Orban Optimod-FM 8300 Operating Manual page 152

3-34
OPERATION
Turning up the F
C
INAL
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
also increases. Although lower settings of the F
they make the sound cleaner.
If the R control is set to its faster settings, the distortion produced by the
ELEASE
back-end clipping system will increase as the M
The F C D and/or the M
INAL LIP RIVE
turned down to compensate. To best understand how to make loudness / distortion
trade-offs, perhaps the wisest thing to do is to recall a factory multiband preset, and
then to adjust the L
ESS
each setting of the L
ESS
and M L T
ULTIBAND IMIT HRESHOLD
grammers made the trade-offs between the settings of the various distortion-
determining controls at various levels of processing.
The 8300's multiband clipping and distortion control system works to
help prevent audible distortion in the final clipper. As factory program-
mers, we prefer to adjust the FINAL CLIP control through 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 Multiband Clipping
control.
The final clipper operates at 256 kHz sample rate and is fully anti-aliased.
COMP DRV ("Composite Limiter Drive") sets the drive level, in dB, into the 8300's
composite limiter.
This control has no effect on the 8300's left and right analog or digital outputs.
The COMP DRV control is set to "0 dB" for most factory presets. At this
setting, it removes a few tenths of a dB of residual overshoot from the
audio processing without affecting audio quality. We prefer to use the
audio-domain overshoot compensation to do most of the work because
it operates at a 256 kHz sample rate and is fully anti-aliased, whereas the
composite limiter will inevitably introduce aliasing around 38 kHz upon
demodulation in the receiver. This is because it introduces spectrum in
the stereo subchannel area when it clips material in the 0 to 15 kHz area.
Clipper Controls
Full Modify Name
---
BASS CLIP
---
BCL MODE
FINAL CLIP
COMP DRV
---
MPX OFFSET
control drives the final clipper and overshoot compensator
LIP
L
ULTIBAND
control to several settings throughout its range. At
-M
ORE
control, examine the settings of the M
-M
ORE
controls. This way, you can see how the factory pro-
Advanced Name
Overshoot Compensator
Drive
Bass Clip Threshold
Bass Clip Shape
Bass Clip Mode
Final Clip Drive
Composite Limiter Drive
Speech Bass Clip
MPX Power Offset
Table 3-5: Clipper Controls
control reduce loudness,
C
INAL LIP
D control is advanced.
ULTIBAND RIVE
T controls may have to be
IMIT HRESHOLD
Range
–2.0 ... +2.0
–6.0 ... 0.00
0 ... 10
Soft, Med, Hard, LLHard
–3.0 ... +5.0
Off, 0 ... 3 dB
–6.0 ... 0.00
0 ... –10dB
ORBAN MODEL 8300
D
ULTIBAND RIVE