Orban OPTIMOD-FM 8700, Operating Manual

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OPTIMOD-FM DIGITAL OPERATION
3-51
HF Clipping determines the amount of protection provided by the 8700i’s high fre-
quency multiband clipper. This control was first introduced in the 8200 and allowed
users to trade off distortion against brightness. Because of subsequent improve-
ments in the clipping system, this control is much less useful than it was in the 8200
and we recommend always setting it to “0.”
Final Clip Drive control adjusts the level of the audio driving the back end clipping
system that OPTIMOD-FM uses to control fast peaks. The
F
INAL
C
LIP
D
RIVE
control
primarily determines the loudness/distortion trade-off.
Turning up the F
INAL
C
LIP
D
RIVE
control drives the final clipper and overshoot com-
pensator harder, reducing the peak-to-average ratio, and increasing the loudness on
the air. When the amount of clipping is increased, the audible distortion caused by
clipping is increased as well. Lower settings of the
F
INAL
C
LIP
D
RIVE
control reduce
loudness, of course, but result in a cleaner sound.
If the M
ULTIBAND
R
ELEASE
control is set to its faster settings, the distortion produced
by the back-end clipping system will increase as the M
ULTIBAND
D
RIVE
control is ad-
vanced. The F
INAL
C
LIP
D
RIVE
and/or the MB L
IMIT
T
HR
(Multiband Limit Threshold)
controls may have to be turned down to compensate. To best understand how to
make loudness/distortion trade-offs, perhaps the wisest thing to do is to recall a fac-
tory multiband preset and then to adjust the
L
ESS
-M
ORE
control to several settings
throughout its range. At each setting of the L
ESS
-M
ORE
control, examine the set-
tings of the M
ULTIBAND
D
RIVE
and MB L
IMIT
T
HR
controls. This way, you can see how
the factory programmers made the trade-offs between the settings of the various
distortion-determining controls at various levels of processing.
The 8700i’s multiband clipping and distortion control system works to help prevent
audible distortion in the final clipper. As factory programmers, we prefer to adjust
the
F
INAL
C
LIP
D
RIVE
control over a very narrow range (typically –0.5 dB to –1.0 dB)
and to determine almost all of the loudness/distortion trade-off by the setting of the
M
ULTIBAND
C
LIPPING
control.
The final clipper operates at 256 kHz sample rate and is fully anti-aliased.
Advanced 8500-Style Peak Limiter Controls
The following Peak limiter control is found only in the Advanced Modify screen.
OSComp Dr (Overshoot Compensation Drive) sets the drive into the overshoot com-
pensator with reference to the final clip threshold, in units of dB. The normal setting
is “0 dB.”
The overshoot compensator can produce audible distortion on material
with strong high frequency content (like bell trees) and this control lets
you trade off this distortion against loudness. (Such material can cause
strong overshoots, forcing the overshoot compensator to work hard to
eliminate them.) We do not recommend operating this control above “0”
because this would reduce the effectiveness of the distortion cancellation
used in earlier processing. However, you can reduce it below “0” if you
value the last bit of high frequency cleanliness over loudness.