dbx 160XT User manual

INSTRUCTION
MANUAL
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Table of Contents
page contents
1 Introduc tion
3 Front Pane l
6 Rear Pane l
8 Connecting The l60XTToYour System
8 System Connections
12 Multi-Channel Connections
13 Special Connec tions (OPTIONAL)
13 UsingExternal Level Detector Inputs
14 Basic Operation (Control Descriptions)
18 Specific Applications
23 Installation Considera tions
23 Power Considerations
23 Mounting the 160XTin a Rack (OPTIONAL)
24 Input Cable Configurations
26 Output Cable Considerations
28 Transformer Balanced (OPTIONAL)
'29 Grounding
30 Maintenance and Techn ical Support
30 Maintenance and Troubleshoo ting
30 Technical support
30 Factory Service
31 Shipping Instructions
32 Specifications
34 Schematic (l60XTMain Board)
35 Glossary
51 Registrat ion. Warranty
51 Registration Card
51 Warranty
51 User-Feedback

CAUTION
RISK OF ELECTR IC SHOCK
00 NOT OPtN
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, whereverit appears,
alerts you to important operating and
maintenance instructions in the accompanying
literature. Read the manual.
This dbx-branded product has been manufactured by AKG Acoustics, Inc. 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 manual is part number 95096-000-01
© Copyright 1990 by AKG Acoustics, Inc.
dbx Professiona l Products
a division of AKG Acoustics, Inc.
1525 Alvarado Street, San Leandro, CA 94577 USA
Telephone [phone] Fax: [phone] Telex: 17-1480
Introduction dbx 160XT
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Congratulations on purchasing the dbx Model
160XTCompressor /Limiter . We recommend you
take a moment and read through the manual as it
provides information that will assist you from sys-
tem installation to operation to special applica-
tions. For a basic understanding of the terms used
in this manual, there is a Glossary of important
terms located in the back of the manual.
Wehave added a few new features to the dbx
Model 160XTwhile maintaining the performance
and ease of operation of its predecessor, the dbx
160X.We have added:
0
0
XL-type Input and Output Connectors -be-
cause the 3-pin XLconnector has been recog-
nized as the most durable and widely used
connector for professional applications.
Balanced Output - can drive a 6000 load to
+24dBu and provides common-mode rejec-
tion of unwanted noise in the audio path
such as RF and 60Hz components.
True Power Summing - When two 160XTunits
are slaved together, the RMS energy of the sig-
nal presented to the slave unit is summed
with the RMSenergy of the signal presented
to the master unit to prevent phase cancella-
tion of the two signals from causing unmusi-
cal compressor action. Note: a 160Xunit can
also beused with the same results as long as
the 160XTis used as the master unit.
Input Ground-Lift Switch -for isolation be-
tween shield ground and signal ground. Use-
ful when trouble shooting hum (AC line
interference).

2
Introduction
Other features include:
OVER EASy®/Hard Knee Selection - allows
selection between our famous Over Easy com-
pression curve and the classic "Hard Knee"
curve popularized by the original dbx 160,
161and 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 pro-
cessed and unprocessed signal.
Front Panel Stereo Coupling Switch -couple s
two 160XTsor a 160XTand a 160X toge ther
for stereo operation at the push of a button.
19 Segment Display -for high resolution mon-
itoring of True RMS input and output levels .
12 Segment Display -indi cating GAIN
REDUCTION.
Meter Calibration -input / output meter cali-
bration, so the 160XTcan be used in a variety
of situa tions where the "O"reference is not
consistent.
¼" Input and Output Connectors - we kept
the 1/4"phone jacks from the 160X, with the
Front Panel
C
dbx • • THREllHOLO ,,18:1
e e e 3:1 10:1
--
160XT BYPASS Bl.AVE THRESHOLD 01/Bl EASY
A B
output capable of driving its own additional
600Q load (single-ended) in addition to any
load at the XLoutput.
Detector Input -useful for specia l applications
including frequency conscio us 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 potenti -
ometer noise as the controls age.
The dbx 160XTis capab le of handling a wide
range of applications. In the studio, the 160XTcan
_be used on everything from vocals to percussion.
In live sound reinfor cement , the 160XTcan 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
160XTwill produce stable voice levels, even with
non-professional subjects.
dbx 160XT
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..._J ·«>301011510 al 1543I101 2,11010•
OUTPUT • • • • • • •• • • • • - GAINAEDUCTlON
- -
OUTPUT OISPI.AY
G.V,I COMPRESSOR/LIMITER
Figure 1:Front Panel
A. BYPASS switch and indicator
Depressing the BYPASSbutton creates a "hard -
wire bypass " of the 160XT's circuitry by con-
necting the input directly to the output; If the
160XTis being provided with AC power , an
LED above the switch turn s ON in Bypass
mode.
B. SLAVE switch and indicator
Depressing the SLAVE button on one 160XTof
a stereo pair determines that the other160XT
will be the Master (the controlling unit ).The
LED above the SLAVEbutton turns ON when
the 160XTis in Slave mode, indicating that the
front panel functions (with the exception of BY-
PASSand DISPLAYselect switches) are deacti-
vated and under control of the Master 160XT.
When neither 160XTis in Slave mode , each will
operate normally as a single channel compres-
sor/limiter.
C. THRESHOLD control
Adjusting this knob sets the threshold of com-
pression from-40dBu (7.8mVrms) to +20dBu
(7.8Vrms).
3

