Orban OPTIMOD-FM 8700, Руководство по эксплуатации

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OPTIMOD-FM DIGITAL OPERATION
3-9
Because the process can subtly alter the stereo spatial effect, it may be inappropriate
of “audiophile” formats, although its advantages in reducing multipath distortion
are likely to be far more subjectively important. It can be smoothly activated and de-
feated via a delay-matched crossfade, so it is practical to do live switching between a
preset with the process active and one where it is inactive.
Because it adds about 250 ms of delay, the phase skew corrector can be bypassed
completely in Setup (step 8 on page 2-32). If you are not using it and do not need to
activate it smoothly “on-air,” bypass it.
Figure 3-1 shows a 10-tone test stereo waveform with a 90 degree phase difference
between each tone in the left and right channels. Power (RMS) in the two channels
is the same. Frequencies range from 250 to 9250 Hz in 1 kHz increments. The 90-
degree phase shift produces a different differential time delay for each tone: Each
time the frequency is halved, the delay doubles. Figure 3-2 shows the effect of the
phase correction: all 10 tones are now in-phase.
Two-Band Gated AGC: The AGC is a two-band device, using Orban’s patented “mas-
ter / bass” band coupling. It has an additional important feature: target-zone gat-
ing. If the input program material’s level falls within a user-settable window (typical-
ly 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.
Figure 3-1: 10-Tone Lissajous Pattern,
250-9250 Hz, 90 degree phase difference
Figure 3-2: 10-Tone Lissajous Pattern, Pro-
cessed by Phase Corrector