INTRODUCTION
The dbx Model 165 is
a
professional single channel
compressor/limiter that features the new dbx Over Easy
compression curve. The dbx Over Easy compression
curve permits extremely smooth, almost inaudible com-
pression due to the
gradual
change of
compression
ratio
around the threshold, instead of the customary sharp
threshold. This curve, plus dbx's true RMS level detector
coupled to a wide-range voltage controlled amplifier in
a feed-forward
circuit,
makes it
possible
to
achieve larger
amounts of compression without adverse audible side
effects.
The RMS level detector is separately accessible,
allowing various signal conditioners
—
equalizers, filters,
delay lines, etc.
-
to be inserted in either the level
detector or signal
path
independently.
This
feature aids
in the compression of certain difficult types of material,
as well as in the creation of
special
effects. In addition
to
dbx's automatically variable attack and release time
circuitry (as on the Models
160, 161,
162, 163 and
164), a
front panel switch and controls provide for
manually adjustable attack and release rates over a
very wide range.
The Model 165 also features stereo coupling for two
165's (at the
touch
of a
front panel button), LED
indicators showing whether the signal is at, above or
belaw the threshold of compression, a 30 d6 dynamic
range
meter
(indicating input, output
and
gain change
levels), and a rear panel zero VU calibration adjustment.
A
hard-wired
bypass
switch,
also located on
the
front
panel, is
convenient for checking the
effect of
the
compression, and assures failsafe flow of audio through
the
unit.
The maximum input level
is
+24
dB (12.3 V
RMS)
and
maximum output level is +23 dBm. The
output amplifiers have
a
source impedance of 47 ohms
and will drive input
loads
of 600 ohms or greater
impedance. Output gain is also adjustable over a very
wide
range
(t20
dB), so
the
Model 165 is
compatible
with virtually all professional sound and creative audio
equipment.
Perhaps the most flexible and useful compressor/
3A
—
Conventional Compressor/Limiter
limiter ever offered, the dbx Model 165 is well suited to
a
wide range of applications including:
tape recording,
disc mastering, radio and TV production and broadcast,
live concert sound reinforcement, and theatrical
production.
More About
Separate Level
Detector Access
Because auxiliary sound equipment can
be used to
process the level detector signal but not the main audio
input signal (or vice-versa), the
1 65
offers the user
an
opportunity to create many unusual effects. By con-
necting
it to
additional signal
processors, such as a
parametric equalizer, the Model 165can be converted
to a
de-esser,
a
vocal stresser
or a level-sensitive filter.
Certain musical or vocal elements in
a
program can
be
suppressed without
affecting others. In addition to these
signal conditioning functions, many creative special
effects
are possible.
More About Over Easy Compression
Conventional compressor/limiters have a sharp knee
at
the threshold point (see
Figure
3A). That is,
when the
input signal is below
the
threshold,
the gain remains
fixed (1:1 ratio or no compression), but when the input
signal goes above the threshold, the gain abruptly
decreases according to the
compression
ratio for
which
the
unit
is
adjusted
(several fixed compression ratios are
shown in Figure 3A). This abrupt change in gain in a
conventional compressor/limiter is often audible and
therefore undesirable
to
the user.
The dbx Over Easy approach utilizes a
soft knee
at the
threshold
of
compression (see Figure 3B). The
Over Easy
compressor/limiter gradually increases its
compression ratio
from 1:1
towards
the
set
compression
ratio
as
the input signal rises through the threshold
region. Thus an age old dream can be realized . .
.
dynamic range restriction without audible, abrupt gain
changes. When properly operated, the Model 165 is
a
highly effective compressor^imiter that you don't
hear working.
3B
“
Over Easy Compraa^or/Limiter
3
Over Easy**^ Varaus Conventional
Compression
5
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