dbx 160X User manual
MODEL
160X/XT
Single-
Channel
Compressor/Limiter
(Preliminary)
I
CAUTION
|
1
AVIS
|
RISK
OF
ELECTRIC
SHOCK
DO
NOT
OPEN
RISQUE
DE
CHOC
ELECTRIQUE
NE
PAS
OUVRIR
CAUTION:
TO
REDUCE
THE
RISK
OF
ELECTRICAL
SHOCK,
DO
NOT
REMOVE
COVER
(OR
BACK).
NO
USER
SERVICEABLE
PARTS
INSIDE.
REFER
SERVICING
TO
QUALIFIED
SERVICE
PERSONNEL
WARNING:
TO
REDUCE
THE
RISK
OF
FIRE
OR
ELECTRICAL
SHOCK,
DO
NOT
EXPOSE
THIS
APPLIANCE
TO
RAIN
OR
MOISTURE.
This
symbol,
wherever
it
appears,
alerts
you
to
the
presence
of
uninsulated
dangerous
voltage
inside
the
enclosure
—
voltage
that
may
be
sufficient
to
constitute
a
risk
of
shock.
This
symbol,
wherever
it
appears,
alerts
you
to
important
operating
and
maintenance
instructions
in
the
accompanying
literature.
Read
the
manual.
Manufactured
under
one
or
more
of
the
following
U.S.
patents:
3,377,792;
3,681,618,
3,714,462,
3,789,143,
4,097,767;
4,329,598;
4,403,199;
4,409,500;
4,425,551;
4,473,795.
Other
patents
pending.
This
dbx-branded
product
has
been
manufactured
by
AKG
Acoustics,
Inc,
AKG
is
a
registered
trademark
of
Akustiche
u.
Kino-Gerate
Ges
m.b.H.,
Austria.
All
trademarks
are
property
of
their
respective
companies.
This
manual
is
part
number
96010-000-02
©
Copyright
1993
by
AKG
Acoustics,
Inc.
150
-
FB
-1/93
dbx
dbx
Professional
Products
a
division
of
AKG
Acoustics,
Inc.
1525
Alvarado
Street,
San
Leandro,
CA
94577
USA
Telenhone
(
1
)
510/351-3500
Fax:
(1)
510/351-0500
QUICK
SETUP
dbx
Professional
Products
Quick
setup
_
To
get
your
unit
up
and
running
as
quickly
as
possible,
do
the
following
steps.
For
more
detailed
information,
refer
to
the
specified
pages.
□
Unpack
and
Inspect
the
160XT
Package.
Page
2
□
Complete
the
Registration
Card.
Page
2
□
Mount
Unit
in
a
Rack
(OPTIONAL).
Page
18
□
Connect
Audio
Inputs
and
Outputs.
Page
19
□
Connect
Power.
Page
22
□
Set
Levels
and
Controls
as
Needed.
Page
4
Inspection
1.
Unpack
and
Inspect
the
160XT
package.
Your
160XT
was
carefully
packed
at
the
factory
in
a
protective
carton.
Nonetheless,
be
sure
to
examine
the
unit
and
the
carton
for
any
signs
of
damage
that
may
have
occurred
during
shipping.
If
obvious
physical
damage
is
noticed
contact
the
carrier
immediately
to
make
a
damage
claim.
We
suggest
saving
the
shipping
carton
and
packing
materials
for
safely
transporting
the
unit
in
the
future.
Verify
that
the
160XT
package
contains
the
following:
□
160XT
Unit
□
160XT
Accessory
Kit
□
Operation
Manual
□
Warranty
Certificate/Registration
Card
2.
Please
complete
the
Registration
Card
and
return
it.
Please
fill
in
the
Registration
Card,
detach
it
from
the
Warranty
Certifi¬
cate,
and
send
the
card
to
us
today.
The
Registration
Card
enables
us
to
inform
you
of
new
applications
and
performance
improvements
that
are
developed,
and
it
helps
us
re¬
spond
promptly
to
claims
under
warranty
without
having
to
request
a
copy
of
your
bill
of
sale
or
other
proof
of
purchase.
2
160XT
INTRODUCTION
Introduction
Congratulations
on
purchasing
the
dbx
Model
160XT
Compressor/Limiter.
We
recommend
you
take
a
moment
and
read
through
the
manual
as
it
provides
information
that
will
assist
you
from
system
installation
to
opera¬
tion
to
special
applications.
We
have
added
a
few
new
features
to
the
dbx
Model
160XT
while
main¬
taining
the
performance
and
ease
of
operation
of
its
predecessor,
the
dbx
160X.
We
have
added:
□
XLR-type
Input
and
Output
Connectors
-
because
the
3-pin
XL
con¬
nector
has
been
recognized
as
the
most
durable
and
widely
used
connector
for
professional
applications.
□
Balanced
Output
-
can
drive
a
6000
load
to
+24dBu
and
provides
common-mode
rejection
of
unwanted
noise
in
the
audio
path
such
as
RF
and
60Hz
components.
□
True
Power
Summing
-
When
two
160XT
units
are
slaved
together,
the
RMS
energy
of
the
signal
presented
to
the
slave
unit
is
summed
with
the
RMS
energy
of
the
signal
presented
to
the
master
unit
to
prevent
phase
cancellation
of
the
two
signals
from
causing
unmusi¬
cal
compressor
action.
Note:
a
160X
unit
can
also
be
used
with
the
same
results
as
long
as
the
160XT
is
used
as
the
master
unit.
□
Input
Ground-Lift
Switch
-
for
isolation
between
shield
ground
and
signal
ground.
Useful
when
troubleshooting
hum
(AC
line
interfer¬
ence).
