc on September 19, 2009, 05:45:12 AM
Hi,
one last question, in the circuit description, Jacob mention that C7 is 10uF/63V AC (ergo 100VDC). Is all the polyester caps listet with AC voltage?!?
C2,102  22OnF 250V POLYESTER    INPUT DC BLOCK
C3,103  470nF 250V POLYESTER    INTERSTAGE V1A-V1B
C4,104  1u5 250V POLYESTER      OUTPUT DC DECOUPLING V1B
C5,105  470nF 250V POLYESTER    STAGE1 OUTPUT
C6,106  68p 50V   CERAMIC         BW LIMITING
C7,107  10u 63V   POLYESTER       GAIN DC DECOUPLING
C10,110 22OnF 250V POLYESTER    SRPP INPUT DC BLOCK   
C11,111 470u16V   RAD.EL.LYT      SRPP CATHODE SHUNT
C12,112 100n 63V POLYESTER      SRPP CATHODE SHUNT
C13,113 4U7 250V POLYESTER      SRPP OUTPUT CAP

I know, it's a pretty lame question...
Title: Re: The official G9 help thread
Post by: flintan on September 23, 2009, 05:25:29 PM
My turn for trouble and stupid questions.. Fired up my G9 today and there was a cloud of smoke somewhere from the heater psu, i think it was from the rectifier diodes D13-D16.

I had some power transformers with single secondaries so i connected both the backward transformer, heater psu and pp psu to the same winding. Is there something obviously stupid in doing that?

Like this:

(http://web.comhem.se/linusandersson/g9_psu_changed.gif)
Title: Re: The official G9 help thread
Post by: Harpo on September 24, 2009, 12:42:47 AM
My turn for trouble and stupid questions.. Fired up my G9 today and there was a cloud of smoke somewhere from the heater psu, i think it was from the rectifier diodes D13-D16.

I had some power transformers with single secondaries so i connected both the backward transformer, heater psu and pp psu to the same winding. Is there something obviously stupid in doing that?
There is a reason for dual secondaries.
Shorted out D15 (look where 0V for heater and 0V for phantom connect).
Not sure if D13 (if the transformer can deliver more current than the diode can take) or the mains transformer (cooking because of shorted secondary for every 2nd halfcycle) will die faster.
-Harpo
Title: Re: The official G9 help thread
Post by: flintan on September 24, 2009, 05:15:31 PM
Yes of course..  ::)

Sometimes the most obvious and easiest things can be a mess. Both D13 and D15 are fried to short circuit but i think the transformer are still ok.
Title: Re: The official G9 help thread
Post by: Harpo on September 24, 2009, 06:37:59 PM
Only D13 should be blown. D15 is protected by the short, so this one is probably alife. ;)
Title: Re: The official G9 help thread
Post by: flintan on September 25, 2009, 02:32:02 AM
No D15 is also fried. Measures 0,5 ohm. I think the reason might be that i fired the unit up again after disconnecting the pp psu, but by then D13 was already dead and shorting out D15..
Title: Re: The official G9 help thread
Post by: rotation on October 27, 2009, 04:33:22 PM

Hi,

i found transformer with 45V/20mA secondary. I would like to use it for phantom power as is on G9 schematic. Of course i would add gretz and wouldn't use voltage tripler..
Is 20mA enough for powering this phantom supply, i don't see any part that would consume much current? I would like to get at least 10mA at the output.

Miha
Title: Re: The official G9 help thread
Post by: Harpo on October 27, 2009, 08:15:36 PM
voltage setting resistors draw about 5mA. A 45V/20mA secondary would be a 0.9VA transformer, so this 20mA might be a typo. If not, you might get an additional hum source with a tiny radiating transformer, probably delivering less current than the tripler. If this 20mA more likely is a 20VA, 2 shorted mic cables with phantom switched on would still keep the transformer ideling at about 33mA. I don't see much benefit. YMMV.
Title: Re: The official G9 help thread
Post by: rotation on October 28, 2009, 06:21:47 AM

No, it's not a typo. I have one transformer with 230V and 7V, the other has 150v and 45V/20mA. I can't use first even if i make voltage tripler.
So i need more like 45V/50mA to get healthy 10mA output? I'm making only one channel.
Title: Re: The official G9 help thread
Post by: Harpo on October 28, 2009, 05:51:30 PM
seems so. Just simulated your 45VAC to fullwave bridge, G9-circuit starting at C20, current draw for one channel with worst case mic cable shorted to gnd (thru 3k4) is 20.6mA. Ideling DC current is 7.2mA. Add some leakage and form-factor 1.8 for fwb.
Spice lies, but healthy 48V @ 10mA out is asking for more than this 20mA transformer in front.
Title: Re: The official G9 help thread
Post by: rotation on October 28, 2009, 05:59:55 PM

Thanks. I will use it anyway and measure what's up. It's cheaper than buying separated transformers:) I tried this back to back thing and never had much luck. One time one of transformers started to overheat really bad. Another time one was humming like mad..
Maybe my target of 10mA for one mic is pesimistic. I read that most of mics only need a couple of mA or even less. Since this is for my own use i don't care so much, i can open it and see how it works.

Miha
Title: Re: The official G9 help thread
Post by: Dnukas on November 02, 2009, 08:22:09 AM
Hi all,

I want to build this great stuff, but I don`t understand one think. The secondary winding of output transformer...in schematic is connected parallel and then goes to the phase switch. ( i hope ???) ,but in PCB layout is serial and then goes to the phase switch.

Which wirring is is correct?

sorry for lame english and question.


Lukas
Title: Re: The official G9 help thread
Post by: Harpo on November 02, 2009, 09:59:11 AM
you noticed the different output transformers ? (LL5402 on schematic is a 2+2:1+1 ; LL1582 on pcb is a 1+1:1+1)
both shown connections seem correct, pcb layout is for Lundahl-LL1582, probably being the latest version.
Title: Re: The official G9 help thread
Post by: audiophreak on November 02, 2009, 10:19:51 AM
  
Quote
you noticed the different output transformers ? (LL5402 on schematic is a 2+2:1+1 ; LL1582 on pcb is a 1+1:1+1)
both shown connections seem correct, pcb layout is for Lundahl-LL1582, probably being the latest version.
   
  I was unaware that there was a different Lundahl output trans option.  Is this a new option for the low end drop off thing ?
Title: Re: The official G9 help thread
Post by: riggler on November 02, 2009, 10:22:48 AM
Nope it's been there all along.
Title: Re: The official G9 help thread
Post by: audiophreak on November 02, 2009, 10:54:23 AM
Thanks, ... must have missed that little detail... :-[
Title: Re: The official G9 help thread
Post by: Kir_For_Pleasure on November 08, 2009, 04:41:24 PM
My finished G9, ended up with the oscillation mod, think i opened it up 5 times for troubleshotting  :o not a easy one !!

(http://i182.photobucket.com/albums/x238/mattssonp/P1000998.jpg)

(http://i182.photobucket.com/albums/x238/mattssonp/P1000999.jpg)

(http://i182.photobucket.com/albums/x238/mattssonp/P1010002.jpg)

(http://i182.photobucket.com/albums/x238/mattssonp/P1010004.jpg)

(http://i182.photobucket.com/albums/x238/mattssonp/P1010005.jpg)
Title: Re: The official G9 help thread
Post by: audiophreak on November 26, 2009, 08:44:49 PM
Hi All,
       On to my second G9, I'm using the ECC88s on the output and was wondering if there is a trick to checking the heater and other voltages on the tubes, unfortunately its all mounted in the case. In keeping true to Gyraf, I've copied the G7 heater circuit on perf board, but am finding it difficult to get my meter probes down to the tube socket base with out destroying anything.

  angled probe tips ?

   Any suggestions ? 

 
Title: Re: The official G9 help thread
Post by: Rob Flinn on November 28, 2009, 11:24:48 AM
Where has the "G9 oscillation problems - solution"  thread gone to.   The link on the G9 meta seems to be duff ?
Title: Re: The official G9 help thread
Post by: audiophreak on November 28, 2009, 04:31:44 PM
Hi,
   I have this graphic, not sure this is what your looking for.

Title: Re: The official G9 help thread
Post by: Rob Flinn on November 28, 2009, 08:03:42 PM
thanks audiophreak that should do it.
Title: Re: The official G9 help thread
Post by: audiophreak on November 28, 2009, 10:56:35 PM
Glad to have helped ...  so many here have helped me   :)
Title: Re: The official G9 help thread
Post by: Tuxa on November 29, 2009, 04:03:07 AM
Hello all,

I have build my  G9 Preamp without problem, but when i have test it , a Clipping Distortion can be listen on all channel.
It's not a Great Warm disto, it a noisy disto totaly small and metalic .

I don't know if it have it distortion before test the Instrument Jack Input  >:(

Now All channel, (Line / Mic / 48v) have the cliping distortion.

Have you a idea where that come from  ?
Do you think i have Break all Tube's when i have test Input Jack ?

PS: Sorry for my basic English Language

Regards,

---
Tuxa
Title: Re: The official G9 help thread
Post by: nashkato on December 09, 2009, 06:09:05 AM
hi
built a G9 quite a while ago .
at first tests i had problems with gainsettings above 7 or 8 .

up to there signal would be fine , but switching to gain 9 or 10 wasn´t possible  , the signal would just disappear.(haven´t checked the osci, though)
didn´t have the time back then to get into it , but still used it on some drumoverheads , and they sounded fine . all i did was the "oscillation fixing" ,
as mentionend above , but that didn´t solve anything.

after not having it used for a long time , suddenly  the problem has disappeared  when i used it recently for a couple of days ??? everything works fine as it´s supposed to.
anyone experienced anything like this .
 i can´t explain it , but the problem got solved all by itself ? the  tubes maybe  got something to do with it ?

 
Title: Re: The official G9 help thread
Post by: Stagefright13 on December 09, 2009, 10:11:10 PM
Nashkato I had a few problems with the lorins after long term use. Just switch them up and down a few times and works perfect. At least for me. Only happened to me once tho after I didn't use it for a long time. Not to say I didn't overheat one soldering it... Built it quite a while ago. But works great.

John

Title: Re: The official G9 help thread
Post by: mamiti on December 11, 2009, 06:42:42 PM
Hi,

I've built two G9's and when measuring max gain I only get around 48dB (+-1dB) from all four channels. I'm guessing there is something wrong because these OEP xformers should give some 60dB. I've checked things like
- Power supply & regulators: I'm getting decent 12.2V, 48.4V and 239V (is this too low as it says 245V in the schematics?)
- Audio transformers are installed correctly
- Audio passes fine and device is working
- All switches and pots work as they should
- Oscillation was fixed by the famous mod
- Tried different tubes (all 4)

I've read most of G9-topics but I'm still out of ideas where to start looking. Any suggestions, please?

Here are some pictures of both builds:
1st:
http://koti.kapsi.fi/~tillander/gallery2/main.php?g2_itemId=11

2nd:
http://koti.kapsi.fi/~tillander/gallery2/main.php?g2_itemId=156

Thanks,

Mikko
Title: Re: The official G9 help thread
Post by: gyraf on December 12, 2009, 03:00:46 AM
Quote
Any suggestions, please?

best guess wrong type OEP transformers. Measure ratio?

Jakob E.
Title: Re: The official G9 help thread
Post by: mamiti on December 12, 2009, 05:01:00 AM
Quote
Any suggestions, please?

best guess wrong type OEP transformers. Measure ratio?

Jakob E.

Hi, sorry should have said that... I've checked trafos countless times... They are right type, in right places and I've also measured them. 1:6.40 on input and 2:1 (EDITED the post, was 1:2) on output if my measurement method is sound. I can remove cans and put a photo in my album to show how trafos are there now.

Thanks for this, anything else that I should check?

Cheers,

mt

EDIT:

Input transformers:
http://koti.kapsi.fi/~tillander/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=205&g2_serialNumber=2

Output transformers:
http://koti.kapsi.fi/~tillander/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=213&g2_serialNumber=2
Title: Re: The official G9 help thread
Post by: mamiti on December 12, 2009, 08:28:42 PM
Hi,

I've made some measurements, all off the values are against signal ground on output xlr bolt.

0.103V - Input signal at input XLR+
0.66V - R6 (tube side)
2.36V - R9 (tube side)
2.36V - R23 (tube side)
19.03V - R25 (tube side)
19V - R26 (C5 side)
9.04V - R26 (C8 side)
24.7V - R30 (V2B G1)
18.1V - R30 (V2A K1)
3.2V - R32 (XLR +)

Hmm, this isn't exactly looking right... Also now it is hard to measure XLR+ because of voltage fluctuation. It's getting late, can't think anymore. Any ideas where to track are welcome.

CHeers,

MT
Title: Re: The official G9 help thread
Post by: audiophreak on December 13, 2009, 08:19:28 PM
Hi All,

  I posted this in the  G9 and its frequency response ?? (impedance matching?) thread, I'm kinda proud of my efforts, so I thought I'd post it here too.


    Here is a link to pix of my second G9, although I went a little over board, especially with the caps  ::)  but I've never tried them, so now I have.  I used the ECC88s on the output and copied the G7 heater circuit for them as keeping with Gyraf, and after talking with Kevin from K&K audio, installed the LL7903s for the output transformers, a little pricey, but I'm glad I did for a trouble free build. The power trans I used have 2.0 amps on each secondary so I was still able to use one secondary to feed both heater circuits with no problem. This thing sounds awesome, just like my first one, with the ECC88s and still being able to have a 2:1 ratio on output, this thing has a TON of gain.

  Thanks as always to Jacob and Gyraf, and to steppenwolf , 1954U1 , and everyone else who trudged through this impedance thing, its way over my head but very interesting to read this thread ( I've done a couple of times ) and see the process of tracing and following and testing to figure it all out.

https://picasaweb.google.com/audiophreeek/UltimateG9#

  I call it the " Ultimate G9 "

  Best to All, and may your holidays be warm and safe,
                                                                          Chip
Title: Re: The official G9 help thread
Post by: Graph on December 16, 2009, 06:01:06 PM
I am building the G9, and i am having troubles to get the transformers. I can only get the toroidals if i ask 10 for them because i cant get them in this country.

The people in shops, are giving me 220:15+15(220:30v, 30v between 2 wires, and 15v betwen any of the side ires with the middle one., but there are only 3 wires, not 4. Can i Use this transformers anyways? or i will blow up everything? or there will be some impedance problem?

If this doesnt work, may i use 2 transformers connected in paralell? 2 220:15 and 2 220:12v ?

Thanks.

Title: Re: The official G9 help thread
Post by: g9builder on December 17, 2009, 11:45:51 AM
Hi,

Obviously 1st posts so Hi to everyone. I have decided to build the G9 and am in the process of getting all the parts together. I am having some problems soucing a couple of items in the UK or in fact anywhere. Can anyone give me any alternatives at all?

IC1 T.I TL783
R31/R131 1.0k 2W 5% Metal Film
R34 100k 2W 1% Metal Film
P01/P101 Piher 47kb (LOG) Pot 6mm

Any help at all would be greatly appreciated.

Regards

Ian
Title: Re: The official G9 help thread
Post by: Stagefright13 on December 17, 2009, 11:45:58 PM
Haha I love the missile switch. And have seen them on drag bikes. Cool touch! Nice build with good sinks too.

John
Title: Re: The official G9 help thread
Post by: gyraf on December 18, 2009, 03:01:48 AM
Quote
Can anyone give me any alternatives at all?

IC1 T.I TL783
R31/R131 1.0k 2W 5% Metal Film
R34 100k 2W 1% Metal Film
P01/P101 Piher 47kb (LOG) Pot 6mm

Hi Ian - welcome to the GroupDIY!

- TL783 - there is no substitute - you need to find this. It's not that uncommon, look some more
- 1.0k 2W - here a 1W will do fine, and 10% tolerance won't be a problem
- 100k 2W 1% - here 1W and 5% will be ok too
- P01/P101 - any type 47K Log pots (that fits your front panel and your knobs) will do fine

Jakob E.
Title: Re: The official G9 help thread
Post by: bpucekov on December 18, 2009, 03:37:07 AM
IC1 T.I TL783
R31/R131 1.0k 2W 5% Metal Film
R34 100k 2W 1% Metal Film
P01/P101 Piher 47kb (LOG) Pot 6mm

Try www.banzaieffects.de
Title: Re: The official G9 help thread
Post by: g9builder on December 18, 2009, 03:50:01 AM
Thanks Jacob and pbucekov,

As you can probably tell - I'm new to all this and wanted to keep strickly to the parts lists so as to reduce the level of problems I will undoubtably run into further down the line.!:-)

Will check these out striaght away.

The TL783 at Farnell says that it is discontinued? Is there an alternative at all?

Many thanks

Ian
Title: Re: The official G9 help thread
Post by: wmtunate on December 18, 2009, 08:31:47 AM
The TL783 at Farnell says that it is discontinued? Is there an alternative at all?

Looks like they have it here:

http://uk.farnell.com/texas-instruments/tl783ckcse3/adj-regulator-high-v/dp/1703396
Title: Re: The official G9 help thread
Post by: g9builder on December 18, 2009, 11:03:45 AM
Thanks wmtunate,

I got one from banzaiessects.de and the resistors too.

I was looking at this one from farnell as per skylar's part list.

http://uk.farnell.com/texas-instruments/tl783ckc/reg-700ma-smd-to-220-3-783/dp/9594582?Ntt=9594582

Cheers

Ian
Title: Re: The official G9 help thread
Post by: audiophreak on December 18, 2009, 04:50:48 PM
Thanks Stagefright13, now I just gotta get my head wrapped around face plate graphics... ;D
Title: Re: The official G9 help thread
Post by: Rob Flinn on December 18, 2009, 05:49:45 PM
the TL783 is available from RS, but there is a minimum order of 5
Title: Re: The official G9 help thread
Post by: MerlynMetal on December 30, 2009, 12:08:55 PM
Hi,

I'm sorry if this was asked before but what is the easiest way to add a VU meter to G9 like the round ones that Farnell carries:

http://uk.farnell.com/anders-electronics/c360vu/meter-circular-0-200ua/dp/7758243

My question is mainly to those who already did it successifuly.
Title: Re: The official G9 help thread
Post by: diyfanatic on December 30, 2009, 01:57:54 PM

I'm sorry ---> you can
if this was asked before ---> yes, 10 000 times
what is the easiest way to add a VU meter to G9 ---> no easy way


more info ----> 0.25 seconds with the google custom search and in the meta

try this:
rule 6. Use the search function (thoroughly) before posting.  It is quite possible your question may have already been answered by knowledgeable members that have been generous with their time.  A tremendous wealth of knowledge is actively updated and compiled in the "Meta" threads--take advantage of them.
Title: Re: The official G9 help thread
Post by: g9builder on January 15, 2010, 05:55:52 AM
-" P01/P101 - any type 47K Log pots (that fits your front panel and your knobs) will do fine"

These are the last components I need. I don't know if it's just me or what but I carn't seem to find them anywhere. Every electronics supplier I try seems to not have them.There must be some out there? Anyone know where or have 2no they want to part with.

As always many thanks and sorry for the stupid question but I'm starting to pull my hair out over this!

Cheers

Title: Re: The official G9 help thread
Post by: ChrisPbass on January 15, 2010, 06:26:12 AM
-" P01/P101 - any type 47K Log pots (that fits your front panel and your knobs) will do fine"

These are the last components I need. I don't know if it's just me or what but I carn't seem to find them anywhere. Every electronics supplier I try seems to not have them.There must be some out there? Anyone know where or have 2no they want to part with.

As always many thanks and sorry for the stupid question but I'm starting to pull my hair out over this!

Cheers



Rapid Electronics have these

http://www.rapidonline.com/Electronic-Components/Resistors-Potentiometer/Control-Potentiometers/24mm-Commercial-potentiometers/65224

or

http://www.maplin.co.uk/Module.aspx?ModuleNo=2205

Most suppliers will carry these as they're of a standard value. The maplin ones are designed for mounting into a PCB so don't have the eyelet for wrapping the wire around but as long as you're good with your soldering, they'll be fine. I'll generally pop to Maplins when I need something quick as they're are a couple local to me. They're generally not as competative or carry a comprehensive stock of component values but can often get you out of a fix.

Chris
Title: Re: The official G9 help thread
Post by: g9builder on January 15, 2010, 06:29:31 AM
Chris,

Many many thanks - appreciated greatly!


Ian
Title: Re: The official G9 help thread
Post by: stitch-o on January 19, 2010, 02:34:07 PM
Ok, I got one:
recently I developed a very nasty and loud rumbling/oscillating LF noise
on channel 2 only (channel one is fine). Its the closest to the PS.
I swapped tubes briefly to see if that was the issue but to no avail.
Over the last few days it has gotten louder/worse.
When turning the Gain and output trim down, the noise dies down then....gone.
I have no doubt some part has decided to die but I thought I'd
toss this out for any idears before I dive in for troubleshooting.

Cheers!
Title: Re: The official G9 help thread
Post by: gyraf on January 20, 2010, 12:38:33 AM
..maybe the 10u polyester cathode-decoupling for the first gain stage gone wrong?

Jakob E.
Title: Re: The official G9 help thread
Post by: stitch-o on January 20, 2010, 07:34:13 AM
..maybe the 10u polyester cathode-decoupling for the first gain stage gone wrong?

Jakob E.

I will check that first.
Thanks Uncle Wonka*/Gyraf!!

* - reference = Willie Wonka and the Chocolate Recording Studio


EDIT: confirmed hum on the scope at position.
Replaced the crappy mylars with nice Solens.
DEAD quiet...there was a TINY hum on the working channel that is now gone as well.
THANK YOU jakob!!
Title: power transformer: 230v-17.5v possible?
Post by: jwk1 on January 24, 2010, 01:09:19 PM
Hi,

Just about to start building a g9.  I've got a couple of nice 35VA 230:17.5+17.5v transformers, shielded with mu cans, lying around.  Would it be within the tolerance to use these for the build, maybe with larger heatsinks?  Or should I order the recommended ones from the BOM?  Just trying to save a few pennies, and use up some of my spare parts...

Thanks,

Josh
Title: Re: power transformer: 230v-17.5v possible?
Post by: Graph on February 04, 2010, 04:15:47 AM
Hi, i am continuing to build the G9 :) i have all the materials exept toroids..

I think i am having 2 problems, i am in a 220v place.

1st, the output of the 12+12v:220v is 275v, the G9 can support till 350v i guess...

2nd, after testing heater and phantom power which they regulated fine, i continued to make the high voltage but i had a problem... R34 started glowing orange!! i guess if i left it on more seconds it would have blown up. Anyways it was the only problem for now, but i want to fix this so i can continue building it :)

Any ideas why this may be happening?

Sorry if it was discussed early, i didnt had much luck using search this time.

But i will appreciate all help, i guess i will change the componentes for the high voltage regulator, with new ones(i hope i dont get this problem again, maybe its a resistor which i messed up with the value). If you need some photo to see this problem i will upload one tomorrow.

Thanks in advance!
Title: Re: The official G9 help thread
Post by: stitch-o on February 04, 2010, 07:37:47 AM
Did you double check all the solder points for the diodes?
Other thought is, how are you heat sinking your rectifier?

I'm not the brightest bulb in the knife drawer, but maybe its somewhere in that area.
The other thought is, it sounds like your 2 problems might actually be one...
Title: Re: The official G9 help thread
Post by: audiophreak on February 04, 2010, 10:46:39 AM
Hi,
    I've got a strange one for ya.  I have two G9s now and have noticed something on the third one and checked the other two and have found something strange.
   I intermittently have a signal drop out to a very faint signal on the right channel only on both units, if I tap the faceplate the sound crackles and comes back, if I continue to tap the front panel it crackles some more goes in and out as if there were a loose connection.
   I have extensively checked for loose connections, poor solder joints ect. but have found none. Could it be the Lorlin switches ?

  any thoughts on this ?  ... anyone ?

 Thanks,
            Chip
 
Title: Re: The official G9 help thread
Post by: Graph on February 04, 2010, 11:43:07 AM
Did you double check all the solder points for the diodes?
Other thought is, how are you heat sinking your rectifier?

I'm not the brightest bulb in the knife drawer, but maybe its somewhere in that area.
The other thought is, it sounds like your 2 problems might actually be one...
I will double check, every diode is in its right position.

Its maybe a transformer issue?

If the R34 is glowing orange, and nearly in fire, i guess it had more than 10 watts there has to be some problems making a bridge or something with that Resistor, all of the other ones were ok, but i couldnt measure the voltage in the exit of the TL783 :(

I am going to bring my camera to post a photo of that section, transformers wires, and tracks.
Title: Re: power transformer: 230v-17.5v possible?
Post by: Harpo on February 04, 2010, 12:36:04 PM
1st, the output of the 12+12v:220v is 275v, the G9 can support till 350v i guess...

2nd, after testing heater and phantom power which they regulated fine, i continued to make the high voltage but i had a problem... R34 started glowing orange!! i guess if i left it on more seconds it would have blown up. Anyways it was the only problem for now, but i want to fix this so i can continue building it :)
Seems, IC1 isn't regulating.
Check, if the current setting resistors R35 and R36 are 470R and 47R, giving a total of 517R as they are wired in series.
If you mistakenly fitted both as 47R (total series resistance 94R), the regulator would be set for theoretical 1331V output and R34 has to dissipate 17.7W. You won't get more out of your regulator than you put in, so unregulated raw DC voltage sets the upper limit. With your 275V raw DC, R34 only has to stand 3.65W with the wrong fitted current setting resistor. With correct values, output voltage is set for 243V and R34 has to stand 0.58W, so a 1W part should be sufficient.
Just an idea ....
good luck
Title: Re: power transformer: 230v-17.5v possible?
Post by: Graph on February 04, 2010, 05:41:41 PM
1st, the output of the 12+12v:220v is 275v, the G9 can support till 350v i guess...

2nd, after testing heater and phantom power which they regulated fine, i continued to make the high voltage but i had a problem... R34 started glowing orange!! i guess if i left it on more seconds it would have blown up. Anyways it was the only problem for now, but i want to fix this so i can continue building it :)
Seems, IC1 isn't regulating.
Check, if the current setting resistors R35 and R36 are 470R and 47R, giving a total of 517R as they are wired in series.
If you mistakenly fitted both as 47R (total series resistance 94R), the regulator would be set for theoretical 1331V output and R34 has to dissipate 17.7W. You won't get more out of your regulator than you put in, so unregulated raw DC voltage sets the upper limit. With your 275V raw DC, R34 only has to stand 3.65W with the wrong fitted current setting resistor. With correct values, output voltage is set for 243V and R34 has to stand 0.58W, so a 1W part should be sufficient.
Just an idea ....
good luck
I will check the resistors when i got home :)

Really, much thanks, if thats the problem i will fix it quick.

Title: Re: power transformer: 230v-17.5v possible?
Post by: Graph on February 05, 2010, 02:03:04 AM
1st, the output of the 12+12v:220v is 275v, the G9 can support till 350v i guess...

2nd, after testing heater and phantom power which they regulated fine, i continued to make the high voltage but i had a problem... R34 started glowing orange!! i guess if i left it on more seconds it would have blown up. Anyways it was the only problem for now, but i want to fix this so i can continue building it :)
Seems, IC1 isn't regulating.
Check, if the current setting resistors R35 and R36 are 470R and 47R, giving a total of 517R as they are wired in series.
If you mistakenly fitted both as 47R (total series resistance 94R), the regulator would be set for theoretical 1331V output and R34 has to dissipate 17.7W. You won't get more out of your regulator than you put in, so unregulated raw DC voltage sets the upper limit. With your 275V raw DC, R34 only has to stand 3.65W with the wrong fitted current setting resistor. With correct values, output voltage is set for 243V and R34 has to stand 0.58W, so a 1W part should be sufficient.
Just an idea ....
good luck

Well, i just arrived to my house. I cut the resistors out, and measured them, they were 47 and 470 ohm. They were not the problem. I will continue cutting the resistors. R37 was fine too and R33 was a bit black, it measured 380ohms. The thing that was left of R34 measured 680ohms.. did this value came really down a lot or the resistence was bad in first place?(i was sured i measured them before soldering it), maybe that was the problem, its a shame that the track was damaged so i will put a small cable tomorrow.

R34 was a 2 watts resistor.

If that wasnt the problem.. the regulator was really cool, it didnt got any hot at all.. its on he correct side. The zener diodes, i guess they were the right value, at least that was the value they were labeled. 1n4007 were alright too, and capacitors are in the correct side, i made a small pcb with the - and 2 separte +, they are 100uf 350v.

Any idea how should i start debugging this if this wasnt the problem? i have removed the resistors for now, tomorrow will buy new ones and try again. If the problems keeps happening. Any ideas? i guess here are no solder bridges and i have not found one between 240v and ground.

Anyways.. sorry for my english, i am from latin america.
Title: Re: power transformer: 230v-17.5v possible?
Post by: Kingston on February 05, 2010, 03:53:28 AM
the regulator was really cool, it didnt got any hot at all.. its on he correct side.

Your regulator is dead. Leave the rest alone and solder a new one in. Then double check all connections. and I mean all traces.

The regulator should get at least warm, but normally you'd even want a small heatsink on it.
Title: Re: The official G9 help thread
Post by: gyraf on February 05, 2010, 09:11:30 AM
Quote
The regulator should get at least warm, but normally you'd even want a small heatsink on it.

Yes, definitely. If your TL783 is dead, you may want to recheck integrity and orientation of your protection-scheme around it - the 1N4007 and the three 39V Zeners.

Jakob E.
Title: Re: The official G9 help thread
Post by: Graph on February 06, 2010, 12:21:46 AM
Quote
The regulator should get at least warm, but normally you'd even want a small heatsink on it.

Yes, definitely. If your TL783 is dead, you may want to recheck integrity and orientation of your protection-scheme around it - the 1N4007 and the three 39V Zeners.

Jakob E.
Ok!! Thanks Kingston and Gyraf, i will buy new ones on monday.

Anyways, the diodes were in the correct position, i checked them lots of times. Maybe they sold me the wrong ones(Zener)..

So, i blew up the tl783 and 2 resistors? Anyway, it has a small heat sink, isolated. But anyways, neither the first time i used it was hot, neither warm. i will change all those parts, i think it will be easier, but if its happening again, either i am really stupid or there is a problem before, with the transformers or something else or maybe the tl783c were broken before buying them.. or i applied too much heat

Thanks!
Title: Re: The official G9 help thread
Post by: g9builder on February 10, 2010, 03:26:29 AM
Hi,

I have a query regarding the transfomers. I have just completed my G9 and fired it up last night for the first time. I had no smoke and the tubes were glowing so I was pretty happy. This is my very first electronics project so was really pleased with myself. Anyway after about 5 minutes I noticed a smell and upon checking 1 of the transformers was really hot!!. I turned it straight off and thought I would ask for advice as I didn't wan't to damage anything.

The transformers have been wired as per frank ng's diagram and I have checked and double checked that it is correct. How hot should the transfromers get exactly. The other one was warm only but this one was pretty hot. The one in question is transformer 2 which is connected to the mains 230v.

Could this just be down to a faulty transformer or should I be looking elsewhere? Is there an easy way to troubleshoot this.

Regards

Ian

Title: Re: The official G9 help thread
Post by: zebra50 on February 10, 2010, 05:41:26 AM
G9 issues

These things have probably come up before but I've just noticed them so thought I'd better share...

1. HUM
If you use one of the cases from Paruska, the thick paint / coating on the case is a good insulator and will stop it connecting electrically to itself, giving you poor screening. This can cause lots of HUM. I noticed with mine that when I put the lid on, the hum got worse because of the induction in the lid! Drilling off the paint around the screws and adding lots of crimped washers fixed this nicely.

2. polarity / 'phase'
Using some boards bought ages ago from Swedish Chef - could be an old version - the absolute polarity gets inverted wrt the front panel labelling. Three places this could be wrong - input labelling or output labelling on the PCB, or the front panel. Injecting a signal (sawtooth) into the instrument input gave correct phase, so I think it may be the labelling of +/- at the mic input on the PCB. Flipping the wires at the input XLR gives an easy fix, but do check polarity of your finished build.

z50
Title: Re: The official G9 help thread
Post by: tmuikku on February 10, 2010, 07:10:45 AM
Thanks z50! Great stuff. Going to fire up mine some day soon with P case:)
Title: Re: The official G9 help thread
Post by: g9builder on February 10, 2010, 09:52:14 AM
Secondary connections to 15v

Right I still carn't work this out. I have seen lots of posts regarding the wiring for 115v models but is there one for 230? I wired it up as ngfrank detail but T2 gets very hot. I'm sure this is not right. I have attached a drawing for the connection to 15v (this is the bit I think I may have got wrong.) Can somebody tell me if this is ok or if not how this connection should be made with the three secondaries I have left.

Regards
Ian
Title: Re: The official G9 help thread
Post by: g9builder on February 10, 2010, 09:53:02 AM
Sorry problem with pic. Please find it here..
Title: Re: The official G9 help thread
Post by: Harpo on February 10, 2010, 12:49:42 PM
Not knowing your specific transformer(s), your coloured wires don't make much sense because every transformer manufacturer uses his own colour scheme.
Your 3 secondaries might/would be 2 secondaries and 1 primary winding or the other way round.
Title: Re: The official G9 help thread
Post by: g9builder on February 10, 2010, 03:28:44 PM
Thanks for taking alook Harpo. I'm ok with the primary connections  - it is just the three secondaries that I just carn't seem to get my head around.

I have redone the drawing - hope this explains it better. Hope you can help.

Cheers and many thanks

Ian
Title: Re: The official G9 help thread
Post by: Harpo on February 10, 2010, 07:07:27 PM
Ian, if your posted colour scheme from your pics text block is the same as printed on the transformer, you connect T1-yellow with T2-yellow and T2-red (in-phase secondary wires), leading to one pin of the 15VAC connector at the right edge of the pcb. Next connect T1-orange with T2-orange and T2-black (out-of-phase secondary wires), leading to the remaining pin of the 15VAC connector at the right edge of the pcb.
In Franks drawing (http://www.nrgrecording.de/Gyraf_G9_trafos.pdf), you're refering to,  he labled your T1 as 'toroid transformer 2' and your T2 as 'toroid transformer 1'.
good luck.
Title: Re: The official G9 help thread
Post by: g9builder on February 11, 2010, 03:29:06 AM
Harpo,

Many thankks indeed - thats exactly what I originally did. That means that all of the '0' v are grouped together and all the '15' v are joined together (on the three secondaries to the 15v connector). This is the way I wired it and everything seemed to work ok except that one of the transformers T1 in my drawing got very hot after only 5 min, so I thought something may be wrong? I therefore tried again as my drawing attached and something smoked immediately!!!! Lookes like I need to now check what fried and replace and retry :-(

Any ideas what would have fried? And what would be the reason for the transformer running sooo hot!! Do you think that needs replacing also?

Many thanks indeed - I'm so near completing this thing I just want to get passing some audio through it!!

Regards

Ian
Title: Re: The official G9 help thread
Post by: Harpo on February 11, 2010, 07:03:20 AM
Check orientation of all polarized parts, especially diodes and look for shorts.
If you ever powered your build with T1 secondaries in parallel, D13 and maybe D15 could be blown.

You could try to isolate the area of fault by disconnecting T2 and one of the T1 secondaries and check for healthy phantom and healthy heater voltage for the other T1 winding. When both work, reconnect T2. Be careful with high voltages.
Title: Re: The official G9 help thread
Post by: zebra50 on February 11, 2010, 07:11:12 AM
Just a thought - is there any chance at all that you have wired the 15V secondaries reverse-phase?
Title: Re: The official G9 help thread
Post by: g9builder on February 11, 2010, 07:41:32 AM
Many thanks Harpo and Zebra50,

I did test all the diodes last night and they all seemed ok ( they were in circuit though and I understand this does not always give a true sign) I will disconnect one lead from each and test again and replace anything that is blown. Strange thing is though that I cannot see any sign on any component that would suggest it has fried but there was definately smoke!!.

I will triple check all wiring before I flick the switch again....

Many thanks

Ian
Title: Re: The official G9 help thread
Post by: MeToo2 on February 13, 2010, 06:47:05 AM
I'm currently building a pair of G9's. One with OEP and one with Lundall transformers.

I have a question for you guys about shielding and earthing.

In the instructions it states that:
- Connect 0V/Gnd to chassis at one - and only one - point: At the input XLR's.
- Connect the power ground from the power inlet to the ground at the input XLS's also.

This I understand. I have employed a star grounding scheme back to the power inlet to avoid any chance of hum loops.

I also understand that on the G9 PCB that the middle/ground pin on the 3 pin output header (K3 & K103) is not connected to anything (it is a blank pad) so only signal+ and signal- go to the output transformer.

My question is the following: Is it good practice to leave pin 1 of the output XLR "floating" and rely on the input XLR of the downstream equipment to provide the overall shield all the way back to the G9 output? Or is it better to strap pin 1 of the output XLR also to ground via a wire to pin 1 of the input XLR? This won't affect the g9 circuit (as I said the pad on the PCB is not connected to anything) but it will ensure an earthed screen on the output cable (at the risk of forming a hum loop with the following bit of kit)

What's the standard practice? Earth pin one of the output XLR? Earth pin 1 of the output XLR and add the option of a ground lift switch? Or leave the output shield floating and rely on the next bit of kit in the chain for earthing the shielding on the output cable?

My gut feeling wants to add that wire between pin 1 input XLR and pin 1 output XLR.
Title: Re: The official G9 help thread
Post by: g9builder on February 13, 2010, 06:40:47 PM
I think i may have the same problem as graph. A faulty TL783. My wiring was right and to double check this I wired the 48v up and got the correct result. Then the heater 12v and got the correct result. I then checked i was getting 220v from the last pair of secondaries and I am. Once connected to the board R34 smoked again straight away. I have checked all the diodes and resisters and they are all correct and placed correctly. I have also checked all solder joints and traces.

I therefore think that the problem must be with Tl783? Would you tend to agree with this? I have been unable to test tl783 because as soon as I turn on the unit R34 takes the hit.


Regards

Ian
Title: Re: The official G9 help thread
Post by: MeToo2 on February 14, 2010, 04:38:59 AM
I think i may have the same problem as graph. A faulty TL783. My wiring was right and to double check this I wired the 48v up and got the correct result. Then the heater 12v and got the correct result. I then checked i was getting 220v from the last pair of secondaries and I am. Once connected to the board R34 smoked again straight away. I have checked all the diodes and resisters and they are all correct and placed correctly. I have also checked all solder joints and traces.

I therefore think that the problem must be with Tl783? Would you tend to agree with this? I have been unable to test tl783 because as soon as I turn on the unit R34 takes the hit.


Regards

Ian
TL783 is difficult to destroy. It has inbuilt short circuit and thermal protection. It's not expensive to replace though. On the other hand, you are irreplaceable, so be careful.

One tip that I read elsewhere and found useful was to wire up a 60W bulb in series with your mains supply. If your g9 is sucking too much power, the bulb will light thus limiting the current to less than 250mA and hopefully protect whatever is causing the problem. Otherwise if all is OK it will glow momentarily (1/2 second or so) and then go out.

I personally would not have thought R34 could be damaged easily. A 100K 2W resistor would not burn out even if it had a full 400V across it (v^2/r = 1.6 watt). R37, perhaps, r33 also. But R34?

Obvious questions. Did you check the values of your resistors with a multimeter before inserting them in the board? It's relatively easy to make mistakes with (modern) 4 and 5 band colour coding schemes.

Suggest taking things step by step from the transformers onwards.

Four potential checks:

1. Remove the TL783. Check that the bridge rectifier is working correctly and that you are getting HT DC out of it at the top of C14. Even without the TL783 in place, C14 / R33 will smooth pretty effectively under no load conditions. You should be seeing more than around 280V DC here.

2. If that is OK, reinsert the TL783. There's a jumper marked "HT" right next to the TL783. Have you tried powering up with both the 'ht' jumper and c15 removed? Then there's virtually nothing that can draw current on the TL783 side of the circuit. So at least that would point you which side to look. If that's still a problem look very carefully for shorts around the TL783 and double check the orientation of the TL783.

3. Also check c15 is still acting as a capacitor and is not short and that it was connected the right way around (it is an electrolytic and polarity sensitive). If that checks OK then reinsert C15 and test again.

4. If that's OK then try removing the valves and then reinserting the "HT" jumper. Again there should be nothing that draws significant HT current.

The HT supply in all cases should power up at somewhere more than 240V DC (I found that the TL783 doesn't actually regulate the voltage very well until it has quite a load on it)

Of course, be very careful to properly discharge the HT capacitors C14 & C15 using say a 10-100K 2W resistor and check the DC voltage on them with a meter before handling them or any other part of the board at all [I actually permanently soldered a 1Meg bleeder resistor across them so that at least they'd always discharge themselves after a few minutes even if I forgot, so have a cup of tea after every test and take it easy].
Title: Re: The official G9 help thread
Post by: g9builder on February 14, 2010, 01:02:02 PM
Many Thankd MeeToo2 - I will  work through your list.... and report back.
Title: Re: The official G9 help thread
Post by: g9builder on February 18, 2010, 06:33:34 PM
My Mistake earlier - it is R33 not R34 that is getting really hot and smoking.

I tried some stuff including removing tl783 and ht jumper and c15 and still no joy - whatever I did R33 smoked. I therefore rebuilt the 245 power section again with all new components and double checked everything diodes/zeners/resistors etc that a they were the correct values and b were not shorted and working ok and that their orientation is correct.

I flicked the switch and R33 smoked again >:(

I really am at a loss with this. I also checked all traces and they appeared ok. I am getting power ok from the transformers. The 12v and 48v work fine.
The transformer is giving me 240v to the 220 connection  - would this have anything to do with it? They are 30va 230v 2x15v.

What am I missing here? My head is starting to bleed from all the scratching...
Title: Re: The official G9 help thread
Post by: mikeyB on February 18, 2010, 07:16:53 PM
Hi G9 builder - not seen any mention of heatsinking/mounting of the TL783 -  -  have you checked isolation of TL783 - ie. make sure that the metal tab is not connected to ground/0V via the mounting bolt - you have got it heatsinked with an insulation pad - yes??
 I've done this a couple of times where i haven't de-burred the holes and when tightening the reg to the heatsink/case the sharp metal edge has pierced trough the insulating washer to the regulator, hence short to ground!!
Note from Gyraf about isolating the 12V reg - even though the tab is grounded - otherwise you can cause earth loop resulting in hum.

Hope this helps
Title: Re: The official G9 help thread
Post by: g9builder on February 19, 2010, 03:13:36 AM
Hi Yes the heatsink is isolated using an isolation kit  - silicon rubber pad  and washer and polycarbonate screw.

Could there be a problem with the pcb?
Title: Re: The official G9 help thread
Post by: g9builder on February 19, 2010, 03:30:23 AM
http://www.groupdiy.com/index.php?topic=36682.0

In doing some more searching in an attempt to sort this out I came across this thread. Now my R33 isn't smoking anymore but It gets extremely hot after a few seconds and gives off a smell - therefore I keep turning off the unit. (I think if I left it on it would begin to smoke again)

Is it right that this is fine to be running hot anyway? Could I change it to another value to help?
Title: Re: The official G9 help thread
Post by: Kir_For_Pleasure on February 19, 2010, 04:24:24 AM
is it a bad way to add a insertpoint into the g9 after r44 with switched jack then to xlr ?
Title: Re: The official G9 help thread
Post by: gyraf on February 20, 2010, 04:49:26 AM
- R33 will get hot when charging the reservoir cap. Should cool down again in a couple of seconds.

- There are no obvious place for an insert point in the G9 because of impedance issues. Attaching to R44 is the same as putting whatever after the G9, dosn't make sense as insert.

Jakob E.
Title: Re: The official G9 help thread
Post by: MeToo2 on February 20, 2010, 11:24:36 AM
My Mistake earlier - it is R33 not R34 that is getting really hot and smoking.

I tried some stuff including removing tl783 and ht jumper and c15 and still no joy - whatever I did R33 smoked. I therefore rebuilt the 245 power section again with all new components and double checked everything diodes/zeners/resistors etc that a they were the correct values and b were not shorted and working ok and that their orientation is correct.

I flicked the switch and R33 smoked again >:(

I really am at a loss with this. I also checked all traces and they appeared ok. I am getting power ok from the transformers. The 12v and 48v work fine.
The transformer is giving me 240v to the 220 connection  - would this have anything to do with it? They are 30va 230v 2x15v.

What am I missing here? My head is starting to bleed from all the scratching...

240V AC sounds perfectly normal for 2 back to back connected 15V transformers on a UK supply.

When you say 2*15V, are they two separate & fully isolated secondary transformer windings 0-15 + 0-15 like this one http://nl.farnell.com/jsp/search/productdetail.jsp?SKU=1419541, or is it a single 15-0-15 winding with a centre tap? It would help if you linked to the manufacturers data sheet. Have you thoroughly checked the wiring of your transformers to make sure there isn't an unexpected earth somewhere? Have you also checked the phase of the windings as you mentioned earlier they were getting hot? [the 220v should be floating relative to ground until you actually connect it to the board, you can test that with the power off and buzz it out to make sure there is no unexpected connection to the chassis or earth, or between windings. Check you're seeing just the expected winding resistance. No more. No less]

It would also help if you posted a zoomed photo of both sides of the HT power supply area so that we can have a look at component orientations. Back lighting the board from the top whilst photographing the trace side from underneath would help identify shorts.

If the TL783 & HT jumper & C15 are removed then there is no way that R33 should smoke. Smoking indicates that too much current is being drawn. If you read the schematic and remove the TL783 and HT jumper & C15 completely, there's no path to anywhere for current to flow through R33 of more than around 1.2mA via D3-5 plus R34-R36 (240V-117V dropped across the 3*39V zener diodes via 100K+470R+47R to earth = 123V/104K ~ 1.2mA). You've got a short either on the board or through a blown diode (e.g. D14) or a short capacitor (C14 C15) or a component connected in the wrong orientation, or something odd in the wiring of your transformers. In other words something is basically wrong in the construction of your HT supply. That's probably not news to you. As it is almost certainly a basic fault you need to apply appropriate basic debugging and not look for anything too complicated. Most likely scenario seems to be a structural mistake that you've repeated also in the rebuild e.g. zener diodes in backwards. IMVHO you're trying to change too much between tests and then expecting it all to work.

