Toying with the FY-2 fuzz circut is loads of fun.

Although I still stand by the virtues of a variable scoop, here's a simple one you can play with.

First, thanks to Stuart Castledine for the basic drawing that I "re-arranged".

1) As per usual, I prefer the Mosrite FUzzrite implementation of the Fuzz control, that pans between two outputs (Tr1 and Tr2), but I used a 100k linear pot insterad of the stock 50k, to provide more contrast between the two extremes.

2) The .047uf cap that straddles the 100k resistor tied to V+ normally provides an emphasis to the mids and top end, and underplays the bottom.  Lifting one end of that cap will give you more bottom.  I just used a SPST toggle, although you can feel free to play with the value of the cap.

3) I installed a 3-position tone control that provides three very different characters to the tone.  As per the stock FY-2 circuit, the 10k/.1uf/15k network connected the Fuzz pot and the Volume pot.  What is different here, is that the 1000pf cap that would normally tie those two controls is left with one end hanging.  The common of the toggle goes to the input of the volume pot, as does the 15k resistor.  The two outside lugs of the toggle go to a 47k resistor (added) and the 1000pf cap.  In the middle toggle position, when neither the cap or 47k are connected, you get a lowpass filtered fuzz that is pleasingly gnarly.  In the outside position where the 1000pf cap is connected, you get the classic FY-2 big-n-buzzy sound.  In the other outside position, where the 1000pf is disconnected and the 47k replaces it, you get a "throaty" sound with lots of lower and middle mids, although it still retains the lows from the 10k/.1uf/15k network that are mixed in with the full signal carried by the 47k.  The three positions are of relatively similar volume levels.  IN tandem with the fuzz control, a lot of tonal variety is attainable.

FWIW, I built this with a pair of 2SC644 transistors with hfe around 240.  Pleasingly nasty.  I'll box it up and see if I can throw a video together.  If you don't want to wait for proof-of-concept, throw one together.  It will take you an hour on perf.  Well worth the time investment.

Cool...