Well, I finally bit the bullet and bought a FatRAT. Traced it and have added the details to my Multi-RAT schematic. The FAT switch mod is kind of interesting. This confirms p.eat's report but note the output JFET is a J109 in my unit. D4 is BAT41. Also worth noting is that the PCB layout is essenti...

the rat isn't a design capable of what you want from it.

I'll see what I can come up with in the next few days, will move that discussion over to the proper forum if I do

the bax IS all tl072, the gain pot IS dual-gang ... however the EQ is different seeing as you have a bax treb/bass and a three knob parametric mid ... plus the boost and cab sim stuff ... and charge pump. also, they split the pcb into two boards. I think the pedal suffers some from the detent pots w...

which parts of the schematic are you questioning the validity of?

I did sort of say something via facebook to him about wanting him to do a pcb. he probably would have done one anyways, because why not?

yes, he is correct according to the product manual

r6 - 47K
r7 - 1M
r8 -1M
looks like low gain is 47K, high gain is 1M in series, med is 500K in series

r21 4K7
c18 1u
could use c8, c15, c17 and of course much better shots of the bass pot area

well the gain switching is in the feedback loop of the first op amp adding series resistance to the gain pot and that should be easy enough to suss out, blurred or not ... R6, R7, R8 in the pictures

that should shorten your work

my notes show the fat switch to add a 6u8 to C7 and the MOSFET clipping to be bs170+1n270 pairs

they're not the only ones to mess with the values in a uni-vibe alike, I just haven't seen a gut shot of an original for comparison and that bit stuck out to me.

I wonder if Earthquaker transposed the 4n7 and 470p or if the schem is wrong ...

re the bypass: http://www.muzique.com/schem/bypass.htm

if I had to guess, probably supreaux deux or similar with a small audio transformer to "saturate" with the final jfet stage. would know more with better pictures of both sides of the PCB

due to the high gain and large amount of off-board wiring, it is going to be noisy and probably more so than a real one which are known to have the same issue. when I built the last one I did, I used higher quality op amps and rotary switches. the only wiring I was really able to shield effectively ...

you may end up removing the jacks to get the PCB out

that said, its probably humming because an electrolytic has failed.

NM ... known info ... will work on the unknowns ... really wish there was an edit function.

tracing out the pot
looks like your power filter cap, 1n4001 protection diode, and pin 1 of the pot go to ground at the same spot.
pin 2 goes directly to output
pin 3 to a 1uf 50v cap

that harness job is dead sexy

another year went by and the answer is that if you follow the schematic and trace things out, it works. if you rely on the pictures in the book with parts circled you get a broken pedal where the tone knob does weird, weird things.