XEQ-9XO Equalizer 9 BAND PREMIUM EQUALIZER/PRE-AMP STEREO PREMIUM EQUALIZATION w/ VARIABLE SUBWOOFER CONTROL: Combine these controls for maximum flexibility with a subwoofer crossover to turn your dashboard into a mini-mixing board, giving you ultimate bass response. MASTER VOLUME CONTROL: This one knob allows the user to raise the volume on your source units to their maximum level, eliminating the need to adjust multiple controls. AUXILLARY INPUT SELECTOR: The SOURCE switch on the front of the equalizer allows the user to switch back and forth between two sources. If you are thinking about adding a video system, DVD player, or extra CD player this feature makes hook-up easy and functional. PRE_AMP LINE DRIVER: Boosts the output voltage of your Radio (head unit) and increases it up to 20dB (10-13volts peak) and then deliver it to the amplifier inputs. NIGHT ILLUMINATION: When the EQ is powered-on the control knobs are back lit with blue illumination for easier adjustment at night