“The reissue Foxx Tone Machine uses Fairchild 2n3565
are volume, sustain (this is gain — just like the Big Muff) and fuzz. Counterclockwise you can get Fuzzrite tone all day,
clockwise and your sounding like a Big Muff Pi. This is what so great
about this pedal — it covers so much range. On top of all that range, being
able to add the octave up, is just a beautiful psychedelic experience. The flip switch is for the octave on and off.”
Apparently the reissues are now discontinued and here is a review that I found interesting.