The official G9 help thread

[Kingston]

1) Could someone post again the fix for the high frequency oscilation? the JPG links aren't working
2) Anyone used flat cables to connect between the main PCB and the Front Panel one without problems?
3) I'm planning to use the OEP for output and the VTB9045 for inputs, is this help to get rid of the low cut problem with OEPs in and out?

1) http://www.gyraf.dk/gy_pd/g9/G9-EDIT.GIF

2) I would not use flat cables. You might get lucky and not have problems, since most of it is just for the phase switch balanced audio, relay 12V and 48V. But there's the somewhat critical high impedance area: gain pot. You might even want an extra shield around those wires.

3) forget all OEP's if you want the low end. They simply aren't cut out for the task. Get a big 2:1 or 4:1 output transformer from edcor instead. same price, much better sound and it won't "duck and cover" when trying to reproduce bass.

 

[bpucekov]

i used flat cable for connecting main pcb with front pcb whitout any problems
no any noticable hum or buz
puc

 

[flintan]

Which is the correct connection for Edcor XS1100 in a G9? I believe the primaries should be in series and the secondary in parallell but I find two different schematics of the pins phase designation:
http://edcorusa.com/Products/ShowProduct.aspx?ID=547
http://purusha.smokinggunrecording.com/MEQ5/XS1100%20Specification%20sheet.pdf

Which is the correct connection? (I know the drawings/schematics don't show primaries in series but look at the phasing information.)

 

[flintan]

Ok. This picture in comparision to LL5402 data sheet does not correspond with the picture at the end of this page but is the same as this one.

Am i wrong or is the phasing info on edcor's site wrong?? Or have they changed the pinout of XS1100 recently?  ???

 

[Kingston]

Don't bother with the XS1100. It's physically too small to handle G9 output. So is the LL5402 actually.

A much better fitting transformer is XSM2.4K/600, or for even better drive capability but slightly lesser gain, the 4:1 ratio WSM10K/600 (would be my pick) or XSM10K/600.

 

[shabtek]

I somewhat agree w/kingston regarding core size.; there have been many pleased builders using the suggested xfmrs though. I've built 2 of these. best with DI bass has a heavy 600:600:600 wired 2:1 opt. The circuit is useful with any transfmrs, even oeps but maybe not always for solid lowend-- there is a difference. I've a shelved board with the XS1100...I was not real confident in this trans so it went back in line (never heard it). otoh people seem to like it it in that gyraf passive eq. I don't think you'll go wrong with an xsm in the out. And I would not say to forget the 1100 either.

 

[flintan]

Ok. I will try XS1100 first, think i've got it wired correct now.. Although i also have some XSM 10k/600 to try later if the XS is too weak..

 

[Kingston]

otoh people seem to like it it in that gyraf passive eq.

That's because there is no impedance mismatch problem with the E88CC tube in SRPP configuration. It can happily drive lesser transformers.

Not so with the 12AU7 in SRPP. You'll have a constant bass roll off with it.

A worthy upgrade to boost G9 capabilities is to simply take the gyraf pultec SRPP, and slap it as the G9 last gain stage. Then change all heater wiring and PSU to handle 6,3V filaments.

Call it G9 mkII.

 

[Kir_For_Pleasure]

I have problems with the phantom power, xlr out pin 2&3 just measures 8,2v ! At the Emitter of the tip 121 i measure 12v should it constantly be 48v there ?

 

[flintan]

Yes you should have 48V at the emitter of TIP121. If you have trimmed it to that voltage? Measure voltage from the power transformer and forward trough the phantom power psu and you shall find where the problem is.

 

[Kir_For_Pleasure]

something is seriously wrong flintan ! nothing happend when i turn the trimmer ?? ok must go in deeper in troubleshooting !!

 

[flintan]

Just measure AC V at transformer, then DC after the diodes D8-D12 etc and compare to the schematic.

 

[guitarguy12387]

Hey everyone! My turn to play the troubleshooting game. Well i just fired up my first G9 the other day. It passes signal well, but i have some hum/buzz. Before tackling that, i'm also having an issue with my phase switch. When off (ccw) it passes signal fine (save the aforementioned hum/buzz...). When i switch the phase switch on (CW), the signal disappears (as does the hum, actually). Anyone have any ideas? Thanks in advance.

 

[Harpo]

Maybe end-stop washer placed to pos.2 before turning the rotary switch full ccw, now switching between pos.2 and 3 instead?

 

[guitarguy12387]

Aaah yup hah! Forgot to adjust the washer. Thanks! AND took a closer look at my ground scheme and fixed it which solved the hum! Thanks!

 

[microc]

Hi,
one last question, in the circuit description, Jacob mention that C7 is 10uF/63V AC (ergo 100VDC). Is all the polyester caps listet with AC voltage?!?
C2,102  22OnF 250V POLYESTER    INPUT DC BLOCK
C3,103  470nF 250V POLYESTER    INTERSTAGE V1A-V1B
C4,104  1u5 250V POLYESTER      OUTPUT DC DECOUPLING V1B
C5,105  470nF 250V POLYESTER    STAGE1 OUTPUT
C6,106  68p 50V CERAMIC        BW LIMITING
C7,107  10u 63V POLYESTER      GAIN DC DECOUPLING
C10,110 22OnF 250V POLYESTER    SRPP INPUT DC BLOCK
C11,111 470u16V RAD.EL.LYT      SRPP CATHODE SHUNT
C12,112 100n 63V POLYESTER      SRPP CATHODE SHUNT
C13,113 4U7 250V POLYESTER      SRPP OUTPUT CAP

I know, it's a pretty lame question...

 

[flintan]

My turn for trouble and stupid questions.. Fired up my G9 today and there was a cloud of smoke somewhere from the heater psu, i think it was from the rectifier diodes D13-D16.

I had some power transformers with single secondaries so i connected both the backward transformer, heater psu and pp psu to the same winding. Is there something obviously stupid in doing that?

Like this:

 

[Harpo]

My turn for trouble and stupid questions.. Fired up my G9 today and there was a cloud of smoke somewhere from the heater psu, i think it was from the rectifier diodes D13-D16.

I had some power transformers with single secondaries so i connected both the backward transformer, heater psu and pp psu to the same winding. Is there something obviously stupid in doing that?

There is a reason for dual secondaries.
Shorted out D15 (look where 0V for heater and 0V for phantom connect).
Not sure if D13 (if the transformer can deliver more current than the diode can take) or the mains transformer (cooking because of shorted secondary for every 2nd halfcycle) will die faster.
-Harpo

 

[flintan]

Yes of course..  :

Sometimes the most obvious and easiest things can be a mess. Both D13 and D15 are fried to short circuit but i think the transformer are still ok.

 

[Harpo]

Only D13 should be blown. D15 is protected by the short, so this one is probably alife.