Orban OPTIMOD-FM 8500S Operating Manual page 172

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OPERATION ORBAN MODEL 8500S
output will pass through any uncompressed digital STL without adding noticeable
overshoot and without the need for distortion-producing overshoot compensation
schemes.
A defeatable 30 Hz 18 dB/octave highpass filter and a defeatable phase rotator com-
plete the input-conditioning block. These have both been features in Orban FM
processors for many years. Most users will defeat the 30 Hz filter and leave the
phase rotator in-circuit, although the choice is always yours.
Stereo Enhancement: The 8500S provides two different stereo enhancement algo-
rithms. The first is based on Orban's patented analog 222 Stereo Enhancer, which in-
creases the energy in the stereo difference signal (L–R) whenever a transient is de-
tected in the stereo sum signal (L+R). By operating only on transients, the 222 in-
creases width, brightness, and punch without unnaturally increasing reverb (which is
usually predominantly in the L–R channel).
Gating circuitry detects "mono" material with slight channel or phase imbalances
and suppresses enhancement so this built-in imbalance is not exaggerated. It also
allows you to set a "width limit" to prevent over-enhancement of material with sig-
nificant stereo content, and will always limit the ratio of L–R / L+R to unity or less.
The second stereo enhancement algorithm is based on the well-known "Max" tech-
nique. This passes the L–R signal through a delay line and adds this decorrelated sig-
nal to the unenhanced L–R signal. Gating circuitry similar to that used in the "222-
style" algorithm prevents over-enhancement and undesired enhancement on
slightly unbalanced mono material.
Two-Band Gated AGC: The AGC is a two-band device, using Orban's patented
"master / bass" band coupling. It has an additional important feature: target-zone
gating. If the input program material's level falls within a user-settable window
(typically 3 dB), then the release time slows to a user-determined level. It can be
slow enough (0.5 dB/second) to effectively freeze the operation of the AGC. This
prevents the AGC from applying additional, audible gain control to material that is
already well controlled. It also lets you run the AGC with fast release times without
adding excessive density to material that is already dense.
The AGC contains a compression ratio control that allows you to vary to ratio be-
tween 2:1 and essentially ∞:1. Lower ratios can make gain riding subtler on critical
formats like classical and jazz.
The AGC has its own silence-gating detector whose threshold can be set independ-
ently of the silence gating applied to the multiband compressor.
Equalization: The 8500S has steep-slope bass shelving equalizer and three bands of
fully parametric bell-shaped EQ.
You can set the slope of the bass shelving EQ to 6, 12, or 18 dB/octave and adjust the
shelving frequency.
The 8500S's bass, midrange, and high frequency parametric equalizers have curves
that were modeled on the curves of Orban's classic analog parametrics (like the