3-40
OPERATION ORBAN Model 8400
is actually considerable protection ±1 kHz from the pilot, but the full 60 dB
of protection is limited to ±250 Hz.
In all cases, the composite limiter protects the baseband to –80 dB from 55
to 100 kHz. This provides a 2 kHz guard band to protect the RDS/RBDS
subcarrier at 57 kHz.
We have noted that the Belar “Wizard” FM stereo monitor indicates some
pilot modulation even when the pilot protection filter is turned on. This is
because the Belar demodulates a bandwidth wider than ±250 Hz around the
pilot. A spectrum analyzer will reveal that, in fact, the pilot is protected by at
least 60 dB in this 500 Hz wide area of the spectrum.
Advanced Clipper Controls
The following Clipper control is found only in the Advanced Modify screen.
OSComp Dr (Compensation Drive)
sets the drive into the overshoot compensator 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 over-
shoots, 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 process-
ing. However, you can reduce it below “0” if you value the last bit of high
frequency cleanliness over loudness.
The overshoot compensator works at 256 kHz sample rate and is fully anti-
aliased.
Hard Clip Shape allows you to change the knee of the input/output gain curve of the
bass clipper when
Bass Clip Mode is set to HARD. It allows you to control the shape of
the “knee”—the transition between no clipping and flat-topping. “0” provides the hardest
knee, and corresponds to the characteristic in version 0.94 and earlier software, where the
transition between linear operation and flat-topping happens abruptly as the clipper’s in-
put level is changed. “10” is the softest knee, where the transition starts 6 dB below
BassClipThresh setting and occurs gradually. The factory default setting is “7.6.”
The Med and Soft bass clipper characteristics use sophisticated, look-ahead
algorithms that produce lower distortion than
Hard mode, regardless of
where the
HardClipShape control is set. However, operating in Hard mode
with the
HardClipShape control set beyond “0” may produce a tradeoff be-
tween punch and bass distortion that is more appropriate for pop music re-
quiring substantial bass punch to make its musical point. In any event, the
HardClipShape control adds a new color to the 8400’s sound palette—one
that is not duplicated by the existing
Med and Soft bass clipper characteris-
tics.
This control does nothing if the
Bass Clip Mode is set to MED or SOFT.
Speech Bass Clip Threshold (“SpeechBCThr”)
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