The HT supply is where you should always start a build (as there is much more potential for frying stuff downstream.) Get that stable and tested first. Suggest you temporarily remove the 15V connections to the transformers for the heater supply and the 48V supply. You can leave the components for the 48V supply and the 12V supply in place. Now remove all components around the HT supply up to and including the HT jumper, check their values individually on a meter, and also buzz it out the pads individually checking for a short to earth somewhere (with no power applied). Then build & test the HT supply step by step, single component by single component, starting with just the transformer connected to the board, test with power connected for correct voltage (approx 240V AC, but it could be higher due to no load), then build the bridge rectifier D17-D20, test again (approx 240V*1.414 peak out of bridge rectifier), then add R33, testing again (same as previous). Add in D2, D3-5, and retest. Up until this point there should be near zero current through R33. Without wishing to insult you in any way, you can of course check for current across R33 by measuring for any voltage drop across it with a well insulated meter....... current (mA) = Vdrop (mV) / 470. It should be as near as 0V as makes no difference up until now. If there's any current at all through R33 you've done something wrong, so go back a step. Now connect in C14, test. There should still be near zero steady state current through R33, except now you'll see an initial burst to charge C14 before it drops back [remember to discharge C14!]. There should be around 300V DC at the top of C14 relative to earth. Then add in r34-36 and test that. The steady state current through R33 should now be around 1.2mA after the initial surge. Then add in R37, C15, and the TL783. Again there should be very little significant current flowing in steady state, and then finally add the HT jumper. At no point should you see smoke. If you don't go step by step you'll probably continue to guess where the problem is [and inhale smoke].
Title: Re: The official G9 help thread
Post by: g9builder on February 22, 2010, 08:12:51 AM
MeToo2 - what can I say other than many many thanks.

I have now solved my problem. I'm a little embarrased to reveal but my problem was R34. I had a 100R and not a 100K resistor there. :-[

I checked my order and I did order 100k but was sent 100R instead. When I dismantled the 245 power section and rebuilt it I even checked this resistor and missed it again. ( what a fool!)

So everything was wired correct - all components were right except this one. I have burnt out 2 tl783's because of this and lost lots of sleep. If there is anything I have learnt, and I have learn't alot building this is to always check components before soldering them to the board and I mean really check them!!!

Thanks to all that have tried to help me on this issue. Now to go and pass some audio through it and hopefully smile!!. (here's hoping I make no more schoolboy errors)

Cheers

Ian
Title: Re: The official G9 help thread
Post by: MeToo2 on February 22, 2010, 09:30:00 AM
MeToo2 - what can I say other than many many thanks.

Cheers

Ian
Glad to be of help. Good luck with the rest of your build!
Title: Re: The official G9 help thread
Post by: g9builder on February 24, 2010, 04:40:47 AM
Dropped in a new tl783 and 100K resistor and everything is now fine. Tried it out last night with a a bass and it sounds great!!. Only two small problems left.

Very slight hum when gain fully cranked. I am using a Perusha case and Zebra50 mentioned something about this so will try what he suggests.

DI on channel 1 doesn't pass any audio - channel 2 is fine. Need to look at this but otherwise I'm very happy.

Once again many thanks to all that have answered my queries and helped me get my first project completed.

Regards

Ian  :)
Title: Re: The official G9 help thread
Post by: zebra50 on February 24, 2010, 04:57:26 AM
Very slight hum when gain fully cranked. I am using a Perusha case and Zebra50 mentioned something about this so will try what he suggests.

Yes, the paint is thick and insulating so you need to make sure the case connects electrically all round to complete your faraday cage. Have a look at my post a page or two earlier.

As a general point, I often troubleshoot hum issues in situ by using crocodile clip leads from one ground point to another. If the connection helps then I solder a thick wire from here to there. (But look out for those high voltage areas like the HT capacitors!) Use of too-skinny wire for grounding can be an issue.


Quote
DI on channel 1 doesn't pass any audio - channel 2 is fine. Need to look at this but otherwise I'm very happy.

Should be an obvious thing like crossed wires, bad solder joint or (less likely) a damaged socket.
Title: Re: The official G9 help thread
Post by: MeToo2 on February 26, 2010, 08:07:54 AM
DI on channel 1 doesn't pass any audio - channel 2 is fine. Need to look at this but otherwise I'm very happy.

Should indeed be very obvious if there is mic audio passing, as suggested: something like a dry joint, or header connections the wrong way round (switched versus straight through on the jack socket)

Thanks for supplying and sharing so much information and effort on this project. Jakob for the design. Gustav for the PCBs. Tat for the cases.

Here's some thoughts and hopefully constructive lessons learned after getting my first one running:

1) I had a problem with one HT supply (short near valve socket on channel 1). Fixed this, although it cost a 7812 due to a current surge. I started with building and testing the 3 power supplies all at once before starting on the audio. But with hindsight I would suggest starting with just the HT supply on its own, with nothing else on the board,  then the 12V heater supply, and finally the 48V, before moving onto the audio sections.

2) I made a dumb mistake with the orientation of one electrolytic capacitor on one 48V supply. Not sure how, as I was very careful and did the other board correctly. Mea Culpa. No damage and easy to find.

3) I had a problem with one of the switch boards. There was a short circuit solder trace hidden under the PCB header which lead to 10KHz oscillation at all gain levels. Was relatively easy to find where the problem was by removing valves to see which was oscillating, swapping out the switch board with the other channel to check if the problem moved or stayed with the channel (and it did swap channels) and then buzzing out the faulty switch board. Next time I'll check the gain boards before installing as it's relatively easy to check the correct resistances are being selected when rotating the switches. Once the short was located (it was well hidden) and then removed, everything worked fine.

4) If I was doing it again I'd probably mount the toroids on the side panel rather than the floor of the case (to stop the large bolt heads protruding below the chassis)

5) Good (star) grounding + screened cables on i/o connections seems to have worked. At least compared to domestic background levels, amp noise and hum seemed very low. Still got to measure the response properly.

6) Not entirely convinced about the layout of the switch board and PCB headers related to valve based projects compared to op amp based ones. Looking at it again it would seem better to run the DI completely separately via its own header, with the possibility of adding a strap so that you did not have to have any DI at all. The 47K gain pot is not PCB mounted which means more soldering. If you count the remaining wires I think you could fit them all into a 12 way ribbon cable (ground is duplicated), although again domestic IDT headers are also a pain. I don't really have a proper solution but I think this is worth some further thought. The "wire to board" puzzle seems to be a major part of this project. Especially around the 7812, things are very crowded if you want to fit in a decent sized heat sink. And the HT connector is physically too close to the 15V ac connector. Next project I'll do will be a point to point wired 660, so I can then compare how much effort the switch-PCB saved.

7) I'm feeling pretty good about myself for having built this, but I'm not convinced it was financially viable as a single project. A lot of DIY'ers have all sorts of additional bits and pieces lying around "for free." If you have to buy all of this stuff and tools just for one project then it can add up very quickly (especially in postage). If you also take into account there's likely to be no second hand resale value then you'll be very pushed to beat an off the shelf unit (if you can get an equivalent of course).

Anyway I think I've got the bug and I'll be building more projects.

The motivation is more for fun, and to be able make things that are simply not for sale, rather than for financial reasons.

Photos to follow.
Title: Re: The official G9 help thread
Post by: g9builder on February 26, 2010, 08:29:50 AM
I agree about the cost. This was my first project and things did stack up as I was starting from scratch, but at the end of the day I am very pleased (and quite proud) of the finished product. The best preamp I had before building this was a SPL Goldmike and this thing blows it away. I like it so much I've aleady started ordering parts to build another!!! Should be cheaper thid time around too....!!

Thanks to everyone involved in this project.... Awesome
Title: Re: The official G9 help thread
Post by: gyraf on February 26, 2010, 10:07:46 AM
Quote
Looking at it again it would seem better to run the DI completely separately via its own header,

Agreed - I'll be implementing this on a future update of the PCB..

Jakob E.
Title: Re: The official G9 help thread
Post by: beatnik on February 26, 2010, 08:45:35 PM
is this transformer ok for the g9?

http://www.musikding.de/product_info.php/info/p1400_Toroidal-transformer-230V----270V--14V.html
Title: Re: The official G9 help thread
Post by: gyraf on February 27, 2010, 12:51:55 AM
is this transformer ok for the g9?

http://www.musikding.de/product_info.php/info/p1400_Toroidal-transformer-230V----270V--14V.html

There is no simple way to tell. If you want to be sure, use the parts specified for the project.

Or try the above one out and let us know if it works.

edit: you'll probably get into trouble getting phantom power with that one.

Jakob E.
Title: Re: The official G9 help thread
Post by: beatnik on February 27, 2010, 04:52:22 AM
can you explain? because it's 14 instead of 15V?

thanks
Title: Re: The official G9 help thread
Post by: MeToo2 on February 27, 2010, 05:27:55 AM
can you explain? because it's 14 instead of 15V?

thanks
It's only got a single 14V secondary.

The original design uses twin 15V secondaries. One for heaters and the other for 48V phantom +HT.
The heater supply takes a fair current, which may load the voltage significantly.

Also what is the 270V? peak or RMS? load or no load?

Your alternative might work, or it might not.



Here's photos of my build as promised. I didn't put them inline as it uses up forum space and bandwidth.

http://i958.photobucket.com/albums/ae69/MeToo2_Prodigy/DSC00514.jpg
http://i958.photobucket.com/albums/ae69/MeToo2_Prodigy/DSC00528.jpg

I think I'll move the power transformers to the side wall and back wall. It seems to make an improvement of about 6dB on noise and mains hum even though it looks crowded.

Experiment with ribbon cable to the sub board was a partial success. The IDT headers are a pain. Next time I might just solder the ribbon directly to the board.
http://i958.photobucket.com/albums/ae69/MeToo2_Prodigy/DSC00524.jpg

I added 1meg bleeder resistors on the HT capacitors for my own peace of mind.
http://i958.photobucket.com/albums/ae69/MeToo2_Prodigy/DSC00535.jpg

I also checked the absolute phase using a 'scope. Following the wiring of the schematic and Gustav's PCB, it came out non-inverting, as you'd expect.
Title: Re: The official G9 help thread
Post by: beatnik on February 28, 2010, 05:51:30 AM
thanks!

i think i will use two transformers as specified in the project, there are rules for keeping the noise as low as possible?
Title: difference between schematic and PCB?
Post by: sirzodiac on February 28, 2010, 06:36:54 AM
Hi all,

am I crazy or did I really spot a difference between the schematic and the PCB?
Have a close look around R11, according to Jakob's schematic:
Schematic:
- One side of R11 is connected to the rotary gain switch and to R13 (680R)
- The other side is connected to R12 (1M) and C7
PCB:
- One side of R11 is connected to the rotary gainn switch, R12 (1M) and R13 (680R)
- The other side is connected to C7

Does anyone agree? What could be the difference in behaviour of the circuit? What would be the right spot for that R12 shunt resistor, before or after R11? Or is there no importance at all?

Thanks in advance!
Title: Re: The official G9 help thread
Post by: MeToo2 on March 02, 2010, 05:17:20 AM
I've just completed my second G9 build (with Lundahl transformers). Worked first time  ;D

On the tests it seems to perform slightly better than my almost identical OEP based built (only component difference is the transformers)
Most noticeable on measured signal to noise ratio. e.g. 50Hz rejection is like 3dB or so better. -72dB versus -75dB relative to a non clipping 1KHz signal.

Question for you. How do you properly mount the OEP shielding cans?

Do you just slip them on physically (which is what I did)?

I've noticed that the upper portion of the shielding cans on only 1 out of 4 OEP transformers is well connected to ground.
The other three are fitted, but look to be floating wrt to chassis.

How do you ensure that they make good contact with the shield pin on the transformer and the lower portion of the can?

Is it a question of nipping the can physically to make a good contact?
Or do you have to solder the lower plate in place to the shielding pin on the transformer before mounting on the board?
And also solder the upper portion of the can to the lower portion to seal it?

[bah probably means quite an effort to to unmount everything to redo this]
Title: Re: The official G9 help thread
Post by: g9builder on March 02, 2010, 05:24:54 AM
The later option is what I did.. solder the shilding pin to the lower plate and the upper secction to the lower plate...
Title: Re: The official G9 help thread
Post by: MeToo2 on March 02, 2010, 08:02:45 AM
The later option is what I did.. solder the shilding pin to the lower plate and the upper secction to the lower plate...
Thanks that's exactly what I've done now. Makes around 3-6dB of difference for 50Hz rejection (not surprisingly perhaps) and they now pretty much match the Lundahls within the limits of my rather poor test gear (yeah it's a sound card and it isn't fully impedance matched etc. etc.) Lundahls seem to be less load impedance sensitive. Every little helps getting that s/n figure up though.

I also got a reply from OEP too. Good customer service :) They suggested exactly the same. Solder the shield pin to the base plate at the shield pin. Then also solder the base plate to the top can at two places (next to the shield pin and in the middle at the diametrically opposite edge) See picture below.

(http://i958.photobucket.com/albums/ae69/MeToo2_Prodigy/a262_can.jpg)

Update: I've spent a couple of days now playing to see how to improve on some minor hum I had. I chased a lot of ghosts in this time, but I think it was well worthwhile.

Here's my tips on getting the S/N ratio up to well over 70dB and even possibly 80dB+ with a following wind (at least according to my crappy measurement kit anyway and of course ignoring those tube induced harmonics that we want.....).

Hope these help someone else.

1. Use screened cables for the sensitive wiring internally e.g. input and output to/from XLR to the PCB headers.
Also on the round trip to DI jack. (I had no oscillation issues without having to re-route significantly).

Make sure your grounding has no loops and goes to a common star point at pin 1 of the input XLR and it is well connected to the case (via a dedicated nut & bolt purely for grounding).

Ground the output XLR pin 1 too, and also connect the shield on the cable to the header K3/K103 (even though it isn't connected to anything at the other end on the board header).

2. The step up transformer was more of a mains noise source than the step down transformer.
Swapping their mounting position over helped a lot for very little effort. Rotating them also helped but not as much.
Keep power transformers are far away as possible from any other circuits. Physical separation is a lot cheaper than screening.

3. Scrape paint off the case around screw holes and used locking washers to ensure Faraday cage effect (thanks to Zebra50).

4. Twisted the wires to the output gain pot for the 2nd stage. This is also a relatively high impedance circuit on long wires.

5. Solder screening cans on OEP transformer properly and make sure they are well grounded.
(see above picture on how OEP recommends doing this)

6. Wait for the lift to stop before performing any measurements  ::)
Really, the heavy duty motor on the lift in my block produced more than 10dB of noise on my local mains.

Beware of refrigerators and other domestic appliances too.

7. Use more gain in the first stage if possible and then set the 2nd stage to around 70% of max

8. Use channel 1 rather than channel 2 for lower level signals.

I still have a difference between channels. Channel 1 is quieter than channel 2, but not by much.
I think that is simply due to physical proximity to the power supply and longer wires to the PCB and output connectors.

9. My Lundahl based build is clearly quieter and less sensitive to load than my OEP build even after all of this.
Whether they "sound better" is a different issue. Most people on the board seem to prefer the OEP sound. I dunno.

10. If you are running the OEPs into a modern (high impedance input) A/D converter, try terminating the output of the preamp (with around 600 ohm to 1K) to reduce hum.
Also when measuring make sure the source has a reasonably high impedance (of around 1-2K ohms) to avoid transformer ringing etc.
I got much cleaner test signals from a mic than a computer sound card.

Proper impedance matching can make another 5-6dB difference specifically for 50 & 100 Hz. Lundahls didn't seem to need this matching as much.

11. Don't use a cheap plastic 6.3mm - 3.5mm stereo jack adapter at the line input on the back of an Apple iMac. Use a solid metal one.
That can lead to a lot less frustration searching for mains noise that is nothing to do with your build  :-[

12. Turn down the sensitivity of your computer input card and use more gain on your G9.  I noticed that the noise spectrum was mainly 100Hz and its harmonics and was largely independent of gain, so I guess most seems to be leaking in either via the power supply or via the output and inter-connect cabling. Turning up the gain on the computer just increases the mains hum, whilst lowering your headroom and encouraging input clipping on the ADC or input amp. Old style valve circuits will drive +28dBU ~ ±15V so give them room to breathe.

13. Use the low cut filter in 'low' mode if you really don't need bass extension. Without the filter in place I measured the 3dB point at round 17Hz on OEPs and 24Hz on Lundahls and it was basically really flat down to around 33Hz which is around the lowest C on a piano (and lower than a standard E bass) so if you don't need it to record that low then filter it. I've heard reports that the bass response is solid and I can see why with that frequency response together with oodles of headroom.

Update March 7th. I've done some experimentation with MuMetal Ultraperm 80 sheet. It wasn't the most scientific test. I placed a cylinder around each of the transformers and checked on a spectrum analyzer whether it made any visible difference. As far as I could see any difference (if any) was negligible. Pretty much what I expected as it is probably saturating with such strong fields, but anyway I thought I'd give it a try. Probably better just to spend your money on decent interconnects and mic cables.
Title: Re: The official G9 help thread
Post by: sonolink on March 24, 2010, 08:06:23 PM
Hi,
I would appreciate your feedback to help me choose my toroids for the G9 I am building. Which pair would you advise me to pick? I don't exactly understand the differences or conveniences between these:

http://es.farnell.com/multicomp/mcfe030-15/transformer-30va-2-x-15v/dp/9531726
http://es.farnell.com/multicomp/mcta030-15/transformer-30va-2-x-15v/dp/9530312
http://es.farnell.com/multicomp/mcfe050-12/transformer-50va-2-x-12v/dp/9531777
http://es.farnell.com/multicomp/mcta050-12/transformer-50va-2-x-12v/dp/9530363
http://es.farnell.com/multicomp/mcta050-15/transformer-50va-2-x-15v/dp/9530371

Thanks for your help and time

edit: a small extra question: a friend told me to use a Light Bulb Current Limiter (Variac) to test a newly built amp to protect from frying expensive parts in case something is wrong. Is this true at all and advisable? Thanks again
Title: Re: The official G9 help thread
Post by: Stagefright13 on March 25, 2010, 01:38:12 AM
MeToo2 did you actually listen to a WORKING G9? And use it on what it rules at? What other pre's did you compare it to? And are you a professional audio engineer?

To me this is a specialty preamp that has a sound that CANNOT be produced from anything else. I also use API style pres too... Arguably they don't produce proper waveforms either.

Actually neither produce the waveforms a scope would want to see. But sound is in the ears. And the G9 produces a special sound. And I personally love it.

John
Title: Re: The official G9 help thread
Post by: MeToo2 on March 30, 2010, 07:21:29 AM
MeToo2 did you actually listen to a WORKING G9? And use it on what it rules at? What other pre's did you compare it to? And are you a professional audio engineer?

To me this is a specialty preamp that has a sound that CANNOT be produced from anything else. I also use API style pres too... Arguably they don't produce proper waveforms either.

Actually neither produce the waveforms a scope would want to see. But sound is in the ears. And the G9 produces a special sound. And I personally love it.

John
No I did not listen to a WORKING G9. Not sure what you mean by this comment. I think my G9's were working just fine. For the record I was looking at a spectrum analyzer, not an oscilloscope. I'm not criticizing the design at all. I was not trying to reduce or modify any tube or transformer dynamics in any way. The harmonics added to the signal by the design were exactly as I'd expect (mainly 2nd 3rd & 5th) and are of course an integral part of the character. I don't count these as "noise" because we specifically want them. I was just trying to improve the general signal to noise ratio of my builds, especially noise due to 100Hz (diode rectifier switching of mains power) and its harmonics, which dominated the general noise floor. That's a comment I've seen from other builders that individual builds of the design can be sensitive to hum (also a comment from the designer, Jakob.)  I don't think it ever does any harm to get the general noise floor as low as possible, as long as it doesn't turn into just a numbers game like discussions on 192KHz 24 bit versus 96KHz 16 bit  [Don't get me started on that. Clock jitter is far more significant than word length at these levels.] Talking about trusting your ears: when I started out, the hum and buzz on my builds were much more noticeable than any hiss at high gain, so that's why I went for that. At the end of my trials and various experiments I could turn up all gain switches to max and I could barely hear any hum at all with zero signal even with max gain on all components in the chain, whilst the signal was obviously deafening at that point. That's the point at which I was happy and I stopped. I just thought I'd share those experiences with others on this board. Your mileage may vary on your own build. As for professional qualifications, I'm a chartered electronic engineer BEng CEng MIET if that makes any difference at all.

Hi,
I would appreciate your feedback to help me choose my toroids for the G9 I am building. Which pair would you advise me to pick? I don't exactly understand the differences or conveniences between these:

http://es.farnell.com/multicomp/mcfe030-15/transformer-30va-2-x-15v/dp/9531726
http://es.farnell.com/multicomp/mcta030-15/transformer-30va-2-x-15v/dp/9530312
http://es.farnell.com/multicomp/mcfe050-12/transformer-50va-2-x-12v/dp/9531777
http://es.farnell.com/multicomp/mcta050-12/transformer-50va-2-x-12v/dp/9530363
http://es.farnell.com/multicomp/mcta050-15/transformer-50va-2-x-15v/dp/9530371

Thanks for your help and time

edit: a small extra question: a friend told me to use a Light Bulb Current Limiter (Variac) to test a newly built amp to protect from frying expensive parts in case something is wrong. Is this true at all and advisable? Thanks again
Jakob specified the transformers as 30VA. He knows what he's talking about. So all of the ones you chose should work. The totally enclosed transformers do look pretty interesting (MCFE030/15). Unfortunately Farnell don't do a 30VA in 12V version (no MCFE030/12.) Check out the physical dimensions of these two: mcfe050-15 & mcfe050-12 to see if they'll fit easily in your case. They are quite a bit bigger physically. It's actually over specified for the power, but I do not think that larger transformers will do any harm because the supply is regulated later, so any over-voltage at low load will be compensated. Might also be worth a look and they only cost a few cents more. Otherwise the others should work.

Yes it can be a good idea to run say a 60W light bulb _in_series_ with your valve project when you first test your power supply.
Title: Re: The official G9 help thread
Post by: sonolink on March 30, 2010, 10:03:33 AM
MeToo2,
thanks for your previous list of tips. I am quite amazed at the noise elevators can put in mains!! The mains in the studio I work should be isolated, but you never know!!

About the Toroids, I agree, it's a shame there isn't a 30VA/12V version. I needed to know if overpowering it at 50VA was ok. I think I'll definitely go with the encapsulated ones with probably a big nylon screw or similar. My OEPS arrived this morning and I've been through my shopping list 3 times already, checking all Lead Spacings and comparing the various BOMs (especially Skylar's) with Jakob's. I just need tubes, knobs and the switch.

I will build first the Variac and a Condenser bleeder. It's been about a couple month reading, planning and shopping, preparing everything.....now I can't wait to begin the battle  ;D

Thanks again for your time and help
Cheers
Title: Re: The official G9 help thread
Post by: ianmgull on March 30, 2010, 10:56:15 AM
Hey all. I'm designing my front panel and ran into a snag. I have the 12 position Lorin rotary switches  for the gain swith. I know the G9 uses 11 steps so I'll have to adjust the switch.

Assuming the normal travel is 300 degrees, should the gain index now be 275 degrees? (12positions/300degee rotation= 25degrees per position). The only reason I'm not really sure is because on all the G9 pics I've seen it appears as though they spaced 11 positions out over 300 degrees.

Thanks
Title: Re: The official G9 help thread
Post by: ChrisPbass on March 30, 2010, 11:56:07 AM

About the Toroids, I agree, it's a shame there isn't a 30VA/12V version. I needed to know if overpowering it at 50VA was ok.


Hi Sonolink, you'll be fine with 50VA tx's. The circuit will only pull the current it need's so using a bigger tx won't 'force-feed' it more juice. You could use a 2000VA tx and it would be ok, but obviously the further increase from spec increases the size/weight/cost/interference factor and makes it less practical.


Chris
Title: Re: The official G9 help thread
Post by: sonolink on March 30, 2010, 06:11:17 PM
Thanks Chris. I have learnt this now and I'm most grateful about it :)
I couldn't find the a toroid that corresponded to Jakob's specs!!
So it's ok now. I have also learnt that Caps work pretty much in the same way +/-, meaning that if the BOM states a 47uF/63V cap, I can use a 47uF/100V, without going through 50 shops!!  ;D

Thanks for your tips and time.
Cheers
Sono

Edit: If I'd like to change the original 12V/50mA pilot light for a 4,4V/50mA would I be ok by putting an 88 Ohms resistor on the positive side of the light? (I'm guessing this using Ohm's Law V=IxR, of course but am unsure if it applies like that)
Thanks for any confirmation before I order :)
Title: Re: The official G9 help thread
Post by: MeToo2 on March 31, 2010, 03:55:02 AM
Hey all. I'm designing my front panel and ran into a snag. I have the 12 position Lorin rotary switches  for the gain swith. I know the G9 uses 11 steps so I'll have to adjust the switch.

Assuming the normal travel is 300 degrees, should the gain index now be 275 degrees? (12positions/300degee rotation= 25degrees per position). The only reason I'm not really sure is because on all the G9 pics I've seen it appears as though they spaced 11 positions out over 300 degrees.

Thanks
Adjusting the Lorlin switches is a piece of cake although a little bit fiddly the first time you do it. Just remove the nut and lock washer and you'll see a 'stop' washer with a tag on it.(assuming you ordered the version with "stop included".) Simply move this little stopper washer tag around to the location marked with the number of positions you want to be able to select. The standard switch version has THIRTY (30) degree indexing. Normal travel for 12 positions is 330 degrees (11 spaces between positions). That means for 11 positions you have 10 spaces * 30 degrees = 300 degrees. I think you were probably counting the positions rather than the spaces between positions.
Title: Re: The official G9 help thread
Post by: sonolink on April 04, 2010, 12:05:45 PM
Please I need to be sure about this:
If I'd like to change the original 12V/50mA pilot light for a 4,4V/50mA would I be ok by putting an 88 Ohms resistor on the positive side of the light? (I'm guessing this using Ohm's Law V=IxR, of course but am unsure if it applies like that)
Thanks
Title: Re: The official G9 help thread
Post by: Graph on April 04, 2010, 07:59:54 PM
I want to make some questions, because i am having some troubles with the 245v PSU of the G9.

I am using a 220:15+15 and 220:12+12 like i said before.

This time i didnt burned R34, but i have made some calculations, and i think there is something wrong with the Voltage.

The output of T2, is 275Vac, after D17-20 regultates 360v. At the Tl783 input i have 360v(), and after the regulation i have 350v aprox(this was measured in the capacitors C14-15). i have Read the TL783 datasheet, and we came with the following formula:

Vo=1.25(1+R2/R1)
Vo=1.25(1+100k/517)= 240v



In the datasheet warns to dont use differential in/out more than 125v.

my question is,
1) Why the TL783 is not regulating fine?
2) If it is really regulating, why if i have 360Vdc in the input i should have 240Vdc?

One another question. I have made some calculations, and its ok with that input voltage to generate 360Vdc, isnt this a really high voltage?

Sorry if this was asked before, i couldnt find an answer with the search function.

PS: Sorry for my bad english, i am not a native english person.

btw:  Look my nice project :)
(http://img203.imageshack.us/img203/4606/imagen122h.th.jpg) (http://img203.imageshack.us/i/imagen122h.jpg/)
Title: Re: The official G9 help thread
Post by: audiophreak on April 04, 2010, 09:20:13 PM
Hi All,
       I have read in different threads including this one that channel #2 on the G9 seams to have a little more noise that channel one. I have three G9s now and absolutely love how they sound, but have noticed that at least on my units this is true, channel 2 does in fact have more noise than channel one.
      I am curious to know if this is due to the approximate position of the PTs, its seams that most people, me included, placed the main PCB in the front left corner of the case  and the PTs in rear right corner, OR is this noise do to proximity of the PSU ciruit on the main PCB in relation to channel 2 on the PCB ?  

    I ask because I was thinking of mounting the PTs on the outside back panel like I've seen on Pultec EQs and other vintage gear but don't want to go through all that trouble if the noise is from the PSU circuit on the PCB.

  any and all advice welcome,
                                       Thanks,
                                                  Chip

   BTW ... Graph ..  I'm in no way any kind of expert, but I think the circuit needs to be loaded with the tubes in place to take accurate measurements ,  anyone please correct me if I'm wrong.
Title: Re: The official G9 help thread
Post by: Graph on April 05, 2010, 08:29:00 PM

   BTW ... Graph ..  I'm in no way any kind of expert, but I think the circuit needs to be loaded with the tubes in place to take accurate measurements ,  anyone please correct me if I'm wrong.

Are you sure? the voltage shouldnt drop to 240v if i connect the tubes.. the voltage is regulated anyways.. thats as far as i know, maybe the TL783 works in other way. I am testing the power supplys, if this isnt working, i will have then 350v running through the 250v caps, i dont think its ok.

I will try with a 220:15+15v using it as T2, i will drop the voltage to a lower value, maybe the TL783 if its not fried up, will regulate better.

Thanks! I hope somebody can give me a confirmation of this or a better explanation :)
I really appreciate the info here.
Title: Re: The official G9 help thread
Post by: audiophreak on April 05, 2010, 09:34:09 PM


  Graph .. take a look at the bottom of page 28 of this thread, don't know if this is the problem your facing, but that's were I got the " Tubes in " reference. as well as I've done some work with building and modding tube microphones and with tube mics, voltages need to be checked with the mic plugged in so tube loads the PSU circuit to get accurate voltage reading.

   Again, if I am wrong or misleading, someone please  correct me.
Title: Re: The official G9 help thread
Post by: sonolink on April 06, 2010, 08:03:45 AM
Please can someone help me with this?
If I'd like to change the original 12V/50mA pilot light for a 4,4V/50mA would I be ok by putting an 88 Ohms resistor on the positive side of the light?  :-\
Thanks
Title: Re: The official G9 help thread
Post by: Graph on April 06, 2010, 11:40:10 PM


  Graph .. take a look at the bottom of page 28 of this thread, don't know if this is the problem your facing, but that's were I got the " Tubes in " reference. as well as I've done some work with building and modding tube microphones and with tube mics, voltages need to be checked with the mic plugged in so tube loads the PSU circuit to get accurate voltage reading.

   Again, if I am wrong or misleading, someone please  correct me.
I have read again the Specs of the  TL783 :)

It needs 14mA of current to regulate.. so maybe... it isnt regulating either... that may be the reason and its probably working fine. With the Tubes Load in, i think it will consume at least 14mA.

But anyways... 360v isnt too much? obiusly the zener will drop itif it goes more than 10v up, but making this happen you are not using the zener as protection, u are using it as a necessary element in the design. With T2 at 220:15+15 it should have 308Vdc aprox, a differential input of 63v instead of 115v(anyways it should work), arent we throwing in so much voltage to the regulator?

Thanks for your answer i am saying this because i want my G9 to work propperly and dont have burned capacitors in a few days or anything, its my first time using a regulator in a Tube design. If this is really ok, i will continue the G9 :)

Thanks again audiophreak, u werent wrong about that.
Title: Re: The official G9 help thread
Post by: MeToo2 on April 09, 2010, 03:26:00 PM
I have read again the Specs of the  TL783 :)

It needs 14mA of current to regulate.. so maybe... it isnt regulating either... that may be the reason and its probably working fine. With the Tubes Load in, i think it will consume at least 14mA.

But anyways... 360v isnt too much? obiusly the zener will drop itif it goes more than 10v up, but making this happen you are not using the zener as protection, u are using it as a necessary element in the design. With T2 at 220:15+15 it should have 308Vdc aprox, a differential input of 63v instead of 115v(anyways it should work), arent we throwing in so much voltage to the regulator?

Thanks for your answer i am saying this because i want my G9 to work propperly and dont have burned capacitors in a few days or anything, its my first time using a regulator in a Tube design. If this is really ok, i will continue the G9 :)

Thanks again audiophreak, u werent wrong about that.
The regulator really does seem to need a very significant load before it starts to regulate. Otherwise you will basically measure the smoothed output of the rectified step up transfomer (which is in itself high because the transformer has no load either)

I had the same concern as you when I first tested.

So before it starts properly regulating, you can measure anywhere North of 220V * 15 / 12 (transformer ratios) * 1.4 (full wave rectifying) = 388V under zero load. So 360V does not sound unusual in a zero load condition.

You can always first test your power supply with a bunch of 5 or 6 off 100K 1W resistors in parallel if you don't want to try live with your tubes the first time. That'll give a load of around 15 - 18 mA and it should start regulating properly then.
Title: Re: The official G9 help thread
Post by: MeToo2 on April 09, 2010, 03:37:01 PM
I am curious to know if this is due to the approximate position of the PTs, its seams that most people, me included, placed the main PCB in the front left corner of the case  and the PTs in rear right corner, OR is this noise do to proximity of the PSU ciruit on the main PCB in relation to channel 2 on the PCB ? 
I would really value hearing the results of your tests. I looked for quite a while at residual noise sources and eliminated quite a few of them in my build: they were nothing to do with design but certainly to do with specific build and layout. I gave up on further testing once I reached a certain level that I was happy with. I *suspect* (not proven!) that the physical layout that everyone uses combined with the proximity of the transformers & rectifier diodes + first line smoothing to both the switching board (high impedance controls) AND the second channel output transformer is the issue, but I have no proof. It doesn't seem to be the 48V voltage multiplier chain or phantom power regulation circuit which I initially suspected: completely disconnecting the 15V supply to that makes no difference at all to the noise floor. I also tried smoothing my mains before it even entered the box, and also a dummy "loopback" cable on my test gear and that made no difference at all either, so any effects are within the box. Another simple test to prove it wasn't the 12V heater supply (which was a suspect because it draws significant current @100Hz and its harmonics) was to unplug the 15V AC supply from the input to the rectifier of the 12V heater circuit and plug in a 15V DC 1.5A lab power supply instead. Required no soldering or difficult testing. But the noise floor didn't change significantly so that wasn't the direct source either. I personally doubt that much significant gets past the regulators (either the 7812 or TL783) to the rest of the amp that way because that would probably show up on both channels. You could eliminate HT noise getting in via the regulator as a cause by placing a 10H choke in place of R33. Haven't tried that yet personally but might do now as I have one lying around spare. Which would just then leave the main suspects as everything upstream of the 7812 & TL783 up to the mains socket (2*full wave rectifiers for heater & HT D13-D20, first stage capacitive smoothing C14 + C16-C18, transformers & wiring). You could always just move them around without actually bolting them on or drilling holes, as an initial test. It would be a very valuable test for a lot of people because I believe many have toyed with external power supplies (in a completely separate box), or shielding, or potted transformers, or enclosing the transformers & rectification in a separate shielding can in the same box, but I haven't seen any definitive results. Damn you've got me all interested again but I've no real time at the moment......
Title: Re: The official G9 help thread
Post by: sonolink on April 13, 2010, 08:06:02 AM
Thanks for your help and time...
Title: Re: The official G9 help thread
Post by: Graph on April 13, 2010, 11:51:14 AM
I have read again the Specs of the  TL783 :)

It needs 14mA of current to regulate.. so maybe... it isnt regulating either... that may be the reason and its probably working fine. With the Tubes Load in, i think it will consume at least 14mA.

But anyways... 360v isnt too much? obiusly the zener will drop itif it goes more than 10v up, but making this happen you are not using the zener as protection, u are using it as a necessary element in the design. With T2 at 220:15+15 it should have 308Vdc aprox, a differential input of 63v instead of 115v(anyways it should work), arent we throwing in so much voltage to the regulator?

Thanks for your answer i am saying this because i want my G9 to work propperly and dont have burned capacitors in a few days or anything, its my first time using a regulator in a Tube design. If this is really ok, i will continue the G9 :)

Thanks again audiophreak, u werent wrong about that.
The regulator really does seem to need a very significant load before it starts to regulate. Otherwise you will basically measure the smoothed output of the rectified step up transfomer (which is in itself high because the transformer has no load either)

I had the same concern as you when I first tested.

So before it starts properly regulating, you can measure anywhere North of 220V * 15 / 12 (transformer ratios) * 1.4 (full wave rectifying) = 388V under zero load. So 360V does not sound unusual in a zero load condition.

You can always first test your power supply with a bunch of 5 or 6 off 100K 1W resistors in parallel if you don't want to try live with your tubes the first time. That'll give a load of around 15 - 18 mA and it should start regulating properly then.
Yeah, its regulating fine now :) i hope this days i will have some time to finish it.



Title: Re: The official G9 help thread
Post by: audiophreak on April 13, 2010, 04:14:16 PM
Glad to hear that Graph  :)   keep us informed as to your progress. 
Title: Triumph of ignorance
Post by: JimboJohnson on April 15, 2010, 08:40:58 AM
Hi all - new here, and may i offer my congrats on a great piece of gear. I'm on here as a mate bought a half finished G9, and had me rewire it properly. It was very ugly, with mistakes everywhere, but i think i've got it working pretty well. There's some oscillation, but I've seen some info previously to fix that....

The main thing that's stumped me, is the phantom out. We had 70 volts coming out....

On further investigation - 56 volts across the zener diode, 70 odd volts out of tip121, 70v out of D12.  I've managed to bodge out 48 volts out by replacing D12 with a link, and r41 with 1k5.  It works, but obviously, would be nice to know why 70v in the first place - seems like there's one too many diodes in the voltage quadrupler, but i'm just a hack....

Many thanks,
Jim
Title: Re: The official G9 help thread
Post by: gyraf on April 16, 2010, 03:28:50 AM
Quote
would be nice to know why 70v in the first place

Most probably a blown P48 regulating transistor, T1. This happens sometimes when shorting the 48V-line.

Or maybe a broken connection from ZD56 over trimmer to base of T1.

Measure base voltage on T1, should be adjustable from ca 40-55V by the trimmer. If not, check circuit vs schematic. If base regulates right, but output stays up at +70, then transistor has a C-E short, replace.

Jakob E.
Title: Re: The official G9 help thread
Post by: PeteSanders on April 23, 2010, 04:43:51 PM
Hello there!

Can I get some suggestions to fix my new G9 please?

Power - p48, 12v and 245v seem to be OK (I get 242v, have 110 mains or something).

It passes audio, but only when phase switch is in the - position.  The gain and output pot aren't kicking in.

If I press on the board around the input tube area, it suddenly sounds fuller and a littler louder.  Checking audio connections - might be my cheesy crimp-pin job on the xlr's.

I'm not sure what to look at.   I hard-wired the panel to the mainboard.  Using a p48 condenser mic for the testing.
Title: Re: The official G9 help thread
Post by: PeteSanders on April 23, 2010, 09:00:55 PM
I'm looking over the r32 and r44 areas and schematic around the output transformer.
Title: Re: The official G9 help thread
Post by: PeteSanders on April 23, 2010, 10:19:26 PM
OK,gain and ouput now work; bad etching job.  Phase prob still there, and sounds etter when I press on the main board - something kicks in.
Title: Re: The official G9 help thread
Post by: gyraf on April 24, 2010, 01:13:38 AM
use ohmmeter to check signal path through phase switch. refer to schematic.
Title: Re: The official G9 help thread
Post by: PeteSanders on April 24, 2010, 10:44:06 AM
Thanks!
Have been doing that; I got the 6-position 2-pole Lorlins - bends my brain.  Have that one set to two-pos.

I had miswired two legs of the relay together; now the bend-board issue has stopped. 

Sounds good, except it's low-volume, maybe half what it should be.   My TL783 gets hot; I have the thin u-shaped heatsink plus 3 large washers on it.  Getting 12.2 volts on the jumper wire.

Not noisy, and the DI works.  I don't think the hi-low filters are working.
Title: Re: The official G9 help thread
Post by: sonolink on April 25, 2010, 09:37:01 AM
Any chance someone can help me with this, please?
If I'd like to change the original 12V/50mA pilot light for a 4,4V/50mA would I be ok by putting an 88 Ohms resistor on the positive side of the light?
Thanks
Title: Re: The official G9 help thread
Post by: Harpo on April 25, 2010, 04:05:32 PM
Any chance someone can help me with this, please?
If I'd like to change the original 12V/50mA pilot light for a 4,4V/50mA would I be ok by putting an 88 Ohms resistor on the positive side of the light?
Thanks
(12V - 4.4V) / 0.05A = 152 ohm will be the resistors min.value.
(12V - 4.4V) * 0.05A = 0.38W, so this resistor should be rated for at least 0.5W.
This 152R (next avail.standard value 160R or 180R) in series with your light for an at least 7.6V drop could be connected to either side of your bulb. This value might apear still too bright, so you might increase it to taste.
Title: Re: The official G9 help thread
Post by: sonolink on April 25, 2010, 09:10:44 PM
@Harpo
Thank you very much indeed. Of course I should have calculated the resistance needed for a Voltage drop of 7,6V!! I don't know how I came up with 88R...still too much of a beginner in circuit analysis...I think a 220R will probably work ok.
I very much appreciate your time and help and definately owe you a beer  ;)
Cheers
Sono
Title: Re: The official G9 help thread
Post by: PeteSanders on April 26, 2010, 04:35:39 AM
I just noticed (  :-[ )  that the 10-pin header on the control panel isn't ordered the same as the main board and I had been wiring them straight across.


I changed one channel's cables so the labels are matched with the identical ones, and now have different-sounding wrong things happening. 

More is going right on the straight-across channel - brain fatigue setting in; going to bed... nuh.....
Title: Re: The official G9 help thread
Post by: gyraf on April 26, 2010, 05:26:36 AM
I just noticedthat the 10-pin header on the control panel isn't ordered the same as the main board and I had been wiring them straight across.

..but they are..
Title: Re: The official G9 help thread
Post by: sonolink on April 26, 2010, 09:44:49 AM
I just noticedthat the 10-pin header on the control panel isn't ordered the same as the main board and I had been wiring them straight across.

..but they are..

They're not on my boards either, Jakob. I have Audiokitchen Rev#1 2002 boards bought a few weeks ago.
10-pin header on my main boards are as follows Left to Right:
NC, P48, Line, From 12V, From 48V, Out-, Out+, Trafo +, Trafo -, To Outamp
10-pin header on my control boards are as follows Left to Right:
NC, P48, Line, From 12V, From 48V, Trafo +, Trafo -, Out-, Out+, To Outamp
Unless this is meant to be like that, Trafo and Out connections seem to be interchanged
Title: Re: The official G9 help thread
Post by: PeteSanders on April 26, 2010, 01:16:04 PM
OK,
thanks; back to the straight-across-wiring then.

Channel 1 is mostly working good now; A couple things to fix. No noise probs.

Ch 2 needs work.

Is that unconnected trace from P1 to the bottom of the Phase switch supposed to be left unconnected?

Looks like it's not needed.
Title: Re: The official G9 help thread
Post by: mattyblue on April 26, 2010, 08:46:10 PM
Has any ever tried the 12av7's in their G9?
Title: Re: The official G9 help thread
Post by: sonolink on April 26, 2010, 10:20:28 PM
I just noticedthat the 10-pin header on the control panel isn't ordered the same as the main board and I had been wiring them straight across.

..but they are..

They're not on my boards either, Jakob. I have Audiokitchen Rev#1 2002 boards bought a few weeks ago.
10-pin header on my main boards are as follows Left to Right:
NC, P48, Line, From 12V, From 48V, Out-, Out+, Trafo +, Trafo -, To Outamp
10-pin header on my control boards are as follows Left to Right:
NC, P48, Line, From 12V, From 48V, Trafo +, Trafo -, Out-, Out+, To Outamp
Unless this is meant to be like that, Trafo and Out connections seem to be interchanged

So are they meant to be connected straight forward or i.e: Out- to Out-, Trafo+ to Trafo+, etc?
Title: Re: The official G9 help thread
Post by: gyraf on April 27, 2010, 12:22:39 AM
Quote
10-pin header on my control boards are as follows Left to Right:
NC, P48, Line, From 12V, From 48V, Trafo +, Trafo -, Out-, Out+, To Outamp
Unless this is meant to be like that, Trafo and Out connections seem to be interchanged

You're right - this is a pcb overlay error that I didn't spot before.

The connectors are meant to go straight over between main pcb and control pcb, 1:1

The marking error only affects absolute polarity of output signal (like flipping the phase switch) - so this is not the problem you're having.

Jakob E.
Title: Re: The official G9 help thread
Post by: PeteSanders on May 16, 2010, 10:18:17 PM
Help!

I don't know what I did, but now my power is escalating; I replaced the IC's, checked diodes and resistors for the power sections - they seem OK.  HT now starts at about 300 and climbs fast; unregulated is higher, p48 gets up to 60v, 12v gets 15v.  I haven't let it stay on very long.  Power was working OK before this, generally was working and sounding good.

When this happened, I was pursuing a little voltage present at input xlr on ch 2; I found that, when the inst jack is selected, the ch 2 relay measures with a short across where the D107 diode is (when the power is off).  But the ch 1 relay gives the coil impedance .288 for all three selections.  I have the omron G5V-2-DC12 ones.  Which channel's relay is the way it's supposed to be?    

I don't know if these happenings go together or not;  the voltage still rises if I don't select the DI jacks.
Title: Re: The official G9 help thread
Post by: gyraf on May 17, 2010, 07:01:50 AM
As mentioned several times before in this thread, measure voltages under load, i.e. mount the tubes and let them heat up (~30sec.) before trusting your reading.

Jakob E.
Title: Re: The official G9 help thread
Post by: PeteSanders on May 17, 2010, 01:17:01 PM
Tubes were in;
This morning the HT voltage wasn't a problem - I think it was my meter & battery - a lot of readings had been moving around.  Maybe tube seating.  I hesitate to blame crystal meth or tequila. 

I'm getting a grip on the other issues; am not whimpering anymore.



Pete
Title: Re: The official G9 help thread
Post by: gyraf on May 21, 2010, 08:26:16 AM
..make sure to heatsink the 7812 very good, or it will overheat and then power down - leaving the HT to rise because of lost heating and thus lost load.

Jakob E.
Title: Re: The official G9 help thread
Post by: ianmgull on May 24, 2010, 07:29:03 PM
Quick question. How important is it to heatsink the TIP121 (48v phantom transistor)? I don't have very much space and I thought that this one doesn't generate much heat. Do you guys think I can get by without a heatsink on this? Thanks!!!
Title: Re: The official G9 help thread
Post by: tmuikku on June 12, 2010, 03:40:38 PM
Hi all!

I bought almost finished G9 from Gustav some time ago. I wired it up and everything seemed to work (voltages seem right, passing audio, all controls work as espected). The unit did not give that much gain with either channel and cranking first stage gave nasty sounding distortion. Since then I really haven't had any time to start troubleshooting until today.

I hooked up a sine generator (unbalanced connections between G9 and my soundcard). If I hook scope to xlr input pin 2 and DI socket there is a lot of attenuation and phase shift, the lower the frequency the worse. Same when measuring from output.

Now, is this something to do with my poor scoping skills, interfacing, bad tubes (tried to swap them, both channels behave similarly) or some fault in the build? I just checked most of the resistors and verified that transformers are correct type (OEPs in cans). All connections to control boards seem to be right and no solder bridges spotted. I also read this thread through and there were about 3-5 people with similar issues PeteSanders and mamiti naming a few but no one got any answers...

