Loosely based on the fuzz face circuit with the addition of a 6 position frequency selector. It is actually a hybrid. Up front it has a Germanium transistor (40 years old, pulled out of early sixties Italian keyboards) for smooth clipping and followed by a high HFE silicon transistor for power. It is an exceptionally loud pedal. You can use it on any amp and it certainly will work well with any Marshall plexi-amp, or a Vox as well. This is the first fuzz pedal on the market that gives you that kind of flexibility. The best way to describe it is to listen to the clips that are posted. Once again, bear in mind that I only have a limited number of those transistors with the proper HFE.