Inovonics DAVID IV 719 N, Инструкция по установке и эксплуатации

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The only truly undistorted audio waveform is a pure tone, a
sine wave. A sine wave is inherently a symmetrical waveform
with the positive and negative halves mirror-images of one an-
other. The PIPP* limiter would divide, limit and recombine
these halves to create a spitting image of the original: an ampli-
tude-limited symmetrical sine wave with no added distortion
components.
An asymmetrical program waveform, notably speech, vocals or
a solo musical instrument, will demonstrate a ‘peaky’ nature in
either the positive or negative direction. This is due to the ad-
dition of natural overtones (harmonics) that assign the source
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, opposite polarity un-
til 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. This is technically accurate; a solo
saxophone will sound more saxophone-like and speech or solo
vocals will exhibit a slight ‘edge’ or character. But pop music
and other program material that contains a plurality of instru-
ments and vocals will have less asymmetry and will be less af-
fected by PIPP* limiting. Anyway, there’s an option to turn this
novel feature off if you are a purist or otherwise don’t buy into
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.’
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 some degree of success in pre-emph-
asized systems like FM broadcasting. More about this later.
ITU, Normal
or PIPP*
Limiting?
Under the
Limiter
heading on the
Processor
Webpage, the choice
of which
Peak Limiting:
option to use is yours.
The first offering,
ITU
, is a special-purpose limiting mode that
ensures compliance with a broadcasting standard practiced in
certain European countries. This mode is important to Europe-
an broadcasters and will be discussed in detail under the next
subheading.
Action of the
PIPP*
limiter has been described above, and
whether or not to use this mode will be predicated on how par-