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OPERATION ORBAN Model 8400
bass harmonic distortion that can improve the apparent bass response of small receivers
like clock radios. The hard clipper also has a shape control, allowing you to control the
“knee” of its input/output transfer curve.
“Intelligent” Clipping: There have been major changes and improvements in the 8400’s
back-end clipper by comparison to the 8200. The clipping system is “what separates the
men from the boys” in on-air processing. A good clipping system is the key to being si-
multaneously loud, clean, and bright.
In general, the improvements come in two areas: (1) more intelligence in preventing au-
dible clipping distortion with difficult program material, and (2) better overshoot com-
pensation. (1) means that the 8400 is much less likely to encounter program material that
unexpectedly causes gross clipping distortion—a particular problem with systems that
rely on simple composite clipping for peak control. (2) means that the 8400 controls
overshoots more tightly than does the 8200, and does so with less audible distortion and
HF loss.
We prevent excess clipping distortion by reducing the drive level to the clippers as re-
quired. Although this is done in a sophisticated, frequency-dependent way using look-
ahead techniques to minimize audible side effects, you may hear some audible compres-
sion and intermodulation artifacts when you use this mechanism to excess. If you hear
such artifacts and find them objectionable, you should reduce the setting of the
MB Clip-
ping
(Multiband Clipping) control.
In most cases, reducing the setting of the Less/More control does this auto-
matically.
One preset,
LOUD-COMPRESSED, exploits these compression artifacts to
achieve a dense, “highly compressed” sound, which some people like to use
for certain rock and pop music formats.
DSP-derived Stereo Encoder: The 8400’s stereo encoder is derived from algorithms
first developed for the high-performance Orban 8218 stand-alone encoder. The 8400’s
stereo encoder operates at 512 kHz-sample rate to ease the performance requirements of
the D/A converter’s reconstruction filter, making it possible to achieve excellent stereo
separation that is stable over time and temperature.
The 8400 has two independent composite outputs, whose levels are both software-
settable. The second output can be configured to provide a 19 kHz-reference output for
subcarrier generators that need it. For convenience, two SCA inputs sum into the 8400’s
analog composite output amplifier.
The 8400 does not digitize SCAs.
Composite Level Control Processor: Orban has traditionally opposed composite clip-
ping because of its tendency to interfere with the stereo pilot tone and with subcarriers,
and because it causes inharmonic aliasing distortion, particularly between the stereo main
and subchannels. Protecting the pilot tone and subcarrier regions is particularly difficult
with a conventional composite clipper because appropriate filters will not only add over-
shoot but also compromise stereo separation—filtering causes the single-channel com-
posite waveform to “lift off the baseline.”
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