Orban OPTIMOD-FM 5500 Operation Manual page 131

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OPTIMOD-FM DIGITAL OPERATION
A defeatable 30Hz 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 30Hz filter and leave the phase
rotator in-circuit, although the choice is always yours.
Stereo Enhancement: The 5500 provides a stereo enhancement algorithm based
on Orban's patented analog 222 Stereo Enhancer, which increases the energy in the
stereo difference signal (L–R) whenever a transient is detected in the stereo sum sig-
nal (L+R). By operating only on transients, the 222 increases 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.
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 5500 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 5500's bass, midrange, and high frequency parametric equalizers have curves
that were modeled on the curves of Orban's classic analog parametrics (like the
622B), using a sophisticated and proprietary optimization program. The curves are
matched to better than 0.15 dB. This means that their sound is very close to the
sound of an Orban analog parametric. They also use very high quality filter algo-
rithms to ensure low noise and distortion.
The 5500 HF Enhancer is a program-controlled HF shelving equalizer that was origi-
nally introduced in Orban's 2200 OPTIMOD-FM. It intelligently and continuously ana-
lyzes the ratio between broadband and HF energy in the input program material,
and can equalize excessively dull material without over-enhancing bright material. It