Other
features
include:
□
OverEasy®/Hard
Knee
Selection
-
allows
selection
between
our
fa¬
mous
OverEasy
compression
curve
and
the
classic
“Hard
Knee”
curve
popularized
by
the
original
dbx
160,161
and
162.
□
True
RMS
Level
Detection
-
senses
the
power
in
the
program
in
a
musical
manner,
much
as
the
ear
does,
giving
results
superior
to
peak
or
average
detection.
□
Hardwire
System
Bypass
Switch
-
allows
the
audio
to
pass
even
if
the
unit
is
unplugged,
and
is
also
useful
for
comparing
the
proc¬
essed
and
unprocessed
signal.
□
Front
Panel
Stereo
Coupling
Switch
-
couples
two
160XTs
or
a
160XT
and
a
160X
together
for
stereo
operation
at
the
push
of
a
but¬
ton.
□
19
Segment
Display
-
for
high
resolution
monitoring
of
True
RMS
in¬
put
and
output
levels.
3
OPERATING
CONTROLS
dbx
Professional
Products
□
12
Segment
Display
-
indicating
GAIN
REDUCTION.
□
Meter
Calibration
-
input/output
meter
calibration,
so
the
160XT
can
be
used
in
a
variety
of
situations
where
the
“0"
reference
is
not
con¬
sistent.
□
V
4
“
Input
and
Output
Connectors
-
we
kept
the
%
u
phone
jacks
from
the
160X,
with
the
output
capable
of
driving
its
own
additional
600ft
load
(single-ended)
in
addition
to
any
load
at
the
XL
output.
□
Detector
Input
-
useful
for
special
applications
including
frequency
conscious
compression
in
which
an
external
equalizer
is
used.
□
DC-controlled
Parameters
-
the
signal
does
not
pass
thru
any
of
the
parameter
controls.
Instead
a
DC
voltage
controls
all
functions
which
eliminates
any
possibility
of
potentiometer
noise
as
the
con¬
trols
age.
Applications
The
dbx
160XT
is
capable
of
handling
a
wide
range
of
applications.
In
the
studio,
the
160XT
can
be
used
on
everything
from
vocals
to
percussion.
In
live
sound
reinforcement,
the
160XT
can
allow
the
engineer
to
get
that
“fat
studio
sound”
out
of
the
drum
kit
or
provide
protection
limiting
for
the
speakers.
In
radio
or
television
broadcast,
the
160XT
will
produce
stable
.
voice
levels,
even
with
non-professional
subjects.
,
;v
Operating
controls
__
Front
Panel
dbx
160
X
T
•20
,
THRESHOLD
■
•
•
•C1.0W
ABOVE
BYPASS
SLAVE
■
s
o
■
40dBm
«20dBm
■■
■
THRESHOLD
OVER
EASY
•
•
•
•
••••••••••••#
•
LEVEL
■
40
30
20
15
10
6
6
1
4
3
2
'
0
t
2
4
6
10
?0
•
OUTPUT
•••
•••••••••-GAIN
REDUCTION
-2050
»20dB
COMPRESSION
OUTPUT
,
COMPRESSOR/LIMITER
Figure
1:
Front
Panel
BYPASS
Switch
and
Indicator
Depressing
the
BYPASS
button
creates
a
“hard-wire
bypass”
of
the
160XT’s
circuitry
by
connecting
the
input
di¬
rectly
to
the
output;
If
the
160XT
is
being
provided
with
AC
power,
an
LED
above
the
switch
turns
ON
in
Bypass
mode.
4
160XT
OPERATING
C
ONTROLS
SLAVE
Switch
and
Indicator
Depressing
the
SLAVE
button
on
one
160XT
of
a
stereo
pair
determines
that
the
other
160XT
will
be
the
Mas¬
ter
(the
controlling
unit).
The
LED
above
the
SLAVE
button
turns
ON
when
the
160XT
is
in
Slave
mode,
indicating
that
the
front
panel
func¬
tions
(with
the
exception
of
BYPASS
and
DISPLAY
select
switches)
are
deactivated
and
under
control
of
the
Master
160XT.
When
neither
160XT
is
in
Slave
mode,
each
will
operate
normally
as
a
single
chan¬
nel
compressor/limiter.
THRESHOLD
Control
Adjusting
this
knob
sets
the
threshold
of
com¬
pression
from
-40dBu
(7.8mVrms)
to
+20dBu
(7.8Vrms).
OverEasy
Switch
Depressing
this
button
selects
the
OverEasy
com¬
pression
characteristic.
The
amber
THRESHOLD
LED
turns
ON
when
the
signal
is
in
the
OverEasy
region.
When
this
button
is
out,
the
160XT
operates
as
a
hard-knee
compressor/limiter.
In
hard-knee
compression
mode,
the
threshold
is
defined
as
that
point
above
which
the
output
level
no
longer
changes
on
a
1:1
basis
with
changes
in
the
input
level.
In
OverEasy
mode,
the
threshold
of
com¬
pression
is
defined
as
the
middle
of
the
OverEasy
threshold
region,
that
is,
“half-way”
into
compression,
as
shown
in
Figure
(See
Figure
3).
THRESHOLD
Indicators
These
three
LEDs
indicate
the
relationship
of
the
input
signal
level
to
the
threshold
of
compression.
The
green
“BE¬
LOW’
LED
is
ON
when
the
signal
is
below
threshold
and
the
red
“ABOVE”
LED
is
ON
when
the
signal
is
above
threshold.
When
the
160XT
is
switched
to
OverEasy
mode,
the
amber
LED
is
ON
when
the
signal
is
in
the
OverEasy
region
(See
Figure
3).
COMPRESSION
RATIO
Control
Rotating
this
control
clockwise
in¬
creases
the
amount
of
compression
from
1:1
(no
compression)
up
to
in¬
finity:!
