AGC (Automatic Gain Control)
AGC adjusts the gain level of a signal based upon the input strength to achieve a more
consistent volume. Below the set threshold, the signal is not affected. Above the threshold,
weaker signals are boosted up to the maximum gain setting to reach a user-defined target
level. As the signal level approaches the target level it receives less gain or no gain at all. Once
the signal level reaches the target level all gain is removed.
Threshold — is the input level where maximum gain
will be applied (after the attack time is exceeded).
On the graph at right follow the red input level from
the lower left to -40dB where the first red circle is.
Signal levels less than -40dB remain at their original
levels. All signal levels at or exceeding -40dB will
have up to 12dB of gain applied (Maximum Gain).
The threshold level can be adjusted from -80.0 to
0.0dB in 0.1dB increments.
Default is -40.0dB.
Maximum Gain — is the highest amplification
applied to a signal exceeding the threshold and up
to the lower limit of the window (see below).
Maximum Gain can be set from 0.0dB to +60dB in
0.1dB increments.
Default is 12.0dB.
Target — is the desired average signal level of the
output when AGC is applied. AGC can vary the gain
according to the input signal level, specified target
level and maximum gain. As the signal approaches
the target level of –10dB, gain is reduced until at
–10dB, gain is no longer applied.
The target level can be adjusted from -40dB to
0.0dB in 0.1dB increments.
Default is –10.0dB.
Window — indicated by the two yellow lines, is a specified range above and below the
target level. Below the lower line maximum gain is always applied to the signal. When the
signal reaches the window, gain control begins scaling in a linear fashion to achieve smoother
results as the signal reaches the target level.
The window range can be set in 0.1dB increments from 0.0dB to 20.0dB.
The default threshold is – 40dB. The default target level is – 10.0dB. The default gain and
window are 12.0dB.
Attack Time — adjusts the time delay for AGC to engage after the input signal level reaches
or exceeds the threshold level.
Attack time can be adjusted from 0.0 to 3000.0 ms in 0.1ms increments.
Default is 500.0 ms.
Hold Time — adjusts how long AGC continues to boost the signal after the input signal drops
below the threshold and before release time begins.
Hold time can be adjusted from 0.0 to 3000.0ms in 0.1 ms increments.
Default is 0.0 ms.
Release Time — adjusts the time it takes to return the signal to normal (unprocessed) levels
after the signal no longer exceeds the threshold level setting. Release time begins only after
hold time is reached.
Release time can be adjusted from 10.0 to 10000.0 ms in 0.1ms increments.
Default is 1500.0 ms.
DMP128 • Software Control 47