MARSHALL: SupaFuzz Prototype, 0.15" Vero Layout

This is the early version of the Marshall SupaFuzz based on a Tone Bender MKI - it's close to the original layout used.  

Strangely it never had a coupling cap on the output, so best to add something decent sized there.  I've also seen a couple of photos with a power cap across V+ / V-  I couldn't see a value, but on an old pedal like this I would expect maybe a 25uf or 50uf - running of battery this is not exactly essential either.

Transistors are OC75, but use whatever you can get with decent amounts of leakage and moderate hfe, which is typical of OC75s.

Being a Tone Bender MKI variant, you can easily add a fuzz pot.  In this circuit the 470k resistor and the 47k resistor bias the base of Q2 (the middle one). 

The 47k resistor from the base of Q2 to ground, is normally where the fuzz pot sits in a MKI circuit.  Just check the standard Sola Sound Tone Bender MKI to see how this works - pretty easy to convert if you want to try this.  Alternatively, one could use a trimmer instead of the 47k resistor to dial it in and leave it set in a happy place.  This might be the best option.  

Unlike the other Marshall Supa Fuzz, the filter control here is actually a filter control...  

MARSHALL SUPA FUZZ PROTOTYPE - VERO LAYOUT

MARSHALL SUPA FUZZ PROTOTYPE - SCHEMATIC

Had to use AC128 in here, as I don't have an OC75 model in LTspice - anyway, you get the idea.

This is with a 100n cap on the output - makes no difference to the response.  Filter takes off a lot of high-end.