The official G9 help thread

[mamiti]

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

 

[gyraf]

Any suggestions, please?

best guess wrong type OEP transformers. Measure ratio?

Jakob E.

 

[mamiti]

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

 

[mamiti]

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

 

[audiophreak]

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

 

[Graph]

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.

 

[g9builder]

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

 

[Stagefright13]

Haha I love the missile switch. And have seen them on drag bikes. Cool touch! Nice build with good sinks too.

John

 

[gyraf]

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.

 

[bpucekov]

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

 

[g9builder]

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

 

[wmtunate]

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

 

[g9builder]

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

 

[audiophreak]

Thanks Stagefright13, now I just gotta get my head wrapped around face plate graphics... ;D

 

[Rob Flinn]

the TL783 is available from RS, but there is a minimum order of 5

 

[MerlynMetal]

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.

 

[diyfanatic]

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.

 

[g9builder]

-" 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

 

[chrispbass]

-" 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

 

[g9builder]

Chris,

Many many thanks - appreciated greatly!


Ian