Orban OPTIMOD 6200, Operating Manual

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OPTIMOD OPERATION
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Limiter meters show the amount of broadband look-ahead peak limiting in the left
and right channels, which are not coupled because of the fast release time of this cir-
cuit. Full-scale is 12dB gain reduction.
Introduction to Processing
Some Audio Processing Concepts
Reducing the peak-to-average ratio of the audio increases loudness. If peaks are reduced,
the average level can be increased within the permitted modulation limits. The effective-
ness with which this can be accomplished without introducing objectionable side effects
(such as pumping or intermodulation distortion) is the single best measure of audio proc-
essing effectiveness.
Compression reduces the difference in level between the soft and loud sounds to make
more efficient use of permitted peak level limits, resulting in a subjective increase in the
loudness of soft sounds. It cannot make loud sounds seem louder. Compression reduces
dynamic range relatively slowly in a manner similar to riding the gain: Limiting and
clipping, on the other hand, reduce the short-term peak-to-average ratio of the audio.
Limiting increases audio density. Increasing density can make loud sounds seem louder,
but can also result in an unattractive busier, flatter, or denser sound. It is important to be
aware of the many negative subjective side effects of excessive density when setting
controls that affect the density of the processed sound.
Clipping sharp peaks does not produce any audible side effects when done moderately.
Excessive clipping will be perceived as audible distortion.
Look-ahead limiting is limiting that prevents overshoots by examining a few millisec-
onds of the unprocessed sound before it is limited. This way the limiter can anticipate
peaks that are coming up.
The look-ahead limiter in the 6200 operates with very fast attack and release
times and is closer to a clipper than a conventional peak limiter.
Distortion in Processing
In a competently designed processor, distortion occurs only when the processor is con-
trolling peaks to prevent the audio from exceeding the peak modulation limits of the
transmission channel. The less peak control that occurs, the less likely that the listener
will hear distortion. However, to reduce the amount of peak control, you must decrease
the drive level to the peak limiter, which causes the average level (and thus, the loud-
ness) to decrease proportionally.