Orban OPTIMOD 5750 Operating Manual page 48

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Orban 5750 Technical Manual Operation
Because there is very little energy above 16 kHz, the 5750's digital 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 complete 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 5750 provides two different stereo enhancement algorithms. The first is 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 signal (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 significant 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" technique. This passes the L–R signal
through a delay line and adds this decorrelated signal 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.
"Multipath Mitigator" Left/Right Phase Skew Correction
The phase skew corrector maximizes the quality of a mono mixdown or blend that might occur in a receiver. At
higher frequencies (where audible comb filtering of the mono sum is most likely to occur), the corrector removes
phase differences between the left and right channels, converting the HF signal into "intensity stereo" while
preserving phase differences at lower frequencies where these differences are important for psychoacoustic
"envelopment." The PHASE CORRECTOR CROSSOVER control in the EQ tab of the active Processing Preset sets the
crossover frequency above which phase correction occurs.
By removing phase shifts between the left and right channels, the process minimizes the amount of energy in the
stereo subchannel, which consequently minimizes multipath distortion without compromising stereo separation. It
can allow more stereo enhancement to occur for a given amount of multipath distortion. The process also minimizes
the amount of peak overshoot during SSB/VSB operation of the stereo encoder, thus minimizing the amount of
composite limiting needed to constrain peak modulation to 100%.
This process can not only correct problems due to phase skew between the left and right channels of an analog
recording due to head gap misalignment, it can also correct comb filtering caused by spaced microphones feeding
the left and right channels, which can occur on drum kits and other sources that have been multi-miced.