GUIDE TO INSTALLATION AND OPERATION
70
| XVP-3901
For reference, the crossover frequencies are:
•
Band 1 (Low Bass): 20 Hz - 60 Hz
•
Band 2 (Mid Bass): 30 Hz - 200 Hz
•
Band 3 (Low Mid): 170 Hz - 1.15 kHz
•
Band 4 (High Mid): 950 Hz - 6.1 kHz
•
Band 5 (Brilliance): 5.2 kHz - 24 kHz
Input AGC
The input AGC is a very slow acting front-end gain control
with a 36dB gain range whose only purpose is to make sure
that the following processing stages are fed with the correct
average audio levels. It is basically the automatic equivalent
of an operator slowly riding a gain control on a console to
keep the audio close to reference level. Wideband in nature,
the AGC is not meant to perform rapid gain reduction or
expansion as its actions will be more audible, as with all
wideband gain processors. As a slow gain rider, its actions
are nearly inaudible thanks to the multiband processing that
follows it. The AGC has two stages of gating where the gain
expansion is slowed or stopped to prevent background noise
increasing.
Adjustable parameters are:
•
Gate Threshold: 0dBFS to -90dBFS (default: -
30dBFS). Gating sets the point at which the AGC
release is made extremely slow to prevent increasing
background noise and allow the AGC to return to unity
gain.
•
Freeze Threshold: 0dBFS to -90dBFS (default: -
42dBFS). Freeze stops all gain change (i.e. when the
audio drops to silence), and remains frozen at its
current gain value until the threshold is exceeded.
NOTE:
Adjust Gate and Freeze to match plant practices. Very quiet audio (such as a golf match) benefits from having
processing frozen when input audio drops below a given level to prevent “boosting the cricket” sounds.
•
Ratio: 1:1 to Inf:1 (default: 12.0:1)
•
Range: 0dB - 36 dB (default: 24dB). Range sets how much gain expansion above unity is performed, and this
amount is subtracted from the total AGC gain range of 36dB, so the default value allows for 24dB of expansion
and 12dB of compression. This adjustment is reflected in real time by changing the AGC meter scale.
•
Threshold: -18dBFS - 0dBFS (default: -16dBFS)
•
Attack: 0 - 150, slowest - fastest (default: 21)
•
Release: 0 - 150, slowest - fastest (default: 47)
•
Progressive Release: 0 - 100, slowest - fastest (default: 50). Sets the speed at which the release time is
increased faster at very low gain values. This feature approximates a logarithmic release to help recovery from
dramatic gain reduction more quickly.
Figure 5.59
ALC Module – Input AGC