Unfortunately I don't have a camera right now to take pictures. I don't have screened cables yet for XLR in/out connections. Grounding is done with all XLR pin 1 to starground and DI socket is wired with screened cable as per oscillation fix mod thingy. What should I test and try next? All help appreciated!

Edit
I've attached an image: pink noise from sound card to G9 input (input to DI looks about the same) and G9 output back to sound card. The roll off slope does not change when fiddling with G9 gain settings... Why there is such a roll off, what can cause it? Also with 100Hz sine this thing seems to distort pretty badly and much much earlier than with say 1000Hz tone.
Title: Re: The official G9 help thread
Post by: Grooveteer on June 13, 2010, 12:07:45 PM
I finally finished my first G9. (it's been on the shelf for 2 years)

Funny thing: gain steps 1-4 are OK.  After that (5 and up) the signal gets weaker. This happens on both channels. I've checked the resistor values around the gain switch and they are correct.  HT voltage is a nice 243V.  Does anyone have an idea what this could be?  '

Thanks,

G
Title: Re: The official G9 help thread
Post by: Kingston on June 13, 2010, 12:42:05 PM
Edit
I've attached an image: pink noise from sound card to G9 input (input to DI looks about the same) and G9 output back to sound card. The roll off slope does not change when fiddling with G9 gain settings... Why there is such a roll off, what can cause it?

Turn the SPAN FFT "slope" setting to 0.0 dB. You're looking at a 3dB per octave tilt on the FFT display only. nothing to do with the preamp.
Title: Re: The official G9 help thread
Post by: tmuikku on June 13, 2010, 02:16:54 PM
@Kingston, hahaa, your are right! But I wish it was the only fault... Here are pictures with white and pink noise (some freeware generator, crest factor was on setting 1.42:1 if it matters? Don't know what that is, some bottom boost?) to DI and line input. The upper screen is directly from DA out to AD in for comparison and the screen below is DA -> G9 DI -> AD with both gain potis at 12 o'clock.

The third picture with three screens is mains hum on top (line input connected but no signal), middle is with white noise to line input and the bottom is pink noise to line input. Low cut seems to be working but it is not on. Can some faulty capacitor do this?

white noise
Title: Re: The official G9 help thread
Post by: tmuikku on June 13, 2010, 02:19:19 PM
same with pink noise ( this is because there is that low end boost in adda loop, changin crest factor seemed to boost more)
Title: Re: The official G9 help thread
Post by: tmuikku on June 13, 2010, 02:20:06 PM
same signals to line input instead
Title: Re: The official G9 help thread
Post by: Kingston on June 14, 2010, 06:58:57 AM
I can't imagine how a faulty or wrong capacitor could cause such a clean tilt.

But a broken transformer, or one connected wrong certainly can.

Double check your transformers, input and output, how you've connected them, or if you actually have the correct types installed. Or maybe even connected mirrored?
Title: Re: The official G9 help thread
Post by: tmuikku on June 14, 2010, 07:05:02 AM
Thanks Kingston, I'll concentrate on that area. I believe OEPs cant be oriented wrong since they have shield pin on one end and it will go to pcb only one way.

Edit:
I checked wiring again and it seems to be correct and measured dcr from transformers and they match OEP spec sheet... Can transformers be still faulty?

I'm retiring for few days and then try to find a spot with a scope where bottom end disappears. The slope seems to be about 6db so it might be some way of resistor somewhere. I don't know if caps can be that way of without remarkable physical size difference?:)
Title: Re: The official G9 help thread
Post by: Graph on June 15, 2010, 12:38:07 AM
Hi again.

I am running oscilation problems and hum problems now. All the cables are shielded.

Most of the hum noise comes from the potentiometers, could it be some grounding problem?

I guess for oscilation i will try the solution of running the shielded cable to the track.

Thanks! :)
I will try to give more information to my problems if they keep happening, and trying other things.

Edit: There is additional noise from the balanced input rather than unbalanced input, can phantom power create noise?
Title: Re: The official G9 help thread
Post by: flintan on June 28, 2010, 03:46:38 PM
I'm having some problems with the 48V supply. I can adjust the voltage with the trimmer but only up to 35V and then it stops there, the trimmer is at it's end.

I have 70V DC after the voltage tripler, as seen in the attached image, but it drops to 35V at the junction of R40 and D6. Could it be the zener that is bad or is it something else?

Everything is built into the case and i've been using it for almost a year but decided to add PP now..so i want to be pretty sure what to change before mounting everything apart.

(http://web.comhem.se/linusandersson/g9_sch_48V.jpg)
Title: Re: The official G9 help thread
Post by: zebra50 on June 29, 2010, 05:11:23 AM
Voltage at the top of the zener diode looks too low.
So my guess would be a faulty or wrong value Zener, and/or bad or wrong value R40, R41 and/or trimmer.
Title: Re: The official G9 help thread
Post by: skeld on June 29, 2010, 11:05:15 AM
Hello, I have just finnished my G9 preamp. I have ran the unit for the first time and I am a bit worried about temperature inside with the unit cover on. After 30 minutes of operation I have put down the cover and measured cooler temperature with results 80°C on small coller and 70°C on large one as shown on the picture bellow. I use cover with perforation (picture). I am afraid this temperature is to high for the unit operation, but I think larger coolers will not solve the problem, because the heat will still stay inside the unit. I am worried if I put the unit into a rack between other units I posses no ventilation will be possible and temperature can cause problems. What should be the normal temperature on cooler? Have someone done any temperature measuring?

(http://www.woodland.mysteria.cz/Gallery/7.jpg)

(http://www.woodland.mysteria.cz/Gallery/8.jpg)
Title: Re: The official G9 help thread
Post by: mamiti on June 29, 2010, 12:03:25 PM
Hello, I have just finnished my G9 preamp. I have ran the unit for the first time and I am a bit worried about temperature inside with the unit cover on. After 30 minutes of operation I have put down the cover and measured cooler temperature with results 80°C on small coller and 70°C on large one as shown on the picture bellow. I use cover with perforation (picture). I am afraid this temperature is to high for the unit operation, but I think larger coolers will not solve the problem, because the heat will still stay inside the unit. I am worried if I put the unit into a rack between other units I posses no ventilation will be possible and temperature can cause problems. What should be the normal temperature on cooler? Have someone done any temperature measuring?

Hi,

I haven't measured temperatures but 78S12 runs really hot, I'd say mine is propably around 70C too. No idea on TL783 because it is on area where I'm not comfortable to put my fingers to. Ventilation holes aren't for decoration in G9 if I'm not totally mistaken.

Cheers,

MT
Title: Re: The official G9 help thread
Post by: skeld on June 30, 2010, 02:57:54 AM
and how do you solve the ventilation of the unit, do you think perforation on cover, like on my picture is enough? Or it is better to make some holes on the back panel as well. I was also wondering to put one large cooler on back panel, outside the unit, with copper bridge connections to the regulators.
Title: Re: The official G9 help thread
Post by: bpucekov on June 30, 2010, 03:30:26 AM
perforations on the lid should be enough if you leave one empty rack space over the device
Title: Re: The official G9 help thread
Post by: Kingston on June 30, 2010, 04:00:29 AM
With that big heat sink even a non-ventilated case is fine. 70 degrees is a "low" temperature with such a big heat sink.

With some more critical projects I have solved this by sticking the heatsink outside the back panel (with a secure hole for regulator wiring to get it outside). But those were regulators working to dissipate at more than 4 amps.

G9 only has to work some 1.2A. Your heatsink is plenty. No need to leave extra space above the rack either.
Title: Re: The official G9 help thread
Post by: barthman.de on June 30, 2010, 04:53:51 PM
I posted some problems here (I think the circuit diagram is different to the pcb):

http://www.groupdiy.com/index.php?topic=39802.0

...found this official G9 help thread to late  :o

Could sombody look to my problem with R44 (my last post at the treatise I linked above) ?

Thank you very much.
Title: Re: The official G9 help thread
Post by: zebra50 on June 30, 2010, 05:02:23 PM
I didn't really understand the problem! The resistor is between the hot & cold XLR outputs - your diagram looks OK.
Title: Re: The official G9 help thread
Post by: barthman.de on June 30, 2010, 05:03:50 PM
So fast :)
Title: Re: The official G9 help thread
Post by: barthman.de on June 30, 2010, 05:22:48 PM
Maybe I'm confused because I was looking one hour to the part of the pcb with the rotary switches  :o

R 44 is there between the both poles of the "+" - input. But of course you are right - R44 is only between "hot" and "cold". I needed this cause for thought  ;) Now I can draw and order my transformer PCB  :-*

Good night.
Title: Phase reverse
Post by: aclac on July 01, 2010, 07:35:49 AM
HI. I had finished G9 and it sounds fine and work well, but... CH1 phase reverse gives signal only one position (+), and (-) pos is death. I was wondering how does this circle work. If I take closer look component layout pdf, I notice, that output transformercoils are connected serial and 10k resistor is between legs, OK. But when I look electrical drawings of connection... hmmm. Output trafo is connected so, that only one output coil work in one direction (can this picture in gyrafs side be wrong)? It is very difficult find solution my problem, because I can't undestand pictures. Btw. I measured, that output 2 resistance is about 40 ohm (-pos) and same (+pos), and output 1 has 0 ohm (-pos) and 40 ohm (+pos). It seems, that I have short circuit somewhere... please tell me where. I wan't loose out this phase reverse SW, before some give me clear thoughts? Aclac
Title: Re: The official G9 help thread
Post by: skeld on July 01, 2010, 08:50:33 AM
With that big heat sink even a non-ventilated case is fine. 70 degrees is a "low" temperature with such a big heat sink.

With some more critical projects I have solved this by sticking the heatsink outside the back panel (with a secure hole for regulator wiring to get it outside). But those were regulators working to dissipate at more than 4 amps.

G9 only has to work some 1.2A. Your heatsink is plenty. No need to leave extra space above the rack either.

Thanx for help
Title: Re: The official G9 help thread
Post by: barthman.de on July 01, 2010, 12:19:51 PM
@aclac

Yes the original circuit design of the Gyraf-site seems to be wrong for output transformer wiring but the PCB is right. The PCB shows it right the output of the transformer must be connected serial. Maybe my drawings will help you.

(look at my discussion http://www.groupdiy.com/index.php?topic=39802.0 )

Title: Re: The official G9 help thread
Post by: aclac on July 01, 2010, 04:52:34 PM
@aclac

Yes the original circuit design of the Gyraf-site seems to be wrong for output transformer wiring but the PCB is right. The PCB shows it right the output of the transformer must be connected serial. Maybe my drawings will help you.

(look at my discussion http://www.groupdiy.com/index.php?topic=39802.0 )



Thanks. Your picture is good, but almost right... In the PCB first is output trafo and resistor R32 (10k). Then is coming SW with R44 (10k) (but seems to be other way, than your picture)... hmm, it doesn't matter. It is only little bit tricky to understand. In my case the lorlin SW seems to give short circuit in the output, when phase is inverted. Can this switch do so? It is guite big job to change new switch or other position, and maybe it can wait...

If you or somebody have some ideas, please let me know. Aclac
Title: Re: The official G9 help thread
Post by: Harpo on July 02, 2010, 12:57:57 AM
If you or somebody have some ideas, please let me know. Aclac
Maybe you placed the end stop washer when the lorlin was not set to its full ccw position. Lorlin now switching between positions 2/3 instead of 1/2.
Title: Re: The official G9 help thread
Post by: aclac on July 02, 2010, 03:51:58 AM
If you or somebody have some ideas, please let me know. Aclac
Maybe you placed the end stop washer when the lorlin was not set to its full ccw position. Lorlin now switching between positions 2/3 instead of 1/2.

Oh, I don't have any end stop washer and all pos is allowed  :o. Btw, there is short circuit (outputpin 2 and 3 are connected together by..)?
Title: Re: The official G9 help thread
Post by: flintan on July 02, 2010, 06:51:52 AM
And you have of course triple checked that the wiring of the switch is correct?
Title: Re: The official G9 help thread
Post by: aclac on July 02, 2010, 08:04:20 PM
And you have of course triple checked that the wiring of the switch is correct?

Thanks for this, but no reason, because it work well other way (+ pos). Maybe I should screw out control PCB and try find something small parts of wiring between the lorlin legs or somewhere. I don't like solve out SW, because it is too messy and too risky to broke PCB. Hmm, this function is not so important to me, and I can live without it. Other channel work well anyway.
Title: Re: The official G9 help thread
Post by: tmuikku on July 03, 2010, 01:52:17 PM
My problem solved:

Didn't have gain and about 6db lowpass all the way - Output didn't have ground reference

G9 was fine, my soundcard unbalanced inputs had trs-sockets and ring was not connected anywere ;)
Title: Re: The official G9 help thread
Post by: aclac on July 03, 2010, 03:30:13 PM
my soundcard unbalanced inputs had trs-sockets and ring was not connected anywere ;)

HAHAA, I bought powerful old PA amp and there is XLR connections and cold- pin was without wire. Some kind "joke" maybe, because there is big label that "balanced input"... Made in england.
Title: Re: The official G9 help thread
Post by: maxime on July 11, 2010, 10:31:15 AM
Hello guys
I was thinking of exchanging my OEP input transformers for some Pikatron. I saw some RÜP 817M/1 on ebay and they state a  1: 3,21 + 3,21 ratio (thus 1/6.4).
would this work ? any experiences?
maxime

Title: Re: The official G9 help thread
Post by: gyraf on July 12, 2010, 02:30:40 AM
they should work
Title: Re: The official G9 help thread
Post by: tmuikku on July 12, 2010, 04:18:06 PM
I was making finishing touch to my G9 but there was 100hz and harmonics peaking -66 dBs and I found this thread: http://www.groupdiy.com/index.php?topic=32559.0

I did the same thing: moved the whole B+ supply to separate board and 100hz hum dissappeared totally (now only 50Hz hum peaking about -95)! well worth doing!
Title: Re: The official G9 help thread
Post by: MasonAtom on July 19, 2010, 12:28:21 PM
Just looking over the schematic for the G9. Is there any particular reason why the second transformer needs to be rated for 30VA? That seems like insane overkill to me, considering that it only has to supply the current for the tubes, which is in the 10s of mA at most. Seems you could save money and space with a torroid rated for much lower output.
Title: Re: The official G9 help thread
Post by: gyraf on July 19, 2010, 11:57:46 PM
The same-rating specified for the second transformer is because smaller transformers behaves very unpredictable in reverse configuration (because of bigger copper loss). Smaller transformer does not save much money anyway, and we have plenty space.

So it's about ease of building - you can always experiment with smaller types yourself, it's just not "plug-and-play"

But be aware that smaller non-toroid transformers do induce a lot of electromagnetic interference.

Jakob E.
Title: Re: The official G9 help thread
Post by: MasonAtom on July 20, 2010, 09:38:34 AM
The same-rating specified for the second transformer is because smaller transformers behaves very unpredictable in reverse configuration (because of bigger copper loss). Smaller transformer does not save much money anyway, and we have plenty space.

So it's about ease of building - you can always experiment with smaller types yourself, it's just not "plug-and-play"

But be aware that smaller non-toroid transformers do induce a lot of electromagnetic interference.

Jakob E.

thanks for the clarification. I figured it was something like this.

mason
Title: Re: The official G9 help thread
Post by: MeToo2 on July 23, 2010, 03:56:21 AM
I was making finishing touch to my G9 but there was 100hz and harmonics peaking -66 dBs and I found this thread: http://www.groupdiy.com/index.php?topic=32559.0

I did the same thing: moved the whole B+ supply to separate board and 100hz hum dissappeared totally (now only 50Hz hum peaking about -95)! well worth doing!
Thanks for the hint. I'm definitely going to have a go at this. I spent quite a bit of time looking for the source of 100Hz and harmonics at around -66dB: just the electronic engineer in me wanted it to be better although you couldn't hear the hum at all. It was definitely something from within the box and presumably the (rectified) power supply that was producing the 100Hz and harmonics, but I couldn't figure out how it was coupling into the rest of the G9. I tried the 48V supply (wasn't that) and suspected the transformers and heater current but couldn't prove it. Veroboard should arrive in a few days so then I can try an exact comparison of having the HT supply components mounted on and off board without altering anything else. (I have spare HT components so I can test in situ without moving any transformers or caps or other things) I'll post a screen shot of the two noise spectra once I've done that.
Title: Re: The official G9 help thread
Post by: MeToo2 on July 23, 2010, 06:22:31 AM
I was making finishing touch to my G9 but there was 100hz and harmonics peaking -66 dBs and I found this thread: http://www.groupdiy.com/index.php?topic=32559.0

I did the same thing: moved the whole B+ supply to separate board and 100hz hum dissappeared totally (now only 50Hz hum peaking about -95)! well worth doing!
Good work!

I lashed up a really rough external PSU from the same component values as the on-board-PSU of the G9 on a piece of tag board. It really was rough: no screening. No careful soldering. Nothing. Just hanging out the back of my G9 box on long flying leads. I then hooked this up to the existing internal power transformers and removed the HT link on the G9 board next to the internal regulator and hooked the external supply in there. So if there was any RF pick up due to long leads or layout, you'd expect it to be much worse with the external supply....

I tested the PSU under load i.e it was amplifying pretty heavily on one channel, whilst the other channel was quiet.

The spectrum chart shows both left & right channels from 0 to 1100Hz. Left = quiet. Right = high signal.

Test 1 =
internal PSU circuit powered from original transformers mounted in the box
 +4dBm output on right channel @500Hz test tone (approx -25 dBm in from an unmatched low Z sound card output to right hand channel)
left channel 0 input (terminated with mic impedance)
gain set to approx 60% on all knobs.
(http://i958.photobucket.com/albums/ae69/MeToo2_Prodigy/4dbm-on-right-mic-impedance-on-left-internal-supply-Screenshot2010-07-23at115908.png)

Test 2 =
External PSU circuit powered from original transformers mounted in the box
 +4dBm output on right channel @500Hz test tone (approx -25 dBm in from an unmatched low Z sound card output to right hand channel)
left channel 0 input (terminated with mic impedance)
gain set to approx 60% on all knobs.

(http://i958.photobucket.com/albums/ae69/MeToo2_Prodigy/4dbm-on-right-mic-impedance-on-left-external-supply-Screenshot2010-07-23at114345.png)

Thus the only difference was the physical location of the HT diode rectifier, HT regulator, off-board capacitors & resistors.

You can see on test 1 that there is some 100Hz and it's harmonics on both channels. It wasn't that high and I could put up with it.
But on test 2 the 100Hz on the left channel almost disappears. The small 500Hz peak that is left is almost certainly cross-channel cross-talk (and could be my test set up to be honest).

As they say on TV: MYTH CONFIRMED. There is 100Hz hum and its harmonics injected into the G9 output that can be avoided via use of a simple external PSU board without changing the circuit design.
Title: Re: The official G9 help thread
Post by: tmuikku on July 23, 2010, 07:04:23 AM
Good work ;)
Title: Re: The official G9 help thread
Post by: haima on July 23, 2010, 08:58:18 AM
i've been meaning to post this for a while...

about a year ago i fixed the niggly little hum problem in my two G9's in a similar way. i made some little external boards with the rectifier, caps and a zener+mosfet pass "pre-regulator" which then fed smoothed DC into the normal G9 regulator.

the difference was dramatic. it went from a quiet, but noticeable and annoying hum level (harmonics of the line frequency), to completely NO discernible hum at all above the noise floor. i have scope shots and audio recordings of before and after the mod. if people are interested i can post what i did.

perhaps for some units the HV power supply recifier/caps etc are inducing ground currents that are being picked up in the preamp stage?
Title: Re: The official G9 help thread
Post by: Kingston on July 23, 2010, 01:22:07 PM
I'm pretty sure every single build with the usual G9 PCB has this 100hz hum + harmonics problem. It's just that for most people it's either good enough, they haven't noticed it, or they haven't any means for measuring it. Only the B+ bridge rectifier causes this problem by the way. Heater rectifier does not pollute the grounds. In fact, just moving the B+ bridge rectifier and the first RC stage out of the PCB should fix the problem.

See all the harmonics from 100hz and above:

(http://www.michaelkingston.fi/files/edcorandlundahlhum.png)

They will be completely removed. I didn't even bother grabbing a screenshot of the fix. There's simply no trace of the harmonics, just a straight line.

I later also removed that 50hz peak by shielding the PSU transformers.

PS. in the above image we see the harmonics with edcor XSM10k/600 and the standard lundahl output transformer. The bass cut due to the too high output impedance of the output gain stage is clearly visible on the lower lundahl screenshot, even on the noise floor. Unrelated to the rectifier harmonics problem of course.
Title: Re: The official G9 help thread
Post by: haima on July 23, 2010, 01:35:54 PM
i agree it's possible that many people either have not noticed this hum problem, or perhaps thought it's just an inevitable part of "the sound". my build it was quiet enough for me to use the pre on many recordings, for a couple of years - but eventually i decided to get to the bottom of it... glad i did.

after trying to kill the hum many ways, (shielding, moving transformers, changing ground paths on and off the pcb etc) i finally tried using an external HV supply jumped over from my hamptone preamp, and instantly the hum disappeared. what a relief that was!

now this was a while ago... i think i tired just moving the bridge rectifier and caps off board first, and from memory that didn't fix the problem, i'm pretty sure i had to do some regulation/smoothing off board first - but as i said it was a while ago so i might be wrong.


Title: Re: The official G9 help thread
Post by: Graph on July 25, 2010, 05:58:43 AM
I am having some problems with my nearly finished G9 :)

I have only made 1 channel for now.. i will make the other one later.

The G9 Works, it has some oscilation which i have to try cutting the traces.

But my greatest problem, is that my G9, the output lvl, is REALLY weak. To understand how weak it is, i will say this... i have to give all gain from my Profire 610, to have a subtle sound, which is approx, 40db, which i normallize and get a distorted sound with a little of noise.

I am using 2 Marshall 12ax7 for now, since i used the ones from my marshall.

If i set the gain to max, it oscilates, so with this, i know the first stage of gain is as it should be. So... is the problem the Phase inverter? Maybe because its a 12ax7 instead of an 12au7? The tubes are both working, i have tested them already, swapped position and they work in my marshall. Is there anything that can be causing this? i will be buying some 12au7 this days, but maybe its not the problem.

I really appreciate your answers :) i am not allknown about electronics, but i understand some basic things.. this is my third project so i am really glad i could make it at this point :)

As always, sorry for my english, its not my primary language.

And Thanks jakob for sharing this great project!
Title: Re: The official G9 help thread
Post by: haima on July 25, 2010, 07:40:10 AM
12AX7 is probably partly to blame for the oscillation - it's a much higher mu tube than the 12AU7.

you might still have oscillation problems when you swap in the 12AU7 - but that can usually be fixed by the "cut traces & run shielded cable to and from DI jack" mod.

the low level/distorted output could be:

- to do the 12AX7 substitution, or
- how you connect your G9 to your profire 610 - are you connecting to an unbalanced 1/4" input? where are three pins of the G9 output XLR going?
- or something else  :-\

BTW, there's no "phase inverter" in the traditional guitar amp sense - only the "input stage" and "output stage"
Title: Re: The official G9 help thread
Post by: Graph on July 25, 2010, 03:15:43 PM
12AX7 is probably partly to blame for the oscillation - it's a much higher mu tube than the 12AU7.

you might still have oscillation problems when you swap in the 12AU7 - but that can usually be fixed by the "cut traces & run shielded cable to and from DI jack" mod.

the low level/distorted output could be:

- to do the 12AX7 substitution, or
- how you connect your G9 to your profire 610 - are you connecting to an unbalanced 1/4" input? where are three pins of the G9 output XLR going?
- or something else  :-\

BTW, there's no "phase inverter" in the traditional guitar amp sense - only the "input stage" and "output stage"

Thanks Haima, the 3 pins of the xlr connector are going to the preamp input of the profire through an xlr-xlr balanced cable.

I will try these days, buyin 2 12au7, to see if the problems are solved. I hope this is the problem and not any other thing.

If there could be any other thing, how should i debug the preamp in that case?

Edit: Could it be that the output transformer has any problem and its deliverying a very low lvl?

Thanks :)

Sorry, if i am not clear..

The questions are:
1) Could it be that the 12Ax7 are delivering SO low output? that has to be add like 80dbs(60db+normalize)
2) Maybe.. the output transformer? should i take the input to a standart plug and check if the lvl is allright? or should i check the primarys of the a2e?
Title: Re: The official G9 help thread
Post by: Graph on July 26, 2010, 10:52:55 PM
12AX7 is probably partly to blame for the oscillation - it's a much higher mu tube than the 12AU7.

you might still have oscillation problems when you swap in the 12AU7 - but that can usually be fixed by the "cut traces & run shielded cable to and from DI jack" mod.

the low level/distorted output could be:

- to do the 12AX7 substitution, or
- how you connect your G9 to your profire 610 - are you connecting to an unbalanced 1/4" input? where are three pins of the G9 output XLR going?
- or something else  :-\

BTW, there's no "phase inverter" in the traditional guitar amp sense - only the "input stage" and "output stage"

Thanks Haima, the 3 pins of the xlr connector are going to the preamp input of the profire through an xlr-xlr balanced cable.

I will try these days, buyin 2 12au7, to see if the problems are solved. I hope this is the problem and not any other thing.

If there could be any other thing, how should i debug the preamp in that case?

Edit: Could it be that the output transformer has any problem and its deliverying a very low lvl?

Thanks :)

Sorry, if i am not clear..

The questions are:
1) Could it be that the 12Ax7 are delivering SO low output? that has to be add like 80dbs(60db+normalize)
2) Maybe.. the output transformer? should i take the input to a standart plug and check if the lvl is allright? or should i check the primarys of the a2e?
Apparently, i Bypassed the Oep A262 with the lundahl holes, and i have signal :):) unbalanced signal, so... i got too much noise :P(i am not using toroidals)
Problem solved... 12ax7 cant drive an oep, but 12au7 can.

I still get channel 2 with high oscillation problems(even at 0 gain) i will be trying to solve this :)

Thanks again for this great project!
Title: Re: The official G9 help thread
Post by: mattyblue on August 05, 2010, 10:26:59 PM
Are there any pictures of the external power supply mod for the G9?
Title: Re: The official G9 help thread
Post by: flintan on August 13, 2010, 09:21:36 AM
Another G9, finished some while ago. I had some issues with getting correct pp voltage because of a wrong value zener. Now it sounds and works like a charm. Lundahl in, edcor out, brimar nos tubes.

(http://forumbilder.se/thumbs/e63201031350P7356.jpg) (http://forumbilder.se/show.aspx?iid=e63201031350P7356)

(http://forumbilder.se/thumbs/b63201031620Pe78d.jpg) (http://forumbilder.se/show.aspx?iid=b63201031620Pe78d)
Title: Re: The official G9 help thread
Post by: mattyblue on August 13, 2010, 02:04:04 PM
What edcor transformers did you use?
Title: Re: The official G9 help thread
Post by: flintan on August 14, 2010, 02:05:19 PM
XS1100 but if i were to build me another one today i think i'd try 10k:600.
Title: Re: The official G9 help thread
Post by: Buzz feedback on August 22, 2010, 10:48:36 AM
Recently finished a G9, OEP transformers all the way. Had some hum and oscillation issues, otherwise it sounds awesome.
Thank you Jakob for an inspiring project!
Title: Re: The official G9 help thread
Post by: ioginy on September 06, 2010, 03:23:36 PM
Goof day everyone.  I just spent the last while pouring over this wonderful thread to make sure I wasn't repeating any questions and had more questions answered then I knew I had.  However, my original ones still elude me. 
I am still quite new to diying, but i have built a few guitar amplifiers so I guess you could say i am not totally green.  That being said, I do still have some trouble wrapping my head around some simple stuff...  here comes the questions.

I want to build a 8 channel g9 for drum mic recording.  Upon thinking about that, it may be a bit ambitious, so I'll drop it to 4 for the sake of keeping things simple but still quantifying my questions. 

As far as the power supply goes, would the provided design have enough juice to drive 4 channels or would I need to make a power supply for each two channel module?

Also, I would like to have a single (grouped) line out as well as the balanced individual channel outs.  I have two theories on how I could do this, but this is coming back to my "working knowledge" and could get a few chuckles and head shakes.  So...  for the sake of argument, I DON'T want individual outputs, could I build a single output circuit and connect each channel after the R45/R28 connection to this stage?  If this is possible, could I just build another output circuit for the single line out, jumper all channels to it as well as the preexisting stages and go from there?  Ooooorrrr, for the sake of pure simplicity, jumper all channels after C13 to a single output and go from there? 

Sorry for the lengthy question.  Thank you in advance for any help anyone can give.
Cory.
Title: Re: The official G9 help thread
Post by: gyraf on September 07, 2010, 06:01:20 AM
Hi Cory,

1) Power supply probably can't drive two units. I say probably, because it gets hot enough as-is - cooling of the regulators (esp. the 78S12) would be an issue. We're drawing around 6-700mA at the +12V heater supply, and maximum for the 78S12 would be 1.5-2A, but very dependent on proper input voltage (large enough rated transformers) and regulator cooling. I'd recommend building the unit as-is - that way you are on known ground.

2) for mixing, you would probably want some kind of a passive (or active) summing stage to avoid crosstalk. Look elsewhere in this forum for ideas.

3) if you don't care about crosstalk (because you only want to use the mixed signal anyway) you could replace R45(1K) with a handful of 47K's and sum them into R28.

Jakob E.
Title: Re: The official G9 help thread
Post by: ioginy on September 07, 2010, 11:31:07 AM
:) thanks!  Yeah, crosstalk isn't going to be a concern at all, so that will work dandy.  Thanks for your input  :) 
Title: Re: The official G9 help thread
Post by: ChrioN on September 12, 2010, 09:11:59 AM
Hows the frequency response with lundahls on in and out?
Title: Re: The official G9 help thread
Post by: RogerB on September 22, 2010, 02:09:35 PM
Hi Everyone

I have completed my G9 and man this thing is so cool!  I let an engineer friend of mine track with my unit at the recording studio he works for. He had nothing but good things to say about it. He recons its better than the Tee El audio pres and the focuswrong r*ds that they have. I picked it up from him a week ago. He called me and said he would like it back for another session in a couple of weeks! I am having a small niggly little issue:

Channel 1 MIC and INST lines pass audio amazingly and Is clean from any hum or bzzz
Channel 2 MIC is clean but the INST has a bzzz on it. I think it may be EMI induced because if I touch with my hand the 2 wires that connect to the terminal connectors Marked 220VAC on the pcb it is reduced quite a bit. Has anyone else also expierenced the bzzz on channel 2 DI? Anything anyone can advise me?

Many thanks
Roger
Title: Re: The official G9 help thread
Post by: haima on September 22, 2010, 02:17:05 PM
I think it may be EMI induced because if I touch with my hand the 2 wires that connect to the terminal connectors Marked 220VAC on the pcb it is reduced quite a bit.

that sounds  a bit scary - i'm not sure if i'm understanding you correctly, but touching something labelled 220vac doesn't sound like a good idea...

have you done the documented "cut pcb tracks & use shielded cable for the DI" mod?
Title: Re: The official G9 help thread
Post by: RogerB on September 22, 2010, 02:21:25 PM
Lol yeah I know but im touching the insulated wires not the terminals - that will gimme a new hairdo! Yes I have done the DI Mod. That fixed the squeeling osciliation probs I had.
Title: Re: The official G9 help thread
Post by: RogerB on September 22, 2010, 04:35:15 PM
I accidentaly got the to jack, and from jack the wrong way round on channel 2 on the jack. It is now working both chanels DI and MIC- Clean no noise or artifacts! YIPPPEEEEE!!!!
Title: Re: The official G9 help thread
Post by: audiophreak on September 22, 2010, 04:42:08 PM
Thats great !  Congratulations  :)
Title: Re: The official G9 help thread
Post by: haima on September 23, 2010, 01:47:41 AM
good! it's often the simplest things that trip us up....
Title: Re: The official G9 help thread
Post by: MeToo2 on October 01, 2010, 12:58:01 PM
Are there any pictures of the external power supply mod for the G9?
Pictures of my _external_ power supply mod.

http://i958.photobucket.com/albums/ae69/MeToo2_Prodigy/DSC00632.jpg

(sorry couldn't resist)  ;D

Here it is installed.

http://i958.photobucket.com/albums/ae69/MeToo2_Prodigy/psu_noise_tests/DSC00635.jpg
http://i958.photobucket.com/albums/ae69/MeToo2_Prodigy/psu_noise_tests/DSC00636.jpg

The only real minimum mod required on the G9 board is to remove R37 (the 470 resistor linking into the original PSU) and re-wiring the capacitors and connectors. The original 3 pin connector for the capacitors can be re-used (using the left most pin and the center pin), so there's no need to butcher the board at all.

http://i958.photobucket.com/albums/ae69/MeToo2_Prodigy/psu_noise_tests/DSC00638.jpg

Just FYI Please don't take this as a criticism, just something to look at as a potential improvement. I suspect a fair amount of the cross talk between channels that I measured earlier is also being communicated via the HT power supply. I can clearly see around 20mV of ripple exactly corresponding to the signal on channel 2 on the HT line of channel 1 (using an HT capable oscilloscope). So maybe there's some more to investigate here too. Again something that is more measurable than noticeable.

[edit]

I performed the following tests:
1KHz tone on right channel adjusted to +4dBm output -25dBm input, left channel input terminated to mic impedance
1KHz tone on right channel adjusted to -16dBm output -45dBm input, left channel input terminated to mic impedance
pink noise on right channel, left channel input terminated to mic impedance 0-2KHz
pink noise on right channel, left channel input terminated to mic impedance 0-10Khz (shows cross talk increases with frequency)
no signal on right channel, left channel input terminated to mic impedance

And then in the following combinations:
oep transformers,  original on board psu
oep transformers, external psu (same design, just physically separated off the board)
oep transformers, new psu (attempt to change filtering = failed)
lundahl transformers, original on board psu
lundahl transformers, external psu (same design, just physically separated off the board)

Which gives 25 tests.

See my test results here: http://s958.photobucket.com/albums/ae69/MeToo2_Prodigy/psu_noise_tests/

My attempt to make some clever modifications to rejig the filtering to avoid inter-channel crosstalk failed I'm afraid (new psu oep). The modified power supply was better at rejecting specific low frequency cross talk, but worse in general. Suspect strongly this is simply a limitation of the TL783 at higher frequencies (results matched the data sheet pretty much)

Anyway the very clear conclusion from my tests was simply to build the original PSU as designed and documented on the schematic, but physically separated from the original G9 board (preferably remove all of the original HT PSU components completely from the G9 PCB, but at the very least you must remove R37 on the main PCB to isolate the existing supply). That gave me an improvement of around 10dB in noise floor figure, which is not insignificant. The Lundahls were really super quiet after the mod.

I did add a couple of extra small capacitors I had spare in parallel with C15 = 220uF 400V electrolytic +10uF electrolytic 450V + 0.47uF 275V polyester for the high frequencies, but to be honest I don't think they really made any difference but I left them in. Try it yourself and see.
Title: Re: The official G9 help thread
Post by: braeden on October 12, 2010, 04:33:24 AM
I'm sorry if this has been posted 1000 times before, but is there an updated parts list/BOM for the Gyraf G9?
I've managed to source most of the parts but I've run into trouble because some components are bulk-buy.

Thanks a lot
Title: Re: The official G9 help thread
Post by: gyraf on October 13, 2010, 03:52:12 AM
No updated list that I know of.

What is bulk-buy?

If you post your location in your profile, it's easier to help with area-specific problems like sourcing...

Jakob E.
Title: Re: The official G9 help thread
Post by: braeden on October 13, 2010, 07:06:54 AM
No updated list that I know of.

What is bulk-buy?

If you post your location in your profile, it's easier to help with area-specific problems like sourcing...

Jakob E.

Thanks for the reply.
I'm located in Sydney, Australia. I've just finished ordering parts for my GSSL which was a bit of a hassle :)
I don't know how great the capacitors are from Jaycar but i'll definitely give them a go.

Anyways, the bulk-buy isn't the issue here any more. I've managed to find all the parts on Mouser, the only problem is the lead time is around 20 weeks for a few capacitors in my order. I can't seem to find any way around this and I'd like to stick with the same manufacturer for the capacitors.

I guess I'll have to keep on searching :/

Thanks once again ;)
Title: Re: The official G9 help thread
Post by: tmuikku on October 13, 2010, 07:13:23 AM
...
Anyways, the bulk-buy isn't the issue here any more. I've managed to find all the parts on Mouser, the only problem is the lead time is around 20 weeks for a few capacitors in my order. I can't seem to find any way around this and I'd like to stick with the same manufacturer for the capacitors.

I guess I'll have to keep on searching :/

Thanks once again ;)

Well, just post which capacitors (designations on schematics) and people will suggest alternatives!;)
Title: Re: The official G9 help thread
Post by: braeden on October 13, 2010, 07:25:54 AM
Code: [Select]
Mouser #: 505-MKS20.022/63/5
Mfr. #: MKS2-.022/63/5

Mouser #: 75-MKT1813410014
Mfr. #: MKT1813410014

2 71-CCF2-J-1K               Vishay/Dale 1.0K 2W 5% Metal Film  (R31,R131)
2 71-CCF02-J-470/R         Vishay/Dale 470R 2W 5% Metal Film  (R33,R37)
1 71-CPF2-F-100K            Vishay/Dale 100K 2W 1% Metal Film  (R34)

Cheers :'(
Title: Re: The official G9 help thread
Post by: tmuikku on October 13, 2010, 10:43:07 AM
Code: [Select]
Mouser #: 505-MKS20.022/63/5
Mfr. #: MKS2-.022/63/5

Mouser #: 75-MKT1813410014
Mfr. #: MKT1813410014

2 71-CCF2-J-1K               Vishay/Dale 1.0K 2W 5% Metal Film  (R31,R131)
2 71-CCF02-J-470/R         Vishay/Dale 470R 2W 5% Metal Film  (R33,R37)
1 71-CPF2-F-100K            Vishay/Dale 100K 2W 1% Metal Film  (R34)

Cheers :'(

For those capacitors you can use any other 22nf and 10nf film caps ( aren't they the highpass filter caps, C8 and C9?). They are on the conrol PCB which has three different holes for different size caps (lead spacing). I'm not sure if you could even fit that radial cap in there? If you want Wima brand Banzai usually have them in stock. http://www.banzaimusic.com/MKS2-5mm/ (http://www.banzaimusic.com/MKS2-5mm/) . I'm almost sure that you can find those resistors too from Banzai ;) You can use any brand resistors with proper wattage rating and resistanse.
Title: Re: The official G9 help thread
Post by: braeden on October 13, 2010, 06:44:42 PM
Ahh Banzai Music, life saver, and the shipping costs aren't too bad either.
Cheers! ;)
Title: Re: The official G9 help thread
Post by: grantlack on October 26, 2010, 10:35:21 AM
Took a good dive into the various G9 threads and never found an answer on this. Is the use of rotaries essential (i.e. are we wanting a shorting style to prevent pops) or is it purely an elegance/ease of build sort of deal? Hoping to condense the frontpanel with some pushbuttons and toggles for a hair-brained scheme, but I figured I'd consult before I get all crazy buying parts.
Title: Re: The official G9 help thread
Post by: JBVries on November 04, 2010, 03:43:50 AM
For anyone starting to build the G9 here is a link to the Mouser ordering form that has been updated to correct out of production or obsolete parts. This is taken right from the PDF I found that Skyler compiled. Cheers!!

http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=b61a0b8df9 (http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=b61a0b8df9)
Title: Re: The official G9 help thread
Post by: lampodigenio on November 06, 2010, 08:36:24 AM
Hi,
I have a noise's problem. (hum???) I've recorded it. Can you help me please?

http://www.antonellodurso.com/hum.wav (http://www.antonellodurso.com/hum.wav)

Thank's
Title: Re: The official G9 help thread
Post by: tmuikku on November 06, 2010, 11:59:06 AM
Hi,
I have a noise's problem. (hum???) I've recorded it. Can you help me please?

http://www.antonellodurso.com/hum.wav (http://www.antonellodurso.com/hum.wav)

Thank's

Hi there!

Have you tried building the HT power supply of board? Check with FFT software what frequency the hum is. If it is mainly 50Hz it is the mains transformer induced hum (tidy your wiring, move mains transformer around). If mostly 100Hz and up it is caused by PCB layout and building external HT supply will help. Check out this thread a few pages back and try search, plenty of info!

Best,
Teemu
 
edit: not heater supply but the HT supply!
Title: Re: The official G9 help thread
Post by: lampodigenio on November 06, 2010, 03:48:18 PM




Is this 100Hz?
Do you think I should build external heater supply?
Thanks
Title: Re: The official G9 help thread
Post by: tmuikku on November 07, 2010, 04:27:02 AM
Is this 100Hz?
Do you think I should build external heater supply?
Thanks

Indeed, there is some layout issues in G9 pcb and building separate HT supply seems to reduce most if not all of the 100hz hum. MeToo2 posted some pictures.
http://www.groupdiy.com/index.php?topic=17980.msg511680#msg511680

edit: not heater supply but the HT supply!
Title: Re: The official G9 help thread
Post by: electrisizer on November 07, 2010, 05:10:43 AM
by the way - same problem here  ::) 100Hz hum
 - i build a new supply next month
Title: Re: The official G9 help thread
Post by: haima on November 07, 2010, 05:12:28 AM
i had 100hz (+ harmonics) hum problems until i made a external (i.e not on the main pcb) high voltage supply - the heater supply was NOT the problem for me, and i believe this is the case for others too?

press "print" and then you can use the search function of your browser to find the info... it's all there in previous pages.
Title: Re: The official G9 help thread
Post by: tmuikku on November 07, 2010, 11:11:15 AM
i had 100hz (+ harmonics) hum problems until i made a external (i.e not on the main pcb) high voltage supply - the heater supply was NOT the problem for me, and i believe this is the case for others too?

press "print" and then you can use the search function of your browser to find the info... it's all there in previous pages.

Ohops, you are correct! I ment the HT supply also, not heater! Fixed my messages above.
Title: Re: The official G9 help thread
Post by: lampodigenio on November 08, 2010, 04:54:42 AM
Quote
edit: not heater supply but the B+!

What's B+

The hum in my picture is 100Hz???

Where I find heater HT Supply?
Title: Re: The official G9 help thread
Post by: tmuikku on November 08, 2010, 05:15:54 AM
Quote
edit: not heater supply but the B+!

What's B+

The hum in my picture is 100Hz???

Where I find heater HT Supply?

sh*t I'm bad with forums :D Look at G9 schematics. There is separate circuits for heater, HT and phantom. B+ = HT. No such thing as heater HT supply, they are separate.
Title: Re: The official G9 help thread
Post by: lampodigenio on November 25, 2010, 03:02:55 PM
(http://www.antonellodurso.com/psu.jpg)

I built the external PSU but I do not know where I have to be wired "heater out" and "Cap 2 out" as shown. Could you help me?

Instead of BR1 and BR2 I used two bridges of 1.5 A. is that correct?

Why cap2 is 245V?

Thanks
Title: Re: The official G9 help thread
Post by: haima on November 25, 2010, 08:05:43 PM
Quote
Why cap2 is 245V?

i believe the "245v" refers to the fact that this is the OUTPUT for the high voltage section of the power supply - which is intended to be around 245v.

you should use a 350v capacitor for "cap2", the same as "cap1"

you also take the high voltage output from this capacitor/that point on the PCB.

check the schematic for the G9 - it's all there....

good luck! :) and be very careful of the high voltage!! always discharge the caps before working on the unit.
Title: Re: The official G9 help thread
Post by: lampodigenio on November 26, 2010, 06:34:14 AM
Excuse me but I did not understand what I do. Where I should wire the cap2 wiring? And heater out?
Title: Re: The official G9 help thread
Post by: microc on November 27, 2010, 07:14:27 AM
I've just Morgan Jones books; Valve Amplifiers and Building Valve Amplifiers, great books btw!
I'm also designing a new PSU for the G9. I see a lot of different designs in here. If we follow Mr. Jones we should have all PSU parts on a different board, and screen the board from the rest of the amplifier, even tho the current is very low, and the star-connect every part that needs power. The 12V, 48V and 245V should be place separably from the main board, and no trace on the main board should be used for power. Star-connected heather etc.

any comments? Have somebody done this?
I have drawn a board in autoCAD and will try when I get my next payment, or maybe in January... x-mas gifts.... ;)




Title: Re: The official G9 help thread
Post by: lampodigenio on November 28, 2010, 07:17:32 AM
anyone help me?
Title: Re: The official G9 help thread
Post by: ChrisPbass on November 28, 2010, 10:45:27 AM
anyone help me?

Haima helped you a page back Lamp.

If I'm reading it correctly, Cap 1(offboard) on the spare psu pcb refers to *C14 and Cap 2(offboard) to *C15 on the schematic.

It says 'TO CAP2/245V OUT', i.e its the 245v output connection and the connection for the Cap(offboard) which is rated at 100uF 350V.

Check the circuit diagram and you'll see 'Cap2'/*C15 wired across the 245V output.

Chris
Title: Re: The official G9 help thread
Post by: haima on November 28, 2010, 06:08:44 PM
I've just Morgan Jones books; Valve Amplifiers and Building Valve Amplifiers, great books btw!
I'm also designing a new PSU for the G9. I see a lot of different designs in here. If we follow Mr. Jones we should have all PSU parts on a different board, and screen the board from the rest of the amplifier, even tho the current is very low, and the star-connect every part that needs power. The 12V, 48V and 245V should be place separably from the main board, and no trace on the main board should be used for power. Star-connected heather etc.

no need to go that far in my opinion. the original designs for the 12v & 48v seem to work fine on board as they are. just moving the 245v off the main board fixed the hum problems in both my units, and other people's too.

my guess is that the having the high voltage power supply regulator and rectifier on the main board results in ground current noise circulating, in some builds, perhaps not all - probably related to the circuit board layout and varying AC input voltages worldwide etc.

i actually left the original 245v regulator and caps on the main board, but removed the rectifier and fed "pre-regulated" DC to the main board, a bit higher than 245v so the regulator would still work. the "pre-regulator" board contained a rectifier, some caps and a zener+pass-mosfet "regulator".

i'm pretty sure you'd get a similar result by just not stuffing the 245v part of the main board and just building that part on a separate board. but the above is what worked for me while i was troubleshooting, so i stopped investigating and got on with life....  ::)
Title: Re: The official G9 help thread
Post by: microc on November 30, 2010, 01:37:53 AM
... so i stopped investigating and got on with life....  ::)

Good call!
Thanks =)
Title: Re: The official G9 help thread
Post by: lukas on December 02, 2010, 05:48:39 PM
Hello. This is my first post here. I buld G9 and works great, but if i switch high pass filter in my speakers i have clip. I wont change it give 10M resistors(look at pics). This will be good, anybody know something ?

http://www.aukcjoner.pl/gallery-demo/4160649.html
Title: Re: The official G9 help thread
Post by: gyraf on December 03, 2010, 07:32:00 AM
that would probably work..
Title: Re: The official G9 help thread
Post by: lukas on December 03, 2010, 12:42:02 PM
Thx for u answer, i check out this soon.
Title: Re: The official G9 help thread
Post by: maxime on December 03, 2010, 04:00:03 PM
Hi,

I changed the OEP transformers for these and it sound nice:

Pikatron RUP 817M/1 Mikrofon 1: 3,21 + 3,21
wired 1:6,42

http://myworld.befr.ebay.be/studioemt1
that seller sold mine for 10 euros per transformer!
It's is cheap!  I guess he still has some stock.

