The AEQ-4XO 4 Band Equalizer and Pre-Amp is the perfect solution to take your sound system from good to excellent by giving you 4 EQ controls subwoofer volume & crossover controls fader and multiple inputs. Most all of us have multiple musical tastes and each one of them require different listening desires. By having the ability to set different EQ settings gives us the ultimate control over the sound reproduction and multiple source inputs with features like Band Active Equalizer Bi-Polar PWM Power Supply Frequency Response: 20Hz-40khz Switchable main/aux input (front mounted 3.5mm jack or Rear RCA). Front/Rear/Sub Output Variable Master Volume Control Select able 120/80Hz Subwoofer Crossover Variable Subwoofer Volume Control Front and Rear Output Fader and 3 Inputs: Front Aux (3.5mm jack for MP3) Rear Aux and Rear CD (Low Level RCA).