Audio Amplifier (If Equipped)

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2011 GMC Yukon XL, 2011 GMC Yukon, 2011 Chevrolet Tahoe, 2011 Chevrolet Suburban, and 2011 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.

Amplifier Interface UQA without Y91

The main amplifier power is provided by a fuse located in the body control module (BCM). A discrete switched 12-volt output is used to control the power state of the amplifier. To respond quickly to audio input and control signals, the amplifier is ON in all vehicle power modes except OFF and CRANK Request. However, when the amplifier is asleep it still must allow chime functionality. The internal amplifier bridges are fully powered and unmuted when the amplifier receives the switched 12-volt input.

The radio provides a remote amp mute output circuit to control overall muting of remote non-serial data amplifiers with rear seat audio (RSA) applications. The amplifier receives PWM signals on the circuit at varying duty cycle percentages for controlling the muted and unmuted functions of the amplifier. The RSA Enable circuit in the radio enables the rear seat channel muting of the amplifier. A Diag Sense circuit internal to the radio monitors the remote amp mute circuit for faults and sets the appropriate DTC when detected.

The function table below shows the four possible amplifier mute functions.

% Duty Cycle Out	Function
0% (Vlow Vdc)	FOUR_CHANNEL_UNMUTE
50%	REARMUTE (input must be 2-channel)
75%	SIX_CHANNEL_UNMUTE
100% (Vhigh Vdc)	ALL_MUTE

Amplifier Interface UQA with Y91 or UQS (Serial Data)

The main amplifier power is provided by a fuse located in the underhood fuse block. The radio controls both the overall muting and the rear seat muting via serial data messaging. For vehicles equipped with UQA, the radio commands the amplifier to perform the following functions through serial data communication.

Volume
Balance
Fade
Bass
Midrange
Treble
DSP Modes
Volume Compensation
Chime Output

Amplifier Operation

The purpose of the amplifier is to increase the power of a voltage or current signal. The output signal of an 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 radio creates a low level stereo audio output signal, which is sent at the user-defined volume level to the audio amplifier. The audio amplifier amplifies the signal and sends it to the appropriate speakers.