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Co-Operator
OPERATION
3-9
Fig.
3-1
:
Release
Shape
Curves
High-frequency
limiting.
The
high-frequency
limiter
is
essentially
a
variable
6dB/octave low-pass
filter
that
adapts
to
the
spectrum of
the
program
material
to
prevent overloading pre-emphasized
media
following
the
Co-Operator.
In addition
to
general-purpose high-frequency
limiting,
the
high-frequency
limiter
may
be
useful in de-essing vocals
which have
already
been mixed
with other
program
material
(it
performs
this
task
significantly
more
smoothly
than
the
Orban
dedicated de-essers
because
its
threshold
does
not
follow the average input
level,
and because
it
cannot
punch
"holes"
in
the
program).
The HF
limit
buttons enable
or
defeat the
high-frequency
limiter.
The HF
limit
but-
tons
do
not introduce gaps
in
the
program
material,
although
waveform
discontinuities
between
the input
and
output
of
high-frequency
limiter
may
result in slight
"clicks"
being heard
if
the buttons are
pressed during heavily-processed
program
material.
Since
their
short release
times preclude
stereo
imaging problems,
the
high-frequency
limiters
remain
in
DUAL mode
(each channel operating independently)
regardless
of
the position
of
the
MODE
button.
The
high-frequency
limiter
is
located
after the
leveler/compressor,
and
is
essentially
independent of
it.
Ordinarily, the
leveler/compressor
controls the input levels to the
limiter.
To
use the high-frequency
limiter
independently,
set
the
level
and
COMPR
buttons
and
the
GATE thresh
controls to
off.
When
the
Co-Operator
is
used
this
way,
adjust the
INPUT
atten
controls
with
particular care to
avoid over-driving
the
high-frequency
limiter
or clipping
the
VCAs.
The HF
LIMIT
pre-emphasis
switches
select
the
pre-emphasis
for the
high-frequency
limiter.
These
are
all
6dB/octave
curves
which
are
up
3dB
at
l/(2nT)Hz,
where
T
is
the
time constant
in
seconds.
25gs produces
the
least
high-frequency
limiting;
150gs
produces
the
most. Generally, the
pre-emphasis curve
should
match
that
of
medium
being
protected
(see the
preceding
"Example
Control
Settings"
and
the
following
table).
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