20
Before proceeding to illustrating the editing and setting of the
AGC
parameters, it is good to remember how
an AGC (Automatic Gain Controller) works.
Refer to the following picture:
The AGC is an Expansion/Compression process applied with slow Attack and Release times, to the INPUT
signal of a Unit, in order to maintain the average amplitude of the OUTPUT signal at a defined level,
independently from the average amplitude of the input sources.
For this purpose, the AGC has to be able to expand the input signal, where the average of the related
output signal is below a defined Threshold (Exp Thr), and to maintain the expanded signal at a constant
expansion level when the averaged signal is beyond a defined Threshold (Thr Hold).
The AGC implemented in the DS-CP25 acts on the evaluation of an input signal which is an averaged one
on a 50ms time frame, and represents the RMS Value of the input signal itself, making a more “Musical”
sounding AGC action.
If the output signal of the AGC process will exceed a defined Threshold (Cmp Thr), becoming too loud, a
compression process is occurring.
The speed and the amount of the Expansion can be defined through the “Exp Time” and “Exp Ratio”
parameters, as the speed and the amount of the Compression can be defined through the “Cmp Time and
”
“Cmp Ratio” parameters.
When the Signal coming out from the AGC process (Output), applied to the AGC input, is above the “Exp
Thr” and below the “Thr Hold”, it is expanded up to the max expansion coefficient defined by the “Exp
Ratio”.
