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its distinctive ‘sound’ or timbre. The PIPP* limiter will hold the
peaky side to the 100%-modulation point, and will ‘expand,’ or
increase the amplitude of the companion polarity until it also
reaches the 100%-modulation limit.
This implies that the waveform, which by definition is already
“distorted” with natural harmonic content, will be further dis-
torted by the PIPP* limiter. Technically accurate, a solo saxo-
phone will sound more saxophone-like and speech or solo vo-
cals will exhibit a slight ‘edge’ or character. But pop music and
other program material that contains a plurality of instruments
and vocals will have less asymmetry and will be less affected by
PIPP* limiting. Anyway, there’s an option to turn this novel fea-
ture off if you are a purist or otherwise don’t buy any of this.
Lookahead
Limiting
The DAVID IV broadband limiter is a
lookahead
limiter, acting
to reduce program peaks essentially before they reach it. No,
this limiter is not a member of the Psychic Friends Network™, it
simply introduces a short delay in the signal path so the limiter
can sense a peak and reduce gain before the peak actually
comes along. The delay is only a couple of milliseconds, but
this practice prevents flat-top-clipping of the program wave-
form during the limiter’s initial gain-reduction ‘attack’ phase.
Avoiding flat-top-clipping through the use of lookahead limit-
ing eliminates short-term (transient) intermodulation distortion
(TIM) of the program audio. Clipping, whether hard or soft, is
generally to be avoided in flat-power-bandwidth transmission,
but can be used with good success in pre-emphasized systems
such as FM broadcasting. More about this later.
Navigate to
Processing / Peak Limiting
:
PIPP*,
Normal
or ITU?
This menu first allows the selection of either the proprietary
PIPP*
limiter, or a more conventional
Normal
limiting func-
tion that does not include our controversial ‘waveshape-
symmetry management.’ The third choice,
ITU
, is a special-
purpose limiting mode that ensures compliance with a broad-
casting standard practiced in certain European countries. This
is discussed in detail under the next subheading.
Action of the PIPP* limiter was described earlier, and use of this
function will be predicated on how particular program material
sounds, which of course also depends on the setup of other
processing parameters. You may wish to proceed with DAVID
IV setup using the
Normal
limiter selection, and then assess
any advantage (or not) by switching back and forth between
Normal
and
PIPP*
.
Summary of Contents for 719
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