Orban OPTIMOD-FM 8500S Operating Manual page 200

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OPERATION
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
AGC gain reduction. For example, if the W
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
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.
The previous explanation was somewhat simplified. In fact, the window has "soft
edges." Instead of switching abruptly between time constants, the attack and re-
lease times morph smoothly between the setting of the W
the setting of the AGC master release and attack controls.
The normal setting for the W
Window Release (see W
AGC Matrix allows you to operate the AGC in left/right mode or in sum / difference
mode. Usually you will operate in left/right mode. However, sum / difference mode
can give a type of stereo enhancement that is different from the enhancement
modes offered in the 8500S's built-in stereo enhancer. This will only work if you al-
low the two channels of the AGC to have different gains. To do this, set the AGC
GR control greater than zero.
M D
AX ELT
It is unwise to set this control beyond 3 dB. Multipath distortion could in-
crease because the amount of L–R energy builds up excessively. We prefer
using the 8500S's stereo enhancer because its built-in gating circuits pre-
vent over-enhancement.
AGC Ratio determines the compression ratio of the AGC. The compression ratio is
the ratio between the change in input level and the resulting change in output
level, both measured in units of dB.
Previous Orban AGCs had compression ratios very close to ∞:1, which produces the
most consistent and uniform sound. However, the 8500S compressor can reduce this
ratio to as low as 2:1. This can add a sense of dynamic range and is mostly useful for
subtle formats like classical and jazz.
Bass Threshold determines the compression threshold of the bass band in the AGC.
It can be used to set the target spectral balance of the AGC.
As the AGC B
C
ASS OUPLING
control affects the sound less and less.
. The window has 2:1 asymmetry around the current
S
IZE
INDOW
control determines the attack and re-
R
INDOW ELEASE
S
INDOW IZE
above.)
S
INDOW IZE
control is moved towards 0 dB, the AGC B
ORBAN MODEL 8500S
S is set to 4 dB, the window ex-
IZE
R
INDOW ELEASE
is 3 dB.
control and
T
ASS HRESH