(no
increase
in
output
level,
regardless
of
input
level
increases
above
threshold);
further
clockwise
rotation
increases
compression
into
the
INFINITY+
region,
up
to
a
maximum
of
—1:1
(i.e.,
a
IdB
increase
in
input
level
above
threshold
causes
a
1
dB
decrease
in
output
level).
In
the
INFINITY+
region,
the
160XT
inverts
the
program
dynamics
for
spe¬
cial
effects.
OUTPUT
GAIN
Control
Adjusting
this
control
varies
the
amount
of
fixed
gain
(up
to
±20dB)
in
the
160XT’s
output
amplifier
stage.
The
OUTPUT
GAIN
control
does
not
interact
with
the
threshold
of
compres¬
sion.
r*
5
OPERATING
CONTROLS
dbx
Professional
Products
DISPLAY
Switch
and
Indicator
Depressing
this
button
causes
the
up¬
per
LED
array
to
display
the
INPUT
level
to
the
160XT.
With
the
button
out,
the
OUTPUT
level
is
displayed.
A
pair
of
LEDs
immediately
above
the
DISPLAY
switch
indicates
the
selected
display
status.
LEVEL
and
GAIN
REDUCTION
Displays
The
upper
row
of
19
LEDs
displays
either
the
INPUT
or
OUTPUT
level,
as
selected
with
the
DIS¬
PLAY
switch.
This
display
is
factory
set
so
that
OdB
is
equivalent
to
+
4
d
B
u
input
or
output
level
(1.23Vrms),
but
may
be
reset
with
the
rear
panel
METER
CALIBRATION
trimmer.
(See
following
pages.)
The
lower
row
of
12
LEDs
displays
up
to
40dB
of
GAIN
REDUCTION
caused
by
the
160XT.
(Fixed
gain
changes
due
to
the
OUTPUT
GAIN
control
are
not
displayed
by
the
GAIN
REDUCTION
LEDs
but
are
re¬
flected
in
the
OUTPUT
level
display.)
Rear
Panel
r3E?F
INP
U
T-BALANCE
D
-
OUTPUT
!QflE>
UNBALANCED
OETECTOR
LIFT
*
©
o
iUBBATIO*
__
-I
tip*
trs
RING
■
DC
CONTROL
SLEEVE
GND_VOLTAGES
Figure
2:
Rear
Panel
SIGNAL
INPUT
Jacks
The
Tip/Ring/Sieeve
phone
jack
and
XLR-type
connector
are
wired
in
parallel;
either
Signal
Input
will
accept
an
audio
signal
for
processing
by
the
160XT.
The
phone
jack
accepts
a
stand¬
ard
TRS
V
4
“
phone
plug
for
a
balanced
input
source,
or
a
2-circuit
(Tip/Sleeve)
V
4
”
phone
plug
for
an
unbalanced
source.
The
XLR-type
plug
connector
is
wired
pin
3
HOT
(+),
pin
2
COLD
(-)
and
pin
1
GROUND.
DETECTOR
INPUT
This
Tip/Ring/Sleeve
phone
jack
accepts
a
stand¬
ard
TRS
Va“
phone
plug,
and
is
of
the
“normalling”
type.
That
is,
when
a
phone
plug
is
inserted,
the
detector
input
is
no
longer
connected
in
parallel
with
the
audio
input.
6
160XT
OPERATING
CONTROLS
SIGNAL
OUTPUT
-
XLR-type
connector
The
160XT
has
an
active-
balanced
amplifier
capable
of
driving
a
600
ohm
(or
greater)
load
to
+24dBu.
Pin
3
is
the
HOT
(+)
lead,
pin
2
is
the
COLD
(-)
lead
and
pin
1
is
circuit
ground.
Do
not
short
either
pin
2
or
pin
3
to
ground.
This
will
not
damage
the
unit,
but
may
increase
distortion.
SIGNAL
OUTPUT
-
Phone
Jack
The
160XT
has
a
separate
single-
ended
(unbalanced)
output
amplifier
also
capable
of
driving
a
600
ohm
(or
greater)
load
to
+24dBu.
In
normal
operation
the
Tip/Ring/Sleeve
phone
jack
is
internally
wired
with
the
TIP
HOT
(+),
and
the
RING
and
SLEEVE
connected
to
circuit
ground.
In
BYPASS
mode,
however,
the
RING
is
connected
to
the
COLD
(-)
leads
of
the
input
jacks,
to
allow
for
1:1
connections.
GROUND
(GND)
Lift
Switch
This
switch
allows
for
troubleshooting
hum
(line
interference)
caused
by
ground
loops.
In
the
“GND”
position,
pin
1
of
the
input
XLR-type
connector
is
connected
to
the
160XT’s
cir¬
cuit
ground.
In
the
“LIFT”
position
it
is
disconnected.
This
is
not
a
chas-
sis-isolate
switch.
The
circuit
ground
is
floating
with
the
respect
to
the
chassis.
METER
CALIBRATION
Control
This
screw-driver-adjustable
trimmer
may
be
used
to
precisely
calibrate
the
front
panel’s
upper
LED
display
so
a
OdB
INPUT
or
OUTPUT
indication
is
equivalent
to
any
signal
from
—15dBu
(138mVrms)
to
+10dBu
(2.45Vrms).
STEREO
STRAPPING
Jack
When
a
TRS
(Tip/Ring/Sleeve)
V
4
“
phone
plug
patch
cable
is
inserted
between
two
160XTs,
stereo
strapping
can
be
achieved
by
depressing
the
SLAVE
switch
on
one
unit
only
.
This
will
provide
accurate
processing
for
a
stereo
programming.
AC
Cord:
Plug
into
mains
power.
Note
that
the
160XT
does
not
have
a
power
switch.
It
is
recommended
that
the
160XT
be
“On”
at
all
times.
Power
consumption
is
low.
