Orban 424A - Page 16

At
faster ATTACK TIME settings, substantial peak
limiting action is produced
with typical program material.
As
the
ATTACK TIME is slowed, the
424A acts
more and more like a pure compressor,
and fast peaks are permitted to
overshoot more and more.
Because
overshoots tend to increase, the
compression threshold
is
automatically lowered
as
the attack time
is slowed
to
avoid clipping
the
Voltage-Controlled
Amplifier
(VCA) used
as
the gain-control element.
At
the
very
slowest attack
times,
the release
time is also lengthened by a factor of
approximately
4:1 to assure
that the
424A is working in a truly "averaging"
mode
at these very
slow attack
times, and that
the attack
time
does not
get
slower
than
the
release
time.
The RELEASE TIME control
'
s cales the
program-controlled release
characteristic faster and slower. (The release
time is not constant; it is varied
according to the previous history of the program dynamics.)
To
avoid
having fast transients punch "holes" in the program material, the
release rate is
automatically speeded
up
after
a
large change in gain reduction.
This creates a fast "peak limiting" function which rides on top of a much
slower
"compression"
function.
It
is
the
recovery rate of the
"compression"
function which
is affected
by
the RELEASE TIME
control.
The RELEASE SHAPE switch further modifies the
action of the
RELEASE
TIME control. It determines if
the
recovery
rate (in dB/second) of the
"compression" function
is
constant (LINear
mode), or if it starts out slowly,
and
then
speeds up
as
it goes along (Exponential mode),
as
in Fig.
C-2.
(The
fast limiting recovery
is unaffected by the RELEASE SHAPE switch.)
The LINear mode almost always
sounds
more natural.
OdB
VCA
GAIN
-20dB
TIME
—
>
Fig.
C-2:
LINear VERSUS
Exponential RELEASE
SHAPES
While the
initial
release
rate
(dB/sec)
in EXPonential mode is
approximately
three times
slower than in
LINear mode for a
given setting
of
the
RELEASE
TIME control, with large amounts
of gain
reduction
it
becomes
approximately
three times faster than LINear mode by the time the
compressor
has fully
recovered.
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