MagiDeal Subwoofer Bass Remote Volume Control Knob RCA Level Frequency Equalizer Boss for Car Audio Amplifier Earbud Used to adjust an amplifier's power level, stereo, equalizer or crossover volume form the dashboard or other remote locations Adds sub-woofer level controls or balances a multiple amplifier installation Compact housing allows the unit to be mounted anywhere so control is at the fingertips Simple in and out connections, no additional wiring needed Connect the RCA from the output of this Controller to the amplifier, and wire the car stereo output to the RCA input of this unit