While I liked the Oep sound, it made my unit sound too bass shy.
Title: Re: The official G9 help thread
Post by: ruckus328 on December 05, 2010, 11:42:30 AM
Hey guys, trying to get my BOM together for my G9 build.  Was thinking of using polypro pretty much everywhere a film is required as opposed to polyester.  Orange Drops where possible, looks like they'll fit most places - the 10uF & 1u5 will have to be something else.  Anyone see any issues with this or has anyone else does this?  Any reason why polyester would be advantageous over polypro that I'm missing?
Title: Re: The official G9 help thread
Post by: marvelouzone on December 05, 2010, 06:57:57 PM
This is My first post, I have found many answers without asking questions, so hopefully I haven't missed an answer while searching...

I'm in the process of building a g9 still haven't purchased transformers Yet. While I'm good with calculating resistance... impedance is my weak area... i was looking at several Jensen input transformers and was wondering if you could give me some advice.

1st question: Does Jensen transformers give a sort of color to the sound or are they transparent? I'm preferring a sort of color for vocals, which is all I track for r&b and hip hop mainly. Even if not I know this g9 will be better than my ga-pre73, eureka presonus, and digi 003 internal preamp...

2nd question: I'm looking at the specs and I believe Jakob says the g9 input transformer should be a 1:5 - 1:10, I see the

JT-13K7-A      (1:5 150:3.8k) http://www.jensen-transformers.com/datashts/13k7a.pdf (http://www.jensen-transformers.com/datashts/13k7a.pdf)
JT-110K-HPC   (1:8 150:10k) http://www.jensen-transformers.com/datashts/110khpc.pdf (http://www.jensen-transformers.com/datashts/110khpc.pdf)
JT-115K-EPC   (1:10 150:15k) http://www.jensen-transformers.com/datashts/115kepc.pdf (http://www.jensen-transformers.com/datashts/115kepc.pdf)
JT-115K-E      (same as above) http://www.jensen-transformers.com/datashts/115ke.pdf (http://www.jensen-transformers.com/datashts/115ke.pdf)
JT-115K-E60   (dual canned for extra emi block) http://www.jensen-transformers.com/datashts/115ke60.pdf (http://www.jensen-transformers.com/datashts/115ke60.pdf)

What impedance does the g9 expect to see on the input? I seen it in one of the threads, and cant seem to find it now. I plan to use different kind of mics sm7/7b, tube mics, condens.,etc I'm assuming for the dynamic mic I would need lots of gain? thats what made me lean towards the 1:10 or 1:8. I also noticed that JT-115K-E60 has 2 shield cans which I thought might be useful when I hear people saying the input transformers pick up hum from toroids depending on placement.

3rd question: If I did use one of these transformers how would I calculate what resistors I would need to match the impedance, if this is the correct way of doing it.

4th question: Would I notice a major difference in using a cheaper input tranny, say like an edcore compared to the jensen?

5th and last: has anyone used the JLM111DC Output transformer http://www.jlmaudio.com/shop/index.php?_a=viewProd&productId=25 (http://www.jlmaudio.com/shop/index.php?_a=viewProd&productId=25) It can be wired 2:1 I seen one post were someone did use it, and likes it, but didnt go into detail.

p.s. I'm doing the ecc88 on second output stage.


Thanks for taking the time to read this long question.
Marvin
Title: Re: The official G9 help thread
Post by: haima on December 05, 2010, 07:39:22 PM
1st question: Does Jensen transformers give a sort of color to the sound or are they transparent? I'm preferring a sort of color for vocals, which is all I track for r&b and hip hop mainly. Even if not I know this g9 will be better than my ga-pre73, eureka presonus, and digi 003 internal preamp...

any transformer with a higher ratio will have more coloration - companies like jensen, cinemag and lundahl make efforts to reduce that color to a minimum. so it will be fairly subtle, but still enough color for most vocals IMHO.

the OEP that lots of people use is quite colored IMHO - not always the best choice for R&B vocals...

there's enough color coming from the valves (tubes) and the output transformer. if you want this to be a good universal preamp for vocals i would suggest a jensen, cinemag or lundahl input transformer.

2nd question: I'm looking at the specs and I believe Jakob says the g9 input transformer should be a 1:5 - 1:10, I see the

JT-13K7-A      (1:5 150:3.8k) http://www.jensen-transformers.com/datashts/13k7a.pdf (http://www.jensen-transformers.com/datashts/13k7a.pdf)
JT-110K-HPC   (1:8 150:10k) http://www.jensen-transformers.com/datashts/110khpc.pdf (http://www.jensen-transformers.com/datashts/110khpc.pdf)
JT-115K-EPC   (1:10 150:15k) http://www.jensen-transformers.com/datashts/115kepc.pdf (http://www.jensen-transformers.com/datashts/115kepc.pdf)
JT-115K-E      (same as above) http://www.jensen-transformers.com/datashts/115ke.pdf (http://www.jensen-transformers.com/datashts/115ke.pdf)
JT-115K-E60   (dual canned for extra emi block) http://www.jensen-transformers.com/datashts/115ke60.pdf (http://www.jensen-transformers.com/datashts/115ke60.pdf)

What impedance does the g9 expect to see on the input? I seen it in one of the threads, and cant seem to find it now. I plan to use different kind of mics sm7/7b, tube mics, condens.,etc I'm assuming for the dynamic mic I would need lots of gain? thats what made me lean towards the 1:10 or 1:8. I also noticed that JT-115K-E60 has 2 shield cans which I thought might be useful when I hear people saying the input transformers pick up hum from toroids depending on placement.

basically my understanding is valve grid inputs are best matched with a very high ratio transformer - but at some point when winding a the high ratio transformer you hit a point where there is trade offs in frequency response, phase etc. this is why the "115K" is the highest ratio transformer jensen make off the shelf - the believe that's the highest ratio they can go while still retaining fidelity.

so i would go for one of the 115K models - the only reason to use a lower ratio transformer is if you want slightly less color or if your signal source is so loud that a high ratio transformer will overload the input stage - and for that you have the "PAD".

a SM7 can need a fair bit of gain depending on your singer, so again i'd go for the 115K (or maybe the 110K if you only record screamers!).

3rd question: If I did use one of these transformers how would I calculate what resistors I would need to match the impedance, if this is the correct way of doing it.

just follow jensen's application sheet #20 http://www.jensen-transformers.com/as/as020.pdf (http://www.jensen-transformers.com/as/as020.pdf) - they show their recommended zobel/loading etc.

you can use their suggested values for the pad too if you like - or the original gyraf ones will work fine too.

one mod to consider is that you may want to wire the 48v/pad switch separately so that you can access the pad while using hot condenser mics... i think it's shares one rotary switch in the standard design? i can't remember.

4th question: Would I notice a major difference in using a cheaper input tranny, say like an edcore compared to the jensen?

i'd say fairly major - do edcor even make mu-shielded input transformers of high ratio? you might be thinking of OEP?

if you want this to be your BEST preamp for the MOST sources, i'd go with a quality input transformer (jensen, cinemag, lundahl) - at least for one of the channels.

5th and last: has anyone used the JLM111DC Output transformer http://www.jlmaudio.com/shop/index.php?_a=viewProd&productId=25 (http://www.jlmaudio.com/shop/index.php?_a=viewProd&productId=25) It can be wired 2:1 I seen one post were someone did use it, and likes it, but didnt go into detail.

JLM joe said to me that his output transformer works REALLY well on the G9, and i'd tend to believe him... he said it fixes the bass droop and headroom issues that make the OEP sound "bad" (some people like this sound, but again, unless you are making a "dirty" preamp, i'd go for something bigger sounding)

the output transformer is a lower ratio than the input transformer and doesn't need shielding - so they are much easier to make, therefore there is more "good" options: JLM, jensen, sowter, and for a cheaper option edcor - have a look though this thread for opinions.

if you have limited funds i'd put all the money you can into the input transformer as this will define the sound the most and then try a edcor for output - especially as you are based in the US... the shipping on the JLM might be expensive?
Title: Re: The official G9 help thread
Post by: haima on December 05, 2010, 08:02:06 PM
Hey guys, trying to get my BOM together for my G9 build.  Was thinking of using polypro pretty much everywhere a film is required as opposed to polyester.  Orange Drops where possible, looks like they'll fit most places - the 10uF & 1u5 will have to be something else.  Anyone see any issues with this or has anyone else does this?  

use whatever caps you like the sound/look of and will fit, within voltage rating i guess. orange drops? i like purple grape fizzy drops :P

i don't know if anyone has done much A/B-ing of different caps on this particular design... (anyone?) but anything anyone says about their preference for tube mic preamp coupling caps will apply here too.

just use the best parts you can afford. if you want to go HIFI and have money to burn then run flying leads to some great big honkin audiophile cap ala manely.

Any reason why polyester would be advantageous over polypro that I'm missing?

price? size?
Title: Re: The official G9 help thread
Post by: marvelouzone on December 05, 2010, 09:27:32 PM
Thanks for the info haima, Just a question on something you said..

Quote
JLM joe said to me that his output transformer works REALLY well on the G9, and i'd tend to believe him... he said it fixes the bass droop and headroom issues that make the OEP sound "bad" (some people like this sound, but again, unless you are making a "dirty" preamp, i'd go for something bigger sounding)
You mean something bigger sounding than the OEP correct?


Title: Re: The official G9 help thread
Post by: maxime on December 06, 2010, 05:39:33 PM
In the past, I have used lundahls and oep for input transformers.
I'd say that their sound was quite different. the lundahls were clean indeed & the oep much dirtier.
for pop vocals, I'd prefer the oep sound.  for drum overheads, jazz vocals, acoustic instruments and general recording, I'd prefer the lundahls.
I think your choice should depend on the other preamps you have in your studio. I like to use the preamp as a colour tool and the choice of options is nice..
my 2 cents...
Title: Re: The official G9 help thread
Post by: haima on December 06, 2010, 07:58:01 PM
Thanks for the info haima, Just a question on something you said..

Quote
JLM joe said to me that his output transformer works REALLY well on the G9, and i'd tend to believe him... he said it fixes the bass droop and headroom issues that make the OEP sound "bad" (some people like this sound, but again, unless you are making a "dirty" preamp, i'd go for something bigger sounding)
You mean something bigger sounding than the OEP correct?

yes, i was implying that to some peoples ears the OEP's distortion and bass shy sound can make things "smaller" sounding. of course, in some cases that is a good thing.

if you are unsure about transformer choice, why not make one channel with OEPs and one with jensen/cinemag/lundahl input and jensen/edcor output? then you can decide.

you could use short, twisted, flying leads to the OEPs for testng, in case you don't like the sound - they can be a ***** to de-solder unless you have a desoldering gun.
Title: Re: The official G9 help thread
Post by: marvelouzone on December 07, 2010, 12:37:58 PM



you could use short, twisted, flying leads to the OEPs for testng, in case you don't like the sound - they can be a ***** to de-solder unless you have a desoldering gun.
Yes I do have one actually.

So my final decision is going to be 1 jensen JT-115K-E60 , with the dual can to try and keep hum out from power supply, which is fully built off main pcb board. with a jlm 111dc out on 1 channel and a oep in and edcor out on another channel. I don't think I should notice the bass roll off to much on vocals, at least if I do, it shouldn't be that bad on vocals as compared to using it as an instrument preamp..

I was getting  ready to really go overboard and throw a couple of different trans in there and put a selector switch with relays to select which trans I wanted to use for input and output on channels 1&2, but decided to get it built and working first..
Title: Re: The official G9 help thread
Post by: haima on December 08, 2010, 08:19:30 AM
sounds like you're on track!  ;) those combos should sound great.

if the super shielded jensen is super expensive, i'm sure the standard one should be fine - i've used the standard one a few times and never had problems with hum pickup....
Title: Re: The official G9 help thread
Post by: Stagefright13 on December 08, 2010, 04:30:52 PM
I have quite a few Jensen transformers. They tend to be really really good and accurate. And expensive. As in clean and uncolored. I have 6 jensen 115's wich I love. Lundhals I believe are similar. Remember ya can always dirty it up after the fact. But bringing dirt in will always sound like dirt. Which may or may not be a good thing. If ya want a darker warmer sound you can just use a deesser in your DAW. Used properly it will make the most transparent pre sound like it was from the 60's. So you have more options come mix time.

John
Title: Re: The official G9 help thread
Post by: Dr-Mbogo on December 08, 2010, 05:08:51 PM

Hi There!

I just finished my G9 build and want to say this device sounds just like whouuh! A big thanks to you Jakob!!! I am grateful for this project.

In the beginning I had some trouble with oscillation. After I conducted the wiring mod with the trace cut, oscillation is no issue anymore. Everything is fine with one exception: I want to get rid of 100Hz hum. The device is properly grounded. I even changed C14 and C15 with no success. After some tests I discovered, the transformer caps were not grounded. I fixed this. There was no change in hum. Even with no input signal.

I use the G9 for my audio book I am just producing. Between the single words and sentences the hum is audible.
I read the post of Metoo2 and his "minimum hum removing mod" relocating the R37 resistor. Is it just an issue of "moving R37 away from the board" and connect it directly to C15? I used my multimeter to measure ripple voltage across C14 and C15. There was "0V". I can borrow a oscilloscope. I think I have to use series resistors between G9 and scope. But what values? Just a ratio of 1k to 100k to make 3V out of 300V ?

Another question about the phantom power. Do I have to adjust the trim pot to 48V with or without load?


Thanks in advance for any answers!

Chris
Title: Re: The official G9 help thread
Post by: haima on December 08, 2010, 07:07:46 PM
Hey Chris - I believe you are describing is a textbook case of the same low level hum I and a few others have experienced with the G9... I fixed it by moving the HV power supply (rectifier, caps, regulator) off the main board - therefore feeding clean DC to the main board. If you read back over the last ten pages or so there should be a few references to this problem.

I think we need a FAQ....  ;D

I really suspect a LOT of G9 builds might have this hum problem - but it's low enough that it doesn't bother some people, or they just think it's what "tube diy" sounds like.... It doesn't have to be that way. I lived with the hum for 3 years (used it on a few released albums!) before i got a chance to try running the pres from an external power supply - now they are dead quiet.

For the phantom power, i'd adjust for 48v at the XLR holes, without load. I believe the 48v will always drop with any kind of load due to those 6k8 series resistors.
Title: Re: The official G9 help thread
Post by: Dr-Mbogo on December 09, 2010, 06:52:31 PM

Today I modded my G9 with an "outsourced" HV-PSU. 100Hz hum completely disappeared. It makes no difference in noise, if the G9 is connected or not; it is dead-quite.  :o

I can go on with my audio book...  ;D

Thanks for the help guys.

Chris



Title: Re: The official G9 help thread
Post by: haima on December 09, 2010, 07:51:07 PM
DING!  ;D

another success story  ;)
Title: Re: The official G9 help thread
Post by: ruckus328 on December 09, 2010, 09:39:00 PM
Today I modded my G9 with an "outsourced" HV-PSU. 100Hz hum completely disappeared. It makes no difference in noise, if the G9 is connected or not; it is dead-quite.  :o

One question - what's the little black box behind the regulator?  Bridge?


Seperate question to anyone that may know - any issue with using 25VA transformers?  Not sure what that's going to do to my voltages, as lower I go in VA, more my voltages will droop under load and not sure what that's going to do as far as the second step up transformer, if it will be enough to matter or not.

Also, anyone have any recomendations for a pilot light?  All the lamps I can find seem to be 100mA.  Thought about just running an LED with appropriate dropping resistor, but again, because of the transformer schemes, will lighten up the load an potentially increase the output voltage on the secondary xfmr (again though, don't know if the difference will be enough to matter)
Title: Re: The official G9 help thread
Post by: haima on December 09, 2010, 10:35:52 PM
One question - what's the little black box behind the regulator?  Bridge?

Looks like it to me!

Also, anyone have any recomendations for a pilot light?  All the lamps I can find seem to be 100mA.  Thought about just running an LED with appropriate dropping resistor, but again, because of the transformer schemes, will lighten up the load an potentially increase the output voltage on the secondary xfmr (again though, don't know if the difference will be enough to matter)

I've done that before- just pull the guts out of a incandescent pilot light, and hot glue a led in there (with appropriate dropping resistor). Works well.
Title: Re: The official G9 help thread
Post by: ruckus328 on December 09, 2010, 11:30:33 PM
I wasn't even thinking of going that route, just planned on using a panel mount LED from the get go.

Any idea if 25VA power xfmr's is ok?  I have them on hand.  I guess if noone knows I can just give it a try, worst case my rails dip and I have my answer.
Title: Re: The official G9 help thread
Post by: Dr-Mbogo on December 10, 2010, 01:29:35 AM
One question - what's the little black box behind the regulator?  Bridge?

Yes! It is a bridge rectifier, I had lying around. Much easier for the connection on a vero board.
Title: Re: The official G9 help thread
Post by: marvelouzone on December 10, 2010, 10:59:10 AM
ok, here's another long question...

I plan on using ecc88 on output stage. So far this is what I know:
Heaters: 6.3 volt 365ma.
My question on this is can I parallel off the output of d13-16(before 7812s)  to run an lm317 to adjust for 6.3v. Will the current from first transformer(secondaries 2*15 50va) be enough to power both regulators? If this is yes, can d13-d16 handle the current draw from both regulators? I believe they are 1 amp.

With using the ecc88, I believe the plate voltage needs to be below 130v if i'm not mistaken.
I seen somewhere in the forum that a resistor needed to be used, but cant seem to find the post now. My question is what value resistor would I need to drop to proper voltage, and were would I put it? Is there somewhere I could just drop it in on the board, or would I have to do something custom to make it work? A small explanation would be appreciated.

question about a tube.. .
1976 Mullard/Amperex A-Frame 6DJ8 ECC88

Anybody familiar with these? I have to admit I wasnt born in 76(I'm a younger DIY'er) ;D The tubes dont say mullard, but the seller says it has been confirmed by date codes GAO over B6I4 GA? over B6I1 they in-disputably were made in Great Briatain by the Blackburn Mullard. I can pick up a matched pair for 75usd Worth it? Whats the big deal with the A-frame if any? I have to admit, I have really little knowledge on tubes and some of there circuits..

last question.. Does 320v on c14 an 310v on c15 seem out of spec? Only reason i'm asking is because I built power supply offboard. I know the voltage regulator will start working once there is a load, but does that voltage seem high to start with? If it matters I used 2 of the triode dual capacitors 100+100 uf caps. So 200uf for c14 and 200uf for c15? good or bad?
Title: Re: The official G9 help thread
Post by: marvelouzone on December 14, 2010, 12:18:36 AM
ok, here's another long question...

I plan on using ecc88 on output stage. So far this is what I know:
Heaters: 6.3 volt 365ma.
My question on this is can I parallel off the output of d13-16(before 7812s)  to run an lm317 to adjust for 6.3v. Will the current from first transformer(secondaries 2*15 50va) be enough to power both regulators? If this is yes, can d13-d16 handle the current draw from both regulators? I believe they are 1 amp.

With using the ecc88, I believe the plate voltage needs to be below 130v if i'm not mistaken.
I seen somewhere in the forum that a resistor needed to be used, but cant seem to find the post now. My question is what value resistor would I need to drop to proper voltage, and were would I put it? Is there somewhere I could just drop it in on the board, or would I have to do something custom to make it work? A small explanation would be appreciated.

question about a tube.. .
1976 Mullard/Amperex A-Frame 6DJ8 ECC88

Anybody familiar with these? I have to admit I wasnt born in 76(I'm a younger DIY'er) ;D The tubes dont say mullard, but the seller says it has been confirmed by date codes GAO over B6I4 GA? over B6I1 they in-disputably were made in Great Briatain by the Blackburn Mullard. I can pick up a matched pair for 75usd Worth it? Whats the big deal with the A-frame if any? I have to admit, I have really little knowledge on tubes and some of there circuits..

last question.. Does 320v on c14 an 310v on c15 seem out of spec? Only reason i'm asking is because I built power supply offboard. I know the voltage regulator will start working once there is a load, but does that voltage seem high to start with? If it matters I used 2 of the triode dual capacitors 100+100 uf caps. So 200uf for c14 and 200uf for c15? good or bad?

Can anyone help???
Title: Re: The official G9 help thread
Post by: jackies on December 14, 2010, 01:41:57 AM
Why do you want to use ECC88? Maybe you should just build it with 12AU7?
I built mine with 12AU7, it works just fine.
You don't need any kind of expensive vintage tubes, regular kind of tubes will be good enough. Neither do you need a matched pair. Tube rolling is of course, fun, so once your preamp is working you can buy a few more different tubes and try and see for yourself if there would be any difference in sound and if you could find something you like/dislike.
310v without load is where it should be. (220*1.4=308)
 ;)
Title: Re: The official G9 help thread
Post by: marvelouzone on December 14, 2010, 10:26:09 AM
Why do you want to use ECC88? Maybe you should just build it with 12AU7?
I built mine with 12AU7, it works just fine.
I could be wrong, but my reasoning Is that I read other members say that ec88 gives 6 more db when used on the output stage. I plan on using 12au7 on input stage, just wanted to try something different on output stage.

So anybody have any recommendations on how to do this?
Title: Re: The official G9 help thread
Post by: audiophreak on December 14, 2010, 11:54:47 AM
Hi,
   Here is a link to a thread you may want to read, - http://www.groupdiy.com/index.php?topic=9813.200  -  I have done the ECC88 mod as well as tried a different out put transformer and it all sounds good,
                          HOWEVER....
                                              I now have three G-9s and find for my taste I like the stock G-9 with 12AU7s in all positions

  Just my 2 cents   ;D

  EDIT :  with Lundahls in input and output
Title: Re: The official G9 help thread
Post by: ruckus328 on December 20, 2010, 02:32:36 AM
Guys, can anyone give me any insight as to the best method of grounding this thing?  Seems the way Jakob indicates to ground it on his page contradicts how I would normally do things.  Is there some reason to run Pin 1 on the xlr's to the board as opposed to chassis/star ground?  And which point on the main board should I pick up ground, the HV supply section I presume?  Any help would be appreciated.
Title: Re: The official G9 help thread
Post by: gyraf on December 20, 2010, 04:20:40 AM
I star the ground on the PCB, at the ground-connection of inputs. And at the XLR's, I chassis-ground pin1 of the first input XLRf, and power-ground to the same point.

So yes, it isn't a "standard" star ground, but needs to be done this way to help grounding integrety on the PCB audio path, where it's most needed.

This scheme works like a charm on current-generation G9 pcb's.

Jakob E.
Title: Re: The official G9 help thread
Post by: ruckus328 on December 20, 2010, 11:22:53 AM
OK, so I'll try it the way you've indicated.  So Pin 1 of the first fem xlr goes to the main board (to the ground connection of the 3 pin connector on the main board).  Power ground from IEC goes to this same pin one on the xlr (basically Pin 1 on the first xlr is the star point).

But 3 questions - where should pin 1 on the other fem xlr go?  Not to the main board, correct?  Jump that over to pin one on the first xlr?

And what about the outputs?  Leave pin 1 floating on them?

Where should I pick up chassis ground to connect to pin 1?

Thanks
Title: Re: The official G9 help thread
Post by: marvelouzone on December 21, 2010, 03:51:50 AM
I'm no guru here, So correct me if I'm wrong, but pin 1 from the chnl 1 input xlr should go to chassis ground. The easiest way for me to do chassis grnd is to get a bolt,2 washers,locking washer, and 2 nuts. Drill a hole through back of case. You want the hole to be same size as bolt, a little bigger wont hurt, but the snugger the better. scrape around the hole with a razor, or something to take paint off, you want bolt/washers to touch bare metal. Put washer on the bolt, and slide the bolt through the hole so that the head is on the outside of case. put locking washer on the shaft of the bolt on the inside of the case and put first nut on. tighten it down. get some ring terminals appropriate for your bolt and wire size. you can use one terminal if you like that you crimp all 3 ground wires in or you can use separate terminals. your choice. you want to attach your IEC(mains) ground, pin1 of input 1(female)xlr. and pcb ground to this bolt. put a washer and nut on the end and tighten down. I dont know if its frowned upon or not, but I usually put a glob of solder on the whole assembly(bolt, nuts, washers..) after everything is working and verified, to prevent any type of vibrations or movement from working bolts/nuts loose. Its also a good idea to tin your wire before you put it in the terminal to crimp, that way you can add a little solder and heat to it once its crimped to add a little mechanical and electrical reinforcement to the durability of the crimp/connection. Some of my techniques are probably overkill, but its nothing like finishing a build and then having to trace down a ground loop, so make sure all grounds are exceptional tight. If I missed something, or made a mistake feel free to correct me....
Title: Re: The official G9 help thread
Post by: audiophreak on December 21, 2010, 11:44:41 AM
Hi ruckus328,

       On page 27 of this thread I posted a link to pix of my first G-9, you can see the green star ground wire I have on the inside of the rear panel.
    The Shield on pin 1 on the INPUT XLRs still goes to the designated pad on the PCB, AND is also wired to the Star Ground point along with the IEC Safety Ground.
 
  Thats what I did anyway, and it works for me   ;D
Title: Re: The official G9 help thread
Post by: ruckus328 on December 23, 2010, 05:03:02 PM
Hey guys, I got my unit up and running, however I'm having terrible noise/oscillation problems.  Noise floor is at about -50dbu with no signal.  Audiophreak - turns out I grounded my unit almost like you have yours, except I don't have the jumper wire between pin 1 of the input xlr's like you do (which creates a ground loop btw if you also have both of these pin 1's going to the main board) 

I have:
Mains ground to star ground bolt.
Pin 1 of each input xlr going to the main board
Pin 1 from only one of the input xlr's going to star ground bolt

It looks like you guys don't have pin 1 of the output xlr's grounded - is this correct?  Leave the outputs floating?

Dr-Mbogo - I tried figuring out how you have your main board/xlr's grounded, but I can't see any wires in the pic you posted going from either of those to the chassis/mains ground?

I'm going to go try the wire mod for the instrument jacks and report back.  I already have the 245V power supply off board so I don't know what else it could be.

Any ideas/suggestions are welcomed.  Thanks.
Title: Re: The official G9 help thread
Post by: Kingston on December 23, 2010, 05:43:57 PM
Now that you already have the external B+ supply fix you can forget all the various voodoo ground tricks. Don't even try to follow the myriad of weird grounding instructions given for G9 as they will only confuse. one applies: the same one that applies for every single balanced audio unit you are already familiar with from other projects. Directly from rane instructions.

1. XLR pin1 all of them, whether that's input or output goes to your star ground, and nowhere else. Doesn't matter if you group them or take them all individually, as long as they all end up in that same point.

2. IEC safety ground goes to that point also.

3. B+ PSU output filter cap "ground" goes to star ground. This is where your whole unit references ground. Some people might tell you to take the first PSU filter cap to star instead, but there's rectifier crud still present past that point. That's why the PSU output filter cap is the better reference.

That's it. Nothing from the PCB touches star ground directly. None of the XLR pin1 touches the PCB.

Now you can start troubleshooting the real source of noise.
Title: Re: The official G9 help thread
Post by: ruckus328 on December 23, 2010, 05:57:51 PM
Kingston, check, check, and check on the pin 1's and IEC ground - it's how I have it now and how I would normally do it.  I have the output xlr's daisy chained and then to star ground, same with the inputs. 

Here's where I get fuzzy though - on the cap banks I have both the input filter cap's and output filter cap's grounds tied together and THEN going to my offboard power supply.  From there a ground wire runs back to my main board.  So I'm confused what to do here or how I should be doing it.  Ultimately though from what your saying I should be running a wire from the offboard power supply to my IEC ground, correct?  This is again how I would normally reference the unit to star ground (same way it's done in my sb4k layout for example).  Thanks.
Title: Re: The official G9 help thread
Post by: Kingston on December 23, 2010, 06:18:33 PM
Here's where I get fuzzy though - on the cap banks I have both the input filter cap's and output filter cap's grounds tied together and THEN going to my offboard power supply.  From there a ground wire runs back to my main board.

From here (your PSU main out) goes one wire to star. Leave the filter caps be.

wait, do you really have an actual external B+ regulator, or are you just talking about having the filter caps off board, but the rest of the B+ circuit still on the main board? a picture says more th...
Title: Re: The official G9 help thread
Post by: ruckus328 on December 23, 2010, 08:00:10 PM
The whole B+ Supply is offboard.  The filter caps are the big JJ chassis mount type so they are right next door and wire to it.

http://dl.dropbox.com/u/4740474/G9/G9_PS.JPG

Title: Re: The official G9 help thread
Post by: Kingston on December 24, 2010, 05:40:58 AM
either star ground point will do, the wire connecting all the PSU filter caps, or the main external PSU output terminal.

those two stacked toroids will be the major source of noise by the way. no matter how you rotate them they will leak 50/60hz to audio circuits. They need shielding sheets or some other form of shielding.

Title: Re: The official G9 help thread
Post by: ruckus328 on December 24, 2010, 10:05:36 AM
Yea, that was my next culprit.  I had hoped their distance from the audio was sufficient enough.  Going to run down to the hardware store and find as thick of steel sheets as I can and try to wrap them.  I have a vocal session on Tuesday and need to use this sucker then.

BTW, my AC voltage going to the B+ diode bridge is about 265VAC.  Is that correct?  Jakob has 220VAC listed on the schematic.  I'm getting 246VDC on the output of the TL783 though like I should be.
Title: Re: The official G9 help thread
Post by: ruckus328 on December 24, 2010, 03:16:46 PM
OK, changed the grounding scheme.  Muuuuuuuch better.  Looks like I'm still getting a bit at the higher gain settings, but nothing like I was seeing before.  Still haven't done the wire mod, going to do that now.  Got me a piece of sheet steel to try and shield the toroid with (will redo it with mumetal later but for now it's all I can do).  Do you think I should try and wrap the toroid or am I better off just putting a wall between it and the audio?  Dumb question but if I wrap it (ala tube) I do wanna tie the tube to chassis ground right?
Title: Re: The official G9 help thread
Post by: haima on December 25, 2010, 04:32:31 AM
GREAT!

The oscillation at high gain will go away when you do the shielded wire mod.  ;)

Once you do that mod, try playing with the shielding sheet - it may, or may not make things better.... sometimes hum gets "reflected". don't forget to do noise tests with the lid on, and the input terminated with a 150-200ohm resistor.

Yes, AFAIK you'd want to ground any shielding material to the case.

If you do end up "wraping" the power transformer in a shield, be careful not to inadvertently connect it's center mounting bolt to the case on both sides - this will effectively create a shorted winding on the power transformer and cause bad things to happen :o

You can also try rotating or moving the power transformer or PCBS to reduce hum...
Title: Re: The official G9 help thread
Post by: Kingston on December 25, 2010, 02:16:12 PM
BTW, my AC voltage going to the B+ diode bridge is about 265VAC.  Is that correct?  Jakob has 220VAC listed on the schematic.  I'm getting 246VDC on the output of the TL783 though like I should be.

This is correct, in fact perfect. The listed 220VAC is the specified transformer output, not the actual measured voltage, which should exactly the 260-280VAC you're getting. The final regulated output could vary much more than your perfect 246VDC. Anything between 220-280VDC would be considered great. Tubes don't care and and you'll barely be able to measure the difference in THD with that variance.
Title: Re: The official G9 help thread
Post by: ruckus328 on December 25, 2010, 10:11:58 PM
Haima, Kingston thanks.

I made this little contraption with what I had laying around the house (nothing like getting crafty in a pinch):

http://dl.dropbox.com/u/4740474/G9/G9_Shield.JPG

Just going to tie the wire to my star ground point.  I know about the center bolt issue with tying both sides of it to ground but wasn't certain of the effects of a grounded tube on the outside as I've never done it before so just wanted to double check as better safe than sorry.

I'm doing the wire mod now (just cutting the traces and running the instrument jack direct with 2 conductor shielded cable).  I'm curious about the other 2 wires going to the 5 pin connectors (the gain and attenuation signals) - is there anything to gain by running these signals with shielded wire as well or is it just the instrument jack signals that are the oscillation culprits?
Title: Re: The official G9 help thread
Post by: Stagefright13 on December 26, 2010, 11:01:42 AM
Cut the traces and be done. Some MU metal don't hurt if ya want to be really nasty about it. :) Think the biggest problem is the torroid's need to be bigger than the bom ones. Less flux or stray field. Just an opinion. Just an amateur tho.

John
Title: Re: The official G9 help thread
Post by: ruckus328 on December 28, 2010, 02:35:48 AM
Well, she's all done.  Noise is non-exsistant now.  I'm actually using it tomorrow on a vocal session.  Going to be using it with an sm7b. 

Was hoping someone might be able to give me some advice regarding the gain/output settings.  Is it better to max the output and set the gain position to get appropriate levels? - or set the gain to one of the higher positions and back off the output knob? 
Title: Re: The official G9 help thread
Post by: marvelouzone on December 28, 2010, 04:48:18 AM
I have a question about c13/113 on the bom the capacitor is listed as a suppression film capacitor when I pull it up on mouser. I dont know alot when it comes to the capacitors besides lytics, mylar, etc... is it ok to use this one? http://www.mouser.com/Search/ProductDetail.aspx?R=MKP4-4.7/250/10virtualkey50520000virtualkey505-MKP44.7/250/10 (http://www.mouser.com/Search/ProductDetail.aspx?R=MKP4-4.7/250/10virtualkey50520000virtualkey505-MKP44.7/250/10)

what is the difference between suppression film caps, and the other different types?
Title: Re: The official G9 help thread
Post by: Kingston on December 28, 2010, 07:49:40 AM
Was hoping someone might be able to give me some advice regarding the gain/output settings.  Is it better to max the output and set the gain position to get appropriate levels? - or set the gain to one of the higher positions and back off the output knob?

Won't matter much either way. This is a very clean preamp that can't really be overdriven

1. Max out the rotary switch and set gain using the output switch is your "dirty" setting (least feedback around the first two stages).
2. Max out the output pot and set gain using the rotary switch is the clean and linear setting (most feedback around the first two stages).

The difference between these two extremes is something like 0.1% THD for "standard line levels". You won't hear much difference, but it's there.
Title: Re: The official G9 help thread
Post by: ruckus328 on December 28, 2010, 09:50:18 AM
I have a question about c13/113 on the bom the capacitor is listed as a suppression film capacitor when I pull it up on mouser. I dont know alot when it comes to the capacitors besides lytics, mylar, etc... is it ok to use this one? http://www.mouser.com/Search/ProductDetail.aspx?R=MKP4-4.7/250/10virtualkey50520000virtualkey505-MKP44.7/250/10 (http://www.mouser.com/Search/ProductDetail.aspx?R=MKP4-4.7/250/10virtualkey50520000virtualkey505-MKP44.7/250/10)

what is the difference between suppression film caps, and the other different types?

Sure, that one's fine.  In fact I used polypropylene everywhere for my build.
Title: Re: The official G9 help thread
Post by: haima on December 28, 2010, 09:53:15 AM
Won't matter much either way. This is a very clean preamp that can't really be overdriven

Hey Kingston - I'm not sure i completely agree..... The G9 is not a fuzz box, that's for sure, but i've found it can get pretty overdriven in some circumstances.

I've found it can do a nice job of absorbing peak transients - allowing you to make sounds louder without raising the peak level - obviously a type of distortion, but as you said, it can be subtle. Not really something you can get with a "clean" pre like a SSL9k etc.

It obviously depends on a number of factors - what you are recording and how hard you drive the input, and what transformers you use etc... so YMMV of course.
Title: Re: The official G9 help thread
Post by: audiophreak on December 28, 2010, 04:47:18 PM
Hi All,
      Question :   is it just the B+ thats moved off board or the whole PSU ?  and were do you re-introduce the B+ from off board ?  

 Thanks,
             Chip

EDIT:   O.K. .. sooo  after looking at the schematic, if I de-populate the B+ on main PCB, I would send off board B+ in to main PCB after C15 ?
Title: Re: The official G9 help thread
Post by: marvelouzone on December 31, 2010, 03:59:58 PM
my b+ at c15 is about 155 with all tubes in socket, 286 without tubes, 190 when just using 2 tubes..... I built power supply off board, when I first did it I had the adj and out pins reversed, it burned up the 100k resistor.. i replaces it, but didn't replace tl783, Dumb on my part... I get 310 across c14 with or without load. I'm using back to back 15v transformers 50va. caps are 100+100 uf dual caps. Is it possible that tl783 is failing under load from my previous mistake, or should I look elsewhere? The g9 is working, but very little gain with condensers and no pad, sm7b is very very low. After building psu off board I sent power in at the point were c15 would normally connect.
Title: Re: The official G9 help thread
Post by: ruckus328 on December 31, 2010, 04:39:01 PM
my b+ at c15 is about 155 with all tubes in socket, 286 without tubes, 190 when just using 2 tubes..... I built power supply off board, when I first did it I had the adj and out pins reversed, it burned up the 100k resistor.. i replaces it, but didn't replace tl783, Dumb on my part... I get 310 across c14 with or without load. I'm using back to back 15v transformers 50va. caps are 100+100 uf dual caps. Is it possible that tl783 is failing under load from my previous mistake, or should I look elsewhere? The g9 is working, but very little gain with condensers and no pad, sm7b is very very low. After building psu off board I sent power in at the point were c15 would normally connect.

I'm assuming when you say 15V xfmr you actually mean a (15V + 15V)?

Assuming that is the case, there's probably your problem right there, you want a (12V + 12V) xfmr to feed the TL783, not a (15V + 15V).  

On a sidenote, just used my G9 on a session all week with the SM7B and my SA-3A compressor, sounds amazing.
Title: Re: The official G9 help thread
Post by: marvelouzone on December 31, 2010, 06:57:59 PM
I'm assuming when you say 15V xfmr you actually mean a (15V + 15V)?

Assuming that is the case, there's probably your problem right there, you want a (12V + 12V) xfmr to feed the TL783, not a (15V + 15V).  
Really I thought that as long as it was above 25 - 30va on the tranny it would be good with the 15v +15V. I do have proper voltage levels before the tl783(c14) 310v and even 286 when loaded. If I'm correct, 15v feeding a second tranny that's 12v + 12v would give me a 1/10 stepup which would probably be 300v before rectifiers multiplied by 1.4 would probably be 420v before regulator right? Seems like overkill to me, when I get 310 out of the 15v+15v, before regulator. Seems like if the tl783 was working properly it would be more than enough Headroom, when the input voltage is only required to be 1.25v higher than then required output voltage. Wouldnt a higher voltage cause the tl783 to work harder and waste energy in heat?  I guess if the voltage on c14 was really low with load then I would suspect the tranny's but this isnt the case. Anybody else have any input.

ideally 220vac out of second trans multiplied by 1.4 would give me 308vdc as long as both tranny's are rated properly they can sustain the proper voltage under load. Are my thoughts and math correct?

Thanks for the insight ruckus, but by theory I think I disagree. If I missed something feel free to let me know.
Title: Re: The official G9 help thread
Post by: ruckus328 on December 31, 2010, 08:59:35 PM
Really I thought that as long as it was above 25 - 30va on the tranny it would be good with the 15v +15V.

Read through the first 5 pages of this thread and you'll see that a 15V+15V isn't enough to drive the TL783, which is why the specifications were changed to a 12V+12V.

I do have proper voltage levels

Actually, I'm not so sure.  You should have somewhere around 260-280 volts with a 12V+12V driving the TL783.  I have 265V using a 25VA transformer.

Which means.......if you're seeing 300V with a 15V+15V then you have something else going on, you should be seeing closes to 200V - 225V if memory serves correct, which is too low.....hence the change to the 12V+12V.  I'd double check my xfmr wiring first and verify and go from there.  

I'm using back to back 15v transformers 50va

This could also be your problem.  If you're using a larger VA xfmr then specified, then in theory you drop is going to be less under load, so you very well may be getting more than 15V on the output of your first transformer, so stepped up through the second transformer, this could account for your higher voltages.  Have you measured the AC here?  Who knows, just a thought.

Best of luck.  And happy New Years.  Shouldn't we be out celebrating?
Title: Re: The official G9 help thread
Post by: marvelouzone on January 01, 2011, 03:00:32 AM
Happy New Years to you, and the rest of the board also, I celebrating at home, so excuse me for slurred typing  ::) I changed the tl783 and all voltage is in spec. A solid 250 sitting at c15.

I did read the 12v theory in the early part of the forum, but it was said that the 15v was sufficient as long as it was more than 25va. What happens with the smaller transformers is that the load on the two 15v primary's of the first trans causes the voltage to drop below 15 probably somewhere around 13, which would cause the voltage to be around 208vac. If the first trans can maintain at least 15v under load then your guaranteed at least 220vac on the output of the second transformer.  Theoretically 220vac after rectified is 308vdc. So I'm right within spec now 302 at c14 under load, and 250 at c15.

My problem now is I have to figure out why I have very little gain.... It did get a little better once voltage was up to spec, but I'm sure i'm only get 1/4 of the gain i should if not less. I've ruled out tubes since I have changed them and put in tested/good tubes... Any Ideas on where I should start. Its on both channels. channel 1 has a jensen 115kpe 1:10 input and oep output(waiting on my jlm audio 2:1 output tranny), channel 2 is both oep.
Title: Re: The official G9 help thread
Post by: Bonke on February 03, 2011, 04:26:46 PM
Hi all.
I know this has been asked several times in this thread but I just want to be 100% sure before plugging in power.
Could someone please confirm that my wiring is correct. After confirmation I am just waiting for my JJ-tubes to arrive and then it is testing time.
Thank you in advance.
Henke

(http://web.me.com/bedahenke/Stuff/G9_files/Skarmavbild%202011-02-03%20kl.%2021.54.06.jpg)
Title: Re: The official G9 help thread
Post by: gyraf on February 04, 2011, 03:30:23 AM
..looks right...

Jakob E.
Title: Re: The official G9 help thread
Post by: Bonke on February 04, 2011, 07:14:07 AM
Thank you Jakob!
I must say it is fantastic that you and all the other pro´s keep helping us newbies out on this forum.
Thank you for this great project aswell!

Henrik
Title: Re: The official G9 help thread
Post by: Bonke on February 05, 2011, 04:41:59 PM
Hi!
Do you guys think it will be possible to isolate the TL783 on a piece of wood like this? (it´s not connected to chassis) I ordered to big heatsink so I have to put it offboard. Or is it getting so hot that it will burn the wood? Also, it IS ok to heatsink the 78S12 to chassis right?

(http://web.me.com/bedahenke/Stuff/Tomt_files/IMG_0402.jpg)

Here is a picture of the guts without tubes.

(http://web.me.com/bedahenke/Stuff/Tomt_files/shapeimage_2.png)

Henrik
Title: Re: The official G9 help thread
Post by: bpucekov on February 07, 2011, 02:59:43 AM
yes
Title: Re: The official G9 help thread
Post by: Harpo on February 07, 2011, 06:21:48 AM
Do you guys think it will be possible to isolate the TL783 on a piece of wood like this? (it´s not connected to chassis) I ordered to big heatsink so I have to put it offboard. Or is it getting so hot that it will burn the wood? Also, it IS ok to heatsink the 78S12 to chassis right?
What's so wrong with using a piece of mica and a TO220 isolation kit for a reliable job ? (your piece of wood will shrink from generated heat inside the box and the screw will come loose one day...)

The length of wires connecting to the off board regulators seem a little long (exceeding 3-4 inches from filter caps). Keeping the regulators stable might require additional bypassing at the regulators input terminal with a smaller cap.

Your build seems to be missing a connection between input-XLR-pin1 and 0V reference voltage to make +48V phantom work.
Title: Re: The official G9 help thread
Post by: Bonke on February 08, 2011, 04:20:20 AM
Quote
What's so wrong with using a piece of mica and a TO220 isolation kit for a reliable job ? (your piece of wood will shrink from generated heat inside the box and the screw will come loose one day...)
I will get a kit next time I order.

Quote
The length of wires connecting to the off board regulators seem a little long (exceeding 3-4 inches from filter caps). Keeping the regulators stable might require additional bypassing at the regulators input terminal with a smaller cap.
Ok, so I move the heatsinks closer to the pcb and shorten the wires.

Quote
Your build seems to be missing a connection between input-XLR-pin1 and 0V reference voltage to make +48V phantom work.
I have input XLR´s pin 1 connected to starground. Is there another connection required?

Thanks Harpo for the answers!

Henrik
Title: Re: The official G9 help thread
Post by: Harpo on February 08, 2011, 05:57:54 AM
Quote
Your build seems to be missing a connection between input-XLR-pin1 and 0V reference voltage to make +48V phantom work.
I have input XLR´s pin 1 connected to starground. Is there another connection required?
You have input XLR's pin 1 connected to case and safety ground.
Additionally connecting 0V reference voltage from your +48V psu to this junction (starground) will provide the else missing current return path for phantom voltage.
Title: Re: The official G9 help thread
Post by: Bonke on February 08, 2011, 06:17:14 AM
Quote
Your build seems to be missing a connection between input-XLR-pin1 and 0V reference voltage to make +48V phantom work.
I have input XLR´s pin 1 connected to starground. Is there another connection required?
You have input XLR's pin 1 connected to case and safety ground.
Additionally connecting 0V reference voltage from your +48V psu to this junction (starground) will provide the else missing current return path for phantom voltage.

I am sorry for not understanding this but isn´t 0V connected via the "gnd" on the input-connection on the pcb?
My input xlr´s pin 1 is connected to "gnd" on the input-connection on pcb and also to starground on chassi. Should I connect another wire from 0V on pcb to starground???

Henrik
Title: Re: The official G9 help thread
Post by: Harpo on February 08, 2011, 06:59:45 AM
I am sorry for not understanding this but isn´t 0V connected via the "gnd" on the input-connection on the pcb?
yes
Quote
My input xlr´s pin 1 is connected to "gnd" on the input-connection on pcb and also to starground on chassi. Should I connect another wire from 0V on pcb to starground???
If so, no other connection required. From your 1st pic, input XLR pin1 looks like to only have the brown wire attached exclusivly and this would be missing a connection. Maybe optical artifact.
Title: Re: The official G9 help thread
Post by: Bonke on February 08, 2011, 07:05:36 AM
Ok! That would be the photo fooling you. :)
Cool, thanks for struggeling with me Harpo!

