Volume, Gain and Tone knobs set the core sound. The Tone control rolls off high frequencies as it turns down, which smooths harsh pickups or bright amplifiers.

A Tone Shift switch changes the voicing of the Tone control. Off gives a flatter response with some low-mid emphasis, while On pushes the mids and high mids forward with a small lift in level.

An internal headroom switch changes the feel of the circuit. The high-headroom setting gives a more open, less compressed response, and the standard setting gives a tighter sound. Bypass is true bypass.