The official G9 help thread

[flintan]

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..

 

[rotation]

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

 

[Harpo]

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.

 

[rotation]

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.

 

[Harpo]

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.

 

[rotation]

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

 

[Dnukas]

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

 

[Harpo]

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.

 

[audiophreak]

 

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 ?

 

[riggler]

Nope it's been there all along.

 

[audiophreak]

Thanks, ... must have missed that little detail... :-[

 

[Kir_For_Pleasure]

My finished G9, ended up with the oscillation mod, think i opened it up 5 times for troubleshotting  not a easy one !!

 

[audiophreak]

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 ? 

 

 

[Rob Flinn]

Where has the "G9 oscillation problems - solution"  thread gone to.  The link on the G9 meta seems to be duff ?

 

[audiophreak]

Hi,
  I have this graphic, not sure this is what your looking for.

 

[Rob Flinn]

thanks audiophreak that should do it.

 

[audiophreak]

Glad to have helped ...  so many here have helped me  

 

[Tuxa]

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

 

[nashkato]

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 ?

 

[Stagefright13]

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