Henrik
Title: Phantom power was 48, now 22V, tips?
Post by: lumpylipton on March 22, 2011, 01:21:05 PM
Hi,
I finally completed my G9, it powered up fine (no smoke!!) passed audio on both channels and other than one switch contact I somehow missed soldering, everything seemed ok......until....now.

The phantom power was originally trimmed to 48v and was working, however now I'm getting about 22V for phantom and the trimmer does nothing.
No parts are obviously smoked, and because it was working, I'm quite sure all the components are correct.

I'm thinking it must be one or more of the tripler caps, since I'm just not getting anywhere near the voltages expected.  Would this be a good place to start?  I've double-checked the AC voltage getting to the tripler is 16VAC, so it's not the transformer.
Thanks, this thing sounds fantastic, I'm excited to try it with condensers once I get this phantom sorted.
Warren
Title: Re: The official G9 help thread
Post by: gyraf on March 23, 2011, 05:03:57 AM
..double-check that the phantom power is not loaded down by a shortcircuit somewhere, doublecheck orientation of electrolytics(!!).

Maybe first try disconnecting P48-stage from rest of G9 for troubleshooting (maybe cut a trace and resolder later).

If it worked initially, and not later, my guess is a electrolytic in the tripler section, try replacing (maybe use higher rated voltage types)

Jakob E.
Title: Re: The official G9 help thread
Post by: ChrisPbass on March 23, 2011, 08:25:57 AM
Has anyone tried the Haufe ST8456 sold by silent arts on the input yet?
Title: Re: The official G9 help thread
Post by: sam system-d on March 25, 2011, 11:40:11 AM
I'm new here, so please, excuse those words :
THANK YOU!
I'll do a real post as soon as I will finish my GIX (very few more stuff to do)
Great project, great sound, I think I'm in love with it :)
I've got to fix something (gain pos #5 doesn't work on both channels) but everything else is ok.
The only negative thing I got to say about it is once you've build one, you just want another :)
Title: Re: The official G9 help thread
Post by: lumpylipton on March 27, 2011, 06:06:06 PM
Thanks Jacob, I fixed my problem, it was one bad cap in the tripler.  I replaced all of them with the next voltage up just to be sure.  Now the phantom does work.  Next problem; I now have a rather loud 60Hz hum that is only present when the phantom is on, both channels.  I'm going to search through the forum to see if I can find something on this.  Obviously a grounding issue somewhere....

Many thanks for the project, it sounds great and I learned a lot building it.

Warren
Title: Re: The official G9 help thread
Post by: haima on March 27, 2011, 06:13:44 PM
Are you sure it's 60Hz?

Or might be 120Hz + harmonics?

Perhaps the phantom supply might have heaps of ripple - that could be heard as "hum" on the output - does it hum in the 48v setting if you just terminate the input without any Mic attached? (i.e. put a 150ohm (or anything between 50 and 1k) resistor between pins 2+3 on the input XLR).
Title: Re: The official G9 help thread
Post by: lumpylipton on March 29, 2011, 09:54:55 PM
It's definitely 60 Hz, I measured it with my DAW.   I tried terminating with a resistor instead of a mic, and the hum is far louder that way.

Any other ideas?  I've rechecked the grounding, and it is XLR inputs pin 1 tied together, XLR input one pin 1 tied to star ground, IEC ground tied to star ground, which is then bolted to the chassis, nothing else is tied to the star ground.

Moving the transformer or power switch wiring around does nothing, just a steady 60Hz hum, only with phantom on, otherwise it's silent.
Thx,
Warren
Title: Re: The official G9 help thread
Post by: Cardinen on April 05, 2011, 02:16:50 PM
Hi,
I finally finished my G9, seem to work fine but i have a few question about.

1- One of the toroidal transformer (12+12V 50VA) make a bit of noise, even when the case is closed. Is that normal ??
(It scared me at first !!)

2- Switching between Line/Mic don't work on channel 1. I've checked the connections from the switch to relay and all is fine. 12V goes to relay but it seem to don't work. is a standard Omron G5V2. maybe is faulty ?? what could try before desoldering it ??

3- I have a bit of noise at high settings using the Direct In whit my guitar/bass while the mic ins are really quite.
the noise appear at step 7 and rise. i think this is normal, can you confirm ??

Thx

Cardinen

Title: Re: The official G9 help thread
Post by: sam system-d on April 06, 2011, 07:26:17 AM
Hi Cardinen,
1 - I got no idea, sorry, I'm a newbie in electronics :)
2 - I would check the 1N4148, I used to do a project with lot of them and relays, and few of them didn't work for no reason, so the relay didn't switch.
3 - you can avoid this problem with a shield cable from input transfo to jack, jack to Input cap. There's a topic about this, search on the meta :) Once you've done it, the G9 is really quiet.
Title: Re: The official G9 help thread
Post by: tmuikku on April 06, 2011, 09:51:45 AM
3 - you can avoid this problem with a shield cable from input transfo to jack, jack to Input cap. There's a topic about this, search on the meta :) Once you've done it, the G9 is really quiet.

Not until HT supply is done out of the board ;) Check this thread a few pages back, there is plenty of info including pics and FFT charts before and after.
Title: Re: The official G9 help thread
Post by: Matador on April 06, 2011, 10:38:53 AM
Quote
Moving the transformer or power switch wiring around does nothing, just a steady 60Hz hum, only with phantom on, otherwise it's silent.

How closely matched are the 6.81K phantom coupling resistors?
Title: Re: The official G9 help thread
Post by: sam system-d on April 06, 2011, 11:02:22 AM
3 - you can avoid this problem with a shield cable from input transfo to jack, jack to Input cap. There's a topic about this, search on the meta :) Once you've done it, the G9 is really quiet.

Not until HT supply is done out of the board ;) Check this thread a few pages back, there is plenty of info including pics and FFT charts before and after.
Thanks for the tip, I'll think abou it for my next G9  ;)
Title: Re: The official G9 help thread
Post by: Cardinen on April 06, 2011, 07:17:43 PM
Ok i've found the problem whit channel 1 relay... i've miss 1 solder joint !!   >:(

Now all seem to work fine except the noise from tranformer 2 but is a minor problem.

Thank's to Jakob for make this possible !!
(http://img855.imageshack.us/img855/255/97154793.th.jpg) (http://img855.imageshack.us/i/97154793.jpg/)

Edit: Added photo




 
Title: Re: The official G9 help thread
Post by: madreza on April 09, 2011, 08:42:29 AM
Hi guys !
I finally bought an Oscillo !
I have a probleme with a friend's G9

when feeding it with a sine 1k

(http://img708.imageshack.us/img708/7274/photoin.jpg)


I get this at the g2 pin of the input tube

(http://img26.imageshack.us/img26/5413/photo2zo.jpg)

My HT voltage is low !!!! ( approx. 216 V )

tubes are OK ( tested on another G9 )

I have the same problem on both channels !
where should I look ?

Title: Re: The official G9 help thread
Post by: sam system-d on April 09, 2011, 08:04:15 PM
maybe here :
http://www.groupdiy.com/index.php?topic=11347
 ;)
Title: Re: The official G9 help thread
Post by: madreza on April 10, 2011, 07:46:22 AM
Merci Sam :)
but I think if the HT voltage is too low, the G9 works
mine doesn't ! I don't think having a low HT can lead to the result I get at g2 !
Title: Re: The official G9 help thread
Post by: MeToo2 on April 11, 2011, 12:52:11 PM
Merci Sam :)
but I think if the HT voltage is too low, the G9 works
mine doesn't ! I don't think having a low HT can lead to the result I get at g2 !
Anyway presuming G2 is pin 2 of the first ecc82 = the grid of the 2nd half of the input = junction C3 and R23.

That waveform looks like is is saturating on one half of the cycle.

Firstly check the grid of the other half of the triode = pin 7 to make sure you have a nice sine wave from your input transformer via C2/ junction of R6.

Next if that is OK (carefully) check the DC voltages on pins 6,7 & 8, plus the heater voltage.

I would initially suspect something structurally incorrect in the wiring on the cathode (wrong value R7? R8? or R9?) (causing a wrong cathode voltage on pin 8 ), because both channels are doing the same thing.

You could also check your G9 with only 2 tubes installed (one channel) and measure your PSU voltage then. Watch out though: the TL783 only really starts regulating once it is supplying about 15mA so do not panic of it is a bit higher than 240V.

BTW you look to be feeding a 3V peak sine wave, which is pretty high for testing. Make sure you're in "line" mode and no 48V phantom power.
Title: Re: The official G9 help thread
Post by: madreza on April 11, 2011, 01:41:56 PM
You are exactly who I needed :)
I'm gonna check these right away !
Thanks !
Title: Re: The official G9 help thread
Post by: alexc on April 19, 2011, 07:06:06 AM
Hi All

Just finished my G9 - seems to be working fine, power supplies are all good, no excessive heat

Extremely quiet using on board psu

-> mains harmonics each less than -92dBu for both channels
-> overall unity gain noise floor of -81dBu (spl) on Motu with -83dBu loop-back noise floor

Lundahl 1530 input traffos (1:7 turns ratio) and Carnhill VTB9057 output traffos (1.73:1 turns ratio)
12AU7 (ECC82) for all stages

- frequency response is very flat with extended low and hi

-> -3dB at 20Hz and -2dB 20KHz  (line input to output), both channels virtually identical

Out of interest, other changes I made were

- seperated the line input from the mic input connections and gave them their own connectors
- used a single psu toroid and changed the onboard rectifier to a 2 diode full wave(traffo hv is centre tapped)
- added led VU meters
- used the DI mod (cut traces and used shielded cable run)
- added relay bypass boards from line inputs to outputs
- changed 48V tripler to a doubler to accomodate the psu toroid available 18VAC winding

Sounds brilliant - very clean, full bass and detailed high, no distortion or oscillations at all!

So - THANX to Jakob (and Swedish Chef for the pcbs circa 2004!).

Very nice performer here, well worth building and worked pretty much first go.
Title: Re: The official G9 help thread
Post by: Phil on April 27, 2011, 09:08:03 AM
Hey Guys,

I'm having problems to get the "C13,113 // 4U7 250V POLYESTER" capacitor anywhere ..

Can somebody maybe tell me some company name or a certain part number for this?

I've already asked in several electronics stores but they all don't have such big polyester caps with 4,7 uF 250V

I've read that i have to look for "FKP" in the name since this is for audio - but i'm not really sure..

thx for the help
Title: Re: The official G9 help thread
Post by: MeToo2 on April 27, 2011, 05:33:51 PM
Hey Guys,

I'm having problems to get the "C13,113 // 4U7 250V POLYESTER" capacitor anywhere ..

Can somebody maybe tell me some company name or a certain part number for this?

I've already asked in several electronics stores but they all don't have such big polyester caps with 4,7 uF 250V

I've read that i have to look for "FKP" in the name since this is for audio - but i'm not really sure..

thx for the help
Not many (physical) electronics stores stock this sort of high voltage high value film capacitor any more.

I'd guess at MKT (metallised polyester) or MKP (metallised polypropylene) rather than FKP. FKP has no metal AFAIK so I guess that'd be some esoteric spend-a-fortune audiophile foil only cap, but I'm not sure they'd ever go up to 4.7uF anyway.

Search for 4.7uF polyester or metallised polyester or metallised polypropylene and then filter on voltage.
Some people say polypropylene is better for audio. I dunno. I'm not one who obsesses about such things.
I think it's one of the less important choices. I'll probably get a flaming for posting such heresy.

Check out the physical dimensions carefully on the following links to make sure they'll fit in your PCB.

Higher voltages would be fine, but they'll tend to be physically bigger too. Do NOT replace with an electrolytic IMHO.

I'm pretty sure I used an Epcos Cap. B32924E3475M in one build and a B32524Q3475K in another.

There are others e.g. Panasonic ECQE2475JF, Vishay BFC237343475 Cornell DME2W4P7K-F
And of course WIMA if you can find them MKM4-4.7/250/5. Some people get excited if you say you've used Wima caps.

Here's a few sites where you can order this sort of cap. I'm sure there are plenty more out there.

http://search.digikey.com/scripts/DkSearch/dksus.dll?lang=en&site=UK&WT.z_homepage_link=hp_go_button&KeyWords=B32924E3475M&x=0&y=0
http://uk.farnell.com/epcos/b32924e3475m/capacitor-class-x2-4-7uf-305vac/dp/1781899
http://uk.farnell.com/vishay-bc-components/bfc237343475/capacitor-4-7uf-250v/dp/1469330
http://gb.mouser.com/ProductDetail/EPCOS/B32924E3475M/?qs=3sWhPqbVdzMIoOKIgh4%2fxw%3d%3d
http://uk.mouser.com/ProductDetail/Cornell-Dubilier/DME2W4P7K-F/?qs=sGAEpiMZZMukHu%252bjC5l7YfjT6scjVP0n3lA19dE5NK8%3d

Be sure to check the specs one more time yourself before ordering....
Title: Re: The official G9 help thread
Post by: gyraf on April 28, 2011, 01:38:10 AM
Thanks, MT2!
Title: Re: The official G9 help thread
Post by: Phil on May 23, 2011, 12:48:25 PM
sorry for the long wait on the answer - wasn't in the country ;)

thx so much for you help - I just ordered the Epcos as well and hope i can finish this project soon to use it for my next recordings ;)

Another question i have is:

Before i plug in anything, are there some kind of instructions with measurement points etc that i can have a look at?

thx again!!
Title: Re: The official G9 help thread
Post by: Majestic12 on June 27, 2011, 06:45:50 PM
Today I fired up my G9 for the first time and it works like a charm.  Both channels are clear without any hum, but both transformers make an annoying 50Hz noise which is really loud. Should I be in worry about that?

(http://img171.imageshack.us/img171/5858/dscf4898g.th.jpg) (http://imageshack.us/photo/my-images/171/dscf4898g.jpg/)

Uploaded with ImageShack.us (http://imageshack.us)
Title: Re: The official G9 help thread
Post by: Phil on August 17, 2011, 04:24:28 AM
hey there,

i just finished the G9 and .. it's not really working.
I don't get any signal from it - the only thing that happens is that when turning up the gain it gives me a high oszillated tone wich geht's higher the more i turn up.

Is there some way i can check the curcuitry step-by-step?

Title: Re: The official G9 help thread
Post by: gyraf on August 18, 2011, 01:55:12 AM
check for shorts on the pcb?

..and read through this long thread for hints..

Jakob E.
Title: Re: The official G9 help thread
Post by: braeden on September 07, 2011, 11:59:04 PM
After a year of having the G9 PCB sitting around I've finally ordered 99% of the components  (caps/resistors/switch/tube sockets/I-O trannies etc.). If there is anyone in Australia who needs my cart from X-ON.com.au/Farnell to purchase all the components pretty quickly send me a private message. It took me the best part of 3 hours to sort through everything and make sure all the parts were suitable (and I still won't know until it's finally assembled).

By the way, does anyone know where I can buy the shielded hookup wire locally (Sydney area)? Would there be any benefit in chopping up a Star-Quad Canare lead and using that?
Also, Is there anything I should be really paying attention to with the first revision of the PCB? I've noticed that we're up to #5 or something now?

Other than that I can't wait to get started... what tubes has everyone used (obviously ECC82/12AU7) but is there any point in buying the more expensive models? I'm guessing I should be using a matched pair regardless of the manufacturer anyway.

Thanks guys

Is there any harm in using two of these http://au.element14.com/multicomp/mcfe030-15/transformer-30va-2-x-15v/dp/9531726?
I noticed that it only requires a 12V supply but the voltage should be regulated by the TL783 right?
Title: Re: The official G9 help thread
Post by: MeToo2 on September 08, 2011, 08:32:59 AM
I'm guessing I should be using a matched pair regardless of the manufacturer anyway.

Thanks guys

Is there any harm in using two of these http://au.element14.com/multicomp/mcfe030-15/transformer-30va-2-x-15v/dp/9531726?
I noticed that it only requires a 12V supply but the voltage should be regulated by the TL783 right?

I looked at those too. Look like good transformers. Problem is that there isn't an mcfe030-12 AFAIK. Using two mcfe030-15 15V transformers back to back might result in weak HT: the G9 PSU uses a 15V step down from mains and a 12V in reverse as a step up to make sure there's enough voltage there for the HT even after losses. You're right that the TL783 regulates this to 245V, but it needs around a 20V "drop out" voltage between input and output to regulate properly. Also note that transformer model does not come with mounting hardware, so you have to buy 5mm bolts as extras. Might work, might not, depending on core losses, regulation accuracy, your local mains voltage (Aus is historically 240V, whereas we're usually closer to 220v in Europe) etc. So you might want to keep a pair of those for another project (like a GSSL). Try them and see.

I used these ones successfully (also from Farnell....)
http://nl.farnell.com/jsp/search/productdetail.jsp?id=9530312&Ntt=9530312
http://nl.farnell.com/jsp/search/productdetail.jsp?id=9530304&Ntt=9530304

As for matched tubes: what is "matched"? At one operating point? At two points. At three points? Over the lifetime of the tube? The G9 circuit doesn't have any balanced / differential stages anyway. IMHO save your money. Or spend it on something else.
Title: Re: The official G9 help thread
Post by: braeden on September 09, 2011, 11:04:16 PM
Thanks for that, I guess I'll just have to try them out 8)
Title: Re: The official G9 help thread
Post by: thelabyrinth on September 20, 2011, 04:45:15 AM
Finished this up about a year ago, spent about 2 years on it...Sifam meters with JLM drive board, bigger filter caps, Leeds Radio NOS RCA knobs, Lundahl transformers, mil-spec resistors, separate 48v light with switch, etc! Wiring isn't the neatest but its quiet and it was for my use only. This was the last project my tech/mentor finished before passing away. Obviously sounds incredible, cheers gyraf!
Title: Re: The official G9 help thread
Post by: thelabyrinth on September 20, 2011, 04:49:36 AM
Bench Testing
Title: Re: The official G9 help thread
Post by: thelabyrinth on September 20, 2011, 04:50:49 AM
Racked up!
Title: Re: The official G9 help thread
Post by: thelabyrinth on September 20, 2011, 04:51:35 AM
Guts
Title: Re: The official G9 help thread
Post by: thelabyrinth on September 20, 2011, 04:55:02 AM
Last one: Transformer box (to keep everything hum-free). We felt that since we were using the best components and going all out custom, the supply should be separate.
Title: Re: The official G9 help thread
Post by: Eskiclown on September 28, 2011, 06:17:05 AM
Hi guys !
Yesterday, I decided to make the external HV PSU mod to reduce the noise of my G9.
While remounting everything, I checked if my heater regulator was still isolated from the chassis (I mounted the 78S12 regulator directly to the case with an electric isolation kit) and I saw that I had a shortcut between the regulator heatsink surface and the case...
I removed all tubes and unscrewed the regulator from the chassis but still I had 0 ohm between the heatsink surface and the case...
So I checked the 78S12 datasheet just in case and read that the heatsink surface is actually connected to the ground pin (which is connected to ground in the G9). So I got my answer !  :)

But my question now is why do we read everywhere (and in particular on Gyraf's G9 page) that the 78S12 should be electrically isolated from the case ? This does not apply to TL783 or LM317/337 regulators that have their heatsink surface connected to the out pin but in the 78S12 case, I think this can be done.
Actually, I think it would be a good idea to connect it directly to the case to send this noisy power supply current to the starground on a least resistance path (though it would require a small mod to avoid a ground loop).

What's your opinion on this ? Maybe I am missing something.
Title: Re: The official G9 help thread
Post by: gyraf on September 28, 2011, 08:20:32 AM
Quote
why do we read everywhere (and in particular on Gyraf's G9 page) that the 78S12 should be electrically isolated from the case

Reason is simple: We want one - and only one - connection from 0V to chassis ground.

And that is preferably the 0V connection at the input connector.

More than one chassis ground connection is asking for trouble - specifically ground loop hum.

Jakob E.
Title: Re: The official G9 help thread
Post by: Eskiclown on September 28, 2011, 10:10:20 AM
Ok.
So this recommendation is indeed to prevent ground loops, not for safety reason. Just wanted to understand why this insulation was needed.

Thank you for the explaination, Jakob !
Title: Re: The official G9 help thread
Post by: Luax on September 28, 2011, 10:17:57 AM
I've recently finished my gyraf g9 project with the instrument mod. (thanks for everybody on the forum)
Besides working on some last details (wiring etc) the preamp seems to be working fine.
There is only one thing that probably has been talked about, but keeps me guessing and that is the instrument input level.

When plugging a synth into the instrument in the signal is coming trough clearly,
but when I plug in a passive bass guitar the signal is just barely above silence.

Since I've no comparison to other g9's in my area I'm just curious if the G9 would normally be capable by amplifying a bass or electric guitar.

If needed I can post some pictures or sound samples.

All the best,

Luax
Title: Re: The official G9 help thread
Post by: gyraf on September 28, 2011, 10:35:53 AM
The G9 inst. input is (extremely) suitable for passive bass guitar.

Check your wiring and/or resistor values around input stage?

Jakob E.
Title: Re: The official G9 help thread
Post by: Luax on September 28, 2011, 11:33:56 AM
Hi Jakob,

That's also what I hoped. I'll check all the components (again :) and verify if everything is ok.

Another thing that never hurts to mention is that I removed the two from- and to- instrument wires from the control panel to the pcb.
Could this be of any influence to the sound?

All the best.

Luax
Title: Re: The official G9 help thread
Post by: Majestic12 on September 28, 2011, 06:42:59 PM
@thelabyrinth: Nice build, very impressive :)
Title: Re: The official G9 help thread
Post by: gemini86 on September 28, 2011, 09:29:57 PM
Hi Jakob,

That's also what I hoped. I'll check all the components (again :) and verify if everything is ok.

Another thing that never hurts to mention is that I removed the two from- and to- instrument wires from the control panel to the pcb.
Could this be of any influence to the sound?

All the best.

Luax

It's influence will be seen quite clearly as a lack of oscillation at high gain settings, which is a good thing and why the mod was implemented. Your output on your bass should be pretty hot, even though it's passive. Is it doing this on both channels?
Title: Re: The official G9 help thread
Post by: Luax on October 02, 2011, 04:28:05 PM
Thanks for all the replies,
I was away for the weekend but i'll post my findings as soon i've checked everything.
Title: Re: The official G9 help thread
Post by: Dok on October 31, 2011, 11:24:38 AM
Hi. I'm very new to this forum and i want firstly thank you all. It's an incredible resource of amazing ideas. Thank you Gyraf for all these amazing gears and for the passion you share them with.  :)

Last year I successfully built a GSSL compressor. No issue, wonderful sound. I'm not new to DIY. Built and modded a lot of guitar stompboxes and various basic electronic stuffs. So i decided to go for a mic pre since i'm planning to record an album in my own home studio. So I built a G9. You can see some images here (my project site, in Italian sorry):
https://sites.google.com/site/dokdude/progetti/g9-2ch-tube-preamp (https://sites.google.com/site/dokdude/progetti/g9-2ch-tube-preamp)

Now I'm stuck with this unit that seems to suffer with serious problems: hum and hiss (loud). I first thought about the oscillation issue but it's  closer to a white noise. Very irregular.
Here is a noise sample recorded:
http://soundcloud.com/dokdude/2011-10-31-g9-hum-hiss (http://soundcloud.com/dokdude/2011-10-31-g9-hum-hiss)
In the sample, after increasing volume (@ Gain 5) when you clearly hear the 'pop' (0:15), i'm switching source from line to mic input, then to line again and decrease volume. No instrument nor mic plugged into the unit. In the past i got some similar problems with some stompboxes and i found it to be the pcb traces not really clear (some dust, hairs, soldering paste, and so on), so i've cleaned very accurately. And still the problem persist. Checked connections, external condensers voltage, and moved power trafo while listening. Nothing.

Have you got some suggestions before I begin to re-solder components again and again?

D.
Title: Re: The official G9 help thread
Post by: bpucekov on October 31, 2011, 11:37:54 AM
Did You make shielded wire mod

If you run into problems with oscillation on the highest gain settings, try running the connections to/from the front panel High-Z jack connector "directly" from the relevant points on the PCB - by cutting the PCB traces, and running a length of shielded cable directly to/from the jack.
Title: Re: The official G9 help thread
Post by: Dok on October 31, 2011, 11:45:40 AM
Not yet. And i will since i want to cancel the hum and the oscillation problem at high gain settings.
But now the biggest problem is the hiss. So loud. Do you think it's because of the shield? A white/brown irregular noise?
Maybe I'm wrong. Surely confused.

Thanx.

Title: Re: The official G9 help thread
Post by: bpucekov on October 31, 2011, 12:57:10 PM
First I will make shielded wire mod just to be sure, and of course  check all ground connections.
some pictures may help
Title: Re: The official G9 help thread
Post by: Dok on November 02, 2011, 06:18:40 AM
Well, i've cleaned main pcb with an iron tool point per point, trace per trace, and then with an iron brush all over the surface.
At fist attempt i got a HUGE noise. Waited a minute, moved something and tried again: only hum (oscillation problem).
Tried with mic and guitar: all Ok. Only oscillation hum.

So it's mainly a contacts problem.

I will clear panel PCBS, make the osc mod and then let's see.

Title: Re: The official G9 help thread
Post by: bernbrue on November 02, 2011, 10:43:44 AM
Check wiring from mainboard to switch boards.
regards
Bernd
Title: Re: The official G9 help thread
Post by: Phil on November 05, 2011, 11:40:25 AM
Hey guys,

I just got my G9 working .. but not all perfect yet ;-)
I have the oscillation problem on the instrument jack wich i will fix later.
Just tested the normal mic input with an sm57: works on both channels, just the right channel has some more noise etc - don't know if the oscillation mod can fix this too?

Also my bigger problem is, that i get only 5 volts when i turn on the phantom power.
I don't really know what to measure or test right now to find out where the solution for this problem could be ..

hope somebody can help here

thx again in advance!
Title: Re: The official G9 help thread
Post by: audiophreak on November 05, 2011, 01:34:19 PM

Also my bigger problem is, that i get only 5 volts when i turn on the phantom power.
I don't really know what to measure or test right now to find out where the solution for this problem could be ..

  I think you test between XLR input pins 1 and 3 , or 2 and 3  ,   and adjust the 10k trimmer ( PR1 ) till you get 48v
 .. hope this helps , good luck , I know you'll love this mic pre :)

EDIT :  reference the G9 PCB layout and schematic on the Gyraf web page
Title: Re: The official G9 help thread
Post by: Phil on November 06, 2011, 08:05:23 AM
I did that - the problem is, that the trimmer is turned all the way up and the max i get is 5 volts
Title: Re: The official G9 help thread
Post by: audiophreak on November 06, 2011, 08:43:04 AM
...  are you getting the 15vac on the power input for that section ?   check orientation of the trimmer ,  check value of the trimmer and other components in that section , check 10 pin header going to and from switch PCBs and also switch positions , (  the position setting washer if using the Lorlin type switches )
Title: Re: The official G9 help thread
Post by: Harpo on November 06, 2011, 09:36:27 AM
I did that - the problem is, that the trimmer is turned all the way up and the max i get is 5 volts
You double checked, the zener D6 is a 56V part (or a series string of lower value zeners that add up to about 56V), not a 5.6V part ?
What is your DC voltage reading between collector of TIP121 (center pin) and 0V ?
Title: Re: The official G9 help thread
Post by: Phil on November 11, 2011, 03:44:23 AM
I did that - the problem is, that the trimmer is turned all the way up and the max i get is 5 volts
You double checked, the zener D6 is a 56V part (or a series string of lower value zeners that add up to about 56V), not a 5.6V part ?
What is your DC voltage reading between collector of TIP121 (center pin) and 0V ?

aaaaahh - thx very much. The zeners were 5.6 & 3.6 .. ;-)
Now it works! yaaay :D

Both channels sound great & most important they sound the same ;-) I think i fell in love with the overall sound, sweeet!

I still have one problem left to solve though. It's very strange but i have a 100 hz hum once i plug in the output to my soundcard (no mic inserted).
There's no 50 hz hum tho, just 100 - shouldn't there be both?!
I'm thinking that i might have to try to plug it into some other plug than the one my PC is in - maybe that could help.. but actually ..  i don't think so ..

Title: Re: The official G9 help thread
Post by: pachi2007 on November 15, 2011, 08:37:11 AM
Hi there. I´ve just powered the G9 and everything seemed ok: 11.9V , 239V, +48V. The thing is it burned the 12V part of the tubes (239V ok and all tubes get hot, though both at channel2 run a bit hotter) . I didn´t notice they burned at first but I tried with another tube I had and I saw it light for a couple of sec. and then die fast.

I´ve used the spare power pcb and connected 239V DC at the main pcb (CAP2+,OV), the 12V at (F+,F- to light)

Any help? Does anybody has a NOS Telefunken to send me so I can try if it burns too?

Thx a lot guys
Title: Re: The official G9 help thread
Post by: pachi2007 on November 15, 2011, 08:38:39 AM
A picture of the power supply :-)
Title: Re: The official G9 help thread
Post by: gyraf on November 15, 2011, 10:35:56 AM
If you have 12V heater voltage, it can't damage the tube heaters. Make sure that you have the right voltages.

Maybe you have a short between heater pins, giving 12V across ½a heater?

What are the supercaps for in the psu image?

Jakob E.
Title: Re: The official G9 help thread
Post by: Phil on November 15, 2011, 10:58:17 AM
hmm .. i've tried disconnecting the ground as a test but no luck, i still have this 100hz hum on the output. it's not very loud but it's there and annoying .. any ideas?
Title: Re: The official G9 help thread
Post by: bernbrue on November 15, 2011, 12:18:59 PM
Hi,
most hum and noise issues in the G9 are caused by incorrect grounding. I learned it the hard way and struggled for about 2 month with my G9. I was almost ready to sell this ungrateful beast until I finally found out that the main board had no ground connection via the input molex connector. This connection is the only one that connects the main board to ground. Double check this. There are also ground bridges on the main board. Verify that you bridged these connections as well. See picture attached. I´m really glad that I finally fixed it and didn´t sell the G9.  We are best friends now. :)
regards
Bernd
Title: Re: The official G9 help thread
Post by: pachi2007 on November 15, 2011, 01:15:32 PM
Hi Jakob.

I checked again at the base of all the tube sockets (F,F+) and it reads 11.9V DC.  I´ll try to check better this weekend.
Why supercaps? I´m building the g9 with a friend and it was only a joke. A golden "uk made" instead of cheap asian unbranded I always buy. I bought a 5 lot for a fair price, didn´t know they were supers :-)

Thx a lot

Pachi
Title: Re: The official G9 help thread
Post by: Phil on November 15, 2011, 03:07:28 PM
Hi,
most hum and noise issues in the G9 are caused by incorrect grounding. I learned it the hard way and struggled for about 2 month with my G9. I was almost ready to sell this ungrateful beast until I finally found out that the main board had no ground connection via the input molex connector. This connection is the only one that connects the main board to ground. Double check this. There are also ground bridges on the main board. Verify that you bridged these connections as well. See picture attached. I´m really glad that I finally fixed it and didn´t sell the G9.  We are best friends now. :)
regards
Bernd

Hey Bernd,

thx for the answer - I double checked everything and it's grounded and bridged .. so this is not the problem.
I also noticed, that when speaking a "test 1, 2" that right after the transients of my words there is some sort of very short feedback exactly in that 100hz hum frequency as if it was amplified ..
Title: Re: The official G9 help thread
Post by: gyraf on November 16, 2011, 04:25:30 AM
Ah - I misread the picture - thanks for clearing that up.

But again, 11.9V can not damage a 12.6V tube, unless it's either set up for 6.3V or has one half-heater shorted (pin9 of the tube connected either to +12V or 0V/gnd - pin9 is NOT a shield like in ECC88).

I have never ever had one single tube dying on me like that.

Jakob E.

Hi Jakob.

I checked again at the base of all the tube sockets (F,F+) and it reads 11.9V DC.  I´ll try to check better this weekend.
Why supercaps? I´m building the g9 with a friend and it was only a joke. A golden "uk made" instead of cheap asian unbranded I always buy. I bought a 5 lot for a fair price, didn´t know they were supers :-)

Thx a lot

Pachi
Title: Re: The official G9 help thread
Post by: gemini86 on November 17, 2011, 01:38:47 AM
Are you sure your regulator isn;t just going into thermal shutdown after a few seconds? Then popping in a new tube gives it enough time to reset?

I've had that happen on a build before. Just one little clip on heatsink was all it needed (only powering one tube for a tube mic at 300mA, thought I could get away without a sink.)
Title: Re: The official G9 help thread
Post by: gyraf on November 17, 2011, 06:35:59 AM
Aah yes, thanks, that would be a classic scenario: I excluded this explanation because I'd expect it to be checked already (has been brought up several times in this thread already)..

Jakob E.
Title: Re: The official G9 help thread
Post by: qwerty8787 on November 24, 2011, 06:44:04 AM
Hi all!
I'm new here!

I recently finished building my G9. Sounds nice but has an annoing hum problem  :-\
When I have the gain and output knobs ALL way down, I get a good amount of noise. the fundamental might be 50 or 100hz, then I have all the harmonics (200, 300 and so on...).
I tried to make and unmake connection from pin 1 to chassis of one of the inputs: no results.
I tried to move around the trafos (2 toroidal ones): the hum only increases, when I get them very close to the pcb top. Also outside of the chassis there are no good results.
I tried to put one trafo upside down on the other one, no result.
I tried to unmake connection from earth IEC pin and chassis (ground lift): no results.

I checked out that the output pots chassis are electrically connected to ground by chassis
I checked out if the OEP shields are connected to ground, and only 3 are.
The tubes are JJ's, and i've mounted them on shielded sockets!!!  :o
I used shielded cables for I/O and also for the front jack, but I haven't tryed the DI mod (I think it's not fault to this because noise is gathering with outputs at 0!!)
Trafos are from RS:  1x220V 2x15V 50VA (code 671-8965) and 2x110V 2x12 50VA (code 671-9090)
The 78s12 has mica and heat sink is mounted directly on it, so is not touching chassis.


I'm getting very frustrated, I can't find the problem.....anyone has ideas?

Thank you in advance


Title: Re: The official G9 help thread
Post by: nashkato on November 24, 2011, 06:57:09 AM
Quote
  I didn´t notice they burned at first but I tried with another tube I had and I saw it light for a couple of sec. and then die fast.
maybe quite a stupid question , but are you sure the tubes are burned ?
older tubes sometimes do have the effect of lightning up a few seconds until the resistance of the heaters is stable.
quite usual and not really something to worry about. (at least to my experience , though it looks like this :
Quote
damn !!
after that the heaters aren´t necessarily visible on a quick look in a bright environment.

please measure the DC heater resistance of the "burned" tubes and compare them to the "still working" ones .
(tubes only of course , not plugged in obviously
Title: Re: The official G9 help thread
Post by: tmuikku on November 24, 2011, 08:01:56 AM
Hi all!
I'm new here!

I recently finished building my G9. Sounds nice but has an annoing hum problem  :-\
...
I'm getting very frustrated, I can't find the problem.....anyone has ideas?

Thank you in advance

Yello! Check with FFT software if the fundamental is 50Hz or what. 50Hz would be from mains xformer induced hum. From 100Hz up is propably coming from poor PCB layout, build the B+ powersupply on veroboard and see if the problem still exists. Here is a thread about it http://www.groupdiy.com/index.php?topic=32559.0 and some results also found from this thread. (Tip: click the Print -link so you can use your browser "Find" function to quickly scan the thread).

Be sure you've followed general guidelines of good grounding scheme. Some of it here http://www.groupdiy.com/index.php?topic=17980.msg527591#msg527591
Title: Re: The official G9 help thread
Post by: MeToo2 on November 24, 2011, 12:45:01 PM

I checked out if the OEP shields are connected to ground, and only 3 are.

I'm getting very frustrated, I can't find the problem.....anyone has ideas?

Thank you in advance

You need to make sure those screening cans are properly installed for a start.

I posted earlier in the thread about a bunch of things I did to reduce hum, including a picture of how to install the OEP cans properly.
In the end my G9s were whisper quiet, even at full gain and full output level, so the problem is build or layout, and not circuit design related.

see http://www.groupdiy.com/index.php?topic=17980.msg468609#msg468609

The tip on trying off-board HT supply worked for me too if you are using a PCB based build.

see http://www.groupdiy.com/index.php?topic=17980.msg497043#msg497043

You can get a good idea of the source by trying simple things.

Is the hum actually in your test set up, outside of your G9? [test with other sources, and a direct bypass of your source to test kit via another pre]
Is the hum equal on both channels? [if it is it points to a common cause like HT supply or heater supply]
Is the hum independent of gain? [if it is it points later in the circuit or output transformer]
Is the hum independent of source impedance? [check with a 200 ohm mic attached]
Is the hum channel related? [swap input and output conenctions and check if hum switches channel]
Is the hum louder on the channel closer to the power transformers [right worse than left => possibly points to HT noise leaking into 2nd stage]
Title: Re: The official G9 help thread
Post by: keninverse on November 27, 2011, 02:40:59 AM
Maybe I can gain some insight to my problem here.

I built up my G9 had some issues with no output on the last two gain settings so I did the gain fix mod. Took care of that.  I noticed some serious noise on the output and looking at the spectrum coming into logic shows a noticeable hump around 100-150hz.  After some reading I built the HT supply offboard using the external power supply but it seems I'm still having this issue.  I didn't build up the heater supply just the B+ and it's being injected to a wire jumper that's labeled HT on the PCB itself.  I'm at a loss here.  Should I build the B+ supply on vero? Is there some other issue I should be looking at after the rectifier.  By the way I'm using fairly large 330uF caps for the psu filter.  I haven't measured for ripple yet but can anyone please suggest something.

Please!!!!
Title: Re: The official G9 help thread
Post by: keninverse on November 27, 2011, 03:38:34 PM
[FIXED]

Intermittent connection on the front panel caused from cold solder joint.  No 100-150hz bump and this thing is extremely quiet.  I'd like to just point out that moving the B+ off the board using the extra psu supplied with my board worked very well to fix this issue.  I also ended up using 330uF caps for filtering. 

I'd like to also point out here for anyone else having this problem.  When I initially fired up this unit stock, I lost all gain in the last two clicks of the gain switch.  I didn't have any oscillation problems at all.  I followed the instruction for the instrument in trace cut and this solved the problem completely.

Quite impressed with this beast.  Extremely smooth on vocals and I'll give it a try on my jumbo guitar tonight.

One more thing....Thanks Jakob for putting these projects out there as well as helping countless others with projects that you aren't compensated for monetarily.  I think it's freaking awesome that you do this and shows you're a stand up dude.
Title: Re: The official G9 help thread
Post by: MeToo2 on November 27, 2011, 03:57:29 PM
When I initially fired up this unit stock, I lost all gain in the last two clicks of the gain switch.  I didn't have any oscillation problems at all.  I followed the instruction for the instrument in trace cut and this solved the problem completely.
Good to hear you've fixed your unit.

FYI The oscillation can be such high frequency that you can only see it using an oscilloscope (and not actually hear it at all) but it can still kill the AF signal gain on the highest gain switch settings. Anyway the fix is the same as you've done already: cut the PCB tracks and add shielding on the DI.
Title: Re: The official G9 help thread
Post by: keninverse on November 27, 2011, 05:39:31 PM
@MeToo2

Thanks! This is exactly what I figured. The oscillation was too high for non-dog ears.  And thanks for keeping up with this thread.  I've read many of your posts trying to make sense of this pre.  A lot of knowledge gained from reading your stuff.  I appreciate all the stuff you've written.
Title: Re: The official G9 help thread
Post by: Maynard on November 29, 2011, 04:16:35 AM
Hi All!

New in here and amazed after finding this cool group about the g9!

I just finished my G9 and so fa nothing exploted or burned down but I get such a small output :( So far I'm trying to check the unit using a XLR-jack cable. I know that passing from XLR to jack will reduce my signal amplitude but so much? I am pluggin the output to a guitar amp and I have to cranck up the volume in order to hear a little. I have to input a nice signal over 400mV to listen something. My gain is at max and also the output volume.
Tonight I wil try to trace signal with an oscilloscope and get a vocals amplifier with XLR hoping this improves.

Any hints? thak you for your help!
Title: Re: The official G9 help thread
Post by: bpucekov on November 29, 2011, 01:14:10 PM
check your wiring from main to control board
clean thoroughly the pcb remains of garbage after soldering can cause some sort of short
at least that was the case with my g9
Title: Re: The official G9 help thread
Post by: Maynard on November 30, 2011, 04:05:06 AM
Thanks bpucekov. Finally found out the problem tracing a tone, I got some mistake in the SRPP stage pcb already fixed. Now I'm working in the noise and hum. Got to clean the ckt since I put all together in a messy way and work in the start ground and a nice faraday case effect.
So far what I notice is that I get more sensitivity with the none phanton powered mic and less noise with the jack input  ::) gotta work that around. Big help with the noise in this post, I`ll keep reading.
Title: Re: The official G9 help thread
Post by: barthman.de on December 10, 2011, 01:13:16 PM
I have a question about the official PCB (look http://www.barthman.de/bilder/g9_pcb.pdf (http://www.barthman.de/bilder/g9_pcb.pdf)).

In contrast to the input tube  the +12V heater connection was mount on the output tube on another (f) pin.   
Is there a particular reason to change +12V and 0V between input and output tube pins? I ask that because I want to build my own PCB's and want to connect all tubes strictly parallel to +12V and 0V.

I even wonder that the "f" pins at one of the input tubes are labeled with + / - 

I think, because it is principle possible to push the heater on AC it should be able to change the connections. Isn't it? Maybe this was made simple because of space reasons?

Sebastian
Title: Re: The official G9 help thread
Post by: gemini86 on December 10, 2011, 09:42:39 PM
The filament is bi-directional, there is no + or - pin. It's simply a matter of PCB layout and where it's convenient to place power.
Title: Re: The official G9 help thread
Post by: telefunk on December 17, 2011, 01:33:55 PM
Hi there!

I'm building my second G9 and it's almost there BUT the Omron relays i had already bought got lost...

So, the only ones i seem to find from Paris right now are these:

http://shop.rabtron.co.za/catalog/relay-4052-12vdc-p-3379.html?osCsid=a71328ea0d3f18ee90b16d8779cbfffc

I dont know the "component scene" in Paris but place called "Cyclades Electronique" is just round the corner and they had those.

Are those as good as the Omrons for the job?

Thanks!

EDIT: I might add, that my first G9 had OEP in/out but this time i'm going for the Lundahl in and Edcor XSM2.4k/600 out. Anyway, i love G9. (Thanks, Jacob!)
Title: Re: The official G9 help thread
Post by: Edward on December 17, 2011, 05:09:43 PM
This maby is a dumb idea, but could G9 be built as a one channel unit leaving out the balanced inputs and phantom power option using the PCB made by Gustav? Interested in building a "deluxe" DI for live audio use for bass/ac guitar.

The G9 really seems perfect in all ways but the size would be a problem for me.

Just a thought.


/E.
Title: Re: The official G9 help thread
Post by: gyraf on December 18, 2011, 01:08:43 AM
Telefunk: no, that relay won't fit the pcb, I think

Edward: yes, you could, but you wouldn't save a whole lot of cost in doing so.

Jakob E.
Title: Re: The official G9 help thread
Post by: masoste on January 26, 2012, 01:29:39 AM
I hope I haven't missed something in the help thread. I have been going through the help thread here for a few days trying to answer my own question, but can't seem to figure it out.

So, ...

1.) Before I go and build an external PSU for my G9 is it possible that I'm getting 60hz him (and it's harmonics) because my C14 and C15 capacitors are undersized?

I'm using 100uf 350V Caps such as these:
http://no.mouser.com/ProductDetail/Nichicon/UPW2V101MRD/?qs=64l3LOSZbCrVK%252bv2Dm%2fH%2fA%3d%3d

1,a.) Should I go to something like these while I'm at it?
http://www.tubedepot.com/cp-jj-100x2-500v.html

2.) Is there some way to tell if I'm getting 60hum from induction, from the 12v PSU, or from the 245V PSU?

I've hot a fluke meter which is telling me that the HT output is 257VDC with about 6mVAC @60 HZ, the 12v output at the panel light is showing 11.89VDC and about 6mVAC. I'm not sure if this much fluctuation is what is causing this hum.

I've done the instrument input mod direct to the PCB with shielded cable and cut the traces, I've tried moving my toroids around in my case and I've shielded them and the power switch from the PCBs, I've grounded the input Pin#1's to the chassis at the same point as the mains ground, and used shilded cable to run from the PCB to the XLR jacks. I'm using the Lundahl transformers.

3.) Where can I find a good description of how to build and hook up the spare PSU board? The layout looks fairly strait forward, but I don't know how to connect the HT caps to it or where to connect the output to the main PCB.

Attached is a screenshot of a scope of the output with nothing connected to the input. When I hook up a mic I get a signal that is amplified and relatively clear except for the 60Hz and its harmonics are overlaid which make it pretty fuzzy. The 60Hz and it's harmonics are present no matter which gain position I use or any other setting and increase (or decrease) along with the output signal as settings are adjusted.

Any help would be greatly appreciated.
Title: Re: The official G9 help thread
Post by: masoste on January 26, 2012, 01:53:15 AM
I just realized that I'm using these 1000uF 25V Nichicon Caps for C16, C17, and C18:
http://ca.mouser.com/ProductDetail/Nichicon/UKZ1E102MHM/?qs=sGAEpiMZZMtZ1n0r9vR22e0BBN1kF1oiP9NzYB%252b2Kf8%3d
Rather than 35V capacitors. Could ripple from those capacitors be what I'm hearing/seeing?

thanks,
-Steve
Title: Re: The official G9 help thread
Post by: masoste on January 31, 2012, 01:42:53 AM
Sorry to have so many questions as a new poster. I keep reading through this thread, but haven't figured out my problem yet.

I had another look at this tonight and think that the problem might still be in the HT supply. I say still be in because the first time I fired it up I had the polarity on C14 and C15 reversed. R34 got really hot right away so I powered it down right away. I turned C14 and C15 around, and replaced IC1 (the TL783), R33, and zeners D3, D4, and D5. I thought that I had everything fixes because HT output is 257VDC but maybe the 6mVAC @60 HZ that I'm also measuring on that is my problem. What else is there that I could have damaged which I should replace?

I can only think that either that's the problem or I've got a grounding problem but I've star grounded input ground pins and the incoming mains ground to the chassis. Am i missing something else. I've read here suggestions of something that sounds like I should run a wire from the ground on the PCB to the chassis as well, but the grounds of the inputs are already connected to the PCB ground. Grounding pin 1 of the outputs with a jumper doesn't seem to make a difference. Am I missing something?