If
you
do
not
plan
to
use
the
160XT
for
an
extended
period
of
time,
unplug
it.
WARNING:
Be
sure
to
verify
both
your
actual
line
voltage
and
the
volt¬
age
for
which
your
Model
160XT
was
wired,
as
indicated
on
the
rear
panel
of
your
unit.
Connection
to
an
inappropriate
power
source
may
result
in
extensive
damage
which
is
not
covered
by
the
warranty.
7
OUTPUT
LEVEL
(dB)
Operating
notes
_
Basic
Operation
Using
the
THRESHOLD
control
In
hard-knee
mode
this
control
sets
a
reference
level
above
which
input
signals
will
be
processed
by
the
160XT’s
gain
change
circuitry
in
the
man¬
ner
defined
by
the
setting
of
the
RATIO
control.
Input
signals
which
fall
be¬
low
this
level
will
pass
through
the
160XT
unprocessed
(except
for
fixed
gain
changes
directed
by
the
output
control).
See
Figure
4.
In
OverEasy
Mode,
signals
begin
to
gradually
activate
the
160XT’s
gain
change
circuitry
as
they
approach
the
THRESHOLD
reference
level
and
they
do
not
get
fully
processed
in
the
manner
defined
by
the
RATIO
con¬
trol
until
they
have
passed
somewhat
above
the
THRESHOLD
reference
level.
In
OverEasy
mode
there
is
no
distinct
point
at
which
processing
be¬
gins,
and
the
THRESHOLD
setting
corresponds
to
a
point
on
the
in¬
put/output
transfer
curve
midway
between
the
onset
of
processing
and
that
point
at
which
the
transfer
curve
corresponds
to
the
setting
of
the
RA¬
TIO
control
(Figure
3).
Figure
3.
also
shows
how
the
160XT’s
THRESH¬
OL
D
in
d
i
c
ator
LEDs
correlate
with
the
compression
curves.
NOTE:
The
THRESHOLD
setting
relates
to
the
signal
level
seen
by
the
DETECTOR
INPUT.
In
normal
operation,
the
program
input
SIGNAL
IN¬
PUT
is
connected
directly
to
the
DETECTOR
INPUT.
If
this
is
not
the
case,
the
signal
actually
present
at
the
DETECTOR
INPUT
will
determine
how
the
160XT
processes
the
signal
coming
into
its
SIGNAL
INPUT.
-15
-10
-5
0
+5
+10
+15
+20
-15
-10
-5
0
+5
+10
+15
+20
INPUT
LEVEL
(dB)
INPUT
LEVEL
(dB)
Figure
4:
Hard-Knee
Compression
Curve
Figure
3:
Over
Easy
Compression
Curve
8
160XT
OPERATING
NOTES
Using
the
COMPRESSION
RATIO
control
When
an
input
signal
is
above
the
THRESHOLD
reference
level,
the
set¬
ting
of
this
control
determines
the
number
of
decibels
by
which
the
input
signal
must
change
in
level
to
produce
a
IdB
increase
in
the
signal
level
at
the
output
of
the
160XT.
A
setting
of
2:1
indicates
an
input:output
ratio
wherein
a
2dB
increase
in
signal
(above
threshold)
will
produce
a
IdB
in¬
crease
in
output
signal.
A
setting
of
°°:1
indicates
that
an
infinite
increase
in
input
level
would
be
required
to
raise
the
output
level
by
IdB.
In
other
words,
the
output
level
is
constant
when
the
input
signal
is
above
thresh¬
old.
The
160XT’s
RATIO
control
covers
the
entire
range
from
1:1
to
°°:1
and,
in
addition,
goes
to
Infinity-*-
(negative)
ratios.
At
a
setting
of-1:1,
the
above
threshold
input
signal
must
increase
by
IdB
in
level
to
decrease
the
signal
at
the
output
of
the
160XT
by
IdB.
See
Figure
5.
The
control
curve
of
the
RATIO
potentiometer
has
been
designed
to
pro¬
vide
total
operator
control,
with
scale
expansion
at
the
subtle
lower
ratios
for
easy,
repeatable
settings.
Figure
5:
Ratio
control
and
lnfinity+
(Negative)
Ratios
9
OPERATING
NOTES
dbx
Professional
Products
Using
the
SLAVE
button
(Stereo
Operation)
Two
channels
of
program
material
do
not
necessarily
constitute
a
stereo
program.
A
stereo
program
is
one
where
the
two
channels
are
recorded
and/or
mixed
to
create
the
illusion
of
a
single
unified
“panorama”
of
sound.
The
stability
of
the
psychoacoustic
“image”
of
each
sound
source
within
the
stereo
program
depends
upon
its
ability
to
maintain
a
specific
phase
and
amplitude
relationship
from
left
to
right
channel.
If
two
independent
compressors
are
used
to
process
the
stereo
program,
a
loud
sound
occurring
in
one
channel
will
cause
a
gain
reduction
only
in
that
channel.
This
gain
reduction
would
cause
the
perceived
image
of
any
sound
spread
between
the
two
channels
to
move
toward
the
side
which
had
not
been
compressed,
because
the
spread
signal
would
be
momen¬
tarily
softer
in
the
compressed
channel.
This
can
be
avoided
by
linking
the
two
compressors
in
such
a
way
that
both
channels
receive
the
same
amount
of
compression.
On
the
160XT,
this
is
accomplished
by
means
of
the
STRAPPING
jacks;
a
cable
between
these
jacks
permits
the
RMS
de¬
tectors
of
both
units
to
“talk”
to
one
another
—
but
only
when
one
of
the
units’
SLAVE
buttons
is
depressed.
The
SLAVE
unit
then
sends
its
signal
to
the
MASTER,
where
the
RMS
power
of
the
MASTER
and
SLAVE
sig¬
nals
are
combined
to
generate
a
control
voltage.
