OPTIMOD-FM OPERATION
3-37
that material with sustained bass (including speech) will sound substantially
less clean than it will with the
Medium or Soft settings.
LLHard
differs in two ways from the normal Hard mode of the bass clipper:
• LLHard automatically defeats the compressor lookahead. This action is
functionally equivalent to setting the
Lookahead control to Out, except
that it reduces input/output delay by 5 ms).
•
LLHard prevents the bass clipper from switching to Medium mode when-
ever speech is detected. By constraining the system in these ways, it en-
sures that the delay is always 15 ms.
To minimize speech distortion, the speech/music detector will automatically
switch the bass clipper to Medium when speech is detected, provided that
the Five-Band structure is active, Latency is High, and the Bass Clip Mode
is set to Hard. (See “Lookahead” on page 3-57 for more about the
speech/music detector.) If the bass clipper is set to
LLHard, the speech/music
detector will reset the clipper threshold to the setting specified by the
SpeechBCThr control. The default setting is “0 dB,” which results in very
little bass clipper action during speech. This prevents audible distortion that
might otherwise occur when speech is applied to this clipper.
Switching the
BassClipMode to LLHard (from any other mode) removes five
milliseconds of delay from the signal path. Switching can cause audible
clicks, pops, or thumps (due to waveform discontinuity) if it occurs during
program material. If you have some presets with
LLHard bass clipper mode
and some without, switching between these presets is likely to cause clicks
unless you do it during silence. However, these clicks will never cause
modulation to exceed 100%.
One of the essential differences between the
Hard and LLHard bass clipper
modes is that switching between
Hard and Med does not change delay and is
therefore less likely to cause audible clicks.
The Hard Clip Shape control (in Advanced Control) offers further control over
the sound of the
Hard and LLHard modes. See page 3-40.
Medium uses more sophisticated signal processing than Hard to reduce distor-
tion substantially.
Soft uses the most sophisticated look-ahead signal processing to reduce distor-
tion further. Using
Soft adds an additional 20 ms of delay to the processing (so
that the total is approximately 40 ms).
MED and SOFT are not available in Low Latency mode. The bass clipping is
always
HARD, but the Hard Clip Shape control is still available to “soften”
the clipping.
HF Clipping determines the amount of protection provided by the 8400’s high frequency
multiband clipper. This control was first introduced in the 8200 and allowed users to
trade off distortion against brightness. Because of the improvements in the 8400’s clip-
ping system, this control is much less useful than it was in the 8200, and we recommend
always setting it to “0.”
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