Thanks,
Steve

Title: Re: The official G9 help thread
Post by: gyraf on January 31, 2012, 03:15:54 AM
Quote
I turned C14 and C15 around

There is a VERY good chance that C14/15 were killed by the powering up with wrong polarity.

Jakob E.
Title: Re: The official G9 help thread
Post by: masoste on February 01, 2012, 02:14:14 AM
Thanks Jacob. I suppose that they could have been killed, but I've just changed them for a pair of 150uf 450V caps (some cheap but new caps that I had hanging around) and I'm still getting about the same hum. It seems to be at the same level no matter what gain or output settings I use though.

With the new caps it seems like I might be getting a bit more hiss at higher output settings, but otherwise about the same results. Here are two images of the output, the first at the lowest gain and output and the second at full gain and output.
Title: Re: The official G9 help thread
Post by: masoste on February 01, 2012, 02:16:34 AM
...and at maximum gain and output
Title: Re: The official G9 help thread
Post by: bernbrue on February 01, 2012, 02:27:52 AM
Sometimes a closeup picture of your build helps a lot. Did you double check connections beetwen mainboard and switch board? When you did the DI mod, verify that the switchboard is still connected to ground.
regards
Bernd
Title: Re: The official G9 help thread
Post by: masoste on February 12, 2012, 09:48:10 PM
Well I just put the whole project in a new enclosure because I had it in a re-used 3u box that was just too big. Unfortunately I've still got the hum, plus now I've got some new problems. I'm not sure if they are because of the fact that I may have shorted something on the rear of the front panel or if the problems existed before. Now I've got an intermittent 12vdc charge difference between the ground on the PCB and the chassis ground. I found this out when I turned it on and then plugged in the output connectors. When I did this the relays clicked and the pilot light went out.

Here are some close up photos.
(http://farm8.staticflickr.com/7037/6866766659_f81c58d954_z.jpg)
(http://farm8.staticflickr.com/7195/6866765147_b34386c248_z.jpg)
(http://farm8.staticflickr.com/7041/6866763457_807c45826f_z.jpg)
(http://farm8.staticflickr.com/7043/6866765915_d04a4571b5_z.jpg)

or http://flic.kr/s/aHsjyGALPV (http://flic.kr/s/aHsjyGALPV) (I'm still trying to figure out how to embed multiple images in a post)

I also tried disconnecting the power input transformers from the board one at a time and the 60hz hum would disappear when I pulled the high voltage supply.

As for the PCB ground having a charge I'm not sure if it's the front panel shorting out or something else. Any ideas?

Thanks for all the help.
-Steve
Title: Re: The official G9 help thread
Post by: gyraf on February 14, 2012, 01:09:58 AM
12V on out ground COULD be one of the 9-pin main-to-front connectors reversed.

Try lifting connectors one at a time until problem goes away, then investigate how 12v gets into that connector.

Jakob E.
Title: Re: The official G9 help thread
Post by: braeden on February 14, 2012, 10:51:30 PM
I'm trying to wire the following LED from the +/- 12v 50mA supply that typically would run to a jewel lamp.
http://au.element14.com/multicomp/mcl053ad/led-5mm-36-orange/dp/1581141?Ntt=1581141

I've tried a fairly large resistor (100k) or so in series with the LED but it just keeps blowing up.
I don't have that many LEDs left, can someone recommend a solution?

Thanks
Title: Re: The official G9 help thread
Post by: gemini86 on February 14, 2012, 11:38:26 PM
do they just blow up, or do they light up, then explode?

at 100k there should be barely any light.

Tell us exactly how it's hooked up, and where...
Title: Re: The official G9 help thread
Post by: braeden on February 15, 2012, 12:05:53 AM
do they just blow up, or do they light up, then explode?

at 100k there should be barely any light.

Tell us exactly how it's hooked up, and where...

Yeah that's exactly what I thought...
They light up and then explode (go up in smoke).

I've taken the +/- supply from the PCB to a breadboard into the +/- rails on that, and then plugged in a resistor in series with the LED. The LED is the correct polarity etc.

Also... is there any reason why I would be getting an extremely insignificant amount of gain from the instrument jack? I plugged in my bass to the D.I. and there is hardly any gain at the highest gain/full output setting.
I have cut the traces as per the example in Gyraf's G9 documentation, the microphone input works fine including the phantom voltages etc.

Edit: After recording some kick drum through an AKG D112 which usually has a fair bit of low-end to it with other pre-amps (API 312) it appears that the pre-amp is lacking a lot of low end, suggestions?

Thanks guys
Title: Re: The official G9 help thread
Post by: braeden on February 15, 2012, 05:39:28 AM
Here's a picture of the frequency response of the left & right channels.

http://i.imgur.com/k2mzS.jpg

This doesn't look right at all for a 1Hz-20kHz sweep :/
Title: Re: The official G9 help thread
Post by: gemini86 on February 15, 2012, 01:16:54 PM
In regards to the LED problem, what do you mean by + and - rails? you're just using the greater supply, right? 12v?
Title: Re: The official G9 help thread
Post by: G-Sun on February 15, 2012, 01:48:22 PM
PSU Question:
If I have 230V in my mains. Why should I use a torroid to get 15V AC and then another one to get back to 230V?
Why not take the 230V out of the mains and use one torroid to get the 15V?
Title: Re: The official G9 help thread
Post by: gemini86 on February 15, 2012, 10:59:37 PM
PSU Question:
If I have 230V in my mains. Why should I use a torroid to get 15V AC and then another one to get back to 230V?
Why not take the 230V out of the mains and use one torroid to get the 15V?

because the transformer is there for your safety...

If you accidentally electrocute yourself, (not as difficult as you may think) the transformer will limit current to a less 'instant death' level. If you went directly from the wall, a quick zap would dump whatever amperage the circuit will carry until the breaker or fusebox trips...

I said this before a few days ago, maybe it should be a sticky... NEVER take power directly from a wall outlet without isolation from a transformer. If you like, you could use a 1:1 isolation transformer. I haven't had much lick finding cheap ones here (may be a different story in 230v country) so step-down transformers or tube specific power transformers are the way to go.
Title: Re: The official G9 help thread
Post by: braeden on February 15, 2012, 11:46:54 PM
In regards to the LED problem, what do you mean by + and - rails? you're just using the greater supply, right? 12v?

The greater supply? I'm running two wires from the PCB where it specifies "TO LIGHT 12V/50mA +/-" straight to the LED. 50mA is obviously too much current, so shouldn't an appropriate value resistor lower the current so I can use it for an LED?

Here's a measurement I did today of the left channel, D.I. input.
(http://i.imgur.com/oRl5B.png)

And a sweep with the microphone XLR input
(http://i.imgur.com/tmmM4.png)

Is this typical of the G9 frequency response curve? It sounds pretty good to me, lacks a bit of low end though but it sounds nicer than the API 3124 in my opinion which is a little too full bodied.

And here's the API 3124+ freq. response for those that are interested...

(http://i.imgur.com/EmBun.png)

The G9 seems to have enough gain to blow me away but the API 3124 has an excessive amount of gain, to the point where it makes the G9 look weak... is this right or have I done something wrong?
Any comments are appreciated!

Thanks
Title: Re: The official G9 help thread
Post by: gemini86 on February 16, 2012, 01:30:25 AM
Sorry, my phone autocorrected me...

meant 'heater' supply... I have no clue why you would be popping LEDs on a 12v supply. Even running at 10mA which is about hald the typical max rating, you should only need 1k current limiting resistor. Are you sure you aren't using a 100ohm resistor instead of a 100k?

---

I do know that some feel the G9 is lacking in the low low end... but if it sounds good to you, why ruin it for yourself and run a frequency response sweep? ;)
Title: Re: The official G9 help thread
Post by: G-Sun on February 16, 2012, 03:49:54 AM
PSU Question:
If I have 230V in my mains. Why should I use a torroid to get 15V AC and then another one to get back to 230V?
Why not take the 230V out of the mains and use one torroid to get the 15V?

because the transformer is there for your safety...

If you accidentally electrocute yourself, (not as difficult as you may think) the transformer will limit current to a less 'instant death' level. If you went directly from the wall, a quick zap would dump whatever amperage the circuit will carry until the breaker or fusebox trips...

I said this before a few days ago, maybe it should be a sticky... NEVER take power directly from a wall outlet without isolation from a transformer. If you like, you could use a 1:1 isolation transformer. I haven't had much lick finding cheap ones here (may be a different story in 230v country) so step-down transformers or tube specific power transformers are the way to go.
Thank you!
I didn't plan to take the ac directly out of the wall, just curious :)
(Sorry for not seeing your previous answer)
Title: Re: The official G9 help thread
Post by: gyraf on February 16, 2012, 03:53:23 AM
G9 frequency response will depend on 1) transformers used for the build, 2) source impedance of whatever driving it's input transformer.

I've only measured Lundahl versions, which gives you something like 34Hz-30KHz @ -3dB, 200 Ohms source into mic in.

OEP transformers are different, less lows, but sonically attractive in another way.

Jakob E.
Title: Re: The official G9 help thread
Post by: braeden on February 16, 2012, 04:19:25 AM
Jakob, while you're here... when I was conducting the frequency sweep measurement, I noticed that when I do not have a 1/4" mono plug connected to the D.I. input and I record the sine sweep through the XLR input the response looks the following way (in blue) when it should look like the red. However, when I plug a cable into the front (even without any connection on the other end) it produces the expected frequency response.

(Gain is on the highest setting, no HPF, positive phase, all the way clockwise on the output pot and the input switched to mic)

(http://i.imgur.com/awnEd.png)

Why is this? could this be the result of a faulty relay? It happens on both channels so I doubt both relays would be faulty  :-\

It's annoying, I want to wrap this project up and get started on my 1176 :-X

Thanks Jakob
Title: Re: The official G9 help thread
Post by: gemini86 on February 16, 2012, 12:14:45 PM
PSU Question:
If I have 230V in my mains. Why should I use a torroid to get 15V AC and then another one to get back to 230V?
Why not take the 230V out of the mains and use one torroid to get the 15V?

because the transformer is there for your safety...

If you accidentally electrocute yourself, (not as difficult as you may think) the transformer will limit current to a less 'instant death' level. If you went directly from the wall, a quick zap would dump whatever amperage the circuit will carry until the breaker or fusebox trips...

I said this before a few days ago, maybe it should be a sticky... NEVER take power directly from a wall outlet without isolation from a transformer. If you like, you could use a 1:1 isolation transformer. I haven't had much lick finding cheap ones here (may be a different story in 230v country) so step-down transformers or tube specific power transformers are the way to go.
Thank you!
I didn't plan to take the ac directly out of the wall, just curious :)
(Sorry for not seeing your previous answer)

I don't even know if I had said it in this thread. So no worries. There are a few really old guitar amps that used the wall voltage directly, but I wouldn't plug a guitar into one without addingan isolation transformer first. They also typically didn't havea three prong chord either, so you run the risk of having your guitar  strings floating at hv if something goes wrong.
Title: Re: The official G9 help thread
Post by: Orphin on February 22, 2012, 10:45:48 AM
I have a question concerning the tele jack/line input. On the PCB there is from, to and ground. How do I wire this to the tele jack?
Title: Re: The official G9 help thread
Post by: gemini86 on February 22, 2012, 01:58:33 PM
You're going to want to look up the Di mod.
Title: Re: The official G9 help thread
Post by: Orphin on February 22, 2012, 04:07:59 PM
You're going to want to look up the Di mod.
Huh?
Title: Re: The official G9 help thread
Post by: gemini86 on February 22, 2012, 04:27:26 PM
Sorry, i'm on my phone right now so, I can't provide the courtesy of doing it for you, so you'll have to use the search function (or google for that matter) and look up the DI mod. It involves citing the traces on the pcb and wiring the jack directly to the board with shielded cable to correct some hum issues associated with that part of three circuit.
Title: Re: The official G9 help thread
Post by: audiophreak on February 22, 2012, 04:39:36 PM
Hi , Look  towards the bottom of page 34 of this thread , the graphic you're looking for is there. 

 
Title: Re: The official G9 help thread
Post by: gemini86 on February 22, 2012, 06:02:04 PM
Thanks audiofreak, mighty helpful of you!

 http://www.groupdiy.com/index.php?topic=17980.msg448605#msg448605 (http://www.groupdiy.com/index.php?topic=17980.msg448605#msg448605)
Title: Re: The official G9 help thread
Post by: audiophreak on February 23, 2012, 06:19:05 AM
Thanks audiofreak, mighty helpful of you!

 http://www.groupdiy.com/index.php?topic=17980.msg448605#msg448605 (http://www.groupdiy.com/index.php?topic=17980.msg448605#msg448605)

  You're  welcome  .....  its nice to get one right every now and then    ;D
Title: Re: The official G9 help thread
Post by: Orphin on February 23, 2012, 10:11:29 AM
Nevermind the mod. Right now I need to figure out what's wrong.
I've wired like this:

To --> tip of tele jack
From --> tip of tele jack that breaks when plug is inserted
Ground --> ground

I only get a faint sound from a guitar when I plug it in. It also seems as it doesn't matter if the routing switch is set to line or mic.
However, with a mic inserted to the XLR input the routing switch seems to work as it is supposed to.
Title: Re: The official G9 help thread
Post by: gemini86 on February 23, 2012, 01:36:49 PM
Swap to and from.
Title: Re: The official G9 help thread
Post by: Orphin on February 23, 2012, 05:59:01 PM
You sure?
It feels so illogical. I'm thinking that when the plug breaks the circuit, signal from a guitar/bass etc. wants to travel "to" the PCB??  :o
Title: Re: The official G9 help thread
Post by: gemini86 on February 23, 2012, 06:25:40 PM
The circuit works like this;

Signal comes out from the mic input transformer to the instrument jack. Then comes from the jack to the grid of v1. The signal is then broken by the plug being inserted into the jack.

Title: Re: The official G9 help thread
Post by: braeden on February 24, 2012, 03:47:34 AM
Nevermind the mod. Right now I need to figure out what's wrong.
I've wired like this:

To --> tip of tele jack
From --> tip of tele jack that breaks when plug is inserted
Ground --> ground

I only get a faint sound from a guitar when I plug it in. It also seems as it doesn't matter if the routing switch is set to line or mic.
However, with a mic inserted to the XLR input the routing switch seems to work as it is supposed to.

I have the same problem, I haven't been bothered to fix it yet, but you'll definitely have to switch to/from over...
Title: Re: The official G9 help thread
Post by: gyraf on February 24, 2012, 04:49:22 AM
..yes - "from" goes to the point that's connected to tip of inserted jack...

Jakob E.
Title: Re: The official G9 help thread
Post by: Orphin on February 24, 2012, 05:10:13 AM
The circuit works like this;

Signal comes out from the mic input transformer to the instrument jack. Then comes from the jack to the grid of v1. The signal is then broken by the plug being inserted into the jack.
That makes sense. Thanks.
Title: Re: The official G9 help thread
Post by: Orphin on February 24, 2012, 07:03:07 AM
OK, I've flipped the "to" and "from" and the line in works now, although the routing switch still doesn't make much sense.
With a microphone plugged in the XLR input, the switch cuts when switching to "Line" which seems normal, however with something plugged into "Line", the line in signal seems to be working even if the switch is set to XLR or Line. It also cuts the XLR signal if one is present (quite logically).

It seems like the routing switch is redundant!? (A phantom power ON switch would be enough)

My other preamps works like this and they don't have a switch for XLR-Line. Please explain why it's even there.

Edit:
When trying to figure out the schematic I can only see that the only thing the switch does (when switching to Line) is to change the input impedance for the XLR input.
Title: Re: The official G9 help thread
Post by: gyraf on February 24, 2012, 10:14:47 AM
No - you're confusing "line" with "instrument" inputs.

Line input - shares XLR with mic input - attenuates mic input some 30dB and raises input impedance to some 10K, still floating and transformer balanced. Meant to handle line-level balanced stuff.  Also allows for very-high output mics, like U47's in front of bass drums (been there, done that)

Instrument - jack inserted overrides line/mic setting. Unbalanced. Very high-Z (>3M).

Jakob E.
Title: Re: The official G9 help thread
Post by: Orphin on February 24, 2012, 04:51:02 PM
I see, thanks.
Title: Re: The official G9 help thread
Post by: masoste on February 26, 2012, 03:03:26 PM
Ok. So I've modified modified the enclosure so that the front panels are no-longer shorting out on the case. Which has fixed the problem that started up when I moved everything to a new enclosure. But the 60Hz hum (and it's harmonics) are still there.

I've checked the 12v and 240V supplies with a scope and they both appear to be pretty clean. (In fact the 240v supply seems a bit cleaner than the 12v supply.)

The volume of the hum seems to be the same independent of the gain or the output settings, but does disappear when I either disconnect the whole 9 pin connector to the front panel on each channel, or when I switch off the power. The hum is equally present in both channels, but when I disconnect the 9pin connector the hum disappears from that channel (along with the rest for the signal). I have tripple checked the pin configuration and have the 9 wires all going from the main PCB to the front PCB in the same order. I haven't tried disconnecting each wire of the 9 pin connectors one at a time, just because it means taking the connector apart. What other kind of things should I be looking for? Would it be possible that I'm shorting something like the ring on the front of the Lorin switches out on the front panel?

Thanks for the help.
-Steve

 (http://farm8.staticflickr.com/7038/6932307591_ac635963cc_z.jpg)

(more photos: http://www.flickr.com/photos/[email protected]/sets/72157629294926171/ )
Title: Re: The official G9 help thread
Post by: gemini86 on February 26, 2012, 09:08:24 PM
If the hum is independent of gain controls, try moving the power  transformers. Also, you'll want to use shielded wire on the instrument jack.
Title: Re: The official G9 help thread
Post by: masoste on February 28, 2012, 10:19:16 AM
Hmm,...
Moving the power transformers doesn't seem to change the hum that I'm getting. I also do have shielded cable on on the instrument jack cables (and the input and output cables). I've had to stop the shield about a half an inch before it is soldered to the jack and the PCB because the terminals are each a bit apart, but aside from that it's shielded.

With a scope it looks like there is no hum when the output connectors are not attached, but the hum appears when I plug the output connectors in to the main board. Does that make sense?

Thanks,
-Steve
Title: Re: The official G9 help thread
Post by: gemini86 on February 28, 2012, 12:36:33 PM
Sorry, mate. It looked like the wiring for your lamp was the jack wiring at first glance. You might try lighting the output xlr from ground at the connector end. You could be creating a ground loop.
Title: G9 HP filter cutoff frequencies
Post by: sircletus on March 01, 2012, 01:04:51 PM
Quick question:  what are the HP filter cutoff frequencies of the G9?  I'm guessing they're the same as those in Gyraf's commercial mic pre, ~80hz and 160Hz.  If this is the case, R for a passive first-order RC filter (using .01uF and .022 uF caps) works out to 100k.    How, exactly, is that 100k calculated from the resistors present in the schematic?  I feel like I must be missing something stupid here.
Title: Re: The official G9 help thread
Post by: telefunk on March 02, 2012, 02:13:32 PM
I built my second G9 with Edcor XSM2,4k/600 output transformers.

My question is: what transformer termination resistor should i use with them?

I know Lundahl suggest using 10k resistor with LL5402 but Edcor does not provide any such info...
Title: Re: The official G9 help thread
Post by: gyraf on March 03, 2012, 12:10:41 AM
Try 10K, probably fine - if that gets you trouble, change it...
Title: Re: G9 HP filter cutoff frequencies
Post by: gemini86 on March 03, 2012, 12:19:28 AM
Quick question:  what are the HP filter cutoff frequencies of the G9?  I'm guessing they're the same as those in Gyraf's commercial mic pre, ~80hz and 160Hz.  If this is the case, R for a passive first-order RC filter (using .01uF and .022 uF caps) works out to 100k.    How, exactly, is that 100k calculated from the resistors present in the schematic?  I feel like I must be missing something stupid here.

.01uF into 50K (output trim pot) gives 318Hz
.022 gives 144...

Could pretty much call it 150 and 300, tolerance in both the pot and Cs will push these around a bit...
Title: Re: The official G9 help thread
Post by: masoste on March 06, 2012, 01:33:12 AM
12V on out ground COULD be one of the 9-pin main-to-front connectors reversed.

Try lifting connectors one at a time until problem goes away, then investigate how 12v gets into that connector.

Jakob E.

Thanks for the advice. I just went through lifting each of the 9 connectors on each channel (the same happens on both channels) and this is the result that I got.

I recorded the audio output too just in case it might be helpful ( http://soundcloud.com/masoste/gyraf-g9-hum )

The recording starts with the unit turned off,
it is turned on and warms up,
the Gain control is increased from the lowest setting to the highest,
Output is cranked from lowest to highest,
Gain is turned back to the lowest setting,
Output is reduced to the lowest setting,
the input, phase and lowcut settings are changed.
Throughout this the hum doesn;t really change much other than the fact that it starts up when the unit is turned on.
Then the connections to the front panel are disconnected and re-connected one at a time in this order:
TO OUTAMP (at this time the hum increases and noise also increases)
TRANSFO- (at this time the hum almost disappears, signal also disappears)
TRANSFO+(at this time the hum almost disappears, signal also disappears)
OUT- (at this time the hum almost disappears, signal also disappears)
OUT+ (at this time the hum almost disappears, signal also disappears)
FROM 48V (no change)
FROM 12V (no change)
then the unit is turned off and cools down.

I also get no change when I remove the LINE or 48V connectors, but didn't bother recording this.

I also tried switching the Out+ and Out- pair with the TRANSFO+ and TRANSFO- pair, but I couldn't perceive a change. (The labeling is different on the main and front PCB, but I though that that was just a labeling error.)

So I'm not really sure what I should be looking for here given these results. Should I still be looking at tracing out the 12V to see if that's getting in to something else on the front panels? It seems like I'm on the right track, but don't know where to go from here.

-Steve
Title: Re: The official G9 help thread
Post by: bernbrue on March 06, 2012, 04:23:50 AM
Steve,
I suppose you did the Di mod. If so, verify that the switch board gets a proper connection to ground. I attached a picture where to check the connections. Good luck!
Title: Re: The official G9 help thread
Post by: masoste on March 12, 2012, 02:14:09 AM
Thanks for the advice. Yes I did do the DI mod. However, as far as I can tell, it looks like I've got a pretty good ground since my multi meter reads about 0.3Ω from the chassis ground to the jumper that you pointed out and to the ground terminal on the front panel.


The hum does go away immediately if I disconnect the output from the second (290VAC output) power transformer from going to the high voltage PSU. So, I'm still thinking that this has something to do with the high voltage supply.

I don't want to start looking in the wrong location if I'm getting close with to the problem by looking at the front panel and grounding. But, I'm now noticing a slight audible hum from one of my toroidal power transformers now. By this I mean that when I hold my ear down near the transformer I can hear a faint hum. (I'm not sure which one it is and it's pretty faint.) The hum is present weather or not there is any load on the second (290VAC output) power transformer. I'm inclined to try a different transformer here, but these things are kind of expensive. Is there any good ways to test these? Or does any audible hum mean that the transformer is shot?

I'm also looking at this thread and think that maybe I should just go ahead and make an external PSU in order to separate the high voltage PSU from the rest of the board.
( http://www.groupdiy.com/index.php?topic=32559.0 )

Any more suggestions? I appreciate all the help so far.

Thanks,
-Steve

Title: Re: The official G9 help thread
Post by: masoste on March 19, 2012, 12:40:18 AM
Aha! I had messed up wiring the outputs to the XLR jacks and switched the output ground and the output hot pins. Now that I've corrected that wiring mistake at the XLR connector what could I have damaged? Could I have damaged my output transformers or part of the phase reversal circuit?

btw. I tried replacing the power transformers one at a time with no change in the hum that I'm getting, so it looks like they were fine in the first place.
Title: Re: The official G9 help thread
Post by: gemini86 on March 19, 2012, 12:54:16 AM
If you just swapped ONE of the output leads with the ground lead, then you're going to be okay (just breath). That means you only wired the output single ended, unbalanced. So, is the hum gone, or not?
Title: Re: The official G9 help thread
Post by: masoste on March 19, 2012, 12:58:27 AM
I had swapped the wires that go to pin 1 and pin 2 on both of the outputs (at the XLR jacks). That would be the ground and the positive outputs being reversed and the positive was grounded out to the chassis for a while. I've swapped them back but the hum is still there.

I had only had a test lead with alligator clips running from the ground (pin1) of the XLR to the chassis because I had fired it up a few time to test testing it, found the hum, and had experimented with removing that line because I figured it was a ground loop. I guess it was a major ground problem! Taking the positive to the ground could not have been good.

Without the ground pin (pin 1) of the XLR connector also connected to the chassis ground I get a lot of hum, with the ground pin (pin 1) of the XLR connector also connected to the chassis ground I get an annoying amount of hum, about the same amount as when I was incorrectly running the positive outputs to the ground.
Title: Re: The official G9 help thread
Post by: synnys on March 24, 2012, 07:25:15 AM
I'm having some difficulties understanding which toroid transformers to get...

I have these two already:

http://www.musikding.de/product_info.php/info/p2883_Toroidal-transformer-230V----2x-15V-50W.html
http://www.musikding.de/product_info.php/info/p2885_Toroidal-transformer-230V----2x-12V-50W.html

What else do i need? And what about the 220v connection on the motherboard?
Also i see no 12v connection on the motherboard..
i'm a bit confused.

Someone care to share?
Title: Re: The official G9 help thread
Post by: braeden on March 25, 2012, 06:28:09 PM
Those transformers should be okay, here is a wiring diagram for this project posted by Skylar.

http://www.groupdiy.com/index.php?topic=16168.0

Obviously the colours are not the same for every transformer so you'll have to figure out which wires go where but this should be a pretty good guide.
Title: Re: The official G9 help thread
Post by: synnys on March 25, 2012, 06:54:18 PM
ok so i get the 2x 15v connections, but where does the 12v come in? and the 220v?

(thanks for the link btw)
Title: Re: The official G9 help thread
Post by: audiophreak on March 25, 2012, 07:07:21 PM
 ... look at page 26 of this thread  ;) 
Title: Re: The official G9 help thread
Post by: synnys on March 25, 2012, 07:38:01 PM
... look at page 26 of this thread  ;)

starting to make sense now... hopefully i'll understand it completely in the morning after some much deserved sleep :)
Title: Re: The official G9 help thread
Post by: synnys on March 26, 2012, 05:17:46 AM
I think i got it:

T1 primary goes to the power inlet, one T1 secondary (15v) goes to 15v @ 220v location, other T1 secondary (15v) goes to the right of the PCB.
T2 primary goes to the 220v at PCB, than i combine, or parallel the two (12v) secondaries of T2 and join them together with the secondary 15v from T1 at the right of the PCB?

Can some one confirm?
Title: Re: The official G9 help thread
Post by: synnys on March 26, 2012, 05:29:12 AM
Let me elaborate :D

This is how i understand it:

(http://img716.imageshack.us/img716/8916/img0828uy.jpg)

Correct?
Title: Re: The official G9 help thread
Post by: synnys on March 26, 2012, 05:40:06 AM
Btw:

Does it matter/make a diiference how i position the two toroids?
Which one of the following is preferred? And do i have to shield them somehow?
Can i wrap a stroke of aluminum foil around the toroids, does that help? Like in picture 3...

(http://img138.imageshack.us/img138/8870/img0829u.jpg)
(http://img100.imageshack.us/img100/1996/img0830av.jpg)
(http://img825.imageshack.us/img825/7032/img0831ix.jpg)
Title: Re: The official G9 help thread
Post by: haima on March 26, 2012, 09:29:43 AM
Hey masoste - Re: your hum problems, this is what fixed it for me:

Hey Chris - I believe you are describing is a textbook case of the same low level hum I and a few others have experienced with the G9... I fixed it by moving the HV power supply (rectifier, caps, regulator) off the main board - therefore feeding clean DC to the main board. If you read back over the last ten pages or so there should be a few references to this problem.

I think we need a FAQ....  ;D

I really suspect a LOT of G9 builds might have this hum problem - but it's low enough that it doesn't bother some people, or they just think it's what "tube diy" sounds like.... It doesn't have to be that way. I lived with the hum for 3 years (used it on a few released albums!) before i got a chance to try running the pres from an external power supply - now they are dead quiet.
Title: Re: The official G9 help thread
Post by: gyraf on March 26, 2012, 10:46:12 AM
Yes, residual hum levels seems to vary quite a lot in different G9-builds, probably depending on amount of hum stray field from the actual transformer type used.

That said, I've always been able to reduce hum to below general noise floor by grounding right and orienting transformers (turning them for minimum hum).

Make sure to mu-shield if OEP's are used - these are much more sensitive to stray fields than Lundahls.

Jakob E.
Title: Re: The official G9 help thread
Post by: synnys on March 26, 2012, 10:47:14 AM
any thoughts on my pictures above?
Title: Re: The official G9 help thread
Post by: gyraf on March 26, 2012, 10:49:43 AM
Pic two, stacked transformers mounted on bottom, is the most used way.

If you use screening, take care that the screening foil doesn't connect electrically to top and bottom holding hardware (would be one turn shorted on transformer)

Title: Re: The official G9 help thread
Post by: haima on March 26, 2012, 10:55:49 AM
Just to be clear - I had a low level hum in both my G9s. Re-orientating the transformers & different types of signal grounding, pin-1 use etc didn't fix my problem (Not to say it may not be a factor for others).

Moving the HV rectifier, caps and regulator off the main board and onto a small piece of veroboard/strip board fixed the problem 100%.

This was the same for both of my G9s.

Just putting it out there in case this helps anyone.... ;)
Title: Re: The official G9 help thread
Post by: synnys on March 26, 2012, 11:37:37 AM
Pic two, stacked transformers mounted on bottom, is the most used way.

If you use screening, take care that the screening foil doesn't connect electrically to top and bottom holding hardware (would be one turn shorted on transformer)

and is my drawing of the power connections correct?
Title: Re: The official G9 help thread
Post by: masoste on March 27, 2012, 10:13:27 PM
Hi haima,

Thanks so much for your suggestion. I'm going to move the HT supply to another board and see if that gets rid of the hum. I guess that I would be moving everything up to C15 off the board. I just noticed that I'm using a IN4007 in stead of an IN04004 for D2, although I doubt that that would make any difference as the IN4007 just has a higher voltage rating.


I suppose that it could be that I'm not grounding something properly. I've run ground lines back to the enclosure from each of the XLR jack ground (pin 1) terminals, and also have the mains ground run to the enclosure. But it seems like I've tried so many things that I don't know what else to try other than moving the HT supply and adding mu-shield to my power transformers.  I've tried moving my power transformers outside the enclosure with no change in this hum. I'm also using lundahl transformers. I'll let you know how moving the HT supply works out.

-Steve

Title: Re: The official G9 help thread
Post by: gyraf on March 28, 2012, 01:51:34 AM
Hum could also come from shorting the 78S12 heat sink tab to ground/chassis, making a ground loop. Make sure to use appropiate TO-220 isolation kit.

Jakob E.
Title: Re: The official G9 help thread
Post by: Spendor on April 01, 2012, 07:50:51 PM
Hi there - I have 2 x 240V - 12V toroids (95VA each). Apart from being overkill will they work OK for the G9?
Thanks!
Title: Re: The official G9 help thread
Post by: gemini86 on April 01, 2012, 08:26:09 PM
Normally I'd say you'll need a 15V transformer for the DC heaters to work, but since they're so big, you may see that they output closer to 15VAC which will work fine. I say, try it. If it doesn't work, get new ones!
Title: Re: The official G9 help thread
Post by: Fablab on April 02, 2012, 04:52:03 AM
Hello, I am realizing my G9 and I have a doubt around the power supply transformers.
Considering that the first one must be 220v:15+15v (30ma) I am not sure for the second one.
Is it better a 220v:12+12v or a 220v:15+15v?
I am sure that this is not a new question, but I have not found a reply (using the search function)
Title: Re: The official G9 help thread
Post by: Kingston on April 02, 2012, 06:02:38 AM
How about looking at the schematic.
Title: Re: The official G9 help thread
Post by: gemini86 on April 02, 2012, 03:35:10 PM
Hello, I am realizing my G9 and I have a doubt around the power supply transformers.
Considering that the first one must be 220v:15+15v (30ma) I am not sure for the second one.
Is it better a 220v:12+12v or a 220v:15+15v?
I am sure that this is not a new question, but I have not found a reply (using the search function)

220:12 is better for the second.
Title: Re: The official G9 help thread
Post by: Fablab on April 03, 2012, 12:37:16 AM
Thank you!
Title: Re: The official G9 help thread
Post by: Winetree on April 03, 2012, 03:11:18 AM
Building a G9 for first time. It's seems like it's highly suggested that the HT Supply
be moved off board to stop any hum. Could someone post pictures or drawings of this mod?
showing;
 The main board without the moved componets,
 The breadboard onboard wiring
 The wiring of the breadboard to main board.
Any help is appreciated.
Title: Re: The official G9 help thread
Post by: gyraf on April 04, 2012, 02:57:48 AM
Quote
It's seems like it's highly suggested that the HT Supply be moved off board to stop any hum.

Not really. Imo, it is a rare problem, just one that is often tried solved by asking in this thread.

I have built quite a few G9's in the diy version - and helped tune/setup many also, and have never yet had to move the psu off-board to get it quiet.

On the other hand, the circuit will be MUCH more forgiving about small circuit and wiring errors if the psu is somewhere else - so it's an easy solution if you have a persisting hum problem in your build.

Jakob E.
Title: Re: The official G9 help thread
Post by: synnys on April 04, 2012, 08:48:42 AM
So i just finished my unit, which looks gorgeous in my opinion.
Le moment supreme, powering it up didn't go so well...
I heard a sound which can probably be best described as rattling, coming from my psu.
Then i heard a tiny tiny explosion ;) coming from my 78s12. After some inspection it turned out be Diode D13 1N4007 as you can see in the picture.

Haven't replaced the diode just yet (i'm 100% sure it was positioned correctly!) Any thoughts? besides replacing the diode? I'm wondering what might have caused this...

Oh and is my heatsink for the 78s12 sufficient??

(http://img841.imageshack.us/img841/7864/d13zh.jpg)
(http://img600.imageshack.us/img600/1525/frontcod.jpg)
Title: Re: The official G9 help thread
Post by: synnys on April 04, 2012, 09:20:02 AM
same thing again, replaced d13, powered up, burned within seconds...
Title: Re: The official G9 help thread
Post by: synnys on April 04, 2012, 09:35:59 AM
so searching thru the forum i may have incorrectly connected my psu.

please bare with me:

T1 primary connected to the power inlet.
T1 secondaries (got two blue wires and two yellow wires, one yellow and one blue have a green sleeve)  i connected the blue/yellow with the sleeves to the 15v input at the 78s12 location. the yellow/blue without the green sleeve is connted to the 15v at the right side of the pcb.

T2 primary goes to the 220v input at 78s12
T2 secondaries (got two black wires and two green wires, one black and one green have a yellow sleeve)
i connected the two blacks (one with sleeve other without) together (with the yellow (without sleeve) from T1 sec) at the right pin of the 15v rightside of the pcb
i connected the two greens (one with sleeve other without) together (with the blue (without sleeve) from T1 sec) at the left pin of the 15v rightside of the pcb

Hope you still understand? ;)

Did i misunderstand the parallel part of the T2 secondaries?
Title: Re: The official G9 help thread
Post by: synnys on April 04, 2012, 06:10:52 PM
i connected the blue/yellow with the sleeves to the 15v input at the 78s12 location. the yellow/blue without the green sleeve is conneted to the 15v at the right side of the pcb.

Mistake 1

i connected the two blacks (one with sleeve other without) together (with the yellow (without sleeve) from T1 sec) at the right pin of the 15v rightside of the pcb
i connected the two greens (one with sleeve other without) together (with the blue (without sleeve) from T1 sec) at the left pin of the 15v rightside of the pcb

Mistake 2.

Unit working fine now after burning a load of D13's :D
Title: Re: The official G9 help thread
Post by: masoste on April 04, 2012, 11:59:01 PM
60Hz Hum Problem Solved!

Thanks (Especially to Haima) for the suggestions. I just moved the high voltage psu to off the main board. I actually used the little extra PSU board that came with the other boards. I wish that I could have figgured out what the problem was without requiring the additional board. But it was easy to move and the hum is 99.9% gone. And I can live with the last .1%.

Thanks again to Gyraf for the design.

Here is a (kind of fuzzy) photo:

(http://farm8.staticflickr.com/7205/6900767050_5feaeca506_z.jpg)
Title: Re: The official G9 help thread
Post by: synnys on April 07, 2012, 01:36:59 PM
well, the instrument inputs sound fine and are working topnotch. guitar sounds great thru it.

Mic input not so good, the last three steps of the gain switch cause an eerbleedingly loud high pitched sound (around 3kHz) each of these three steps has it's own characteristic distorted sound.. will try to sample it after the weekend. i used an 12 step endless rotary switch, like this: (advantage of being very rugged, disadvantage that you can't lock any position like the plastic lorlin type switches.

(http://img205.imageshack.us/img205/5909/screenshot20120407at734.png)

I do hear some sound coming from the mic input, although it is very soft and especially very thin and hollow...

About the 78S12, i checked the datasheet and it's operating temperature is between 0 and 150 degrees celsius. The heatsink is getting quite hot, I can't touch for longer than a couple of seconds without hurting myself. I had the unit on for a couple of hours this afternoon when recording some guitar riffs, but it seems it can manage the high temp. Will a bigger heatsink extend the life of the 78S12 perse, or is just  got a picture of the heatsink at the top of the page...

any suggestions?
Title: Re: The official G9 help thread
Post by: synnys on April 07, 2012, 01:38:08 PM
btw on which pins of the xlr plug can i measure how much volt the phantom power gives me?
Title: Re: The official G9 help thread
Post by: Sergio on April 07, 2012, 01:56:51 PM
Here is a pic of my G9 ;D
Title: Re: The official G9 help thread
Post by: Sergio on April 07, 2012, 02:21:54 PM
btw on which pins of the xlr plug can i measure how much volt the phantom power gives me?

i think phantom power stays on pin 2 and 3. Pin 1 is gnd.
Title: Re: The official G9 help thread
Post by: synnys on April 07, 2012, 02:55:02 PM
no matter in which direction i turn the little trimpot on the pcb, when i select 48v (and mic and hi-z too) on the frontpaneli measure absolute 0 volt on the XLR's...

how is this possible?

Title: Re: The official G9 help thread
Post by: Sergio on April 07, 2012, 03:02:30 PM
no matter in which direction i turn the little trimpot on the pcb, when i select 48v (and mic and hi-z too) on the frontpaneli measure absolute 0 volt on the XLR's...

how is this possible?

You have to set the Pot on the frontpanel to [48] and then turn the trimpot clockwise. The voltage should rise slowly.
Do you have the 15V from the Transformer?
Title: Re: The official G9 help thread
Post by: Sergio on April 07, 2012, 03:07:24 PM
Phantom Power should just run by setting the Forntpanel pot to 48.
The hi z jack intermids the singnalpath after the input transformers.
You could also measure the 48V voltage on the front panel connector look for P48 on the PCB before and after the switch.
So you can check out if the switch is working correct.
If there is no voltage you could follow the path with the circuit diagram to check for bad components.
Title: Re: The official G9 help thread
Post by: synnys on April 07, 2012, 05:50:20 PM
yeah but it doesn't ;) 0 volt
Title: Re: The official G9 help thread
Post by: Sergio on April 07, 2012, 05:59:49 PM
That's true :o
I can't help you without any useful answer  ;)
Title: Re: The official G9 help thread
Post by: synnys on April 07, 2012, 06:08:01 PM
I'll measure some more points tomorrow night... just gonna follow the trail...
Title: Re: The official G9 help thread
Post by: haima on April 07, 2012, 08:21:12 PM
Mic input not so good, the last three steps of the gain switch cause an eerbleedingly loud high pitched sound (around 3kHz) each of these three steps has it's own characteristic distorted sound..

This sounds like you need to do the the "DI mod" - involving cutting the PCB traces that run to the DI and wiring shielded cable in it's place. This is well documented earlier in the thread...
Title: Re: The official G9 help thread
Post by: Sergio on April 09, 2012, 04:21:12 AM
Here is a pic of my G9 ;D

Any idea??????
To locate the crackeling source?

Title: Re: The official G9 help thread
Post by: Majestic12 on April 09, 2012, 04:25:24 AM
Another question concerning the phantom power. I adjusted it to exactly 48V with no mic hooked up.

When connecting a condensor mic to the input, the voltage drops down to 33V.

Should I check the TIP121 or is this just normal behaviour ?

Title: Re: The official G9 help thread
Post by: synnys on April 09, 2012, 04:29:59 AM
Another question concerning the phantom power. I adjusted it to exactly 48V with no mic hooked up.

When connecting a condensor mic to the input, the voltage drops down to 33V.

Should I check the TIP121 or is this just normal behaviour ?

very normal behaviour
Title: Re: The official G9 help thread
Post by: Sergio on April 09, 2012, 04:41:01 AM
Another question concerning the phantom power. I adjusted it to exactly 48V with no mic hooked up.

When connecting a condensor mic to the input, the voltage drops down to 33V.

Should I check the TIP121 or is this just normal behaviour ?

For most condensor mic s this is no problem. I dont know if this is normal because i've never looked for it. Most not all condensor mics run between 9-52V
Title: Re: The official G9 help thread
Post by: synnys on April 09, 2012, 06:13:52 AM
Wow, DI Mod totally solved my problem! still no 48v at xlr though, gonna follow some trails next..

below is a picture of the output noise/hum with gain and output at absolute maximum. starts at -76dB not bad at all! (using OEP btw)

(http://img84.imageshack.us/img84/9705/capturekw.jpg)

Title: Re: The official G9 help thread
Post by: synnys on April 09, 2012, 07:46:31 AM
I measure 39,3 Volts of phantom power, but it's on "ground and +" or "ground and -" if i meausre between "- and +" there's nothing! Also i can't get higher than 39,3 volt,  i have the little trimpot completely turned to the left.. if i turn it to thr right the voltage drops.

how is that possible? I connected xlr correct by looking at the schematics, am i missing something?
Title: Re: The official G9 help thread
Post by: synnys on April 09, 2012, 09:00:13 AM
also i measure two different voltages on the two 100uf 350 caps.

one gives me 239 volt the other gives me 312 volt. 73 volt difference between the two... is that ok?
Title: Re: The official G9 help thread
Post by: masoste on April 09, 2012, 10:56:16 AM
Looks like I'm back to the work bench...One channel is super quiet and I don't know why.

Moving the high voltage power supply off the main board did get rid of the hum and now I've got a channel that is perfectly clear with great gain. But he other channel is now super quiet. Plus, when I flip the phase switch for that channel it gets even quieter. I've changes the tubes with no help. I'm just searching through here to see if anyone else has had a similar problem.  Does this sound familiar?

Thanks,
-Steve
Title: Re: The official G9 help thread
Post by: Majestic12 on April 09, 2012, 12:09:59 PM
I measure 39,3 Volts of phantom power, but it's on "ground and +" or "ground and -" if i meausre between "- and +" there's nothing!

It's supposed to be this way. Phantom power is fed to hot and cold. When you measure between + and -  you will always read 0V...
Title: Re: The official G9 help thread
Post by: synnys on April 09, 2012, 12:14:48 PM
I measure 39,3 Volts of phantom power, but it's on "ground and +" or "ground and -" if i meausre between "- and +" there's nothing!

It's supposed to be this way. Phantom power is fed to hot and cold. When you measure between + and -  you will always read 0V...

ok thanks for confirming! i now read exactly 48v so that's nice, gonna hook it up now and do some testing.
Title: Re: The official G9 help thread
Post by: synnys on April 09, 2012, 12:36:49 PM
ok so left channel is working fine now, mic incl. 48v also confirmed. Right channel is still a bit messy, got about 25dB more noise and hum!
pictures below we're taken with no mic or instr. attached with gain and output at maximum:

LEFT CHANNEL
(http://img3.imageshack.us/img3/4567/leftgc.jpg)
RIGHT CHANNEL
(http://img267.imageshack.us/img267/9292/rightuq.jpg)
Title: Re: The official G9 help thread
Post by: synnys on April 09, 2012, 02:44:19 PM
whenever i put a jack cable into ch.2 the hum and noise, immediately drops about 20/25dB.

any ideas why the second channel could be messed up?
Title: Re: The official G9 help thread
Post by: synnys on April 09, 2012, 03:10:47 PM

Is the hum actually in your test set up, outside of your G9? [test with other sources, and a direct bypass of your source to test kit via another pre]
Is the hum equal on both channels? [if it is it points to a common cause like HT supply or heater supply]
Is the hum independent of gain? [if it is it points later in the circuit or output transformer]
Is the hum independent of source impedance? [check with a 200 ohm mic attached]
Is the hum channel related? [swap input and output conenctions and check if hum switches channel]
Is the hum louder on the channel closer to the power transformers [right worse than left => possibly points to HT noise leaking into 2nd stage]

My hum is loudest on the rigth channel, closest to the PSU (almost 30dB louder!). I Swapped channels and that didn't help. It is most certainly NOT independant of gain. i got all audio connections shielded thoroughly. haven't tried moving to the HT board yet. will be my last resort...
Title: Re: The official G9 help thread
Post by: Sergio on April 09, 2012, 05:25:37 PM

Is the hum actually in your test set up, outside of your G9? [test with other sources, and a direct bypass of your source to test kit via another pre]
Is the hum equal on both channels? [if it is it points to a common cause like HT supply or heater supply]
Is the hum independent of gain? [if it is it points later in the circuit or output transformer]
Is the hum independent of source impedance? [check with a 200 ohm mic attached]
Is the hum channel related? [swap input and output conenctions and check if hum switches channel]
Is the hum louder on the channel closer to the power transformers [right worse than left => possibly points to HT noise leaking into 2nd stage]

My hum is loudest on the rigth channel, closest to the PSU (almost 30dB louder!). I Swapped channels and that didn't help. It is most certainly NOT independant of gain. i got all audio connections shielded thoroughly. haven't tried moving to the HT board yet. will be my last resort...

WOW -76db. I think thats great!
I had the same problem with the other channel and solved that with an external psu. Have used my old phonopre supply.

Title: Re: The official G9 help thread
Post by: synnys on April 09, 2012, 05:42:19 PM
you think it would change much if would mount the PSU's on the outside of the case? i currently have them on the inside (on the right) next to eachother..

i'll try tomorrow.
Title: Re: The official G9 help thread
Post by: Sergio on April 10, 2012, 01:04:16 PM
Hi sunny,

NO... NOT OUTSIDE   > JUST AWAY FROM THE MAINBOARD <
I think there are many individual problems with the G9. You can hopefully clarify your problem by moving your PSU away from the preamp.
But i wonder that there are people who build this "diva" together without any problem. I dont know if there are some really "no compromise" units out there....Don't misunderstand my statement....I love that unit :)

Let's be grateful for Jakobs work.