This
control
voltage
is
then
used
to
compress
both
the
MASTER
and
SLAVE
units
equally.
When
compressing
a
stereo
program
with
a
pair
of
160XTs,
only
the
MAS¬
TER
unit
controls
need
to
be
adjusted.
METER
CALIBRATION
control
The
INPUT/OUTPUT
LEVEL
DISPLAY
in
the
160XT
is
factory-calibrated
to
indicate
“0"
when
the
signal
is
+4dBu
(1.23Vrms)
at
either
the
input
or
output
of
the
160XT,
depending
on
the
DISPLAY
function
switch
position.
(The
METER
CALIBRATION
control
does
not
affect
the
GAIN
CHANGE
LEDs.)
To
recalibrate
the
LEVEL
DISPLAY,
depress
the
DISPLAY
button
to
me¬
ter
the
INPUT
LEVEL,
and
feed
a
1kHz
signal
at
the
selected
nominal
op-
.
erating
level
(the
level
desired
for
a
”0dB"
meter
indication)
to
the
160XT’s
SIGNAL
INPUT.
Then
adjust
the
rear
panel
METER
CALIBRATION
con¬
trol
until
the
meter
indicates
“OdB.”
10
160XT
OPERATING
NOTES
Specific
Applications
Smoothing
out
variations
in
microphone
levels
When
the
distance
between
a
vocalist
and
a
mic
changes,
variations
in
signal
level
occur.
To
smooth
out
these
variations,
start
with
the
160XT
adjusted
for
a
low
COMPRESSION
RATIO
(e.g.,
4:1)
and
adjust
the
THRESHOLD
control
for
optimum
results,
then
increase
COMPRESSION
RATIO
if
necessary.
Due
to
the
gentle
OverEasy
characteristic
of
your
160XT
you
will
find
that
even
fairly
high
ratios
are
handled
transparently.
Smoothing
out
variations
in
musical
instrument
levels
To
achieve
a
smoother
electric
bass
sound,
compress
the
instrument’s
output
with
a
ratio
of
about
4:1
(the
COMPRESSION
RATIO
control
set
at
approximately
12:00).
Compression
lessens
the
loudness
variations
among
the
strings
and
increases
the
sustain.
Other
instruments,
such
as
horns,
vary
in
loudness
depending
on
the
note
being
played,
and
benefit
similarly.
NOTE:
When
compressing
a
stereo
program
with
a
pair
of
160XTs,
the
factors
affecting
a
compression
curve
and
the
actual
compression
ratio
and
threshold
settings,
are
like
those
previously
covered
with
reference
to
single
channels
of
program
material.
However,
it
will
generally
be
found
that
large
amounts
of
compression
are
more
audible
in
a
mixed
stereo
program
than
they
might
be
on
the
separate
tracks
that
were
mixed
to
cre¬
ate
the
program.
Raising
a
signal
out
of
a
mix
Since
reducing
dynamic
range
increases
the
average
signal
level
by
a
small
amount,
a
single
track
can
be
raised
out
of
a
mix
by
boosting
its
level
slightly
and
applying
compression.
It
is
also
possible
to
separate
cer¬
tain
vocals
or
instruments
from
a
mono
program
already
mixed
by
fre¬
quency-weighted
compression
(see
page
12).
Using
your
EQ
to
reduce
feedback
in
live
settings.
You
can
use
your
160XT
and
EQ
to
reduce
feedback
in
clubs
or
halls
by
placing
the
160XT
at
®o:i,
Hard
Knee,
and
a
low
threshold.
Increase
con¬
trol
gain
until
the
first
feedback
“ring”
occurs.
The
160XT
will
catch
it,
and
hold
it
as
a
constant
tone
so
you
can
adjust
your
EQ
to
minimize
it.
Con¬
tinue
to
increase
your
console
gain
and
set
your
EQ
until
the
3
or
4
“ring”
frequencies
have
been
compensated
for.
Preventing
tape
saturation
With
programs
of
widely
varying
levels,
compression
can
prevent
record¬
ing
levels
from
saturating
tape
tracks
(see
Frequency-weighted
compres¬
sion,
page
12).
11
OPERATING
NOTES
dbx
Professional
Products
Speaker
protection
Compressors
are
frequently
used
to
prevent
excessive
program
levels
from
damaging
drivers
in
a
sound-reinforcement
system.
Limiting
also
benefits
intelligibility
by
allowing
low-level
input
signals
to
be
reproduced
through
the
system
at
higher
volume.
In
a
musical
performance,
this
pro¬
vides
additional
intimacy
as
the
vocalist’s
whispers
are
heard
clearly
at
every
seat
in
the
house.
The
OverEasy
curve
available
with
the
160XT
permits
a
very
high
amount
of
COMPRESSION
(10:1
or
greater)
to
be
used
in
many
situations.
Vocalists
and
musicians
don’t
get
the
sense
of
being
held
back,
but
high
average
levels
can
be
maintained
without
speaker
damage
due
to
excessive
heat
buildup.
In
circumstances
where
the
160XT
is
expected
to
cause
no
change
in
gain
unless
an
emergency
arises
(wildly
excessive
levels)
some
operators
set
the
COMPRESSION
RATIO
to
°°:1,
the
THRESHOLD
to
the
highest
permissible
level,
and
operate
the
unit
in
hard-knee
mode.
As
a
general
rule,
the
compressors
should
be
as
close
to
the
amplifiers
as
possible
in
the
signal
chain.
If
the
160XT
is
placed
before
the
EQ,
for
example,
a
po¬
tentially
damaging
boost
in
EQ
won’t
be
seen
by
the
160XT
and
the
speakers
may
be
damaged,
(see
Multi-way
speaker
systems,
page
14).
r
For
maximum
sound
pressure
levels,
large
sound
reinforcement
systems
frequently
use
a
separate
compressor
on
each
output
of
the
electronic
crossover(s).
