ProCo

Engineer Scott Burnham designed early RAT units in the late 1970s in the company’s basement workshop; custom builds appeared around 1978 and full production followed in 1979. The circuit became a long-running distortion platform, later joined by variants such as the Turbo RAT, You Dirty RAT and Deucetone RAT.

For players comparing hard-clipping distortion and filter-style tone controls, the RAT family remains a reference point: a Kalamazoo-originated design that still frames many discussions of aggressive, amp-like pedal distortion.