The official G9 help thread

[Audio_Ape]

@A-Ape        do you have ps loaded with rest of circuit; you should have some kind of load or voltage may be high\regulators may fail\to regulate

No, no load. I checked with the schematics and saw that at C15 I should have 245V, so that's where my build stops.

If you measuring PSU only without the rest of the circuit, then it should be correct. WIth the load (tubes) voltage should drop.

Ok, cool thanks! I already thought so but wasn't sure as 30V difference seemed a lot for me.

 

[Alexandru marian]

It will definitely drop, no worries. 


If anyone is going custom trafo or shopping among ready mades (there are a couple that work) see if you can have it built with a magnetic shield. More expensive but worth it!! 

Heater winding could be 12V rather than 15, it should reduce the heat generated by the regulator. Right?    10V should work too (makes 14V DC before the reg)

Have a  separate winding or small trafo for the phantom, you can't feed both heater and phantom supplies from the same tap (the bridge will blow, don't ask me how i know ) 

 

[Alexandru marian]

Gave it a test at 10V.    The "bad"part is that the DC drops to 11.68V under load (3A winding), which is still close enough (I've read +/-10% is acceptable).  The good part is the regulator heatsink (a chunky computer heatsink, full copper) stays really nicely cool, while with a 15V input it goes to 50 deg C and really burning with ECC99 tubes.    I guess 12VAC would be a nice compromise between power dissipation and "headroom"

 

[skeld]

Hello, after using my G9 for 3 years, I started to deal with slight channel bleed from CH1 to CH2, but not viceversa. I checked the capacitors, but they are OK. Do you have an idea, what might go wrong? Thank you.

 

[PitchFork38]

Hi everyone !

I built a G9 (two channels) with OEP transformers and JJ ECC82 tubes.
All caps are Wimas MKP.

On both channels, outputs are weak but clean  and if I put the Gain and Output on 10/10, in my DAW it's like there is a Limiter who cuts everything above -8dB, I can't go higher.

Do you think the problem is from the Line input of my soundcard ? (Presonus audiobox 1818vsl)
I know it's not a good one but still.

All voltages are good and I checked all resistors and caps values before soldering them..

Thank's

Pierre

 

[Deepdark]

If you put your gain at 10, i don't know your input, but it seems a pretty high level, it's possible your soundcard dont like it. Try getting your signal at about -10 dbfs, it will helps.

 

[Voodoobeat]

Hi,

my G9 is working and its great, but i still have some noise issues around 100Hz.
So i figured out i have to check for ripple on the power supply. Can someone tell me how to do this?
thanks a lot

 

[PitchFork38]

If you put your gain at 10, i don't know your input, but it seems a pretty high level, it's possible your soundcard dont like it. Try getting your signal at about -10 dbfs, it will helps.

Hi  Deepdark
Yes, you right but I wanted to say that even with Gain at 10,  I can't get close to 0 dbfs. Everything is cut from -8dbfs. It's not normal, right ?
When I use the mic preamp of my Presonus, I can have a higher level.
I suspect Line Inputs of my Presonus, I have to try a different audio interface.

Pierre

 

[Deepdark]

Hi,

my G9 is working and its great, but i still have some noise issues around 100Hz.
So i figured out i have to check for ripple on the power supply. Can someone tell me how to do this?
thanks a lot

How is your ground scheme?

 

[Alexandru marian]

Voodoo, your hv regulator might not be working.  Measure the ac before the bridge then dc at every point after, including each zener.  Try not to fry yourself while at it!

 

[Voodoobeat]

How is your ground scheme?

I've connected all XLR-Grounds, at Input1 to its inlet. Power- and Transformer-Ground go there aswell.
Pcb-Ground is connected only at XLR-Input1.  In the analyser the 100 & 200Hz is way above the 50Hz so i dont think its a grounding problem.

Voodoo, your hv regulator might not be working.  Measure the ac before the bridge then dc at every point after, including each zener.  Try not to fry yourself while at it!

its working, there are 246V at the Tl783 output and 238 after R37.
I've just changed the regulater and  c14+15 to new 220uF ones, but its still there.

thank you,

voodoo

 

[Alexandru marian]

It might be appear to be working while it is not.  Really need to post everything: AC, DC after the rectifier and what is happening after each zener. 

 

[Voodoobeat]

It might be appear to be working while it is not.  Really need to post everything: AC, DC after the rectifier and what is happening after each zener.

Hi Alexandru,

now i had a moment for some measurements without frying anything and thats what i got. All taken after the parts, hope this helps .

• AC: 247,4V
• rectifier: 308V
• C14: 296,2V
• TL783-Input: 302,7V
• D3: 264V
• D4: 245,4V
• D5: 246V
• TL783-Output: 246V
• C15/HT: 238V
  

cheers,

voodoo

 

[Alexandru marian]

That looks good I think. When the regulator is dead or wonky, the zeners will start dropping the voltage instead and you'll see large differences after each one.

Try doubling the capacitors with the old ones.  400uf will surely reduce the 100Hz by a few db.  Might be enough.  I use 470 for the first and 400 the second.   

 

[Deepdark]

may you tell us how you ground the unit? It has a great influence on the hum performance. You should do it has stated on the schematic.

 

[Voodoobeat]

That looks good I think. When the regulator is dead or wonky, the zeners will start dropping the voltage instead and you'll see large differences after each one.

Try doubling the capacitors with the old ones.  400uf will surely reduce the 100Hz by a few db.  Might be enough.  I use 470 for the first and 400 the second. 

good idea, but its still there damm.  ive attached a picture of what it looks like in rmes digicheck at full gain

may you tell us how you ground the unit? It has a great influence on the hum performance. You should do it has stated on the schematic.

I've connected all XLR-Grounds, at Input1 to its inlet. Power- and Transformer-Ground go there aswell.
Pcb-Ground is connected only at XLR-Input1.  In the analyser the 100 & 200Hz is way above the 50Hz so i dont think its a grounding problem.

 

[Voodoobeat]

now i've tried 470uF Caps and the hum got some dBs louder.
Any ideas what it could be?

thanks,

voodoo

 

[APL]

I may have misunderstood, but you mention grounding transformer to input 1. Not sure which transformers your talking about but I didn’t think there should be any separate connections. As I understand it audio transformers are grounded via the PCB connection only. I didn’t think power transformer was grounded. I used  2 toroid’s don’t know about other types.
Other more experienced people may like to comment on this.

 

[Deepdark]

Could you post some picture of your build, please? I have a hard time figurating your wiring

 

[Voodoobeat]

Hi,

Sure. The wiring is horrible at the Moment, i hope you can figure it out.
Its also the only picture i have right now.

The power transformer has an extra ground wire, which i've connected.

Other behavior ive noticed is, when Power is turned off the hum disappears and signal is clean as long as the caps unload.
The hum also got a bit louder with higher capacitator values (c14&15).

Thanks guys,

Voodoo