Level - Sets the volume of the overdrive signal.
Drive - Dials the level of saturation in the overdriven signal.
Blend - Blends the clean input with the overdrive signal. The clean signal stays fixed at unity gain, while the volume of the overdriven signal is set with the Level knob, providing fine control of the blend ratio. Turn clockwise to blend in the clean signal.
Tone - Controls the high-frequencies of the sound. A variable low pass filter from 3 kHz to 8 kHz. Turn anti-clockwise for a brighter tone.
Grunt - Engaging this delivers a low-end boost to add huge thickness your sound.
MBoost - Gives a subtle 6 dB boost from 300 Hz to 1 kHz to help you cut through the mix.