For
a
stereo
sound-reinforcement
system,
stereo
strapping
cables
should
be
run
between
the
160XTs
in
each
band
(low-low,
mid-
mid,
etc.).
The
160XT
as
a
line
amplifier
To
use
the
160XT
as
a
line
amplifier,
adjust
the
COMPRESSION
ratio
control
to
fully
counterclockwise
(1:1
position),
THRESHOLD
to
full
clock¬
wise
position
(+10)
and
OUTPUT
GAIN
to
whatever
setting
is
required
for
the
application.
Remember
that,
as
with
any
amplifier,
excessive
gain
may
lead
to
output
clipping
of
high
level
signals.
To
add
compression,
ad¬
just
the
COMPRESSION
ratio
and
the
THRESHOLD
controls
to
the
de¬
sired
settings.
Side-chain
applications
Frequency-weighted
compression
It
is
possible
to
separate
certain
vocals
and
instruments
from
a
mix
by
fre¬
quency-weighted
compression.
With
an
equalizer
inserted
ahead
of
the
detector
input
(but
not
in
the
audio
path),
the
equalization
settings
do
not
shift
the
timbre
or
frequency
response
of
the
audio
signal.
They
merely
al¬
ter
the
threshold
response
of
the
compressor
on
a
“frequency-weighted”
basis
(see
Figure
6).
12
1
6
0
X
T
OPERATING
NOTTS
Figure
6:
Frequency-Weighted
Compression
With
this
arrangement,
raising
certain
frequencies
on
the
equalizer
causes
them
to
be
suppressed
in
the
audio
signal.
A
relatively
high
THRESHOLD
setting
can
allow
normal
sounds
to
be
unaffected
while
solo
and
very
loud
sounds
are
held
back.
(Of
course,
when
compression
does
occur,
the
level
of
the
entire
program
is
affected.)
Depending
on
the
THRESHOLD
setting,
lower
level
fundamentals
or
harmonics
will
not
cause
compression,
and
the
program
is
not
subject
to
the
phase
shift
nor¬
mally
caused
by
program
equalization.
During
the
recording
of
cymbals
and
tom-toms,
a
compressor
with
an
equalizer
in
the
detector
path
can
help
prevent
tape
saturation.
The
equal¬
izer
can
be
adjusted
for
boost
with
a
peak
of
about
5kHz,
causing
the
cym¬
bal
to
be
compressed
on
a
very
loud
crash,
stopping
tape
saturation
at
high
frequencies,
where
there
is
less
headroom.
However,
gentle
tapping
of
a
drumstick
or
brushing
of
the
cymbal
will
not
be
held
back.
Assuming
the
tom-tom
is
a
lower
frequency
instrument
and
can
be
better
tolerated
by
the
tape,
it
has
less
need
for
compression.
The
equalization
in
the
de¬
tector
circuit
means
that
the
compressor
is
not
triggered
as
readily
by
a
loud
tom-tom
beat
as
by
an
equally
loud
cymbal
crash.
The
converse
of
the
above
EQ
technique
may
be
used:
dipping
the
equal¬
izer
bands
causes
any
sound
with
dominant
energy
in
the
affected
regis¬
ter
to
pull
the
level
up
because
the
160XT
will
detect
a
need
for
less
compression.
De-Essing
To
apply
de-essing
to
vocals
(i.e.,
a
reduction
of
sibilance),
use
a
paramet¬
ric
equalizer
in
the
level
detector
circuit
and
set
it
for
high
frequency
boost
in
the
specific
frequency
range
where
the
vocal
“hiss”
or
lisp
occurs
(gen¬
erally
in
the
4-6kHz
region).
This
pre-emphasizes
the
already
“hissy”
vo¬
cal
input
to
the
detector.
Used
in
conjunction
with
a
moderate
to
high
threshold
and
compression
ratio,
this
arrangement
greatly
attenuates
the
“essing”
without
affecting
the
basic
sound
quality
or
balance
of
the
voice.
13
OPERATING
NOTES
dbx
Professional
Products
While
it
is
true
that
all
frequencies
are
lowered
in
level
when
the
compres¬
sor
is
triggered,
generally
the
“sss”
sound
occurs
alone,
before
or
after
the
dominant
tone
in
the
voice.
Increasing
sustain
To
increase
the
sustain
of
a
musical
instrument
(e.g.,
a
guitar
or
bass),
use
an
equalizer
in
the
level
detector
circuit
and
boost
the
EQ
in
the
domi¬
nant
frequency
range
of
the
instrument,
along
with
a
fairly
low
threshold
and
a
moderate
compression
ratio.
Using
a
Filter
in
the
Level
Detector
Circuit
The
results
of
inserting
a
filter
in
the
level
detector
circuit
are
basically
the
same
as
obtained
with
an
equalizer,
as
previously
described.
Those
fre¬
quencies
passed
by
the
filter
are
subject
to
compression
(or
at
least
they
are
subject
to
considerably
more
compression
than
those
frequencies
out¬
side
the
passband).
Because
a
passive
filter
can
have
insertion
loss,
it
may
be
necessary
to
lower
the
160XT’s
THRESHOLD
setting
to
maintain
a
given
amount
of
gain
reduction
within
the
filter
passband;
this
can
be
de¬
termined
by
monitoring
the
160XT’s
threshold
indicator
LEDs.
Multi-way
speaker
systems.
If
a
single
compressor
is
to
be
used
with
a
multi-way
speaker
system
(i.e.,
before
the
crossover,
after
EQ),
the
system
operator
is
faced
with
the
problem
of
keeping
levels
below
the
point
of
destruction
of
the
most
sensi¬
tive
part
of
the
system.
