Park Custom Shop Supa Sound

The Supa Sound is Marshall's early fuzz circuit, the one known for carrying more bass than the fuzzes it shared a decade with. That extra low end is its whole character: it sits thicker under a guitar than the thinner, more nasal fuzz voicings of the same period, which is why players who find most vintage fuzz too brittle tend to end up here. Park builds it in the Custom Shop around PNP germanium transistors.

The addition is a Transistor Bias control, and it addresses a real historical problem. Germanium transistors are sensitive to how hot they are run, so in the late sixties and seventies finding a unit biased the way you wanted meant working through a lot of pedals. The Bias pot puts that in your hands instead: run the transistors cold for a gated, spitty sound, warm them up for something smooth, keep going and it turns spitty again, with a lot of usable ground in between.