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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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