Orban OPTIMOD 6300, Руководство по эксплуатации

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OPTIMOD 6300 DIGITAL OPERATION
3-7

Input Conditioning , including sample rate conversion, defeatable highpass fil-
tering, and defeatable phase rotation

Stereo Enhancement

2-band Gated AGC , with target-zone window gating and silence gating

Equalization , including high-frequency enhancement

Multiband Compression in either two or five bands, depending on the proc-
essing structure

Look-Ahead Limiting
A sample rate converter converts the sample rate at the digital input to the 6300’s
internal 48 kHz rate. This 48 kHz rate accommodates a 20 kHz audio bandwidth with
a comfortably wide 4 kHz transition band for the anti-aliasing filter. We are aware
of no bias-controlled double-blind studies that have ever demonstrated that sample
rates higher than 48 kHz are audibly superior to 48 kHz (or even that there is any
audible difference at all). Moreover, the noise and distortion produced by a given
digital filter at 48 kHz is about 6 dB lower than the N&D produced by a filter having
the same frequency response but operating at 96 kHz. The 6300 uses many digital
filters, both in its equalizer section and for the crossovers in the multiband compres-
sor. Hence, we believe that 48 kHz is the ideal rate for the 6300’s audio processing.
A sweepable 18 dB/octave highpass filter and a defeatable phase rotator complete
the input-conditioning block. The highpass filter is useful for production applica-
tions where it is necessary to remove low frequency rumble from a recording. The
phase rotator makes speech more symmetrical, reducing its peak-to-average ratio by
as much as 6 dB without adding nonlinear distortion. Hence, phase rotation can be
very useful for loudness processing of speech.
Stereo Enhancement: The 6300 provides two different stereo enhancement algo-
rithms. The first, called L–R D
ELAY
, 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 tran-
sients, the 222 increases width, brightness, and punch without unnaturally increas-
ing 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.
2-band Gated AGC: The AGC is a 2-band device, using Orban’s patented “master /
bass” band coupling. It has an additional important feature: target-zone gating. If