Orban OPTIMOD-FM 8600Si, Operating Manual

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OPTIMOD-FM DIGITAL OPERATION
3-39
Note: If the
M
ULTIBAND
G
ATE
T
HRESH
(Gate Threshold) control is turned
O
FF , the
DJ B
ASS control (in the Equalization screen) is disabled.
AGC Bass Coupling control clamps the amount of dynamic bass boost (in units of
dB) that the AGC can provide. (In V1.x, the unit of measure was percent.)
The AGC processes audio in a master band for all audio above approximately 200 Hz
and a bass band for audio below approximately 200 Hz. Starting with V2.0 software,
the AGC Master and Bass compressor sidechains operate without internal coupling.
The gain reduction in the
B
ASS
audio path is either the output of the Bass compres-
sor sidechain or the output of the Master band sidechain. The
AGC B
ASS
C
OUPLING
control sets the switching threshold. For example, if the
AGC B
ASS
C
OUPLING
control
is set to 4 dB and the master gain reduction is 10 dB, the bass gain reduction cannot
decrease below 6 dB even if the gain reduction signal from the Bass compressor
sidechain is lower. However, the audio path bass gain reduction can be larger than
the master gain reduction without limit. In the previous example, the bass gain re-
duction could be 25 dB
The normal setting of the AGC
B
ASS
C
OUPLING
control is 0 dB, which allows the AGC
bass band to correct excessive bass as necessary but does not permit it to provide a
dynamic bass boost.
Note that the operation of this control was changed in 8600Si V2 software to work
as explained above. You may have to tweak this control to achieve the same bass
balance that you had previously with V1.x software.
AGC Max Delta GR determines the maximum gain difference permitted between
the two channels of the AGC. Set it to “0” for perfect stereo coupling.
This control works the same regardless of whether the AGC operates in
left/right or sum / difference
M
ATRIX
modes, in both cases controlling the
maximum gain difference between the “channels.” Depending on the
M
ATRIX mode setting, the “channels” will handle left and right signals or
will handle sum and difference signals. When the AGC operates in sum /
difference
M
ATRIX mode, this control determines the maximum amount
of width change in the stereo sound field.
Window Size determines the size of the floating “slow zone” window in the mas-
ter band of the AGC. (The Bass band is not windowed.)
The window works by slowing down changes in the AGC gain reduction that are
smaller than the
W
INDOW
S
IZE . The window has 2:1 asymmetry around the current
AGC gain reduction. For example, if the
W
INDOW
S
IZE is set to 4 dB, the window ex-
tends 4 dB in the release direction and 2 dB in the attack direction.
If the AGC needs to respond to a large change in its input level by making a gain
change that is larger than the window, then the AGC’s attack and release controls
determine the AGC’s response time. However, if the change in input level is smaller
than the window size, the
W
INDOW
R
ELEASE control determines the attack and re-
lease times. This is usually much slower than the normal AGC time constants. This
prevents the AGC from building up density in material whose level is already well
controlled.