Time constant setting for audio equipment with AGC - varies feedback time constant according to input and output levels

摘要

The time constant control, for audio equipment with automatic gain control, increases the feedback time constant of the control loop to its greatest value (a few minutes) once the input signal has appeared. It is maintained at this value until a given delay time (1-5 sec) has elapsed. The time constant is then changed to a very short value (c. 1sec) provided that the output signal falls below a given reference level throughout the whole of the given delay time (due to a drop in input level). When the output falls below the given reference level the sensitivity of the AGC amplifier is increased again and the control loop's time constant is increased from its low value to its greatest value when the output is equal to a second reference voltage.