The official G9 help thread

[LolloTheMad]

Lundahl LL5402, connected as shown in the attached picture to obtain a 2:1 ratio.

 

[gyraf]

Why not connect it like the original G9 (look at layout) - windings connected series-series?

http://gyraf.dk/gy_pd/g9/g9_pcbs.pdf

If you connect in parallel, you are looking at entirely different inductances to drive, and I'm running this tight already..

Jakob E.

 

[LolloTheMad]

Isn't your schematic a series-parallel configuration? The output is connected in parallel and i would get a 4:1 ratio. Am i wrong? I connected parallel-parallel to mantain the 2:1 ratio, but i didn't think it would be that bad for the bandwidth.

 

[gyraf]

The pcb is known working, small details different from schematic. Like transformer pin numbers and ratios..

Jakob E.

 

[LolloTheMad]

Ok, if you think this could be what is causing my issue i'll cut the traces and wire it manually. Thanks alot for the help, Lorenzo

 

[LolloTheMad]

I connected the output trafo as you suggested and this is the result. It looks pretty good to me. Is this in line with other g9's?
Thanks again, Lorenzo

 

[gyraf]

-3dB points at 30Hz and 30KHz are definitely in the right area. This was probably it..

Jakob E.

 

[lestatdog]

New to this tube DIY but learning a lot. Ive read through a few pages but haven't found this answer, it's probably here some where?

Is there anything special about using the 2 power transformers, would this work with a 250v HT power supply with a 6v heater supply?

 

[LolloTheMad]

Hello again, just a quick answer to be sure about the wiring.  I connected the LL 1528 input transformer as showed in the picture, is it correct?
Thanks in advance, Lorenzo

 

[tamtamstudio]

G9 phase issue. I would like to share this issue occurred me in my G9.
Put same sine on signal to left or right channel and reverse phase. Normally I can't see any differences, but with G9, on phase reverse, the signal is higher than normal phase.
On both channels. I can't explain me what's up.
The sound seems good, but with a strange cut on low-end, could be OEP traffo?
Any suggestion?
thanks in advance, Corrado

 

[patzo]

Hi . I finished my G9. But I want a little more gain. Now is 53db. I noticed if I  reduce R26 from 47k  to 27k there is more gain. Or can I increase R9 to 150k – is that  going to increase the gain. Which one of this solutions is better. Maybe if I  reduce R26 it will affect lower gain settings but that’s OK for me if it does’t affect something else.

 

[gyraf]

I don't think you can push more gain without compromizing frequency resoonse..

Jakob E.

 

[liquidcolor]

Finished my first G9. About to start on the second. Wonderful sounding unit.

 

[gyraf]

Darn, it looks good too...!  8)

 

[TillM]

When I start building my own studio gear and finding our lovely forum I always think to myself: "Someday, when I've enough experience, maybe I can build the Gyraf G9"

I had always much respect for Tube buildings (and still have).
So it was clear for me, that I first will build some 500-modules and FET-microphones until I start in the tube world.
After some M49 and U47 builds, I finally realized it !
I buy the pcbs two years ago. When I had some resistors or capacitors laying around from other projects, I soldered it to the PCB.
When I find some nice tubes, who fit the G9, I buy them and so.

Last week I placed my last order. A nice case from Frank.
Now it's done. Lundahl Transformers in and out and NOS Phillips 5814a tubes.
Everything works perfect and I'm totally in love with this Pre.
The Led should be purple, but they turned out pink.

Thanks Jakob, for sharing your knowledge to our community and this nice Preamp !

 

[gyraf]

*like*

can I ask - where did you get the small/pointer knobs?

Jakob E.

 

[TillM]

Thank you so much ! Means a lot to me.

Sure you can ask.
These are from Mentor.
Get them here.
https://www.reichelt.de/potentiometerknopf-fuer-achse-6-mm-schwarz-zeiger-20-6-sw-p42118.html?&trstct=pos_7

You just need a cap for it. I choose this one.
https://www.reichelt.de/abdeckkappe-fuer-knopf-20-zeiger-20-schwarz-deckel-20m-sw-p42096.html?&trstct=lsbght_sldr::42118

 

[gyraf]

Nice. We like Mentor...!

 

[13bernep]

Hey guys,

I just want to make sure that both my transformers are wired to the pcb correctly so I won't destroy my preamp. My transformer windings (both, the 115+115:15+15 and the 115+115:12+12) are as follows:

Prim: blue-white and violet-brown
Sec: black-red and orange-grey

Transformers are intended for EU-operation (230V mains voltage). I'm using a single pole switch (SPDT) where I‘m only using two of the three lugs - yielding a SPST action (connection on or off). Here are the connections the way I figured them out - hope I‘m right:
I would connect the 15v trafo's blue wire with the switch (a wire from the phase is connected to the switch as well) and the violett wire directly to the neutral conductor. The brown and white wires are connected together. The black and the red wire go to the terminal marked 15VAC/1A. The grey and the orange wire go to the terminal next to c23. Also the 12v transformer's sec black/orange and grey/red go to this same spot. So I actually have three wires (orange from 15v transformer and black and orange from the 12v transformer) that come together to one hole and three (grey from 15v/grey and red from 12v) to the other hole at this terminal. The 12v transformer's blue and violett wire will go to the terminal named 220v while brown and white are again connected together.

Any help would be deeply appreciated.

 

[gyraf]

Prim: blue-white and violet-brown
Sec: black-red and orange-grey

We need to know
1) what is your local mains voltage (your location) and
2) what exactly is marked on the transformers. Phase matters: If you run 230V to the primaries, the winding must be connected in series, observing correct phase. If transformers are marked exactly as written above, then the intrinsic information is: white connects to violet, black is live and brown is neutral (blk/brn can off course be swapped).

Jakob E.