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INTRODUCTION
2
The dbx 160 and
161
are
single-channel
compressor/
limiters
combining
sophisticated
technology
and
user-
oriented features
in a
compact
package.
Unique
circuit
designs,
such
as
true
rms
level-detection
and
feed-forward
gain
reduction
,
place the
160 and
161
in
a
completely
different
class
from
conventional compressor/limiters.
The dbx
technique
of true
rms
level-detection gives
you
audible
benefits.
Most
compressor/limiters use
some
form
of
peak
detection,
with
fast
response
characteristics that
can have
a
disturbing
effect
on program
material.
True rms
level
detection
closely
simulates the response
of
the
human
ear.
Even
at
high
compression
ratios,
the gain
changing
action of the
160
Series
is
highly
listenable
and
natural
sounding.
Because
of the
unique
feed
-forward approach,
dbx
160
and 161
limiters
can
achieve
infinite
compression with
complete
stability
and
inaudible
distortion.
The dbx
approach
is
quite unlike gain
reduction
in a
conventional
compressor/limiter. Traditional
gain
reduction
is
accom-
plished
by
sensing
signal level
at
the
device's
output and
applying
a
correction
signal, via a
feedback
loop.
At
progressively higher
compression
ratios,
the
feedback
loop's
gain increases, distortion increases,
and
eventually
instability
or oscillation occurs.
To
avoid
this
problem,
many
con-
ventional
units
restrict
the
maximum
amount
of
feedback,
thus
restricting
the
maximum
compression
ratio
to
some
lower
ratio,
such
as
10:1 or 20:1.
The dbx 160 and
161 are
free of
the
instability
of excessive
loop
gain,
and
can
provide
infinite
compression (approximately
120:1).
In
addition
to increasing the
stability
and
the
available
range
of
compression, dbx's feed-forward
approach makes
it
possible for the attack
and
release
times
to
"track"
the
signal
envelope.
In
conventional compressor/limiters,
the
attack
and
release
times
depend on
feedback loop
gain,
which means
they constantly
must
be
readjusted for
optimum
results
at
different
compression
ratios.
Since the
attack
and
release
times
of
dbx
units
vary automatically
with the
rate
of
level
change
in
the
program
material
(the
envelope
shape),
operation
is
simplified;
no manual
attack/
release
adjustments
are required.
At
the
same
time, the
"naturalness" of
any
given
sound
is
better preserved.
GENERAL INFORMATION
Models
The Model 160
is
a
fully
professional
compressor/limiter
with
a
balanced
differential input,
with
an
automatic
ground-loop
compensated output
(hum
resulting
from any
ground
loop
at
the
output
is
automatically sensed
and
attenuated
at least
40dB),
and
with
a
special
protection
circuit
that
blocks
power
turn-on
and
turn-off transients
from
the output.
The Model
161
is
nearly the
same
as
the 160, but
is
priced for the smaller studio,
or the semi-pro
user.
It
has
the
same advanced rms
detection
and
feed-forward
circuitry as
Model
160,
but
it
lacks
turn-on/turn-off
transient protection,
and ground-loop compensation.
The
1
61
's
input
and output
are
unbalanced and terminated
in
RCA-type phono
jacks.
Both models have
adjustable threshold,
and
a
pair of
LED's
that indicate
when
the input
level
is
above
or
below
the threshold.
An
illuminated
meter
displays
a
full
60dB
range
and
is
switchable
to
read input
level,
output
level,
or
gain
change.
The
meter's
sensitivity
is
continuously
variable,
so
"zero
VU"
can be
adjusted
to
equal
your
system's
nominal
operating
level,
anywhere from +10
to
-10dB.
Output
line level
is
also adjustable,
±20dB.
Maximum
output on
the
160
is
+26dB
(1
5.5V)
into a high
impedance,
or
+24dBm
(12.3V)
into
600
ohms.
Maximum
output
on
the
Model
161
is
+18dB
(6.14V)
into
a
high
impedance,
or
+16dBm
(4.89V)
into
600
ohms.
Attractively styled
and
functionally designed, either
model
can stand alone
or
can be
mounted
in a
standard
19"
rack.
Two
units
can be
mounted
side-by-side
in
just
2
V
2
'
of
panel
space with
the optional
dbx RM-150-C
rack
mount
kit;
the
RM-150-D
is
for
rack
mounting
of
a
single
unit.
Applications
dbx
noise
reduction systems
now
make
it
possible to
process
programs
with
lOOdB,
or
greater,
dynamic
range.
Unfortunately,
in
some
applications
it
is
necessary
to
restrict
dynamic
range.
While
dbx
noise
reduction systems
are
used
in
the studio,
for
record production,
to
maintain
wide
dynamic
range,
this
range
must
often be
restricted to
optimize
the
sound
for
broadcast
and
home
playback.
The
restriction
of
dynamic
range
is
usually
done
with
a
com-
pressor,
in
the
final
stages
of recording
(or
record master-
ing). In
the
broadcast
field,
where
many
stations
compete
for
an audience,
a
high average audio
level
can
make
a big
difference to radio
station
ratings.
Compression
is
used
to
attain
high average
levels.
However,
unless
a
high-
quality
compressor/limiter
is
utilized,
distortion
and
unwanted
audible
side-effects
may
degrade
the
sound
so badly
that
the
advantages of
high average
level
are
overcome, and audience
interest
can
be
lost.
The
160
and
161
do
a
great
job
in
both
recording
and
broadcast
applications.
The dynamic
range
of
a
live
musical
performance can be
even
greater
than
lOOdB.
A
high-quality compressor/limiter,
used
judiciously,
can
restrict
the
dynamic
range,
raise
the
average
level,
help the operator avoid
clipping distortion,
and improve
the
overall
sound
quality.
Because
the
160 and
161
sound
so
natural,
they
won't
displease
performers,
making them
especially well suited
to
sound
reinforcement
applications.
Compressor/limiters
can
be
useful
in
other applications
too.
The 160 and
161
are
ideal for
use
as
a
high quality
line
amplifier
because
of
their
low
noise
and
distortion
and
high
output
drive.
The 160
and
161 have the
added
advantage
of
allowing
you
to
conveniently
dial
in
compression
at
any
time.
In
any
application requiring high-quality
compression