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OPTIMOD-PC
AGC Release ("AGC Master Release") control provides an adjustable range from 0.5
dB/second (slow) to 20 dB/second (fast). The increase in density caused by setting the
control to fast settings sounds different from the increase in density
AGC R
ELEASE
caused by setting the Five-band's M
the two off to produce different effects.
Unless it is purposely speeded-up (with the AGC R
gain control (AGC) that occurs in the AGC prior to the multiband compressor makes
audio levels more consistent without significantly altering texture. Then the multi-
band compression audibly changes the density of the sound and dynamically re-
equalizes it as necessary: booming bass is tightened; weak, thin bass is brought up;
highs are always present and consistent in level.
The various combinations of AGC and compression offer great flexibility:
•
Light AGC + light compression yields a wide sense of dynamics, with a small
amount of automatic re-equalization.
•
Moderate AGC + light compression produces an open, natural quality with au-
tomatic re-equalization and increased consistency of frequency balance.
•
Moderate AGC + moderate compression gives a more dense sound, particularly
as the release time of the multiband compressor is sped up.
•
Moderate AGC + heavy compression (particularly with a FAST multiband release
time) results in a "wall of sound" effect, which may cause listener fatigue.
Adjust the AGC (with the AGC D
action, and then fine-tune the compression and clipping with the Five-Band struc-
ture's controls.
AGC Gate ("AGC Gate Threshold") control determines the lowest input level that
will be recognized as program by OPTIMOD-PC; lower levels are considered to be
noise or background sounds and cause the AGC or multiband compressor to gate,
effectively freezing gain to prevent noise breathing.
In sound for picture, the setting of the gate threshold controls are quite critical if
you want the processing to be undetectable to the audience. If this control is set too
low, then OPTIMOD-PC will pump up quiet sounds such as ambience and underscor-
ing to unnaturally high levels.
There are two independent silence-gating circuits in OPTIMOD-PC. The first affects
the AGC and the second affects the multiband compressor (2-band or 5-band).
Each has its own threshold control.
In the five-band structure, the multiband silence gate causes the gain reduction in
bands 2 and 3 of the five-band compressor to move quickly to the average gain re-
duction occurring in those bands when the gate first turns on. This prevents obvious
midrange coloration under gated conditions, because bands 2 and 3 have the same
gain.
R
ULTIBAND
ELEASE
ELEASE
control) to produce the desired amount of AGC
RIVE
control to F
. You can trade
AST
control), the automatic
3-43
OPERATION
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