Orban OPTIMOD-FM 8500S, Operating Manual

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OPTIMOD-FM DIGITAL OPERATION
3-37
The interaction between the AGC B
ASS
T
HRESH
control and the AGC B
ASS
C
OUPLING
control is a bit complex, so we recommend leaving the
AGC
B
ASS
T
HRESH
control at its factory setting unless you have a good reason
for readjusting it.
Idle Gain . The “idle gain” is the target gain of the AGC when the silence gate is ac-
tive. Whenever the silence gate turns on, the gain of the AGC slowly moves towards
the idle gain.
The idle gain is primarily determined by the AGC D
RIVE
setting—a setting of 10 dB
will ordinarily produce an idle gain of –10 dB (i.e., 10 dB of gain reduction). How-
ever, sometimes you may not want the idle gain to be the same as the
AGC D
RIVE
setting. The I
DLE
G
AIN
control allows you to add or subtract gain from the idle gain
setting determined by the AGC D
RIVE
setting.
You might want to do this if you make a custom preset that otherwise
causes the gain to increase or decrease unnaturally when the AGC is
gated. For example, to make the idle gain track the setting of the
AGC
D
RIVE
control, set the I
DLE
G
AIN
control to zero. To make the idle gain 2
dB lower than the setting of the AGC D
RIVE
control, set the I
DLE
G
AIN
con-
trol to –2 .
AGC Bass Attack sets the attack time of the AGC bass compressor (below 200 Hz).
AGC Master Attack sets the attack time of the AGC master compressor (above 200
Hz).
AGC Bass Release sets the release time of the AGC bass compressor.
Master Delta Threshold allows you to set the difference between the compression
thresholds of the sum and difference channels. (This control is only useful when you
set the
AGC M
ATRIX
to
SUM
/
DIF
.) By setting the threshold of the difference channel
lower than the sum channel, you can have the AGC automatically produce more
gain reduction in the difference channel. This will reduce the separation of material
with an excessively wide stereo image (like old Beatles records). To make this work,
you must set the
M
AX
D
ELTA
GR
control away from zero. For example, to limit an ex-
cessively wide image while preventing more than 3 dB difference in gain between
the sum and difference channels, set the
M
AX
D
ELTA
GR control to 3.0 and the
M
ASTER
D
ELTA
T
HRESHOLD
control to some positive number, depending on how much
automatic width control you want the 8500S to perform.
Bass Delta Threshold works the same as
M
ASTER
D
ELTA
T
HRESHOLD
,
but applies to
the bass band. You will usually set it the same as M
ASTER
D
ELTA
T
HRESHOLD
.
AGC Crossover allows you to choose
A
LLPASS
,
L
I
N
O
D
LY
, or
L
INEAR
modes.
A
LLPASS
is a phase-rotating crossover like the one used in the 8200’s two-band AGC.
It introduces one pole of phase rotation at 200 Hz. The overall frequency response
remains smooth as the two bands take different degrees of gain reduction—the re-
sponse is a smooth shelf without extra peaks or dips around the crossover frequency.
The two bands are down 3 dB at the crossover frequency.