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Since
the
compressor
dynamics
stay
natural
even
at
high
levels
of
G/R,
the
primary danger of using large amounts of G/R is that the level of soft portions of
wide- dynamic- range
input
material
may
eventually
be
increased
unnaturally,
and
optical sound track hiss may be increased to unpleasant levels in presence of signal
above the GATING threshold.
Experience has
shown that
correct
adjustment
of
the GATE THRESHOLD
control
is quite critical if undetectable gain riding is to be achieved. This is because the
level
of background sound is often rather close to the level of dialogue or other
foreground
sound.
Settings
between " 5"
and " 6"
seem
to
give
the
best
results.
The
TOTAL
MASTER
G/R
and
COMPRESSION
MASTER
G/R
meters
are
calibrated from + 10 to - 15dB G/R; the BASS G/R meter is calibrated from + 10 to
-20dB
G/R.
If
the
GATE
were
defeated,
both " Master"
and " Bass"
compressors
would
recover to + 10dB
in the absence of signal. Thus "+ 10dB" on the meters is
actually no gain reduction.
However,
if the GATE is activated, the release time is slowed by a factor of 10
or
so,
and
the
gain
slowly
drifts
toward
10dB
gain
reduction.
Because
the
gain
reduction meters will therefore sit at 10dB gain reduction in absence of signal, we
have
calibrated the meters so that
this point is " 0" to avoid confusing operators
who might otherwise think that the compressors were faulty.
Because
of
this design
feature, smoothest
performance
is
obtained when
average
levels out of the console or switcher are made to cause 10dB gain reduction ( i.e.,
to
indicate
approximately " 0"
on
the
G/R
meters).
This
way,
noise
will
neither
increase nor decrease during pauses in the audio.
When
OPTIMOD-TV
is
operated
with
fast
release
times ( particularly
in
LINear
mode),
the
sound
will
change
substantially
as
more
gain
reduction
is
used.
This
means that operator gain riding is more critical, and also that you must decide on
the basis of listening tests how much gain reduction gives you the dense sound you
want without a feeling of overcompression and fatigue.
If
aggressive
gain
riding
is
desired,
the EXPonential
mode
is
usually
preferable,
sounding less " squashed"
than LINear
mode. ( To demonstrate this, the comparison
must
be made with the RELEASE TIME control readjusted in each mode to obtain
the same speed of correction for large gain errors.)
Unlike the metering on some familiar processors, the red in the OPTIMOD-TV gain
reduction
meter means business! When the meter is in the red, it means that the
compressor
has
run
out
of
gain
reduction
range,
that
the
circuitry
is
being
overloaded, and that nastiness is likely to commence. Because the compressor has
25dB of gain reduction range, this problem should never occur if OPTIMOD-TV has
been set up for a sane amount of gain reduction under ordinary program conditions.
But beware the different peak factors on voice and music -- if voice and music are
peaked identically
on
a VU meter,
voice may
cause up to
10dB
more
peak
gain
reduction than does music!
High Frequency Limiting This control trades off distortion against high frequency
loss.
When the control
is moved toward " soft" ( more HF limiting), the sound will
become duller but less " gritty". When the control is moved toward " hard", the sound
will become brighter, but more gritty and " smeared".
Because the clipper in OPTIMOD-TV cancels distortion at low frequencies, the HF
LIMITING control will have a different effect on clipping distortion than you might
expect. Gross breakup ( principally sibilance splatter) will not occur, and you must
listen
to
the
upper
midrange
and
the highs
to
hear
the
effect
of
the
clipper.
5-6
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