If,
for
example,
mid-range
drivers
are
frequently
damaged,
the
whole
system
must
be
operated
at
a
lower
sound-pressure
level,
or
additional
mid-range
drivers
must
be
added.
By
inserting
an
equalizer
in
the
detector
path
to
the
160XT,
it
can
be
made
more
sensitive
to
frequencies
in
the
range
handled
by
the
sensitive
drivers.
The
system
can
then
be
run
at
higher
levels
and
will
only
be
dropped
back
when
dam¬
aging
signals
are
present.
Pre-emphasis
for
broadcast
applications
By
inserting
a
pre-emphasis
filter
network
in
the
detector
path
of
a
160XT
processing
pre-emphasized
audio,
higher
levels
can
be
run
within
the
headroom
limitations
of
the
broadcast
chain.
Anticipated
Compression
By
feeding
the
program
directly
to
the
160XT’s
detector
input
and
sending
the
audio
signal
through
a
delay
line
before
the
audio
input,
the
unit
can
anticipate
the
need
for
a
gain
change.
See
figure
7.
With
some
experimen¬
tation,
the
effect
can
be
that
of
zero
attack
time
at
a
given
frequency.
Addi¬
tional
signal
delays
beyond
this
zero
time
will
then
cause
the
compressor
to
finish
reducing
the
gain
before
the
leading
edge
of
the
loud
passage
14
160XT
CONNECTING
THE
160XT
TO
YOUR
SYSTEM
even
enters
the
signal
input.
This
will
suppress
the
program
material
pre¬
ceding
this
loud
passage.
The
160XT
will
then
begin
to
release
(recover
from
compression)
before
the
loud
passage
has
ended.
IN
DETECTOR
'
IN
AUDIO
OUT
160XT
Figure
7:
Anticipated
Compression
Connecting
the
i6oxt
to
your
system
Basic
Connection
Figure
8:
Basic
Connection
The
160XT
can
be
connected
for
basic
operation
as
shown
in
Figure
8.
For
more
specific
installation
information,
refer
to
Installation
Considera¬
tions,
page
18.
15
dbx
Professional
Products
For
all
connections,
refer
to
the
following
steps:
A.
Turn
Off
all
equipment
before
making
any
connections.
B.
Make
connections
via
XLR
or
%"
TRS
jacks
according
to
your
requirements.
C.
Plug
in
the
AC
power
cable
to
power
On
the
unit.
Multi-Channel
Connections
The
160XT
can
be
“strapped”
to
another
160XT
for
2-channel
stereo
op¬
eration.
This
will
force
one
of
the
units
(SLAVE)
to
track
the
other
(MAS¬
TER)
to
preserve
proper
stereo
imaging.
A
Va“
stereo
phone
cable
is
required
to
connect
the
two
160XTs
together.
To
operate
in
stereo,
designate
one
of
the
two
units
to
be
a
“MASTER”
(SLAVE
button
OUT)
and
switch
the
other
unit
to
“SLAVE”
mode
(SLAVE
button
IN,
SLAVE
LED
ON).
The
master
160XT
will
now
respond
to
the
combined
inputs
of
the
160XTs.
The
master’s
controls
will
adjust
the
amount
and
nature
of
the
compression
and
the
slave
will
track
accurately.
When
the
SLAVE
switches
on
both
units
are
not
depressed,
the
160XTs
operate
completely
independently.
If
both
SLAVE
buttons
are
depressed,
both
units
will
be
bypassed
(i.e.,
fixed
at
unity
gain).
The
strapping
cable
with
1
4“
TRS
plugs
on
both
ends
may
be
left
in
place
when
both
160XTs
are
to
be
used
independently
(i.e.,
both
as
MASTER).
‘MASTER"
"SLAVE”
TRS
"STEREO”
CABLE
(Shield
plus
two
conductors)
Figure
9:
Multi-Channel
Connections
16
160XT
CONNECTING
THE
160XT
TO
YOUR
SYSTEM
Using
External
Level
Detector
Inputs
To
control
the
compressor
by
signals
other
than
the
audio
input
(via
an
auxiliary
device),
connect
the
auxiliary
device’s
output
to
the
160XT’s
De¬
tector
Input
jack,
and
feed
the
auxiliary
device’s
input
with
the
same
sig¬
nal
fed
to
the
160XT’s
Signal
Input
(Figure
10).
This
will
require
a
Y-adaptor,
or
you
can
take
advantage
of
the
160XT’s
parallel
input
jacks.
In
certain
situations,
the
auxiliary
device
may
need
to
be
inserted
in
the
signal
path,
not
in
the
detector
path.
In
such
cases,
signal
is
fed
to
the
in¬
put
of
that
device,
and
also
to
the
detector
input,
and
the
auxiliary
de¬
vice’s
output
is
fed
to
the
160XT
signal
input
(for
example,
using
a
delay
to
create
“negative”
attack
times)
(Figure
10).
Figure
10:
Using
the
160XT
with
a
Sampler
Specific
System
Connections
The
160XT
has
balanced
inputs
and
outputs,
and
can
be
used
with
any
line-level
device.
Some
common
examples
include:
mixing
consoles,
mu¬
sical
instruments,
patch
bays,
and
other
signal
processors.
Mixing
Board
If
you
wish
to
compress
a
particular
track
of
a
multi-track
recording
or
one
channel
of
a
live
performance
mix,
the
160XT
output
can
be
directly
con¬
nected
to
a
line
input
jack
(balanced
or
not),
or
wired
to
an
Insert
point.
In
the
latter
case,
the
signals
will
most
likely
be
unbalanced.
Musical
Instruments
(i.e.,
Electric
Guitar,
Bass,
Keyboards)
The
output
of
an
electric
guitar
is
sometimes
not
“hot”
enough
to
drive
the
160XT’s
input.
