The BQS Control is essentially the same as the BQC Control but the bass and treble controls are on separate pots. The mid-control is concentric (stacked). This active EQ circuit for bass guitars works by rotating the control clockwise to boost, counterclockwise to cut. There is a center detent for flat response. The mid-range control has a variable frequency knob that allows you to sweep through the mid-frequency range from 100Hz to 1KHz. This selects the frequency to boost or cut. The BQS Control will also work with active or passive pickups. 2 extra volume knobs are included.