BRAND NEW. Retails $240. An ACDelco GM Original Equipment Audio Amplifier is part of the audio system, and is a GM-recommended replacement for your vehicle’s original component. The purpose of the amplifier is to increase the power of a voltage or current signal. The output signal of an audio amplifier may consist of the same frequencies as the input signal or it may consist of only a portion of the frequencies, as in the case of a subwoofer or midrange speaker. The audio amplifier amplifies the signal and sends it to the appropriate speakers. Each of the audio output channel circuits (+ and ?) at the audio amplifier have a DC bias voltage that is approximately one half of the battery voltage. The audio being played on the system is produced by a varying AC voltage that is centered around the DC bias voltage on the same circuit. The AC voltage is what causes the speaker cone to move and produce sound. Both the DC bias voltage and the AC voltage signals are needed for the audio system to properly produce sound. These original equipment audio amplifiers have been manufactured to fit your GM vehicle, providing the same performance, durability, and service life you expect from General Motors.