When
this
is
the
case,
you
should
use
the
“PREAMP
OUT”
of
your
guitar
amp
(if
so
equipped),
or
the
output
of
some
other
device
that
is
designed
to
accept
low-level
instrument
inputs
(including
various
stomp
boxes
and
rack
mount
audio
products,
like
the
dbx
Performer
Se-
17
INSTALLATION
CONSIDERATIONS
dbx
Professional
Products
lies
processing
units).
Such
sources
can
be
balanced
or
unbalanced
—
this
is
no
problem
for
the
160XT.
Microphones
and
bass
guitars,
like
guitars,
typically
have
low-level
out¬
puts.
Instruments
like
keyboards
typically
produce
a
line-level
signal
and
can
be
connected
directly
from
the
instrument’s
output
to
the
160XT’s
input.
Patch
bay
In
the
studio,
the
160XT
may
be
connected
to
a
patch
bay
to
allow
it
to
be
used
anywhere
in
the
studio
system.
Do
not
ground
Pin
2
(or
3)
of
the
XLR-type
output
connector
(distortion
can
result).
If
your
studio
is
not
fully
balanced,
you
should
leave
pin
2
disconnected
or
use
the
%“
phone
jack
output,
which
is
single-ended.
Another
option
is
to
install
an
output
trans¬
former,
which
will
allow
grounding
of
either
pin
2
or
3
of
the
XLR-type
out¬
put
(see
page
24).
Sound
reinforcement:
To
compress
a
live
mix
or
to
protect
loudspeakers,
connect
the
160XT
be-
v
:
tween
the
source
(mixing
board
or
distribution
amp)
and
the
power
amp(s).
If
multi-way
loudspeakers
with
low-level
electronic
crossovers
are
used,
the
160XT(s)
should
go
after
the
crossover(s).
For
a
stereo
system,
you
can
separately
stereo
couple
the
two
high
band
crossovers,
low
band
crossovers,
etc.
(see
page
16).
If
limitations
require
that
you
use
a
single
160XT
before
a
crossover,
adding
an
equalizer
to
the
side
chain
may
pro¬
vide
some
additional
protection
to
your
high
frequency
component
(see
“Speaker
Protection,”
page
12).
Installation
considerations
_
Mounting
the
160XT
in
a
Rack
(OPTIONAL)
Mount
the
160XT
in
a
1U
rack
space
(1.75
inches,
4.45
cm).
Mounting
the
unit
directly
over
large
heat-producing
devices
(such
as
a
vacuum-tube
power
amplifier)
may
shorten
component
life
and
is
not
rec¬
ommended.
Ambient
temperatures
should
not
exceed
113°F
(45°C)
when
equipment
is
powered.
Caution:
Never
remove
the
cover.
There
are
no
user-serviceable
parts
in¬
side,
and
you
run
the
risk
of
an
electric
shock.
18
160XT
INSTALLATION
CONSIDERATIONS
Input/Output
Cable
Configurations
Hookups
and
Cabling
The
160XT
is
a
6000,
balanced
(differential)
unit
designed
for
nominal
+4dBm
levels;
inputs
and
outputs
are
tip/ring/sleeve
phone
jacks
and
XLR
connectors.
The
160XT
can
be
used
with
either
balanced
or
unbalanced
sources
and
outputs
can
be
used
with
either
balanced
or
unbalanced
loads,
provided
you
use
proper
cabling.
A
balanced
line
is
defined
as
two-conductor
shielded
cable
with
the
two
center
conductors
carrying
the
same
signal
but
of
opposite
polarity
with
re¬
spect
to
ground.
An
unbalanced
line
is
generally
a
single-conductor
shielded
cable
with
the
center
conductor
carrying
the
signal
and
the
shield
at
ground
potential.
Connect
Audio
Inputs
The
160XT
has
an
actual
input
impedance
of
lOOkO
in
balanced
configu¬
ration
or
50kO
if
unbalanced.
This
makes
the
160XT
audio
input
suitable
for
use
with
virtually
any
source
impedance,
low
or
high.
The
160XT’s
in¬
put
connectors
are
wired
in
parallel.
That
is,
the
phone
jack
TIP
(+)
con¬
nection
is
internally
wired
to
the
XLR-type
pin
3,
the
RING
(-)
is
wired
to
pin
2,
and
the
SLEEVE
(shield)
is
wired
to
pin
1.
Note
that
pins
2
and
3
are
the
reverse
of
certain
other
manufacturer’s
equipment,
but
if
the
same
connection
is
used
at
the
output,
the
signal
will
be
correctly
polarized
(“in
phase”).
Reversing
the
input
wires
to
the
input
terminals
will
result
in
the
output
sig¬
nal
polarity
being
the
opposite
of
the
input
signal
(“180°
out
of
phase").
The
160XT
has
a
rear-panel
GROUND
LIFT
switch.
This
switch
discon¬
nects
the
input
XLR-type
pin
1
from
the
160XT’s
circuit
ground
This
is
to
allow
troubleshooting
of
hum
and
other
grounding
problems
without
having
to
change
the
cabling.
We
advise
starting
with
the
switch
in
the
LIFT
position
(shield
disconnected
at
the
160XT
input).
Output
Cable
Considerations
Connect
Audio
Outputs
The
model
160XT
has
two
separate
outputs:
one
single-ended
amplifier
driving
the
1
4“
stereo
phone
jack,
and
a
separate
active-balanced
ampli¬
fier
driving
the
XLR-type
output
connector.
Each
is
capable
of
driving
a
600
ohm
load
to
+24dBu.
NOTE:
Contact
our
Customer
Service
Department
for
information
regard¬
ing
factory
installation
of
the
optional
balanced
transformer.
Our
phone
number
is
listed
on
the
inside
of
the
front
cover.
19
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