Harman 4800, 4820 Automatic Gain Control AGC Insert, DriveRack, Section, Detailed Parameters

Section 6
		DriveRack
		®
	Detailed Parameters

6.12 - Automatic Gain Control (AGC) Insert

The Automatic Gain Control Insert is available in the DriveRack 4800 and 4820 in both the Input and Output Insert modules. Automatic Gain Control (or AGC) is used to keep the average level of a signal constant. This is done by selecting a desired Target output level and the Window around that Target. The AGC keeps the signal within the Window around the selected Target by slowly adjusting the gain. The maximum gain that can be applied to the signal is selected by the Gain parameter. When the input signal falls below the Threshold parameter, the AGC stops adding gain and returns to unity. This prevents the AGC from adding gain when there is no signal present and raising the system noise floor. Within the AGC, high level peak signals are reduced by a fast acting Limiter to prevent clipping and distortion. The AGC Threshold meters show what region of the AGC the input signal is in. The T (yellow) indicates the signal is within the Window. A red + indicates the signal is above the target window, and a green - indicates the AGC is adding Gain and is at or below the window. When the Threshold meter is turned off, the signal is below the Threshold. The Limiter also has a Threshold meter indicating when the signal has crossed the Limiter Threshold.

AGC On/Off switch

This turns the AGC module On and Off.

Threshold fader

The Threshold sets a lower limit to the AGC. It prevents the AGC from adding gain below the Threshold and raising the noise floor. The Threshold range is between -80 to -50dBFS.

Gain fader

This adjusts the maximum amount of Gain that can be added by the AGC, and ranges between 1 and 20dB.

Target fader

The Target parameter defines what you would like the average output level of the AGC to be. If the average level of the signal rises above the Target the gain will be reduced. If the average level of the signal is below the target Gain will be added. The Target range is between -40 and -1 dBFS.

52 DriveRack® 4800/4820 User Manual