A complete control system for bass guitars Active Balance, Master Volume and EQ circuits are included The EQs allow you separate control over bass, range, and treble all 2 concentric/stacked pots Rotate the control clockwise to , counterclockwise to cut is a center detent for flat response.The -range control has a variable frequency to sweep through the -frequency range from 100Hz to 1KHz.This selects the frequency to or cut