The official G9 help thread

[ilikeit]

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??

 

[maxime]

did you try the instrument input ?
what are the results?

best
maxime

 

[josh]

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?

 

[ilikeit]

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???

 

[jdr]

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, 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:

 

[rascalseven]

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

 

[rascalseven]

Bump??

:sad:

JC

 

[Godders]

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

 

[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

 

[Godders]

Cool, glad it helped, now you can enjoy your G9! :thumb:

Yeah the pics will stay.

Cheers

 

[MrZpliff]

[quote author="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[/quote]

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...

 

[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

 

[MrZpliff]

[quote author="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[/quote]

Ok ! Thank's ... I use mine as a DI very often and I love the sound :grin:
so I won't try that one......

 

[objectx]

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

 

[gyraf]

240V-versions should work fine as direct-subs for 220V-versions...

Jakob E.

 

[objectx]

thanks jakob, much appreciated :grin:

 

[analogical]

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

 

[gyraf]

Are you sure you have ground present at output xlr's? Usually we make a link bar across all XLR pin1's...

Jakob E.

 

[madreza]

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 !

 

[madreza]

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