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When
the CLIPPING control
is operated at " 0" or below and slower release time
settings are used, it is possible to operate the HF LIMITING control at " 10" ( full
hard) without objectionable distortion, provided that the program material is super-
clean.
If the CLIPPING control is operated beyond " 0" and/or faster release times
are used ( such that greater level and density is produced), it is usually necessary to
readjust the HF LIMITING control closer to " soft" to avoid objectionable distortion.
Fortunately,
the
HF
limiter " knows"
that
greater
density
and
level
have
been
produced when these other controls are operated more
aggressively, and
most
of
the
necessary increases in HF limiting will occur
automatically. In fact, you will
clearly
hear
a loss
of
highs
when
you
adjust
any
control
to
produce
greater
loudness
and
density --
this
is
an
automatic
response
to
the
loudness/brightness/distortion
tradeoff
discussed
above. ( The
main
reason
for
readjusting
the
HF
LIMITING
control
is
to
compensate
for
the
HF
limiter's
relatively low compression ratio.)
Because excessive loudness in TV audio is usually not desired ( as discussed above),
the CLIPPING control will ordinarily be operated low enough to permit operation of
the HF LIMITING control at " 10" ( full " hard") without difficulty.
Gate Threshold: The GATE THRESHOLD control
is adjusted so that
noise is not
brought up during short pauses.
As
discussed
in
more
detail
in
Release
Time
and
Amount
Of Gain
Reduction
above, in GATED mode, the gain drifts slowly towards 10dB gain reduction (" 0" on
the G/R meters).
For
most stations, the noisiest program material is 16mm optical sound and news
actualities. The GATE THRESHOLD control should be adjusted until quieter parts of
16mm
sound tracks do not permit compressor recovery ( which would result in an
approximate 10dB increase in hiss levels underneath the desired audio). Determining
what " quieter
parts"
means
is
a subjective
decision.
The
tradeoff
is
excessive
dynamic
range
versus
audible
hiss
pump- up.
Generally,
we
have
found
that
best
results are obtained when the control is set between " 5" and " 6".
Ordinarily, the faster the RELEASE TIME, the higher the GATE THRESHOLD must
be
set
to
avoid
problems,
as
faster
RELEASE
TIMES
will
pump
up
hiss
more
quickly.
ON EXCESSIVE
COMMERCIAL
LOUDNESS
The
OPTIMOD-TV
loudness
controller
will
control
the
loudness
of
most
commercials
sufficiently
well
to
eliminate
viewer
annoyance
and
subsequent
complaints. However, the equalization used in the original recording of certain spots
may still be unpleasant and unnatural.
If this problem is observed, it may be desirable to re- equalize the individual spots
upon
transfer to video tape or cart, subduing an unnaturally boosted midrange, for
example,
by reducing 2kHz to 4kHz energy as necessary to achieve more natural
frequency balances. The Orban 672A ( mono) and 674A ( stereo) equalizers are good
choices
for
such
work ( and
other
audio
production
as
well)
because
they
are
extremely flexible, yet easily used by only modestly experienced station personnel.
SUMMARY
The
basic
TV
audio
medium
is
capable
of
very
high
quality.
More
and
more
viewers are equipped to receive and appreciate such quality when it is broadcast. In
addition, many people are now being exposed to the excellent quality of " Beta Hi -
Fi" and of the "Laservision" videodisk stereo sound tracks.
5-7
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