The official G9 help thread

[gyraf]

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.

 

[dinesh]

Thanks Jakob.

 

[dinesh]

Hi there,
I have a couple of Sowter 9145 & 8751 Transformers. Can I use these in G9 or 1176?
Regards

 

[ioaudio]

[quote author="dinesh"]Hi there,
I have a couple of Sowter 9145 & 8751 Transformers. Can I use these in G9 or 1176?
[/quote]

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

 

[analogical]

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

 

[analogical]

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.

 

[gregcs1]

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

 

[Black Dog]

[quote author="gregcs1"]Hello.

My G9 is almost complete[/quote]

Nice one :thumb:

[quote author="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?[/quote]

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

[quote author="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?[/quote]

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

You will need something like this:

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

 

[crazytooguy]

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!

 

[gyraf]

Yes, the Hi-Z input will work even without input transformer

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.

 

[gregcs1]

Can be done like this?

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

 

[gyraf]

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.

 

[ChrioN]

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.

 

[gyraf]

..exactly..

 

[radiance]

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......

 

[needlz]

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.

 

[radiance]

Where's the official G9 help? :wink:

 

[gregcs1]

Can all these connections (rounded with circles on picture) be connected with zero ohm resistors? (,25W, 5%)

 

[gyraf]

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.

 

[gregcs1]

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.