Orban OPTIMOD-FM 8600Si, Operating Manual

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OPTIMOD-FM DIGITAL OPERATION
3-35
attempt to make this ratio constant as the program material changes. It can there-
fore create a bright, present sound without over-equalizing material that is already
bright.
30HZ HPF (“30 Hz High Pass Filter”) determines if a 30Hz 18 dB/octave highpass fil-
ter is placed in-circuit before other processing. Although not a stereo enhancer con-
trol, it is found on the stereo enhancer page (for convenience) because, like the ste-
reo enhancer, it can be adjusted without eliminating
L
ESS
-M
ORE functionality.
PH-ROTATE (“Phase Rotator”) is not a stereo enhancer control. It determines if the
phase rotator will be in-circuit. The purpose of the phase rotator is to make voice
waveforms more symmetrical. This can substantially reduce distortion when they are
peak limited by the 8600Si’s back end processing.
In most cases, we recommend that the phase rotator be left active. However, be-
cause it can slightly reduce the clarity and definition of program material, you can
defeat it if you are operating the 8600Si conservatively and not attempting to
achieve very high on-air loudness.
You have somewhat more leeway than you do in older Orban FM processors like the
8200 because the 8600Si’s new distortion control will work to help prevent audible
speech distortion even when the phase rotator is switched out.
Stereo Enhancer Controls
The stereo enhancer is common to the FM and HD processing chains. You can oper-
ate it in one of two modes or “styles.” The first emulates the Orban 222 analog ste-
reo enhancer, while the second mode, called Delay, emulates a popular enhancer
from another manufacturer that adds a delayed version of the L–R signal to the
original L–R to create stereo enhancement. (See
Stereo Enhancement on page 3-8
for more information.)
Both modes have gating that operates under two conditions.
•
The two stereo channels are close to identical in magnitude and phase.
In this case, the enhancer assumes that the program material is actually
mono and thus suppresses enhancement to prevent the enhancement
from exaggerating the undesired channel imbalance.
•
The ratio of L–R / L+R of the enhanced signal tries to exceed the threshold set by
the L-R / L+R Ratio Limit control.