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DESCRIPTION
AND
FUNCTION
OF
FRONT PANEL
FEATURES
I
i
While
the following control
descriptions
might
seem
unnecessarily
complex
on
first
reading,
they
have been
crafted
to
answer
any
reasonable
question
either
the
novice
or
the
experienced
user
might
ask.
The
effects
of,
and
interactions
between,
the
controls
have been
designed
to
promote
ease
of use,
facilitating
good
results
with
minimum
effort.
Some
of these
interactions
and effects
are
subtle,
and
are
much
more
easily
appreciated by
actual practice than by reading.
Refer
to
the
Quick Operating Guide above
for
an
overview,
and
to
the
Front
Panel Photograph
at
the front
of
this
Manual.
The
INPUT
ATTENuator
adjusts
the
drive
level
to
the
compressor/limiter,
thus
determining
the
amount
of
gain
reduction
for
a
given
setting
of
the
THRESHOLD
control.
In
most
cases (such
as
recording
studios)
where
a relatively
constant
level at
the
414A
output
is
desired,
this
control
is
used
(instead
of the
THRESHOLD
control)
to
determine
the
amount
of
G/R,
since there
is
no need
to
readjust
the
OUTPUT
ATTENuator
to
compensate
for
INPUT ATTENuator
adjustments
(except
when
very
low
ratios
are
used).
In
addition,
adjusting
either
the
ATTACK
TIME
or
RATIO
controls
also
adjusts the threshold
to
keep
the
peak
output
level
approximately
constant.
However,
this
automatic
threshold
adjustment does
not affect the
amount
of
G/R
available.
The
GAIN
REDUCTION
meter
is
electronically
conditioned
to
show
the
true
peak
gain
reduction
of
the
VCA
(Voltage-Controlled
Amplifier)
in
dB.
The
G/R
OVERLOAD
lamp
lights
when
no
further
G/R
is
available.
When
this
lamp
is
lit,
the
gain
of
the
VCA
is
"stuck"
at
its
lowest
available
value.
Further
increases
in
input
level
will
cause
proportional
increases
in
output
level,
rapidly driving the
VCA
into clipping.
The
amount
of
available
gain
reduction
changes
with
the
setting
of
the
THRESHOLD
control:
When
the
control
is
set
to
"+1D",
15dB
of
G/R
is
available.
This
increases
to
35dB
when
the control
is
set
to "-10".
Therefore,
G/R
overloads cannot be cleared with
the
THRESHOLD
control,
because
the
available
gain
reduction
is
reduced
in
exact
proportion
to
the
increase
in
threshold.
G/R
overloads
must
be
cleared
by
turning
down
the
INPUT
ATTENuator.
The
THRESHOLD
control
determines
the
threshold
of
compression
(and
thus
the
amount
of gain reduction)
without changing
the
below-threshold
gain.
It
is
mostly
useful
in
sound reinforcement
applications
where
the
system
gain
must
be constrained
to a
maximum
value
(to
avoid feedback), while control over the
amount
of
gain reduction
is
retained.
Adjusting the control
will
proportionally
change
the
nominal compressor output
level.
This
control
has been
carefully
implemented
to
avoid
compromising
the
signal-
to-noise
ratio
of
the
compressor
regardless
of
the
setting
of
the
control.
Accordingly,
the
amount
of
available
gain
reduction
available
from
the
compressor
varies
in
direct
proportion
to
the
setting
of
the
THRESHOLD
control: there
is
less
G/R
available
at
high thresholds
(where
less
G/R
will
be
produced)
than
at
low
thresholds
(where
more
G/R
will
be
produced).
Best
VCA
distortion
and
signal-to-noise
performance
are
achieved
with
the
control
at
its
detented
"0"
setting.
However,
performance compromises
are
extremely
small over the
range
of the
control,
and
it
can
be
used
freely
to
achieve your
goals.
15
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