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1)
Input
Attenuators ( Left
and Right):
Determine
the
amount
of
gain
reduction
(for
a given audio level going into the processor), and therefore how much the
loudness of soft program material is increased. OPTIMOD-TV has been designed
to work best with a nominal gain reduction of 10dB ( corresponding to " 0" on the
G/R meter).
[In
a mono
installation
with
both
channels
driven
in
parallel,
it
is
important
that both channels be in balance. After the LEFT INPUT ATTEN is adjusted for
the
desired
amount
of
gain
reduction,
and
assuming
that
the
OUTPUT
ATTENUATORS
have
been
correctly
balanced
by
following
the
instructions
in
Part
4,
balance
can
be
achieved
by
connecting
a sensitive
AC
voltmeter
between the LEFT (+) OUTPUT and the RIGHT (+) OUTPUT, and by adjusting
the RIGHT INPUT ATTEN until the meter nulls.]
2)
Release
Time:
Determines
how
fast
the
gain
of
the " Master"
compressor
increases when the program material gets soft. Mostly, this control affects the
density
of
the
sound,
which
is
a fundamental
fatigue- determining
factor.
3)
Release Shape: Determines if the Master band of the dual- band compressor will
release at a constant number of dB/second ( LINear) or if the release will start
out
slowly
and
speed
up
as
it
progresses ( EXPonential).
LINear
often
sounds
most natural on musical programming. However, EXPonential is useful when the
"open" sound of a slow release time is desired, yet the compressor must quickly
gain- ride
program
material
with
wide
or
uncontrolled
dynamic
range --
a
newscast, for example.
4)
Clipping:
Determines
the
drive
level
to
the
Hilbert- Transform
Clippers,
and
therefore how much of the signal is peak- limited by these circuits. While this
peak
limiting
circuit
creates
substantially
less
audible
distortion
than
conventional clipping, distortion can nevertheless become audible if the circuit is
driven too hard. Thus the loudness/distortion tradeoff is primarily determined by
this control.
(The threshold of the loudness controller is forced to track the threshold of the
compressors as determined by the CLIPPING control. This forces the maximum
permitted
loudness
to
be
proportional
to
the
overall
average
loudness,
and
prevents the loudness controller from " fighting"
the
desired changes
in overall
average loudness which result from adjusting the CLIPPING control.)
5) High Frequency Limiting Determines a tradeoff: the degree to which the highs
are controlled by filtering ( which can make them dull), or by clipping ( which can
make
them
distorted). CCW settings ( SOFT)
cause
more filtering;
CW settings
(HARD) cause more distortion.
6) Bass
Coupling:
Determines
if
the
compressor
will
operate " wideband",
completely " independent", or somewhere in between. In " wideband" mode, the air
sound
is
most
faithful
to
the
sound
of
the
original
program
material;
in
"independent" mode, bass balances are more uniform and bass is often increased.
To avoid pulling up stage rumble and other low frequency noise, OPTIMOD-TV is
ordinarily operated towards the " wideband" mode.
7)
Gate
Threshold:
Determines
what
input
level
the
system
considers " noise".
Below this level, the release time of the compressor is slowed by a factor of 10
or
so
to
prevent " breathing",
and
the
compressor
releases
towards
10d8
gain
reduction (" 0" on the G/R meter).
5-3
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