PRESENCE:controls the amount of definition and upper harmonic content.
DRIVE: adjusts the overall gain structure and overdrive.
LEVEL: regulates the XLR and effected 1/4" output levels.
BLEND: allows you to mix the direct bass signal with SansAmp Tube Amplifier Emulation circuitry (which is particularly useful for basses equipped with piezo pickups).
BASS & TREBLE: are active EQ controls, specifically tuned for bass guitar, that cut or boost +/- 12dB.