Cheers!

Sergio 
Title: Re: The official G9 help thread
Post by: masoste on April 16, 2012, 11:56:28 AM
Any suggestions on why I've got one channel on my G9 that isn't working?

Here are the symptoms:

-Output from the first channel does not have any gain.
      -With the Gain and Output settings at maximum I get about unity gain output. In other words I get an output that is the same level as the output from a mic that I feed in to it.
      -When I flip the phase (polarity) switch for the first channel I get no output. Nothing at all.

-The second channel is great. I guess that this isn't really a symptom, but I have no problems with the second channel which is producing nice clean signal with lots of gain, no hum, and very little noise.

Here are things I've tested or tried:

-I tried plugging the front panel controls from the second (good) channel in to the first (bad) channel. But I got the same results. So I guess that rules out a problem with the front panel.

-I've tried swapping the output transformers, but didn't get any change. (There was a post by someone with a similar problem a while back and it had turned out to be a bad output transformer for them.) Looks like both my output transformers are fine though.

-I appear to be getting the same voltage in the V1 tube sockets for both channels. I'm not really sure what I'm looking for here though.

Thanks again for any help offered here. I'd be lost without this help thread.

Title: Re: The official G9 help thread
Post by: Sergio on April 16, 2012, 12:37:16 PM
Any suggestions on why I've got one channel on my G9 that isn't working?

Here are the symptoms:

-Output from the first channel does not have any gain.
      -With the Gain and Output settings at maximum I get about unity gain output. In other words I get an output that is the same level as the output from a mic that I feed in to it.
      -When I flip the phase (polarity) switch for the first channel I get no output. Nothing at all.

-The second channel is great. I guess that this isn't really a symptom, but I have no problems with the second channel which is producing nice clean signal with lots of gain, no hum, and very little noise.

Here are things I've tested or tried:

-I tried plugging the front panel controls from the second (good) channel in to the first (bad) channel. But I got the same results. So I guess that rules out a problem with the front panel.

-I've tried swapping the output transformers, but didn't get any change. (There was a post by someone with a similar problem a while back and it had turned out to be a bad output transformer for them.) Looks like both my output transformers are fine though.

-I appear to be getting the same voltage in the V1 tube sockets for both channels. I'm not really sure what I'm looking for here though.

Thanks again for any help offered here. I'd be lost without this help thread.

Ok.

You can change the tubes maybe one is broken.
After you have found out that the tubes are all right you should follow the signal path with a multimeter from one to the next component. Maybe you have a cold solder joint.....Check the frontpanel connection from the Point [ J1 ].
If there is nothing wrong you should check the resistors functionality and values....

Have fun and take care!




 
Title: Re: The official G9 help thread
Post by: sirblue52 on April 19, 2012, 01:49:38 AM
grounding problem?

New to this forum, lurking for a few months, but finally decided to post a question.  Really love this project.

So in my original build I failed to isolate the 78S12 from ground.  On power on I could hear the tiniest bit of hum coming through with gain 5 and output 6.  When I say tiniest bit, I could probably be convinced it was not there when mixed to a track.  The noise is louder when either gain or output level is raised higher towards 11 though.

Searching this forum on how to squash that tiny hum, I found that I was supposed to isolate the 78S12.  As it turns out, isolating it caused even more noise, in addition caused erratic behavior of the output dial - noisy and quiet spot.  Grounding 78S12 again turned it back.

I double checked that the XLR input was correctly grounded - yes.
I checked other 0V points on the board were leading XLR input ground - yes

I must be doing something wrong if I am not supposed to ground the 78S12....
Title: Re: The official G9 help thread
Post by: Sergio on April 19, 2012, 07:27:17 AM
Hi Sirblue52!

I think the hum is normal because the power supply is not a high end design.
How loud is the hum? Can you quantify the hum in db on highest gain settings?
Title: Re: The official G9 help thread
Post by: gyraf on April 19, 2012, 08:28:06 AM
Actually, the G9 powersupply is not bad at all, if made right.

I usually get diy-G9's to an equivalent noise distance of some 120dB, i.e. some 65dB s/n @ 55dB gain, unweighted..

But you need to take care of grounding (and make sure the whole chassis is grounded) - and be aware that some types of power transformers are quite noisy.

Jakob E.
Title: Re: The official G9 help thread
Post by: sirblue52 on April 20, 2012, 08:36:37 PM
I'll check on how to properly quantify the hum.  If anyone knows a quick and easy way, please let me know. 
I'll also double check that the whole chassis leads to ground.
Hopefully its that simple.  Thanks!
Title: Re: The official G9 help thread
Post by: Sergio on April 21, 2012, 06:39:40 AM
Hi Sirblue / Aarhus!

I know that there are some G9 out there without any problem with hum and noise.
I had a lot of problems with my preamp. Maybe because i am not a specialist....
Now after two years of construction (not all the time) all my problems with the G9 are gone.

I have used two very cheap power transformers (4€ each) and they are not really quiet. So i decided to put them out of the chassis. After this experiment the hum was not gone but quieter and i have used the G9 on some records....After a while i decided to change the psu design by using my old phono pre power supply. I figred out that 12.6V for heating my tubes is better than 12.0V and the high voltage part should be exactly 250V and not 238V or similar.
After my mod i had a little problem with some noisy resistors but by now i have a unit with more gain and less hum (just a little at the highest gain settings).
This are just my experiences with the G9 and i think with some experiments you should get what you want.
 



Question to Aarhus:
How much gain delivers the G9 by maximum settings? On which position will this preamp deliver 55db gain?
How is it possible to check the linearity of the unit?


regards!
Title: Re: The official G9 help thread
Post by: gemini86 on April 21, 2012, 04:19:15 PM
Just a note, some tubes can be sensitive to heater voltage, but most tubes are NOT that sensitive to B+... the difference between 250 and 238 is negligible, in my experience. 
Title: Re: The official G9 help thread
Post by: Maynard on May 16, 2012, 08:22:08 PM
Hi again!

Well, the preamp is working pretty nice so far but I am having some anoying problems with the voltage regulator TL783. A few days ago when no signal input start to hear like a far away low hit so I check the high voltage to the plates with an oscilloscope and saw how the voltage was not steady. It was fluctuating randomly a few volts up and down with an average of around 190Vdc.

Checking the TL783 data sheet decide to include a cap in order to avoid fluctuations due to the distance of C15, no result. Finally change the TL783, the voltage was steady at 220Vdc and no more anoying noises. But, after a few days the problem appear again. The fluctuations now seem less frequent but I feared it get worst since the TL783 might be degrading again.

Anybody experienced something like this? So far I have rechecked the PWS and everything seems right. Any suggestion is really appreciated.
Title: Re: The official G9 help thread
Post by: braeden on May 16, 2012, 09:03:17 PM
Hi guys, I'm having a bit of trouble.

I've moved the power supply off the main board onto the separate B+ PSU provided. I believe everything is connected properly.

The first transformer supplying the mains voltage and it's first secondary winding (15Vac/0V) is connected to the 15VAC/1A connection on the B+ board.
That second secondary winding on that same transformer is then connected to the main board's second 15VAC input (for the +48V phantom power) which also has the second transformer's secondary windings also attached to it.

The CAP1 +/- section is connected to C14 and the CAP2/245V out is connected to C15 capacitor and the C15 CAP2+ input on the main board. The 0V from the PSU in the same section is connected to the 0/- part of the main board as well. I am getting a sufficient voltage at the HT link on the main board but I don't believe the +12V heater supply is working and the tubes aren't glowing. Have I connected the +12V out from the B+ PSU in the right spot?

I'm not sure what the problem is, I'm hoping this is easy enough to understand.

Thanks,
Braeden

If someone else has used the B+ supply could you provide photos of your G9 and how you wired it? Also, is it possible that the bridge rectifiers that I have used are of the wrong values and this could be preventing the heater supply from working?
Title: Re: The official G9 help thread
Post by: braeden on May 16, 2012, 10:11:35 PM
Nevermind, problem solved... all hum issues gone as far as I know!
Title: Re: The official G9 help thread
Post by: gyraf on May 17, 2012, 04:00:32 AM
the voltage was not steady. It was fluctuating randomly a few volts up and down with an average of around 190Vdc

Try changing the protection diodes around the 783?
Make sure that the second high-voltage reservoir electrolytic (the one after the 783) is in good working order.
Check input voltage to 783 while failing - should be at least 275V DC.
Measure HT current draw (dc voltage drop across the 470R resistors in series with HT)?

Jakob E.
Title: Re: The official G9 help thread
Post by: Maynard on May 17, 2012, 05:37:27 AM
Thanks Jakob for those hints.

Actually I just built one channel and my power transformers are two toroidal 15VA (220 - 2x15) and may be I am a little short in that  :-\
I was checking voltage and currents like you suggested and you are right, I am getting around 240Vdc in the TL783 input, actually the transformer is giving around 200Vac......so, I guess it can not keep up with the juice requirements. Could that be the problem?
If I tested the power supply with no load the transformer output is 230Vac wich rectified gives me around 285Vdc. Also find out that at turning on the preamp the high voltage is around 245Vdc until  the tubes start to conduct and it falls to 220Vdc.

I though 15VA would be enough since two channels are working with 30VA transformers. May be I should go to 20VA. Thanks in advanced.

Got a second though since right now buying new transformers is over my budget. I was thinking about reducing plate voltage (wich already is....) to around 224Vdc replacing R35 and R36 for a single resistor of 560 Ohms. I hope that will make it easier on the transformers, not sure yet.
I know the load lines will change but I guess the bias point will be cooler and as far as I do not get too much distortion for cuttoff in early gain positions is OK with me. Could this high output voltage adjustment be viable? Thank you!
Title: Re: The official G9 help thread
Post by: gyraf on May 17, 2012, 09:08:39 AM
Could this high output voltage adjustment be viable? Thank you!

It seems simple enough - try it and see (hear) what happens?

Jakob E.
Title: Re: The official G9 help thread
Post by: braeden on May 18, 2012, 07:05:52 AM
It's finished! Thanks Jakob for wasting a year of my life! ... just kidding ;-)

(http://i.imgur.com/IyQKW.jpg)

... but seriously.
Title: Re: The official G9 help thread
Post by: Maynard on May 30, 2012, 05:29:31 AM
Sorry late reply, didn't got too much time to deal with the problem  >:( but it is resolved.
I adjust plate supply and the feeding improved in exchange for headroom. I recal power requirements since I did some mods to the original design and no way it needed more than 15VA....so as Jakob said I checked the zeners and susrprise one of those guys was open, no wonder why the TL was having trouble keeping up. Everything is smooth and quiet now! Thanks Jakob!
Title: Re: The official G9 help thread
Post by: redmojosteve on June 03, 2012, 10:04:09 AM
Just got my G9 up and running. Both channels seem fairly similar in performance. One of my transformers (15V T2) seems to be getting very hot and I was wondering if this was normal. I haven't had this with other power transformers on other projects so far, apart from when I incorrectly connected my first GSSL! Both the transformers are 50VA. I am only getting 235Vdc rather than 245Vdc on the board. However T1 (12V) is pushing out around 280AC, which seems like it ought to be enough after rectifying for the regulator to work on.
My front panel instrument inputs need some working on so I might go for the direct to PCB mod before going any further.
Title: Re: The official G9 help thread
Post by: MeToo2 on June 09, 2012, 05:11:14 AM
Just got my G9 up and running. Both channels seem fairly similar in performance. One of my transformers (15V T2) seems to be getting very hot and I was wondering if this was normal.
HT voltage looks normal (280V). 235V sounds low. But voltage drop doesn't say much due to the regulator.

I would say that was definitely not normal for a 50VA transformer to get hot in a G9.

Check the current draw on each of the different portions of the PSU and then we can compare values.

You can check the current draw:
on the HT indirectly by measuring the voltage drop across the 470R R33 using a multimeter in voltage mode.

on the 12V heater directly at the PCB connector with a multimeter in AC current mode (be careful! and only connect and disconnect with power off and reservoir caps C14 C15 discharged) Check the heater voltage is 12V.

on the 48V directly at the PCB connector with a multimeter in AC current mode (be careful! and only connect and disconnect with power off and reservoir caps C14 C15 discharged) Check your 48V phantom is 48V.

Check that the mounting bolt of the transformer is only touching the chassis at one end. Check you've got your rectifier diodes correctly oriented. Also the caps on the voltage tripler can be confusing with their orientation.

You may some oscillation at high gain settings if you haven't done the PC board mod. Does the transformer still get warm at lower gain settings? But I'd get the thing stable at low gain settings first before doing any mods.
Title: Re: The official G9 help thread
Post by: redmojosteve on June 09, 2012, 08:13:48 AM
Thanks for the helpful response. I haven't got the time to do the checks right at the moment but I will do as soon as possible. As a quick reply, I can confirm I am getting 48V and I have checked the caps and diodes and they are in the correct orientation. I didn't really get much time at high gain settings as I was concerned that the transformer was a bit hot even at low gain settings. There was some oscillation at high gain. I haven't bolted the transformers in place yet as I was going to complete that task when I was sure they were in the best location to keep hum pickup to a minimum.
For information the unit did pass audio signals both from the line/mic input (from a sig gen) and also the inst input (a Gibson Les Paul with P90 single coil pickups). Both gain and noise seemed reasonably satisfactory for a first trial  but I am sure it isn't right!
Thanks for your help
Steve
Title: Re: The official G9 help thread
Post by: MeToo2 on June 09, 2012, 09:13:44 AM
Thanks for the helpful response. I haven't got the time to do the checks right at the moment but I will do as soon as possible. As a quick reply, I can confirm I am getting 48V and I have checked the caps and diodes and they are in the correct orientation. I didn't really get much time at high gain settings as I was concerned that the transformer was a bit hot even at low gain settings. There was some oscillation at high gain. I haven't bolted the transformers in place yet as I was going to complete that task when I was sure they were in the best location to keep hum pickup to a minimum.
For information the unit did pass audio signals both from the line/mic input (from a sig gen) and also the inst input (a Gibson Les Paul with P90 single coil pickups). Both gain and noise seemed reasonably satisfactory for a first trial  but I am sure it isn't right!
Thanks for your help
Steve
OK if it's that bad a simpler test is just to disconnect all 3 power supply connectors to the PCB (assuming you're using the Gustav's PCB) and see if the problem clears for the transformer getting warm when powered up with no load. And then connect the connectors for the supplies one at a time. 1st the 48V on its own (2 pin connector on side of the board). Then the heater on its own (2 pin connector on the back of the board). Finally the HT (3 pin connector on the back of the board) + heater. Then check for excessive warming each time. Shouldn't cause any problems to run them one at a time and check like this, but be sure the HT caps C14 C15 are discharged before connecting/ disconnecting. Also if the heater current isn't flowing properly the HT supply voltage might measure high (as there'll be little load on the HT regulator which needs ±15mA before it starts regulating)
Title: Re: The official G9 help thread
Post by: redmojosteve on June 16, 2012, 07:32:09 AM
At last I have been able to get back to the G9. I am using Gustav's board incidentally. I rechecked my transformer connections, swapped a couple over and I can confirm the voltages on the PCB seem OK, that is, 12V, 48V and 265V on the HT. Following discharge of C14, C15 I have disconnected the various connectors and with no load the 15V toroid is still getting warm. I then disconnected the other 15V secondary (which feeds the 12V secondary on the other transformer and provides 15V to the side connector on the board, thus providing no load at all to the transformer) and it runs cooler.  It doesn't produce any mechanical hum either. On this basis it would seem that I have either got something connected wrong between the two transformers or the transformer just gets rather warm.   Thanks for the wisdom and support
Steve
Title: Re: The official G9 help thread
Post by: MeToo2 on June 16, 2012, 08:40:52 AM
At last I have been able to get back to the G9. I am using Gustav's board incidentally. I rechecked my transformer connections, swapped a couple over and I can confirm the voltages on the PCB seem OK, that is, 12V, 48V and 265V on the HT. Following discharge of C14, C15 I have disconnected the various connectors and with no load the 15V toroid is still getting warm. I then disconnected the other 15V secondary (which feeds the 12V secondary on the other transformer and provides 15V to the side connector on the board, thus providing no load at all to the transformer) and it runs cooler.  It doesn't produce any mechanical hum either. On this basis it would seem that I have either got something connected wrong between the two transformers or the transformer just gets rather warm.   Thanks for the wisdom and support
Steve
Can you draw diagram of how you wired the transformers?
Do they have split/dual secondaries?
And if so, did you make sure the phasing was correct?
Title: Re: The official G9 help thread
Post by: culteousness1 on June 16, 2012, 09:34:54 AM
Short question on C23:

I could only source a 22uF instead of a 10uF cap at Reichelt.

Will this be a problem?

Best,
Carsten
Title: Re: The official G9 help thread
Post by: redmojosteve on June 16, 2012, 12:59:34 PM
It's taken me a bit longer than I expected to draw the transformer connections but here they are.
Sorry but the yellow isn't too prominent against the other colours
Thanks
Steve
Title: Re: The official G9 help thread
Post by: bernbrue on June 16, 2012, 01:14:44 PM
 :)
Title: Re: The official G9 help thread
Post by: MeToo2 on June 16, 2012, 01:41:35 PM
It's taken me a bit longer than I expected to draw the transformer connections but here they are.
Sorry but the yellow isn't too prominent against the other colours
Thanks
Steve
Sorry. Can't read the doc. Can you attach as gif, jpeg or png?

Presume you are located in the UK (Warrington) with 240V 50Hz mains.

If so, I suggest you do NOT follow the example posted above by bernbrue.
That is for a 115V supply as far as I can see (primaries of first transformer in parallel)
Title: Re: The official G9 help thread
Post by: bernbrue on June 16, 2012, 02:51:39 PM
Yes, your are absolutely right as far as the primary is concerned. So, Steve, connect the first transformer as you did in your drawing and do the rest according to my picture and you should be allright.
regards
Bernd
Title: Re: The official G9 help thread
Post by: MeToo2 on June 16, 2012, 04:01:56 PM
Yes, your are absolutely right as far as the primary is concerned. So, Steve, connect the first transformer as you did in your drawing and do the rest according to my picture and you should be allright.
regards
Bernd
Exactly.

Managed to read the doc now (browser issue at my end)

Steve, I don't know why you've marked many transformer terminals "0V" on your diagram. They are NOT 0V, and must NOT be connected to ground, or to each other in your wiring outside of the PCB. The mains neutral is normally grounded at your electricity meter in most old style UK installations, but may not be the same 0V as your Earth pin. This could be very dangerous if you've connected mains neutral to the chassis. Some mains sockets may be wired incorrectly in your house, which would then connect live to the chassis. If you're still in doubt, please post detailed photos and transformer model numbers.
Title: Re: The official G9 help thread
Post by: redmojosteve on June 16, 2012, 04:34:05 PM
Thank you MeToo2 and Bernd for the quick response. You are correct and I have 240V 50Hz mains. Believe it or not, the diagrams I used for the transformers were cut and pasted from the Nuvotem/Talema transformer datasheet (the transformers I am using). I couldn't find a nice schematic for a transformer quickly enough to get the sketch on the forum so I used the diagram on the datasheet, which could be misleading. Nonetheless, thank you for your very important message regarding safety, and to put everyone's mind at rest, including mine, I have not grounded the terminal marked "0V"!
I'll connect up as per Bernd's diagram and let you know how I get on.
Cheers
Steve
Title: Re: The official G9 help thread
Post by: MeToo2 on June 16, 2012, 05:58:42 PM
Thank you MeToo2 and Bernd for the quick response. You are correct and I have 240V 50Hz mains. Believe it or not, the diagrams I used for the transformers were cut and pasted from the Nuvotem/Talema transformer datasheet (the transformers I am using). I couldn't find a nice schematic for a transformer quickly enough to get the sketch on the forum so I used the diagram on the datasheet, which could be misleading. Nonetheless, thank you for your very important message regarding safety, and to put everyone's mind at rest, including mine, I have not grounded the terminal marked "0V"!
I'll connect up as per Bernd's diagram and let you know how I get on.
Cheers
Steve
Cool.  8) I'm surprised at that data sheet. Normally they mark the transformer connections as normal and inverted phase with a dot. But those points sure ain't 0V DC relative to ground, and they way they were wired would explain the heating and vibration. Don't hesitate to ask questions if you're not 100% sure.
Title: Re: The official G9 help thread
Post by: redmojosteve on June 17, 2012, 11:41:55 AM
Again, thanks for your greatly appreciated assistance. I have reconnected the transformers, but I am still getting a warm 15V one. It all works and passes audio nice and quietly. As before, the 12V, 48V are OK but I am getting just 235V on the HT. I checked the voltage across R33 which was 9.15V which suggests a current of around 19.5mA. The comment on grounding got me curious. I have only grounded the build at the No 1 channel input XLR ground, and the incoming IEC earth connection to the case of course. I'll come back to it in a couple of days and check it over again as I am sure I must have missed something.
Cheers
Steve
Title: Re: The official G9 help thread
Post by: bernbrue on June 17, 2012, 12:05:48 PM
Hi Steve,
you can try using only one secondary winding of the transformer that transforms 15V to 236V. I did this in my build and transformer noise/heat went away. Proper grounding is essential for correct voltages. There are a few ground bridges on the main board as well. Verify that you soldered them in.
regards
Bernd
Title: Re: The official G9 help thread
Post by: MeToo2 on June 18, 2012, 02:57:59 PM
Hi Steve,
you can try using only one secondary winding of the transformer that transforms 15V to 236V. I did this in my build and transformer noise/heat went away.
regards
Bernd
hmmm would that suggest non-identical 15V secondary windings on your step up transformer?
One winding shouldn't be a problem for the amount of HT power used if you're only drawing 20mA through R33 (which sounds about correct) 20mA *240V = ±5W.
Title: Re: The official G9 help thread
Post by: redmojosteve on June 19, 2012, 03:50:40 PM
Thanks gents for patience and the ongoing helpful suggestions. I have disconnected one of the secondaries of the step up transformer and the first transformer seems a little cooler, but not much. I had a spare 230/15V traffo for my planned second G9 and tried that and it is the same, so it rules out a transformer fault. This begs the question, and I am sorry if this sounds stupid, but how hot would you expect the trafo to get?
Thanks
Steve
Title: Re: The official G9 help thread
Post by: MeToo2 on June 19, 2012, 04:45:19 PM
Thanks gents for patience and the ongoing helpful suggestions. I have disconnected one of the secondaries of the step up transformer and the first transformer seems a little cooler, but not much. I had a spare 230/15V traffo for my planned second G9 and tried that and it is the same, so it rules out a transformer fault. This begs the question, and I am sorry if this sounds stupid, but how hot would you expect the trafo to get?
Thanks
Steve
Pretty much standard 40VA toroidal transformers here. Nothing special. Block RK40/12 & RK40/15. Can't hear them (no buzz at all). Can't feel them (not even hand hot) The only things that get warm in my build are the 12V heater regulator heat sink, and the tubes themselves. [Don't be tempted to touch the heatsink on the TL783. It'll be at ±240V!]
Title: Re: The official G9 help thread
Post by: redmojosteve on June 19, 2012, 05:54:05 PM
Good evening guys. I have gone back a few steps and taken some measurements of current. HT current draw about 20mA, on the 12V connector around 1.05A, and at the 48V connector it's 0.175A. I think the noise will be minimal by effective mounting and putting the lid on the case! Interestingly I have also found that hum pickup at max gain is minimised to a very low level by rotating the toroidal transformers by about 20 Deg so I'll create an angled mount for them to take advantage of this.
Thanks again
Steve
Title: Re: The official G9 help thread
Post by: Majestic12 on June 22, 2012, 05:31:09 AM
I just checked my second G9 build and I'm wondering why the polarty knob changes the frequency response.
With the knob in reversed position, I get more bass and top end. Same behaviour on both channels. (Of course every channel was tested on its own, no summing of phase reversed signals)
Can anybody give me an explanation for this ?
Title: Re: The official G9 help thread
Post by: daal on June 22, 2012, 05:58:11 AM
Have you recorded the same signal in each position to see if it actually nulls or not ? Because in my case, everytime I pull a "reverse phase" button, I have the sensation that the new sound is much more plain, but it's a psychoacoustic effect due to the phase change. If I record both, I can see that they null correctly.
Title: Re: The official G9 help thread
Post by: Majestic12 on June 22, 2012, 06:05:43 AM
I can clearly see the difference in the two frequency responses..
I'm taking exact measurements this afternoon, but I have no idea where this stange behaviour is caused....

EDIT: Problem solved. It was just a mistake in my measurements...
Title: Re: The official G9 help thread
Post by: redmojosteve on June 22, 2012, 10:55:49 AM
Re my ongoing saga of the hot transformer, I have just checked the current drawn by the secondary of the second transformer (12V-12V) from the secondary of the first (15V-15V) and it is around 4.4A which is rather more than I would have expected. I also think this is greater than the manufacturer's data sheet, which would explain the excessive temp.
Title: Re: The official G9 help thread
Post by: MeToo2 on June 22, 2012, 11:57:00 AM
Re my ongoing saga of the hot transformer, I have just checked the current drawn by the secondary of the second transformer (12V-12V) from the secondary of the first (15V-15V) and it is around 4.4A which is rather more than I would have expected. I also think this is greater than the manufacturer's data sheet, which would explain the excessive temp.
On the PCB you have:
12V heater 1.05A = nominal
48V = 175mA = nominal
so they don't look like the problem.

Neither is the HT supply pulling 20mA. (9V drop on the 470 ohm resistor R33) also pretty nominal

Assuming the step up transformer is acting something like 80% efficient (which is poor)
HT 20mA @ 260V would imply 260/12*20mA /0.8 => ± 550mA RMS on the 12V side.

Certainly not 4.4A sustained (although you may get peaks over a portion of the cycle as the smoothing capacitors charge).
But 4.4A sustained @ 15V is 66W and would certainly explain excessive heating on the 15V transformer.

So it looks to me like there's something very suspicious either with that 2nd 12v step up transformer or your HT bridge rectifier (D17 - D20).
Is your TL783 isolated from the case?
Are your HT rectifier diodes (D17 - D20) correctly oriented?
Is the point where D19 & D20 meet isolated from 0V (chassis)?
Title: Re: The official G9 help thread
Post by: redmojosteve on June 22, 2012, 01:15:57 PM
Thanks MeToo2 for your patience!
I checked the diodes and they are all correct, D19 and D20 are isolated from the chassis too. The TL783 has a finned heatsink which is not bolted to the chassis. Therefore I put my spare transformer in (for my next G9) and I am getting a slightly lower current of 3.5A but the 15V transformer is still getting quite warm, although not as bad. Would very low ESR of C14 and C15 cause a problem by any chance?
Cheers
Steve
Title: Re: The official G9 help thread
Post by: MeToo2 on June 22, 2012, 01:32:04 PM
Thanks MeToo2 for your patience!
I checked the diodes and they are all correct, D19 and D20 are isolated from the chassis too. The TL783 has a finned heatsink which is not bolted to the chassis. Therefore I put my spare transformer in (for my next G9) and I am getting a slightly lower current of 3.5A but the 15V transformer is still getting quite warm, although not as bad. Would very low ESR of C14 and C15 cause a problem by any chance?
Cheers
Steve
Don't think so. How exactly are you measuring the 4.4A (12V transformer sample 1) or 3.5A (12V transformer sample 2) ? Is that 3.5A or 4.4A measured as RMS with an ammeter? I guess so, because you are getting substantial heating. It'd be normal to get a short peak current surge for a few seconds as you first switch on as the large reservoir caps charge up, and then a few mS per mains cycle as they top up, but not sustained current draw over a long period. Anyway your voltage drop across R33 seems to rule out anything to the right of this point, as the current draw of the HT of 20mA is pretty much nominal. That 3.5A or 4.4A has to be going somewhere. If it isn't going through R33 where is it going? 4.4A would translate to 160mA at 260V or >40W. All I can think of is into the chassis somehow. Seems unlikely two transformers would be faulty. Unless it's systematic and there's some sort of nasty eddy currents in the transformer cores. Do you have model numbers for the 12V transformers? Or maybe your diodes are breaking down at high voltage. Are they true 1N4007's? Have you taken them out and tested them individually?
Title: Re: The official G9 help thread
Post by: redmojosteve on June 22, 2012, 01:57:22 PM
Hi again.
The current is measured as RMS using a multimeter. It's puzzling me and I completely agree that it has to be going to the chassis somehow. I checked the diodes before I put them in the board but it would seem a good idea to check them again. I presume they are true 1N4007's as that is how they are marked. Is there any way of telling the difference? I have used them on other builds without any problem but my "stock" are not all from the same source and I think this project may be more demanding. The transformer is a Nuvotem RS0050P1-2-012. I have used this make on other builds and they have been OK.
Cheers
Steve
Title: Re: The official G9 help thread
Post by: redmojosteve on June 24, 2012, 06:40:27 AM
Just a quick addition to my last message. I removed the diodes D17 to D20 and even though they tested satisfactorily, I have replaced them. Although they were from the same pack, it turns out that at least 2 were 1N4004's so I thought this could have been a problem due to HV breakdown as suggested by MeToo2.  I know I should have checked! These have been replaced with 1N4007's, which hopefully are correctly marked, but frustratingly it hasn't made any difference.
I have also checked for any solder bridges, bits of stray wire etc just in case, but again there's nothing obvious.
Cheers. Steve
Title: Re: The official G9 help thread
Post by: Luax on June 26, 2012, 04:17:37 AM
Hi Guys,

Recently I've completed my G9 build. The left channel was superb, but the right channel had some noises and a slight buzz.
I couldn't help not opening my G9 again and decided to place some alu to shield the circuit form the toroids.
I also decided to use the external PSU instead of the main board. One thing that I could get quite clear (after reading the schematic).
Is that on the external PSU there is bridge 1 and 2 but with what diodes do they correspond on the main board?
If somebody has any knowledge on the matter i'd love to hear it.

All the best!
Title: Re: The official G9 help thread
Post by: barthman.de on June 26, 2012, 01:47:06 PM
I finished a G9 which I made "my own way" - some pics you can find here ... http://www.groupdiy.com/index.php?topic=48522.0

But I have some questions:

1) Hum  >:(

I put a SM57 into the preamp, layed the sm57 under my pillow and set "Gain" and "Output" to maximum.

The noise floor:

(http://www.barthman.de/diy/g9/noisefloor.jpg)

Looking not bad but if I turn on my headphones I can hear clearly "eeeehhhhhhhhh". Any ideas to further reduce the 50 Hz hum? Or do I hear the fleas coughing?

2) Is there a difference between big caps or smaler caps with near the same value? I built in smaller 100 uF / 350V  (diameter 18mm, height 32 mm) at first and changed them later to 220uF / 350V (diameter 35mm, high 62 mm)? There was no difference in hum. Can I use the smaller ones solid without problems (the big ones need so much space inside the housing)?
Title: Re: The official G9 help thread
Post by: MeToo2 on June 26, 2012, 03:25:51 PM
I finished a G9 which I made "my own way" - some pics you can find here ... http://www.groupdiy.com/index.php?topic=48522.0

But I have some questions:

1) Hum 

Before you start chasing ghosts, I'd humbly suggest you check 4 things related to correct gain staging.

1) The G9 is a mic pre. I'd therefore suggest that you test it with a 200 ohm shielded resistive dummy load on the input (not a live mic, even if it has an output impedance of 200 ohms), and perhaps a 600 ohm shielded resistive dummy load on the output. Your A/D converters might only present a high impedance load (>10K)

2) What is the noise floor of your measuring set up (200 ohm shielded resistive dummy load connected directly into your converter via the same XLR test cables, without the G9 in place)? In other words, is the limit the G9, or the native noise in your test set up/ converters?

3) What is the calibration on your graph? Does -102dB correspond to -102dB relative to digital Full Scale Deflection (FSD) or relative to +4dB into 600 Ohm or what?

What signal level would 94 dBA SPL directed into your mic correspond to at the same gain setting at the output of your G9?

[an SM57 has a sensitivity or open circuit voltage of -56.0 dBV/Pa* (1.6 mV) *(1 Pa = 94 dBA SPL @ 1KHz) at the input to your G9. A G9 will generally produce around 56dB or so of gain when cranked up near max, but you should measure that. That'll give you around 0BV (1V) of signal. 94dBA SPL @ 1KHz is a pretty loud source but not excessively so]

4) How much signal voltage can your A/D converter take before it clips (0dB Digital FSD)?

So what signal can you aim to have at the input to your A/D whilst still allowing 20dB for dynamics and 6 dB of cushion to avoid digital artifacts? Is your G9 gain too high, so that the A/D is in danger of digital clipping? Do you need to turn the gain down?

Then you can work out your equivalent signal to noise ratio at the input and output under real use conditions, which is IMHO more important than the absolute level of the noise at the input or output, and something you can compare with other people's builds. Equivalent Input Noise (output noise + gain) should be around 120dB or even better, resulting in a real life s/n ratio of ±66dB at nominal signal level, whilst still allowing you to keep 20dB or more of headroom for dynamics/ peaks + 6dB cushion.

That'll tell you if you're listening to fleas coughing or not.
Title: Re: The official G9 help thread
Post by: barthman.de on June 27, 2012, 09:09:03 AM

Before you start chasing ghosts, I'd humbly suggest you check 4 things related to correct gain staging.

1) The G9 is a mic pre. I'd therefore suggest that you test it with a 200 ohm shielded resistive dummy load on the input (not a live mic, even if it has an output impedance of 200 ohms), and perhaps a 600 ohm shielded resistive dummy load on the output. Your A/D converters might only present a high impedance load (>10K)

2) What is the noise floor of your measuring set up (200 ohm shielded resistive dummy load connected directly into your converter via the same XLR test cables, without the G9 in place)? In other words, is the limit the G9, or the native noise in your test set up/ converters?

3) What is the calibration on your graph? Does -102dB correspond to -102dB relative to digital Full Scale Deflection (FSD) or relative to +4dB into 600 Ohm or what?

What signal level would 94 dBA SPL directed into your mic correspond to at the same gain setting at the output of your G9?

[an SM57 has a sensitivity or open circuit voltage of -56.0 dBV/Pa* (1.6 mV) *(1 Pa = 94 dBA SPL @ 1KHz) at the input to your G9. A G9 will generally produce around 56dB or so of gain when cranked up near max, but you should measure that. That'll give you around 0BV (1V) of signal. 94dBA SPL @ 1KHz is a pretty loud source but not excessively so]

4) How much signal voltage can your A/D converter take before it clips (0dB Digital FSD)?

So what signal can you aim to have at the input to your A/D whilst still allowing 20dB for dynamics and 6 dB of cushion to avoid digital artifacts? Is your G9 gain too high, so that the A/D is in danger of digital clipping? Do you need to turn the gain down?

Then you can work out your equivalent signal to noise ratio at the input and output under real use conditions, which is IMHO more important than the absolute level of the noise at the input or output, and something you can compare with other people's builds. Equivalent Input Noise (output noise + gain) should be around 120dB or even better, resulting in a real life s/n ratio of ±66dB at nominal signal level, whilst still allowing you to keep 20dB or more of headroom for dynamics/ peaks + 6dB cushion.

That'll tell you if you're listening to fleas coughing or not.

I'll try to answer the questions but because I'm not a pro I have to tell more questions :)

1) OK. Can I put some 600 ohm resistors on input and output between hot and cold? Can I go after the resistor on output to my Metric Halo 2882 A/D (this is my only way to picture the frequency response via DAW)

2) The limit is the G9, here the response without the G9:

(http://www.barthman.de/diy/g9/noisefloorsystem.jpg)

3) The calibration of the graph is dbFS. I zoomed in so you can't see the range above -18dBFS.

4) My Metric Halo 2882 takes +26 dBU. I drive the levels usually at -10 dBFS till -6 dBFS to reduce distortion and have enough headroom in the DAW. So if I understand you right 26dBU-20dBU-6dBU = 0 dBU = - 9 dBFS. So I can turn down the output gain on the G9 to get a peak level round about -9dBFS. So I have a lower noise floor on output.

Let's say after reducing the output gain to "8" I would get maximum noise peeks on output at 95 dBFS + 45 dB Gain = 140 dB = better than 120 - no problems.

Is this calculation right?   
Title: Re: The official G9 help thread
Post by: MeToo2 on June 27, 2012, 02:53:28 PM

I'll try to answer the questions but because I'm not a pro I have to tell more questions :)

1) OK. Can I put some 600 ohm resistors on input and output between hot and cold? Can I go after the resistor on output to my Metric Halo 2882 A/D (this is my only way to picture the frequency response via DAW)
yes, you can try that. Terminating 600 ohm busses is less common that it used to be. The Metric Halo 2882 apparently also has a soft switchable level input impedance, so I'm guessing you should set these to +4 level (for pro equipment).
Quote
2) The limit is the G9, here the response without the G9:
yep it's clearly higher, but that could just simply be due to the additional gain of the G9. If your G9 is providing 36dB of gain it ain't effectively any higher at all, just the whole reference is moved up (noise floor as well as signal). Which is why I suggest you look at signal to noise ration rather than absolute levels.
Quote
3) The calibration of the graph is dbFS. I zoomed in so you can't see the range above -18dBFS.
OK.
Quote
4) My Metric Halo 2882 takes +26 dBU. I drive the levels usually at -10 dBFS till -6 dBFS to reduce distortion and have enough headroom in the DAW. So if I understand you right 26dBU-20dBU-6dBU = 0 dBU = - 9 dBFS. So I can turn down the output gain on the G9 to get a peak level round about -9dBFS. So I have a lower noise floor on output.

Let's say after reducing the output gain to "8" I would get maximum noise peeks on output at 95 dBFS + 45 dB Gain = 140 dB = better than 120 - no problems.

Is this calculation right?   

I'm not convinced about that max +26dBU specification on the input. That must be with the 20dB pad engaged. 26dBU is 45 volts peak to peak, which no computer interface that I know can handle raw without clipping.  26dBu - 20dBu pad would give 4.5 volts at the analogue digital converter, which sounds much more normal. I believe placing an input on the Metric Halo 2882 in "+4dB professional" mode automatically engages the 20dB input pad (at least according to the manual).

I don't understand exactly how you get from 26dBU-20dBU-6dBU = 0 dBU [for RMS pink noise] to -9 dBFS [for peaks] in your calculation. I'd assume there'd be 20dB of dynamics on top of the -26dB RMS, which gets your peaks back to -6dBFS. Either way, this matches almost exactly with your current practice to "drive the [peak] levels usually at -10 dBFS till -6 dBFS" which sounds good.

But whatever. If when you do your real-world gain-staging you measure that your noise peaks are at -95dBFS and your signal peaks are at -9 to -10 dBFS without any clipping or distortion (on whatever nominal scale) you've got a signal to noise ratio of >> 70dB, which is pretty excellent IMHO. I found this article (http://broadcastengineering.com/newsrooms/broadcasting_analog_audio_noise/) that gives quite good explanation of the relationships between levels through the system (although it does not address digital overs).

You could even possibly afford to allow yourself up to another 6dB of headroom [peaks at ± --16dBFS to -12dBFS] and you shouldn't hear the noise on a real recording. Bear in mind when you mix multiple tracks into an overall mix that uncorrelated noise adds up as power, whereas correlated signal adds up as voltage, so you effectively hear less background noise the more tracks you have in the mix (assuming you record one track at a time). Also I find digital clipping and overs are far more annoying than some low level hum. You can almost always use a high pass filter or an expander or gate in your DAW.
Title: Re: The official G9 help thread
Post by: barthman.de on June 28, 2012, 08:28:22 AM
Thank you METOO2 this are the informations to getting better. Good article. I work more practice-oriented because recording music and building all around is hobby for me. So I have to learn the more physical details while building some equipment  :D
Title: Re: The official G9 help thread
Post by: kent on June 29, 2012, 09:05:44 PM
Hello all.  It has been literally years since I've posted but time has finally allowed me to work on something new. Now that I'm stuck it's time to ask for some help. My G9 is put together but on first fire up my voltages are reading quite high (among other issues but I'll start there). I used 115+115:15+15 and 115+115:12+12 torroidial I got from parts express. The voltages straight off the transformers with a load are as follows - heater=21v, phantom=21v, HV=344v. Double and triple checked wiring and it seems fine. Any ideas?
Title: Re: The official G9 help thread
Post by: gyraf on June 30, 2012, 12:54:01 AM
Voltages measured under load - tubes mounted, unit heated up (some 30 sec.)? In that case you got a wrong transformer for the first (15V).

Jakob E.
Title: Re: The official G9 help thread
Post by: kent on July 01, 2012, 11:42:33 AM
Here is a pic. Everything seems to be right. 15v for the first Tx and 12v for the second. Should I be suspect of the factory specs?

(http://farm9.staticflickr.com/8025/7479592884_03dbc14489.jpg) (http://www.flickr.com/photos/[email protected]/7479592884/)
G9 power transformers (http://www.flickr.com/photos/[email protected]/7479592884/) by kentpdog (http://www.flickr.com/people/[email protected]/), on Flickr

Here is the wiring. Kind of hard to see but I figure it has to be correct or my readings would be even farther off.

(http://farm8.staticflickr.com/7247/7479599862_dbf4a0784e.jpg) (http://www.flickr.com/photos/[email protected]/7479599862/)
G9 transformer wiring (http://www.flickr.com/photos/[email protected]/7479599862/) by kentpdog (http://www.flickr.com/people/[email protected]/), on Flickr
Title: Re: The official G9 help thread
Post by: Maynard on July 01, 2012, 12:15:32 PM
This topic never ends being interesting! Kent I know you have check wiring several times, anyway if I were you I would get the transformers out and test them separately just to make sure they'r not the problem.

And I got a new one, what could make R33 toasted as badly as to destroy it without affecting the rest of components? too much current drawn but why?  I am still trying to find out. Yesterday turn it on and leave it heting as I have done for the last months and it start smelling a little bit funny. The unit was on, evertything look good but no output at all.
Today I opened and find out R33 toasted but the rectifying diodes, TL783 and protection diode and zeners are ok  :o
I just took the toasted resistor out, replaced it, turn unit on, got a voltage drop of around 5V (just using one channel) and a steady plate voltage of 243V. Used the unit for a while without any problem. So I have been uneable to reproduce the problem and got no idea what caused it, some kind of short? bad state of the resistor? Oh yes, reservoir C14 positive lead conection was loosed (could this be part of the problem?)

If anyone can give me a hint I will appreciate. I Will let you know if I find the cause so might be helpful to someone.

Ragards
Title: Re: The official G9 help thread
Post by: kent on July 04, 2012, 11:17:23 AM
So I finally got around to pulling the transformer and measuring it by itself without a load. I am reading 21v on each winding. Is that normal for an unloaded 15v output?
Title: Re: The official G9 help thread
Post by: MeToo2 on July 04, 2012, 12:58:15 PM
So I finally got around to pulling the transformer and measuring it by itself without a load. I am reading 21v on each winding. Is that normal for an unloaded 15v output?
Regulation depends on the spec of each particular transformer. Larger wattage transformers tend to regulate better.

Your transformers (Y236103 & Y236102 in your photo) should have a spec (http://avellindberg.com/pdf/avel_y23_range.pdf) of 3% variation in voltage at normal input (115V parallel primaries as you're located in the US) and full load, and 13.7% regulation (http://www.avellindberg.com/transformers/tech_notes/tech_notes9.htm), which is pretty good.

So (no load - full load V)/ no load V = 13.7% or in other words a no load output voltage of around 17.4V for 115V parallel input.

21V looks too high to me. But check your mains voltage too....
Title: Re: The official G9 help thread
Post by: redmojosteve on July 08, 2012, 12:03:35 PM
Hi again,
It's been a few days since I have been on the forum and I have checked my G9 but I am still getting a warm transformer (the 15V one). As I have a second PCB and all the components for anpther build I am going to get this one together and swap the boards over to see if it makes any difference. I'll obviously be super careful with component selection and mounting.
Cheers
Steve
Title: Re: The official G9 help thread
Post by: kent on July 08, 2012, 01:56:11 PM
Ha!  Checked voltage out of the wall and got 155v!  Couldn't be right so I checked my meter and found the battery wire was frayed and shorting out on the board. I hate when you have to troubleshoot a problem to troubleshoot a problem!  In any case - back to testing and an update when I'm done.
Title: Re: The official G9 help thread
Post by: phelar on July 15, 2012, 03:12:01 PM
Hi!
I just finished my g9 and it was up and running for like 5min.
After 2min the transformers, most likely the 2x15v, turned so warm that I could feel the heat on the casing. All tubes was glowing. There was also a 50hz hum from the case.
I tried a guitar through the instrument input, no sound, just something like a ground noise unaffected buy the gain. Turned it off, checked component placement, wiring....everything seemed ok. When I turned it on again it was all dead.
I checked the 2x15v transformer (Velleman 230v 30va 2x15v with 130 degrees C thermal fuse), measured resistance on the primary winding and there was nothing. So I thought the fuse was blown. The second transformer (2x12v) measured ok.

Ok, so. What to do now? First of all, is this a crappy choice of transformer..? (It`s kind of cheap I know. I don´t think this problem IS the transformer but anyways).
I have to replace the transformer and start measuring, I know that,  but I´m fishing for some theories for this transformer breakdown.

Does anyone got a clue?

Title: Re: The official G9 help thread
Post by: MeToo2 on July 16, 2012, 02:35:28 AM
Ok, so. What to do now? First of all, is this a crappy choice of transformer..? (It`s kind of cheap I know. I don´t think this problem IS the transformer but anyways).
I have to replace the transformer and start measuring, I know that,  but I´m fishing for some theories for this transformer breakdown.

