b)
The compressor/limiter is manually
defeated
by means
of the
COMPRESSOR OPerate/DEFEAT switch.
This feature,
in either mode, enables
the operator
to avoid sudden,
unpredictable gain
changes under
typical "real-world"
conditions.
In
mode
(a),
the gain
is
prevented from freezing
permanently at an
abnormally
low or
high
value during low-level program or pauses
which
have
automatically activated
the gate. (The gate
is
activated when the
input
level drops below a level
adjusted by the operator
means of the
GATE THRESHold control.)
Instead of
freezing
permanently, the gain drifts
very slowly
,
up or down,
toward the point
set
by the operator by means of the
IDLE GAIN control.
The IDLE GAIN control is ordinarily set to match the
average amount of gain
reduction used. If
the
gain were too high when
the program restarted, then
hiss
or
noise
would
be unnecessarily increased. If
the gain were too low
,
a
"hole" would occur until the compressor had
a chance to recover through the
normal release process.
Thus the
IDLE
GAIN control permits the
compressor to unobtrusively bridge
through low-level program and silence, neither pumping
up
noise during
pauses
nor introducing "holes"
once
the program restarts.
Unlike a conventional
noise
gate, it does
not
cut off ambience and/or instrument
decays
and
is thus more
subtle, particularly on mixed program material.
If
the gating feature
is
not
activated, then
the
compressor/limiter will
recover
to full
gain during pauses or low-level
passages,
and
the
IDLE
GAIN
control
is
ineffective. This mode tends to
pump up noise such
as
tape hiss at
the beginning of
a
mix, and
use
of the
gating and
IDLE GAIN
features can
avoid this and other similar problems.
Similarly,
when the
compressor/limiter function is manually defeated (mode
(b)), the compressor/ limiter gain moves fairly
quickly
(but not
abruptly)
to the
value
preset by
means of
the
IDLE GAIN control.
If
the
gain of
the
compressor/limiter was already at
this value (or close to
it), then the
fact
that the compressor/limiter
was
defeated
will be
not
be detected. Under any
circumstances,
the switching will be smoother
than that
resulting from a
conventional abrupt in/out
switch.
The
compressor/
limiter
OPerate/DEFEAT switch defeats
the gain reduction
action
of the compressor/limiter section only
.
(The de-esser
is
unaffected). In
DEFEATed
mode, the switch
smoothly forces
the VCA
gain to
a
constant value
fixed by the
setting
of
the
IDLE
GAIN control.
This
switch
is
NOT
a
hard-wired bypass switch; if a bypass
is necessary
to
keep a sound system
functioning in an emergency mode despite a
failure in the
424A,
this function must be provided externally.
The de-esser
SENSITIVITY control determines the threshold
of de-essing.
As
it
is
rotated clockwise, "ess" sounds will be suppressed
more and
more.
Unlike similar
controls on the other Orban de-essers,
the
424A
SENSITIVITY
control adjusts the threshold relative
to an absolute level,
rather than
relative
to the
average level of the input program
material. This means
that
the 424A
de-esser works most consistently
only when the vocal has
been
gain-ridden
by
the preceding compressor/limiter. A significant
advantage of
this
arrangement
is
that de-essing
of
vocals in
mixed tracks
is
far more practical,
since
the de-
esser is
less likely to affect low-level
high
frequency
musical
material
unrelated to the vocal.
15
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