GTFO - Full tube high-gain pedal (2x 12AX7)

[Ripthorn]

Well, I have mine working.  I love it!  I have the marshall tone stack on the end as I intend to run this into the power amp in of one of my amps.  I have a 5751 in the V1 position, so I don't get quite as much gain as is possible, but I will get another 12ax7 soon enough.  I may have to do one using Groovenut's layout.  Anyway, I don't have the enclosure done yet, so no pics yet, but they will come.

[PetMan]

is it working now?

with a 7025 would be Gr8t

[PetMan]

Hi,

would like to divide the Gain with a switch and a resistor,  to make a crunchy channel,
how  would you procede ?

regards

Pet,

[Groovenut]

Hi,

would like to divide the Gain with a switch and a resistor,  to make a crunchy channel,
how  would you procede ?

regards

Pet,

Probably the easiest way is to place a 82k - 100k (or to taste) from the wiper of the gain pot to ground on a switch. Note this will also reduce the bass response when engaged.

[PetMan]

Thx lawrence ,

i'll try that , i'm making mine based on your layout actually , still not received the pcb ! i've bough this box  to make space
http://www.ebay.com/itm/261045281109?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

i'm isolating the irf on a big heat sink  away from pcb on the box side  witch is all aluminum , i've separated this box in 4 channels to add  a boost mxr and others fx !

i know you set around 320Vdc on C11 , do you feel it enough now you made it ?  

regards

[Groovenut]

i know you set around 320Vdc on Drain of the switcher, is it enough now you made it ?

Yes I think so. I've experimented with the B+ levels quite a bit and like to run mine around 280Vdc. It gives it a little more compression and browns the tone ever so nicely.

[PetMan]

280vdc on C11, i'll try that, i'm more crunch edge guy, Warren haynes sound kind of!

thx Lawrence for the advices , i got somes Nos  12ax7 phillips and GE, got somes 12 ay7 and 12 at7 too, did you tried those ones?
regards

[Groovenut]

280vdc on C11, i'll try that, i'm more crunch edge guy, Warren haynes sound kind of!

thx Lawrence for the advices , i got somes Nos  12ax7 phillips and GE, got somes 12 ay7 and 12 at7 too, did you tried those ones?
regards

I havent tried anything other than current production 12AX7s, but if you are into lower gain sounds using a 12AY or 12AT in V1 would probably sound ok without having to alter the circuit values. Realistically if you wanted to run the lower gain tubes you would need to adjust the circuit values to accommodate them.

[PetMan]

Agree,   With lower gain tube it might  get  saturation quicker  in V1, in V2 this could be to experiment  for output level !

Thx Lawrence,

P,

[PetMan]

can't get over 240v C11 for the moment     , it works but sound euhhh ,  pants,  had somes issues with  tone stack,  nothing serious !

waiting for an order of uf4007 in the place of by255 i had avaible,   i hope  will fix this problem .

[PetMan]

all is working well, the UF brings lot of more current,  having space into my big box, i bough two big can JJ capacitor, 2x32uf to remove switching bjt pulses , would help i lil bit to improve tone!

thank Lawrence for your help!

i appreciated

[gtudoran]

Excelent PeteMan, glad to see that this project is still alive... i didn't build a pedal since ... 2 month ago.

Best regards,
Gabriel Tudoran
Analog Sound

[J0K3RX]

Excelent PeteMan, glad to see that this project is still alive... i didn't build a pedal since ... 2 month ago.

Best regards,
Gabriel Tudoran
Analog Sound

I am thinking of making a couple similar to the GTFO but based on the ENGL E530 and one based on the Bogner Triple Giant Sharp channel both with full tone stack... What do you think? I could almost do some modding to the GTFO layout and probably get either one or pretty close...

~Jim

[PetMan]

thx alot this thread has been  a great help ..

have nice hollidays ,

Regards

[PetMan]

making another one for a pal, i would like more gain, i'm using the pot about  9 , around 200k ,  witch resistor  would you change with a 200k less on the interstage ? plates?

thx alot

[J0K3RX]

making another one for a pal, i would like more gain, i'm using the pot about  9 , around 200k ,  witch resistor  would you change with a 200k less on the interstage ? plates?

thx alot

With these high gain tube or jfet preamp disto pedals most guys including myself use a tube screamer in front of them to give them a little more gain/bite and tighten up the bottom end etc.. I know this one is not really a preamp per say but it's based around one so I would do the same with it rather than try to make many changes to it to try to squeeze more gain out of it.

Just my opinion...
~Jim

[PetMan]

Hi,

Thx really, but don't bother, i just checked patch jacks, one of them between stompboxes was eating all guitar tone and gain, i've just thrown it in the waste, and now all my gain came back!

i'll try my okko diablo with ,  nice hint

thx

P

[PetMan]

hello friends,

i endeavoured about this device a lil bit,  after  adding JJ 32uf to rail, i bypassed them with 0.1uf 600v films ones (old mallory i had), and it added grit, clarity to hight and medium tone, opened the headroom  and sustain,  its almost singing now!

i've put 340v on rail,  making edgy sound to brown with gain pot  acceptable !  this circuit beeing almost slo carbon copy!

thx alot for you help!

[PetMan]

got a lil error on Voltage divider  with slo tone stack ,  on the vol 1M pot wiper, a 470k to ground before the 220k,  is this 470k shouldn't be after the 220k on output junction to be a voltage divider?

thx

[Hilli]

The newest members of my GTFO family.    One is for a friend of mine.