Does anyone got a clue?
I would not just replace the transformer and start measuring. A transformer gets hot because of too much current flowing. The root cause of "too much current flowing" is generally something pretty simple, like a short circuit, wrong spec transformer, induction loop, mis-oriented diodes. The transformer itself is very unlikely to be the root cause. So I would start measuring, and only once I'd found all the likely fault(s) I'd replace the transformer. You already know there's something wrong...... You can then power on your circuit either using a variac (to limit input voltage to the transformer) or use the light bulb test (http://diyaudioprojects.com/Forum/viewtopic.php?f=5&t=1051) to limit the current, but first without the 3 loads connected (heater, HT, P48). Then you can connect the loads one by one. My experience is the slower you proceed, the faster you'll solve your problem.
Title: Re: The official G9 help thread
Post by: phelar on July 16, 2012, 02:53:55 AM
Thanks!
I´m going to use a variac. ........maybe i messed up the phasing on the secondaries :/ there is a chance i´m afraid. If so, is this the reason for the hot(and dead) transformer.
I´ve got 230 primary winding by the way.
Title: Re: The official G9 help thread
Post by: sonolink on July 20, 2012, 07:55:43 AM
Hello,
If this is not the right place where to ask for this I apologize. I'm building a G9. I'm wiring Inputs and Outputs with shielded wire. Basically I understand that Input screens are connected to the ground pins on the board and pins 1 on input xlr connectors, but Output screens are only connected to pins 1 on output xlr connectors.
Then all pins1 (inputs and outputs) are connected together to chassis and safety earth. is this correct, please?
Thanks
Title: Re: The official G9 help thread
Post by: phelar on July 20, 2012, 02:22:46 PM
As far as i know you only ground the mains socket to the case. In and output xlr pin 1 to the ground pins on the pcb. Never heard that you should leave the output screen, not connected to pcb ground trace.
....but i hope to get this confirmed though
Title: Re: The official G9 help thread
Post by: MeToo2 on July 20, 2012, 04:26:57 PM
As far as i know you only ground the mains socket to the case. In and output xlr pin 1 to the ground pins on the pcb. Never heard that you should leave the output screen, not connected to pcb ground trace.
....but i hope to get this confirmed though
Sonolink had it right. Check the PCB layout. The screen pin (centre of the 3 pins) isn't actually connected to any PCB trace at header K3 & K103 (that connects to the XLR Out), so you don't have to do anything special there.

See http://www.rane.com/note110.html http://www.rane.com/note151.html
Title: Re: The official G9 help thread
Post by: phelar on July 21, 2012, 01:41:51 AM
Oh, thanks............i´ve really messed with the wiring :/
Title: Re: The official G9 help thread
Post by: sonolink on July 23, 2012, 04:31:38 AM
@MeToo2

Thanks for confirming, mate :)
I've finished my build now, but something is wrong.....troubleshooting.....   :-\
Cheers
Title: Re: The official G9 help thread
Post by: sonolink on July 31, 2012, 10:26:41 AM
Hi everybody,
I finished my G9 build some days ago. Ch1 had no output. Ch2, massive hum. Voltages seemed ok. Left the unit on for a few hours and everything ok. Decided to go for Ch2 first, so after some chopsticking I noticed the trafo wiring was the cause for the hum. So, I redid the trafo wiring. After doing so, I noticed there was no voltage getting to the board and one of the trafos was getting VERY hot. Quickly switched the unit off and corrected the wiring. Now everything seems ok BUT, the big caps are not charging at all: 0V!!
Any ideas?
Thanks

Title: Re: The official G9 help thread
Post by: gyraf on August 01, 2012, 03:53:57 AM
Sonolink,

No charge at all could indicate either no 220V ac from power transformer, wrong/broken/wrong-oriented 4007 diodes, or wrong/broken 1KOhm/2W (470?) resistor. Or some wireing fault

Take care when troubleshooting


Double check your measurements and the integrity of your voltmeter


Take care


Jakob E.

Title: Re: The official G9 help thread
Post by: sonolink on August 03, 2012, 08:08:20 AM
Thanks for your answer, jakob. I'll recheck everything and report back.
Cheers
Sono
Title: Re: The official G9 help thread
Post by: sonolink on August 08, 2012, 10:00:42 AM
Hi again,
To make sure I'm wiring the trafos correctly could you please confirm this is correct?


Tx1 (12V)
PRI (blue/brown) -> 220VAC socket
SEC1 black -> left pole of 15V terminal close to d8
SEC1 red  -> right pole of15V terminal close to d8
SEC2 (orange/yellow) -> 15V terminals close to d13

Tx2 (15V)
PRI (blue/brown) -> 220V terminals close to d16
SEC1 black and SEC2 orange -> left pole of15V terminal close to d8
SEC1 red and SEC2 yellow -> right pole of 15V terminal close to d8

Thanks for your time and help
Sono
Title: Re: The official G9 help thread
Post by: gyraf on August 09, 2012, 01:18:59 AM
Sonolink - that looks right.

Jakob E
Title: Re: The official G9 help thread
Post by: sonolink on August 10, 2012, 06:53:21 AM
Thanks for checking, jakob :)

This is probably a bit of a noob thing, but I checked and R33 checks 470R, and the Trafos seem to be wired fine (although on my previous post Tx1 should be 15V and Tx2 12V, but I guess this is irrelevant to the caps no charge problem). I checked D17-D20. I don't know how to check a diode really, so I used common sense and checked continuity in both directions. I consistently read 0.5 and 1 on all four diodes. Any ideas? Thanks

Cheers
Sono
Title: Re: The official G9 help thread
Post by: gyraf on August 10, 2012, 10:15:42 AM
- check that you have some 210-240V AC going to the 1N4007 rectifier diodes (measured at diode legs)
- check that you have some 240-290V DC on the other side of the diodes

if you have no AC coming in, check wireing and transformer(s)
if you have AC going in, but no DC coming out, the diodes may be blown
Title: Re: The official G9 help thread
Post by: sonolink on August 10, 2012, 06:42:07 PM
I apologize: the 220V terminal on the board had a bad solder joint. My bad.
I'll get to the other problems the unit has tomorrow.
Thanks for the help :)
cheers
Sono
Title: Re: The official G9 help thread
Post by: sonolink on August 12, 2012, 08:14:56 PM
Hi again,
The caps are charging now :)
BUT,
I have the following problems:
Channel 1: no audio at all. Phantom ok.
Channel 2: no Phantom at all, Mic Ok (a bit rough sounding but that's probably because I'm using EH 12AX7 for testing), Line position = massive hum that increases when plugging a guitar in and when increasing gain and volume. When chopsticking the shielded cable going from the jack to the board it sounds microphonic (I don't know if you say that in english but I mean it makes noise like when you tap on a mic). I did the DI mod. I didn't have switched mono female jack sockets, so I used switched stereo female jack sockets without connecting anything to the ring. I mention it in case that could be the cause.

I have measured voltages several times with different voltmeters and. I get this:
230VAC from socket
Tip121: 50 80 50
78S12: 18 0 12
TL783: 243 244 355

I've attached some pics in case they're helpful...


(http://img23.imageshack.us/img23/4491/imag0293z.th.jpg) (http://imageshack.us/photo/my-images/23/imag0293z.jpg/)

(http://img528.imageshack.us/img528/8196/imag0294u.th.jpg) (http://imageshack.us/photo/my-images/528/imag0294u.jpg/)

(http://img194.imageshack.us/img194/3663/imag0291ro.th.jpg) (http://imageshack.us/photo/my-images/194/imag0291ro.jpg/)

All ideas and/or suggestions are very welcome :)
Thanks for your time and help
Cheers
Sono
Title: Re: The official G9 help thread
Post by: gyraf on August 13, 2012, 02:05:47 AM
voltages are alright. Now time for checking your components, soldering and cabling
Title: Re: The official G9 help thread
Post by: sonolink on August 13, 2012, 12:59:28 PM
Ok :)
Incidentally, is there a way I can check the audio path with a sinewave and an oscilloscope? If so, how do I do it? Thanks

Cheers
Sono
Title: Re: The official G9 help thread
Post by: sonolink on August 16, 2012, 06:20:56 PM
Nobody?

Ok. Let me have a go at it. My scope is digital and has 2 channels. Basically, I guess I connect the black lead of one channel to ground and then I poke with the other end around the path I want to check, right? If this is correct, that's great but my concern is, what if I fry the scope? How do I know that?

I would appreciate some help with that pretty pretty pretty please...

Other than that, I guess it's all about checking continuity, resistors and caps, right? My God what a pain....
;-)

Thanks
Sono

Title: Re: The official G9 help thread
Post by: MeToo2 on August 17, 2012, 06:17:03 AM
Nobody?

Ok. Let me have a go at it. My scope is digital and has 2 channels. Basically, I guess I connect the black lead of one channel to ground and then I poke with the other end around the path I want to check, right? If this is correct, that's great but my concern is, what if I fry the scope? How do I know that?

Sono
Poking about is definitely not a good idea. Plan what you are going to test and what you think the waveform should look like: Connect up test gear: power up: check results: power down: think: repeat. Watch you don't fry your PC or scope. I use an external signal generator and don't connect up any PC kit until I'm sure the working voltages on both input and output are safe. Be sure to check out the maximum safe working voltage on your scope. I use a good old analogue Tektronix 2445B scope on tube kit for that very reason. It can easily handle 400V DC on the input. Also remember there's galvanic isolation (transformers) on the input and output. Connect your scope ground the the chassis. You may be better off measuring voltages on the outside of the transformers using 2 inputs in differential mode.
Title: Re: The official G9 help thread
Post by: redmojosteve on August 19, 2012, 05:43:57 AM
It's been a while since I wrote on this thread but with the Olympics out of the way and my decorating finished I am back to my G9. Although I started on my second one I have decided to get the first sorted out. I still need to check out why I had the hot transformer problem. Looking through this thread it seems there have been a couple of other instances where this has cropped up. I need to work through it again, and in particular make sure the transformer connections are correct. I have done this so many times I can't imagine that I have ended up with the wrong configuration so many times.  On a different point, apart from the above issue, I had got the G9 working well on both channels with low noise but when I tried the inst input on the front panel (and this was the same for both channels) I still got a very small amount of the input from the XLR bleeding through. This is manageable from an operational standpoint i.e. switch off the input to the XLR! However looking at the schematic I can't figure how anything from the XLR input gets through as it is mechanically isolated by the switched INST jack input. Any hints would be much appreciated.
Cheers
Steve
Title: Re: The official G9 help thread
Post by: sonolink on August 21, 2012, 06:16:49 AM

Poking about is definitely not a good idea. Plan what you are going to test and what you think the waveform should look like: Connect up test gear: power up: check results: power down: think: repeat. Watch you don't fry your PC or scope. I use an external signal generator and don't connect up any PC kit until I'm sure the working voltages on both input and output are safe. Be sure to check out the maximum safe working voltage on your scope. I use a good old analogue Tektronix 2445B scope on tube kit for that very reason. It can easily handle 400V DC on the input. Also remember there's galvanic isolation (transformers) on the input and output. Connect your scope ground the the chassis. You may be better off measuring voltages on the outside of the transformers using 2 inputs in differential mode.

Sorry for my late reply.
Also, I apologize for giving the wrong impression: poking about was not the idea I had in mind. I always tend to be over careful with gear, instruments and myself (although of course, nobody is perfect).

I have a no output problem on one channel and a no phantom on the other. My guess is the signal gets lost somewhere. Probably a bad joint. I just thought that instead of tediously checking every joint and path for continuity,  I could maybe use an oscilloscope to follow the audio path and trace where it breaks. I have an Owon digital scope that I have always used to calibrate heads on my tapemachines, so I'm not familiar with any other use for it. Hence my question. Maybe it was just a silly idea and continuity is the way to go.
Anyway, thanks for your reply.
Title: Re: The official G9 help thread
Post by: MeToo2 on August 21, 2012, 11:48:48 AM

Poking about is definitely not a good idea. Plan what you are going to test and what you think the waveform should look like: Connect up test gear: power up: check results: power down: think: repeat. Watch you don't fry your PC or scope. I use an external signal generator and don't connect up any PC kit until I'm sure the working voltages on both input and output are safe. Be sure to check out the maximum safe working voltage on your scope. I use a good old analogue Tektronix 2445B scope on tube kit for that very reason. It can easily handle 400V DC on the input. Also remember there's galvanic isolation (transformers) on the input and output. Connect your scope ground the the chassis. You may be better off measuring voltages on the outside of the transformers using 2 inputs in differential mode.

Sorry for my late reply.
Also, I apologize for giving the wrong impression: poking about was not the idea I had in mind. I always tend to be over careful with gear, instruments and myself (although of course, nobody is perfect).

I have a no output problem on one channel and a no phantom on the other. My guess is the signal gets lost somewhere. Probably a bad joint. I just thought that instead of tediously checking every joint and path for continuity,  I could maybe use an oscilloscope to follow the audio path and trace where it breaks. I have an Owon digital scope that I have always used to calibrate heads on my tapemachines, so I'm not familiar with any other use for it. Hence my question. Maybe it was just a silly idea and continuity is the way to go.
Anyway, thanks for your reply.
It's absolutely the right idea to step methodically through the schematic stage by stage looking for where the signal disappears, but
a) you have to have some idea of what to expect at each test point, otherwise how do you know it isn't correct?
I guess you could compare channel A with channel B assuming one is working.
b) the Owon should be OK (max voltage = 300V on a PDS5022S) but check your G9 power supply with a multimeter first to see if it's stable at 240V and make sure your probe is set on 10:1 mode and the sensitivity is on minimum. Also check beofre connecting up your tone generator that there are no stray high voltage AC and DC voltages on the input.

No phantom power on one channel is almost certainly a continuity issue on the 10 pin header to the control card and phantom switch plus return (pin 2 & pin 5), so buzzing that out with no power on will be the quickest.
Title: Re: The official G9 help thread
Post by: sonolink on August 26, 2012, 02:09:48 PM
@MeToo2,
Thanks for your reply :-)

Quote from: MeToo2
You may be better off measuring voltages on the outside of the transformers using 2 inputs in differential mode.

Please excuse my ignorance  but I don't know what you mean. Could you please explain?

Quote from: MeToo2
a) you have to have some idea of what to expect at each test point, otherwise how do you know it isn't correct?

If I send a sine wave shouldn't I see a sine wave (with probably different amplitudes) at each stage?

Quote from: MeToo2
b) Also check beofre connecting up your tone generator that there are no stray high voltage AC and DC voltages on the input.

You mean like a power leak ? I guess I have to check with a voltmeter at input and output connectors that I have 0V AC and DC, right?

Thanks a lot for all the input and for your time and help :-)
Cheers
Title: Re: The official G9 help thread
Post by: redmojosteve on August 27, 2012, 03:05:18 PM
I have finally got round to checking everything thoroughly. All diodes and caps correctly located and I can't find any stray paths to earth. The expected voltages are present and correct. I connected the transformers correctly but I am still getting the 15V traffo running very warm. I turned the pre-amp on for about 30 minutes, it works and passes signal just fine, but I reckon the traffo must be getting to about 70 Deg C, which I am sure is too hot. It is certainly frustrating to say the least.
Steve
Title: Re: The official G9 help thread
Post by: sonolink on August 29, 2012, 05:29:00 AM
Steve,
Sorry to hear you're still having trouble. I had a similar issue a few posts back with the 15V iron, the one connected to the outlet. You might have already done so but I would try the following:
-disconnect completely the iron from the pre
-connect it's PRI  to the outlet and check SECs voltages are correct.
-Leave it on for a few minutes
-disconnect and check temperature.
If the temp is ok redo your wiring. If it's not get a new iron.

I assume of course that you have checked continuity, diodes and resistors and they're ok.
Hope it helps
Cheers
Sono
Title: Re: The official G9 help thread
Post by: sonolink on August 29, 2012, 05:41:56 AM
I wanted to ask if the DI input (jack input) is balanced. If so, "to instrument" = hot, and "from instrument" = cold.
Could someone confirm this is correct, please?
Thanks a lot
Sono

P.S. :btw, phantom power sorted. Bad joint as usual   ::)
Title: Re: The official G9 help thread
Post by: gyraf on August 29, 2012, 06:22:21 AM
The G9 front panel jack input is unbalanced, switching, after input transformer, before first gain stage. This is why we can have such high input impedance (>3MOhm), which is partly why it sounds so good.

See schematic for reference

Jakob E.
Title: Re: The official G9 help thread
Post by: sonolink on August 29, 2012, 08:58:15 AM
Jakob, thanks for your reply.
May I reformulate my question? The female jack connections are:
Ground to shield, input transformer (to inst) and first gain stage (from inst) to tip, correct?
Btw, I'm using stereo female jack connectors with nothing connected to ring. That is ok, right?
Thanks
Cheers
Sono
Title: Re: The official G9 help thread
Post by: gyraf on August 30, 2012, 04:28:26 AM
If using stereo jack connectors at the front panel, connect ring to ground. This will also de-balance a possibly-balanced signal, should one come by.

Jakob E.
Title: Re: The official G9 help thread
Post by: sonolink on August 30, 2012, 08:34:55 AM
Thanks J  :)
Title: Re: The official G9 help thread
Post by: redmojosteve on August 31, 2012, 11:11:07 AM
Hi Sono
Thanks for the supportive words. I am continuing with the same problem, it's just that I have been busy with other stuff over the summer. I have just disconnected the 15V transformer (T2) completely,so its secondaries are open, and it's cool so that seems to rule out shorted windings I guess. On this no load setup I was getting 18.6V per winding which is slightly less than the datasheet suggests, which is 20.39V. I then connected it to the two secondaries of the 12V transformer and it starts to warm up. I didn't leave it on too long as I could tell where it was going! Some time ago on this thread I did measure the current flows to the 48V and HT sections of the power supply and they were satisfactory. So at the moment the only place I can see where I can be taking excess current is somewhere around diodes D17 to D20. I am using one of Gustav's PCBs and set out the diodes as per the silk screening. I had hoped to have my second G9 up and running by now so it's been quite frustrating. 
Cheers
Steve
Title: Re: The official G9 help thread
Post by: redmojosteve on September 02, 2012, 06:11:16 AM
Hi
Just to put my mind at rest I ran a few tests on my G9, mainly to check current flows. I am getting 35mA at 265V from T1 to the PCB, 200mA to the 15V AC connector (right side of PCB) 1A to the 15V connections at the top of the board (as annotated on the board), and 4A from T2 to T1 secondaries. It drops to 3.5A if I disconnect one of the secondaries of T1, so T1 seems to be drawing far more current than I would have expected. Incidentally I made a mistake in my last note, the manufacturers datasheet (Nuvotem  ref RS0050P1-2-015) indicates 17.2V for the secondaries of T2 which is closer to the figure I am getting.
I am sure it will be something very obvious in the end.
Cheers
Steve
Title: Re: The official G9 help thread
Post by: sonolink on September 06, 2012, 05:24:00 AM
Hello
I'm having quite a bit of problems troubleshooting my G9. So I've been thinking of rebuilding the whole thing p2p. I know many here have built a g9 p2p although in my searches I couldn't find a thread specifically about this.
Can anyone give me some insight about this please? I'm particularly concerned about layout and knowing other people experiences.
Thanks a lot.
Title: Re: The official G9 help thread
Post by: redmojosteve on September 07, 2012, 05:30:18 AM
Hi Sono
Looks like the G9 can be a bit challenging. I still have my hot transformer issue which I haven't resolved but everything else works fine. I have never built a P2P G9 but many years ago, when I knew even less than I do now, I built a guitar preamp using a readily available PCB. I had unbelievable ground loop issues which, if I knew what I know now, I probably could have solved. Of course this fine forum didn't exist back then. However I decided to go for a rebuild using a point to point approach and it never worked again! I built a P2P guitar amp a few years back and that works just fine, but it was designed as a P2P project from the start which helped. I know this doesn't answer your question but just be cautious. In my case it was definitely a case of  throwing the baby out with the bathwater, as we say.
Cheers
Steve
Title: Re: The official G9 help thread
Post by: MeToo2 on September 07, 2012, 10:10:09 AM
Hi
Just to put my mind at rest I ran a few tests on my G9, mainly to check current flows. I am getting 35mA at 265V from T1 to the PCB, 200mA to the 15V AC connector (right side of PCB) 1A to the 15V connections at the top of the board (as annotated on the board), and 4A from T2 to T1 secondaries. It drops to 3.5A if I disconnect one of the secondaries of T1, so T1 seems to be drawing far more current than I would have expected. Incidentally I made a mistake in my last note, the manufacturers datasheet (Nuvotem  ref RS0050P1-2-015) indicates 17.2V for the secondaries of T2 which is closer to the figure I am getting.
I am sure it will be something very obvious in the end.
Cheers
Steve
I agree with your reasoning. Your loads look reasonable.
35mA at 265V from T1 to the PCB: check, that looks pretty nominal idle current on the tube plates
200mA to the 15V AC connector (right side of PCB): check, that looks pretty nominal 48V phantom current
1A to the 15V connections at the top of the board (as annotated on the board): check, that looks pretty nominal 12V heater current

35mA at 265V should translate to maybe 0.8A at the "secondary" of the step up transformer
(remembering that the step up transformer is wired backwards).
4A looks unreasonable. I have no suggestion as to the root cause.

Is it worth trying a different transformer for the step up from 12V to 240V?

I had success with these transformers in my G9 builds:

http://uk.farnell.com/block/rk40-12/transformer-40va-2-x-12v/dp/1419540?Ntt=1419540    1    RK40/12 TRANSFORMER, 40VA, 2 X 12V    RK40/12
http://uk.farnell.com/block/rk40-15/transformer-40va-2-x-15v/dp/1419541?Ntt=1419541    1    RK40/15 TRANSFORMER, 40VA, 2 X 15V    RK40/15
Title: Re: The official G9 help thread
Post by: redmojosteve on September 08, 2012, 06:22:33 AM
Thanks MeToo2. I reached the same conclusion that it had to be some sort of transformer issue so I have just ordered new transformers from Farnells to exclude that problem. I'll let you how things work out.
Cheers
Steve
Title: Re: The official G9 help thread
Post by: MeToo2 on September 08, 2012, 09:19:12 AM
Thanks MeToo2. I reached the same conclusion that it had to be some sort of transformer issue so I have just ordered new transformers from Farnells to exclude that problem. I'll let you how things work out.
Cheers
Steve
OK. FWIW I wouldn't mount them on top of each other on a single bolt. There should be enough room in the case to be able to try a number of locations (to reduce any residual hum)
Title: Re: The official G9 help thread
Post by: sonolink on September 08, 2012, 05:54:15 PM
Steve,
Thanks for  your kind reply. I've built myself quite a few p2p guitar amps in the past. The main reason why I'm considering a G9  p2p is because it's much easier to troubleshoot.  Alternatively maybe I could just desolder the whole pcb and start from scratch. The thing is that this project has been lying on a shelf for about 5 years. My knowledge: experience and electronic skills have changed quite a bit in all this time and I get the feeling that starting from scratch many times is a shorter path...
Thanks for your time and help :)
Title: Re: The official G9 help thread
Post by: MeToo2 on September 09, 2012, 03:13:29 AM
@MeToo2,
Thanks for your reply :-)

Quote from: MeToo2
You may be better off measuring voltages on the outside of the transformers using 2 inputs in differential mode.

Please excuse my ignorance  but I don't know what you mean. Could you please explain?

A transformer decouples the 0v signal Earth connection. An oscilloscope is generally unbalanced and requires a chassis/earth connection to measure relative to. If you don't have a good signal earth for the scope, you can't take reliable readings and the signal will generally be swamped by noise as the scope input is such a high impedance. Sometimes, if you connect the scope earth to the outside of the transformer to measure the input or output signal, you can induce a classic hum loop (that's after all the main reason why the transformers are there in the first place). What you can do to avoid this is leave the scope earth connected to the chassis earth. Then connect channel A to the hot leg of the transformer and Channel B to the cold leg, and use the maths function on the scope to display "A-B".

http://www.youtube.com/watch?v=VWodjUSkYVE

Quote from: sonolink

Quote from: MeToo2
a) you have to have some idea of what to expect at each test point, otherwise how do you know it isn't correct?

If I send a sine wave shouldn't I see a sine wave (with probably different amplitudes) at each stage?
Yes if you're just measuring the signal path to check for basic continuity problems. But you need to know the gain of each stage too if you've got a problem in the feedback section. Checking DC voltage on the grids and cathode to see if the valves are correctly biased. Checking voltages on the anodes to see if they're sagging or oscillating etc. etc. I don't want to sound smart. If it's just a basic problem, you'll probably find it simply by comparing a point on the working channel with the same point on the faulty channel for both AC and DC coupling, starting with the least sensitive setting each time (highest V/division).
Quote from: sonolink
Quote from: MeToo2
b) Also check beofre connecting up your tone generator that there are no stray high voltage AC and DC voltages on the input.

You mean like a power leak ? I guess I have to check with a voltmeter at input and output connectors that I have 0V AC and DC, right?
Exactly. Don't risk breaking your expensive computer sound interface if you can do the same test with a simple tone generator and/or voltmeter.
And check your phantom power settings before connecting up anything.
Quote from: sonolink
Thanks a lot for all the input and for your time and help :-)
Cheers
Title: Re: The official G9 help thread
Post by: sonolink on September 10, 2012, 12:17:30 PM
@MeToo2

Thanks a lot for your reply. I'll give it another go before considering the p2p build. I was considering desoldering the components from the PCB and going p2p as this build is offering a lot of resistance (no pun intended) and it's a pain to take the whole thing out of the enclosure everytime I have to check something, but I feel again eager to troubleshoot after reading your post :)

Quote from: MeToo2
http://www.youtube.com/watch?v=VWodjUSkYVE
Thanks a lot for the link :)

Quote from: MeToo2
I don't want to sound smart.

Not at all. On the contrary, I appreciate and am very grateful for you taking the time to give complete and complex answers.

Thanks a lot for all the input and for your time and help
Cheers
Sono
Title: Re: The official G9 help thread
Post by: redmojosteve on September 11, 2012, 02:07:31 PM
MeToo2
I must admit that it wasn't the first solution that sprang to mind but I followed your suggestion and replaced the trafos with  exactly the transformers you have used and guess what, it works just fine and the transformers are as cool as cool things. Clearly the previous transformers weren't the right type for some reason. They will always come in handy for power supplies anyway. Thank you very much for your help and patience.  I'll now move on to G9 number 2.
Good luck with yours Sono

Cheers

Steve
Title: Re: The official G9 help thread
Post by: MeToo2 on September 11, 2012, 04:16:35 PM
MeToo2
I must admit that it wasn't the first solution that sprang to mind but I followed your suggestion and replaced the trafos with  exactly the transformers you have used and guess what, it works just fine and the transformers are as cool as cool things. Clearly the previous transformers weren't the right type for some reason. They will always come in handy for power supplies anyway. Thank you very much for your help and patience.  I'll now move on to G9 number 2.
Good luck with yours Sono

Cheers

Steve
I'm genuinely happy for you that you've got your build working properly. I've had a lousy day in the office today and this made me smile. Glad I could help :)
Title: Re: The official G9 help thread
Post by: sonolink on September 13, 2012, 08:33:04 PM
Happy to hear that, Steve and thanks for your encouraging words. I have to find some spare time now for my G9 troubleshooting. We just got a little puppy and my daughter was born a few days ago :)
I'll be back very soon. Promised...
Cheers
Sono
Title: Re: The official G9 help thread
Post by: rmaier on September 14, 2012, 12:00:43 AM
Congratulations! The birth of a child is by far the most intensely rewarding DIY project we're lucky enough to get. All the best to you and family. :)
Title: Re: The official G9 help thread
Post by: psychedelnick on September 21, 2012, 02:17:34 AM
First power up tonight, tubes all glow nicely but oh no! A little bit of smoke, a burnt out resistor! R 40. I listened to both channels on PT and it's a sad and sh*tty loud buzzing humming everything. Identical on both at least and signal is passing. Everything else seems cool. I'll check voltages tomorrow. Any thoughts? Thanks
Title: Re: The official G9 help thread
Post by: MeToo2 on September 21, 2012, 06:03:26 AM
First power up tonight, tubes all glow nicely but oh no! A little bit of smoke, a burnt out resistor! R 40. I listened to both channels on PT and it's a sad and sh*tty loud buzzing humming everything. Identical on both at least and signal is passing. Everything else seems cool. I'll check voltages tomorrow. Any thoughts? Thanks
D6 installed the wrong way around? It's a zener. If it's reverse biassed then the voltage across the zener is 56V and the current through R40 is max 3mA. If D6 is forward biassed then the voltage drop is ±.6V and the current through R40 = ±27mA = 1.6W or enough to burn out R40.
Title: Re: The official G9 help thread
Post by: bigswole on September 21, 2012, 08:40:47 AM
Will 2 115+115 : 15+15 power transformers work?

Title: Re: The official G9 help thread
Post by: psychedelnick on September 21, 2012, 12:40:47 PM
Thanks MeToo2 I will check tonight!  8)
Title: Re: The official G9 help thread
Post by: gyraf on September 22, 2012, 01:14:58 AM
Will 2 115+115 : 15+15 power transformers work?

Yes, they should.

Jakob E.
Title: Re: The official G9 help thread
Post by: psychedelnick on September 22, 2012, 01:32:58 AM
You were right MeToo2. The diodes I used were 5.6 V! So hopefully once I swap that out with the right one it should be good! Thanks a million! ;D
Title: Re: The official G9 help thread
Post by: psychedelnick on September 24, 2012, 03:54:34 AM
Okay, installed the 56V Zener and no smoke! Tubes glow evenly.... bad sound, no signal, a bit of RF, that's it! Voltages all within reason except! the terminal next to C 29 is getting nothing, zero. But the one just next to it, literally next to it, is getting 15V on the nose. Is this normal? Could I have a bad toroid? My real problem may exist elsewhere but this is all I got for now. The group of wires in question are at the bottom of the 15 V terminal to the very right in the attached image, Black Orange and Yellow. Thanks
Title: Re: The official G9 help thread
Post by: MeToo2 on September 24, 2012, 11:37:56 AM
Okay, installed the 56V Zener and no smoke! Tubes glow evenly.... bad sound, no signal, a bit of RF, that's it! Voltages all within reason except! the terminal next to C 29 is getting nothing, zero. But the one just next to it, literally next to it, is getting 15V on the nose. Is this normal? Could I have a bad toroid? My real problem may exist elsewhere but this is all I got for now. The group of wires in question are at the bottom of the 15 V terminal to the very right in the attached image, Black Orange and Yellow. Thanks
errm that's ~15V AC on those PCB terminal blocks: not DC. One terminal connects directly to signal ground, so it should measure 0v. Measure the voltage on C23 (to check your 48V phantom) doubt this is the issue, but it's a start (and will check if D6 was the only problem with the phantom supply).
Title: Re: The official G9 help thread
Post by: tobi.pl on September 29, 2012, 10:48:47 AM
So I nearly got my G9 finished and have to sort out some Problems that appeared.
First of all I got some really annoying hum with [email protected] (Gain and Output closed) and [email protected] if Gain and Output are cranked up and a SM57 Mic is connected.
Beeing audible hum, theres no way leaving it there. As I only have 100µ on C14 and C15 it would be my first guess to change them to 220µ. The AC Voltage measured at C14 and C15 is about 0.9V (I guess that might be why it is audible  8)), but  I do not really trust my measurement equipment. HT Voltage is about 205V as I accidentally bought 2x 230V/15V transformers, so the second thing would be to change one of them into 230V/12V to get a decent HT Voltage.
My second problem is a [email protected]  if Gain and Output are turned fully clockwise. If I turn down the output Volume, the 50Hz hum disappears, if the Gain is down and the Volume turned up it is still there. The Hum is all the same at both Channels,
The Box is properly grounded (I think) with the Input XLR's Pin 1 being connected to the Case and this point itself to the AC inlet ground.
I'm using shielded Wires for the output Connection. Anyone got some Ideas how to fix this? I read about 40 pages of this thread and all Metas about this topic and I'm pretty fed up with this thing keeping me from recording  :P

Title: Re: The official G9 help thread
Post by: MeToo2 on September 30, 2012, 04:35:14 PM
So I nearly got my G9 finished and have to sort out some Problems that appeared.
First of all I got some really annoying hum with [email protected] (Gain and Output closed) and [email protected] if Gain and Output are cranked up and a SM57 Mic is connected.
Beeing audible hum, theres no way leaving it there. As I only have 100µ on C14 and C15 it would be my first guess to change them to 220µ. The AC Voltage measured at C14 and C15 is about 0.9V (I guess that might be why it is audible  8)), but  I do not really trust my measurement equipment. HT Voltage is about 205V as I accidentally bought 2x 230V/15V transformers, so the second thing would be to change one of them into 230V/12V to get a decent HT Voltage.
My second problem is a [email protected]  if Gain and Output are turned fully clockwise. If I turn down the output Volume, the 50Hz hum disappears, if the Gain is down and the Volume turned up it is still there. The Hum is all the same at both Channels,
The Box is properly grounded (I think) with the Input XLR's Pin 1 being connected to the Case and this point itself to the AC inlet ground.
I'm using shielded Wires for the output Connection. Anyone got some Ideas how to fix this? I read about 40 pages of this thread and all Metas about this topic and I'm pretty fed up with this thing keeping me from recording  :P
205V HT is way too low. The TL783 won't be regulating at all: It needs about 5-10V drop out voltage which means at least ±250V on the input after the smoothing caps. So the PSU will be passing through 100% of the ripple from C14/C15 straight onto the anodes of your tubes (which explains all of your 50 and 100Hz problems). You need that replacement 12V step up transformer as your first modification. Replacing the 100uF caps with 220uF caps might help eventually on the margin to improve some residual low level hum, but they are certainly not the primary problem.
Title: Re: The official G9 help thread
Post by: tobi.pl on October 02, 2012, 12:04:59 PM
Well, this new transformer made all my problems vanish into thin air =) thanks a lot. Now it doesn't make any noise at all. Just pure Signal =)
I just have two more little questions. As one of my Output Pots was doa i ordered new ones, but oversaw that their power rating is just 0,05W instead of 0,1W. Can i use them as well or do i have to get some, that stand a little more Power. Second. As I built the whole unit in my prototyping case I need to get a decent Box for this one. Where did you all get these nice cases and Front Panels that I saw in the finished G9 threats.
Title: Re: The official G9 help thread
Post by: gyraf on October 03, 2012, 05:13:40 AM
0.05W post should be fine in G9.

Title: Re: The official G9 help thread
Post by: Luax on October 03, 2012, 02:54:35 PM
Hi Guys,

First the good news:
I'm typing this message with a smile on my face. The project was on break for a while after I had some humm issues on my second channel, that led to a lot of insecurities, depressions and what not…
This week I found strength again to rebuild some weak spots and now I have superb clean audio signal from both my mic channels! After I tested it with a matched pair of mics!

The bad news:
In my rebuilding I also changed the instrument cable for 3 seperate shielded cables. (maybe i overdid it in my enthusiasm) The problem I have now, is that there is a big ground humm in both instr. channels.
Could it be that using three separate wires don't ground well?

Any insights on the problem are more than welcome. (Before I screw anything up or make things worse)
Can't wait to have a pristine working G9!

Cheers!
Title: Re: The official G9 help thread
Post by: gyraf on October 04, 2012, 03:23:52 AM
The instrument input "mod" only takes two screened cables: One from input-transformer to the switch (that closes to tip terminal when no jack is inserted) - and one from tip terminal back to input capacitor. Shield on both from audio gnd (at input-transformer 0V) to jack ground (and ring if you have stereo input jack)

Jakob E.
Title: Re: The official G9 help thread
Post by: Luax on October 04, 2012, 06:29:59 AM
Thanks Jakob,

I already concluded that the schematic uses a stereo input were I was using mono.
Things are getting clear now. I'll change it after the weekend.
And hopefully bring another finished working G9 to this world.
I'll let everybody know in case of succes :)

All the best!
Title: Re: The official G9 help thread
Post by: tobi.pl on October 16, 2012, 08:47:27 AM
And here we are again. Got my new case, put everything in place, took some measurements and listened closely a last time. And again... hum. It's [email protected], but constantly. No matter how much gain and output. I have a 12V to 230V step-up transformer now (which improved it about 10dB), the voltage at the caps before the regulator is 320V after it it's 242V. If I turn power off the hum vanishes and the tubes still amplify for some time, so it should be from the power section. I already changed the TL783, the Diodes, 2W Resistors and C14 and 15 to 220µ 500V VishayBC (before 50 + 50 JJ) in the HT Circuit and still no improvements. What makes me wonder is the ripples, before the regulator it's about 1,5V and after it 1,05V but my multimeter is not the best one, so it could be less. Grounding Scheme is the pin 1 of the input xlr's at chassis bolt and this to power inlet ground, the output xlr's use shielded wires. I've also cut the traces of the DI inputs and wired it directly to the pcb. Any Ideas what else could be done? I want to do some orchestra and vocal recordings with it, so it should be as quiet as possible...
Title: Re: The official G9 help thread
Post by: Majestic12 on October 16, 2012, 10:30:08 AM
Hi there,
I am collecting parts for my G9. Is that Toroidal Transformers are must for G9? or can i use normal PSU transformers?
Regards
Dinesh


You can use normal transformers but the chances that you will get hum problems are much higher than with toroids
Title: Re: The official G9 help thread
Post by: tobi.pl on October 16, 2012, 11:24:23 AM
Hi there,
I am collecting parts for my G9. Is that Toroidal Transformers are must for G9? or can i use normal PSU transformers?
Regards
Dinesh


You can use normal transformers but the chances that you will get hum problems are much higher than with toroids

I'm already using toroids, so this can't be the issue. As it's level is all the same, regardless how much gain or output level i'm using, it isn't induced by the transformers (at least that's what i'm thinking).
Title: Re: The official G9 help thread
Post by: sonolink on October 22, 2012, 07:28:53 AM
Sorry if these are silly questions but I'm trying to do my homework with the schematic and fully understanding it.
-V1a and V1b are the same tube right? A and B are each half of V1 (same for V2). Please confirm.

-what does "ff" stand for in "Heater 12V (ff)". It also appears at the V2 tube filament.

- what do the small circles with a dash mean. Does the angle of the dash mean anything? (seems like some are angled differently than others.

-Some switches are marked "cw". Is that "clockwise"?

Thanks a lot for your time and help
Cheers
Sono
Title: Re: The official G9 help thread
Post by: psychedelnick on October 23, 2012, 01:11:05 AM
OK! I've got my G9 in the ballpark of good sounding. However....Noise! 2 kinds! Ch 1 is white noise, and 2 is a loud hum. Before I star grounded everything it was waaaayyy worse. How much difference does the MU shield make? More importantly Ch 1 is quieter than Ch 2. A LOT quieter. Checked all resistors (are 32 and 132 supposed to be 22R? I ask cause the value is 10K on parts list) but all others, diodes, caps, tubes. Good. All the right sh*t is heat sinked. Worried it could be a bad tranny? Is this common? Right out of the gate? Gonna test for continuity tonight but if anyone has a different idea, i'd love to hear it. Thanks!
Title: Re: The official G9 help thread
Post by: gyraf on October 23, 2012, 02:29:07 AM
Very common problem - have you looked through this thread for possible fixes?

Did you do the recommended mod with cable-mounting the front panel jack?

Have you tried rotating/moving power transformers?

Jakob E.
Title: Re: The official G9 help thread
Post by: sonolink on October 23, 2012, 05:45:36 AM
Well thanks a lot for answering, J
Title: Re: The official G9 help thread
Post by: psychedelnick on October 23, 2012, 12:46:09 PM
Hi Jakob, yes, I did the line mod.  I have been reading the thread all morning and have a few new ideas to try. On the upside, this thing sounds great! Thank you so very much for turning me on to the very addicting world of DIY! I also now have a clean quiet GSSL thanks to you and everyone on this forum.  8)
Title: Re: The official G9 help thread
Post by: MeToo2 on October 23, 2012, 03:52:23 PM
Sorry if these are silly questions but I'm trying to do my homework with the schematic and fully understanding it.

-V1a and V1b are the same tube right? A and B are each half of V1 (same for V2). Please confirm.
confirmed
Quote
-what does "ff" stand for in "Heater 12V (ff)". It also appears at the V2 tube filament.
heater filament. ff is traditionally 12v6. On tube pin out diagrams, the two pins of the end of the heater filament were each marked 'f' whilst the pin at the centre of the filament was marked 'c' (for 6V3 heaters) thus 'ff' = the two halves of the heater in series =12v6 heaters
Quote
- what do the small circles with a dash mean. Does the angle of the dash mean anything? (seems like some are angled differently than others.
generally these are just connections from a wire to a PCB track. AFAIK the angle has no significance
Quote
-Some switches are marked "cw". Is that "clockwise"?
confirmed
Quote

Thanks a lot for your time and help
Cheers
Sono
You're welcome.
Well thanks a lot for answering, J
Patience will be rewarded.
Title: Re: The official G9 help thread
Post by: sonolink on October 23, 2012, 06:14:13 PM
Thanks a lot for your fast and kind reply MeToo2 :)
Title: Re: The official G9 help thread
Post by: psychedelnick on October 26, 2012, 01:47:52 AM
Okay seems like a no brainer but, my switched line in on both channels stays on in mic, 48V and line. Does this mean I wired it wrong? Haha. Seriously though....
Title: Re: The official G9 help thread
Post by: gyraf on October 26, 2012, 04:56:46 AM
If you mean the front panel jack - that is NOT line, but Hi-Z input.

Line is through the xlr at back - only looking into ~10k in stead of 600R (that is, when "line" is selected).

Xlr inputs are disabled/switched out when front panel connector is used.

Jakob E.
Title: Re: The official G9 help thread
Post by: psychedelnick on October 26, 2012, 03:04:59 PM
AH! Thanks!
Title: Re: The official G9 help thread
Post by: Nick-ES on October 27, 2012, 11:00:37 PM
Hi,
I'am building a G9 at the moment and have some question
concerning C3, C103 Cap.

In the shematic there the value of C3 and C103 is 470 nf
On the PCB and component layout it is  220nf

whats the right value ? if both are possible witch one is better ?

regards
Nick
Title: Re: The official G9 help thread
Post by: haima on October 28, 2012, 01:17:01 AM
And here we are again. Got my new case, put everything in place, took some measurements and listened closely a last time. And again... hum. It's [email protected], but constantly. No matter how much gain and output. I have a 12V to 230V step-up transformer now (which improved it about 10dB), the voltage at the caps before the regulator is 320V after it it's 242V. If I turn power off the hum vanishes and the tubes still amplify for some time, so it should be from the power section. I already changed the TL783, the Diodes, 2W Resistors and C14 and 15 to 220µ 500V VishayBC (before 50 + 50 JJ) in the HT Circuit and still no improvements. What makes me wonder is the ripples, before the regulator it's about 1,5V and after it 1,05V but my multimeter is not the best one, so it could be less. Grounding Scheme is the pin 1 of the input xlr's at chassis bolt and this to power inlet ground, the output xlr's use shielded wires. I've also cut the traces of the DI inputs and wired it directly to the pcb. Any Ideas what else could be done? I want to do some orchestra and vocal recordings with it, so it should be as quiet as possible...

This sounds like the problem I had with my two G9s. The fix for me was to move the high voltage aka "B+" PS off the main board. Move the B+ rectifier, caps & regulator off the main board and building them on a small piece of vero/strip board. Run clean B+ to the main audio board.

The constant low level hum has completely gone from both my units once I did this - hum levels are now below the background hiss, which is VERY low.

I have scope photos & audio samples from before and after and it's very noticeable - I'll try and find them and post them some time.

Before I did the off board PS fix I noticed that if you unplug the mains and listen to the preamp the hum will go away for a few seconds - before the HT caps completely die. I then tried running the preamp with an external B+ and the hum was gone. So I built the B+ supply off board - hum gone.

I think I've mentioned the fix in a bit more detail in some previous posts in this thread if you have a search.

Good luck!
Title: Re: The official G9 help thread
Post by: Nick-ES on October 29, 2012, 07:05:40 AM
just a bump to all that that allready built the G9

Hi,
I'am building a G9 at the moment and have some question
concerning C3, C103 Cap.

In the shematic there the value of C3 and C103 is 470 nf
On the PCB and component layout it is  220nf

whats the right value ? if both are possible witch one is better ?

regards
Nick
Title: Re: The official G9 help thread
Post by: psychedelnick on October 29, 2012, 10:48:05 AM
My finished G9. Thanks Jakob and everybody else! What should I make now?  ::)
Title: Re: The official G9 help thread
Post by: gyraf on October 29, 2012, 11:22:25 AM

In the shematic there the value of C3 and C103 is 470 nf
On the PCB and component layout it is  220nf
whats the right value ? if both are possible witch one is better ?

Does not matter really (that's why I didn't change it). Put in whatever you have that fits the space.

Jakob E.
Title: Re: The official G9 help thread
Post by: sonolink on October 30, 2012, 09:42:27 AM
Hi all,
I noticed this difference between the schem and the board. I don't know if it matters but just thought I'd point it out. Also, in case I'd go for a point to point which should I follow? I guess the rev.8 schematic, right?
Cheers
Sono

http://img31.imageshack.us/img31/5165/c7network.jpg
Title: Re: The official G9 help thread
Post by: gyraf on October 31, 2012, 02:47:26 AM
Both should work very-very close to the same. If in doubt, follow the pcb, as this is known working.

Jakob E.
Title: Re: The official G9 help thread
Post by: sonolink on October 31, 2012, 05:32:44 AM
Ok. Thanks J :)
Title: Re: The official G9 help thread
Post by: sonolink on November 07, 2012, 09:06:15 AM
Hello again everybody,
http://img526.imageshack.us/img526/8188/outputo.jpg
This is my p2p layout of the Phase Reverse switch section. I've been checking and rechecking but I still feel insecure.
Would someone kindly check if it is correct, please? I would appreciate it very much.
The 6 pads in the center are for a DPDT switch. They are numbered left to right and correspond to the DPDT pin numbers
Cheers
Sono
Title: Re: The official G9 help thread
Post by: sonolink on November 12, 2012, 03:38:16 PM
Nobody? Ok, nevermind.

A question about the schem if you guys don't mind: the schem power supply reads: C16-18 3x25V 1000u. My question is: these caps are connected in series or parallel? I guess it's parallel but it never hurts to check

Thanks
Sono

EDIT: would a pair of these bridge rectifiers do for the G9? (I mean in a p2p build)
http://www.banzaimusic.com/DB107-Bridge-Rectifier.html?quantity=1
Title: Re: The official G9 help thread
Post by: gyraf on November 13, 2012, 02:51:25 AM
The reservoir caps for the heater voltage are in parallel - you can use a 2200u or a 4700u instead.

That bridge rectifier is a bit tiny - will probably do for the HT, and probably not for the heater voltage (use at least a 1.5A type here)

Jakob E.
Title: Re: The official G9 help thread
Post by: sonolink on November 13, 2012, 04:17:38 AM
Thanks for your reply Jakob. Do I need 1000V? I'm asking cos at that shop at 1.5A they have 560V max.
If it's not enough then I'll just go with 1N4007s on turrets then.
Please let me know what's best
Thanks again
Cheers
Sono
Title: Re: The official G9 help thread
Post by: gyraf on November 13, 2012, 05:12:39 AM
If you follow the schematic function you see that HT is at max ca. 500V peak, heater is max. ca. 40V peak, and phantom is probably max around 100V peak...

Jakob E.
Title: Re: The official G9 help thread
Post by: sonolink on November 13, 2012, 08:15:09 AM
Please excuse my ignorance but I don't understand what you mean by schematic function. Is it something you calculate? Is it indicated on the schematic? The only similar thing I could see was the ~60V indication on the PSU...tried also google but it gets more conf