The Beavis Audio Four Knob Rat 2.1 is a versatile distortion stompbox that allows users to create a wide range of sounds. It started as a clone of the Rat, but with modifications such as the removal of the input buffer stage and the addition of true-bypass switching. The pedal also features a separate circuit stage for the 2-diode clipping components, offering options for stock, asymmetric clipping, LED, and MOSFET.

The pedal incorporates the Ruetz Mod, which replaces one of the fixed resistors in the feedback loop with a potentiometer. This modification enables users to adjust the sound from a slightly dirty boost to mild overdrive or intense distortion.

Beavis also added an extra clipping section to the feedback loop of the LM308 opamp. This section offers options for no loop clipping, red LED, or MOSFET clipping, essentially adding a Tube Screamer-like overdrive to the pedal. This can be activated simultaneously with any other clipping mods for an even wider range of sound possibilities.

Summary created by AI from the original source.