Orban OPTIMOD-FM 8700, Operating Manual

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OPTIMOD-FM DIGITAL OPERATION
3-41
by the setting of the AGC D
RIVE
control, by the level at which the console VU meter
or PPM is peaked, and by the setting of the MB D
RIVE
(compressor) control.
Master AGC 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
AGC R
ELEASE
control to fast settings sounds different from the increase in density caused by set-
ting the Multiband’s
MB R
ELEASE
control to F
AST
, and you can trade the two off to
produce different effects.
Unless it is purposely speeded-up (with the MB R
ELEASE
control), the automatic gain
control (AGC) that occurs in the AGC prior to the multiband compressor makes audio
levels more consistent without significantly altering texture. Then the multiband
compression and associated multiband clipper audibly change the density of the
sound and dynamically re-equalize 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
RIVE
control) to produce the desired amount of AGC
action and then fine-tune the compression and clipping with the Five-Band struc-
ture’s controls.
AGC Gate Thresh (Threshold) control determines the lowest input level that will be
recognized as program by OPTIMOD-FM; 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.
There are two independent gating circuits in the 8700i. The first affects the AGC and
the second affects the multiband compressor . Each has its own threshold control.
The multiband compressor gate causes the gain reduction in bands 2 and 3 of the
multiband compressor to move quickly to the average gain reduction 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.
The gate also independently freezes the gain of the two highest frequency bands
(forcing the gain of the highest frequency band to be identical to its lower neigh-
bor) and independently sets the gain of the lowest frequency band according to the
setting of the
DJ B
ASS
boost control (in the Equalization screen). Thus, without in-