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).
MID, BASS & TREBLE are active EQ controls, specifically tuned for bass guitar, that cut or boost +/- 12dB. MID SHIFT switch changes the frequency from 500 HZ to 1000 Hz. BASS SHIFT switch changes the frequency from 40 Hz to 80 Hz.