This is a simple yet VERY effective 1 transistor subtle to high gain boost that can push any nice valve amp into saturation and has a very usable 1 transistor active tone control. The FREQ foot switch takes you from a type of treble/mid boost to a full linear boost. Full frequency response makes it usable for both guitar and bass and you can get from the Shellac type “clang” right through to BIG “stoner” type bottom end. This version is now in the small MXR size enclosure but sideways like some ZVEX pedals ? It’s a CLEAN boost (approx 30dB) with a modified “BigMuff” tone control and a switch for full (linear) boost or mid/top boost (pulls bottom end out) It stays clean all the way to the top so there’s NO distortion in the pedal. Just pushes your already sweet amp into breakup or increases the volume for solos etc.