Audio Amplifier
WARNING: This page is about a different car, the 2008 Pontiac Torrent and 2008 Chevrolet Equinox. However, it is still accessible from the selected car via links, so may be relevant.
The purpose of the amplifier is to increase the power of a voltage or current signal. The output signal of an amplifier may consists of the same frequencies as the input signal or it may consist of only a portion of the frequencies of the input signal as in the case of a subwoofer or midrange amplifier.
When the radio is turned ON, it sends a voltage signal to the audio amplifier via the radio on signal circuit. The gain control signal circuit allows the radio to recognize that the amplifier is present. Once the radio detects the amplifier, the radio will output low-level signals to the amplifier. With the amplifier enabled, the signal that drives the speaker is now amplified.