4
Front Panel
E F G
0 N'UT
dbx • • -10 THRESHOLD 4:1 1:1
-ec,~0 ..:.•~ 3:1~~~ 1
40~•10 -· 2:1~.;:,1
-10 • +10 --,__ e e e e e e ee e ee e e eee e e e I.E\IEL
--------.r--=-«> SO 10 1G10 e e 6 4 3 I 1 0 1 2 4 I 10 10 +
160XT 40 Bm +20dlm 1:1 •1:1 OUT1'IIT • • • • • e eee e e e -GAIN REDUCTION
-+l!Ooll
BYPASS 61.AIIE ~- COMPRESslON
THRESHOID ~= EASY RATIO ~T OISPI..AY COMPRESSOR/LIMITER
D H
Figure 2: Front Panel
D. OVER EASY switch
Depressing this button selects the Over Easy©
compression characteristic. The amber
:n:1RESHOLD LED turns ON when the signal
1s1nthe Over Easy region. When this button is
out, the 160XT operates as a hard-knee com-
pressor /limiter.
In hard-knee compression mode, the threshold
is defined as that point above which the output
level no longer changes on a 1:1basis with
changes in the input level. In Over Easy mode,
the threshold of compression is defined as the
middle of the Over Easy threshold region, that
Front Panel
F. COMPRESSION RATIO control
Rotating this control clockw ise increases the
amount of compression from 1:1 (no compres-
sion) up to infinity:1 (no increase in output
level, regardless of input level increases above
threshold); further clockwise rotation increa ses
compressio n into the INFINI1Y + region, up to
a maximum of-1:1 (i.e., a ldB increasein input
level above threshold causes a 1dB decreasein
outp ut level). In the INANl1Y + region, the
160XT inverts the program dynamics for spe-
cial effects.
G. OUTPUT GAIN control
Adjusting this control varies the amount of
fixed gain (up to +20dB) in the 160XT's output
amplifie r stage. The OUTPUT GAIN·contro l
does not interact with the threshold of compres-
•
s1on.
H. DISPLAY switch and indicator
Depressing this button causes the upper LED
array to display the INPUT level to the 160XT.
With the button out, the OUTPUT level is dis-
played. A pair of LEDs immediately above the
DISPLAY swi tch indicates the selected display
status.
is, "half-way" into compress ion, as shown in
Figure (See Figure 13).
E. THRESHOLD indicators
These three LEDs indicate the relation ship of
the input signal level to the threshold of com-
pression. The green "BELOW" 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 Over
Easr ~ode, the amber LEJ? is ON when the sig-
nal 1s 1nthe Over Easy region (See Figure 13).
dbx 160XT
I. LEVELand GAIN REDUCTION displays
The upper row of 19 LEDs displays either the
INPUT or OUTPUT level, as selected with the
DISPLAYswitch. This display is factory set so
that OdBis equivalent to +4dBu input or output
level (1.23Vrms), but may be reset with the rear
panel METER CALIBRATION trimmer. (See fol-
lowing 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
con trol are not displayed by the GAIN REDUC-
TION LEDs but are reflected in the OUTPUT
level display.)
5

6
Rear Panel
A C
1 INPUT- BA1..ANCEO-OUTI>llf 1
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DC~
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Figure 3: Rear Panel
A. SIGNAL INPUT jacks
The Tip/Ring/Sleeve phone jack and XL-type
connector are wired in parallel; either Signal
Input will accept an audio signa l for processing
by the 160XT.The phone jack accepts a stan-
dard TRS l/4" phone plug for a balanced input
source, or a 2-circuit (Tip/Sleeve) 1/4" phone
plug for an unbalanced source . The XL-type
plug connector is wired pin 3 HOT(+), pin 2
COLD(-) and pin 1GROUND.
B. DETECTOR INPUT
This Tip/Ring/Sleeve phone jack accepts a
standard TRS ¼" phone plug, and is of the
Rear Panel
"norrnalling" type. That is, when a phone plug
is inserted, the detector input is no longer con-
nected in parallel with the audio input.
C. SIGNAL OUTPUT -XL-type connector
The 160XThas an active-balanced amplifier ca-
pable 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, unless
you have installed the opt ional transformer.
This will not damage the unit, but may increase
distortion. (See page 28 for transformer balanc-
ing options.)
dbx 160XT
D. SIGNAL OUTPUT -phone jack G. STEREO STRAPPING jack
The 160XThas a separate single-ended (unbal-
anced) output amplifier also capable of driving
a 600 ohm (or greater) load to +24dBu. In nor-
mal operation the Tip/Ring/Sleeve phone jack
is internally wired with the TIP HOT(+), and
the RING and SLEEVE connected to circuit
ground. In BYPASSmode, however, the RING
is connected to the COLD (-) leads of the input
jacks, to allow for 1:1connections.
E. 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 XL-type
connector is connected to the 160XT's circuit
ground. In the "LIFT" position it is discon-
nected. This is not a chassis-isolate switch. The
circuit ground is floating with the respect to the
chassis.
F. METER CALIBRATION control
This screw-drive r-adjus table trimmer may be
used to precisely calibrate the front panel 's
upper LED display so a OdBINPUT or OUT-
PUT indication is equivalent to any signal from
- lSdBu (138mVrrns) to +lOdBu (2.45Vrrns).
When a TRS (Tip/Ring/Sleeve) ¼" phone plug
patch cable is inserted between two 160Xs,ste-
reo strapping can be achieved by depressing
the SLAVEswitch on oneunitonly.This will
provide accurate processing for a stereo pro-
.
gramrmng.
H. AC line voltage requirement indicator
This recessed indicator displays the nominal
AC line voltage for which the 160XThas been
set at the factory.
I. AC power cable
Connect this cable to any SOHzor 60Hz AC
power source of the correct line voltage, as
shown by the AC LINE VOLTAGE requirement
indicator above. The Model 160XT consumes a
maximum of 12 watts AC power.
WARNING: Besure to verify both your actual
line voltage and the voltage for which your
Model 160XT was wired, as indicated on the
rear panel of your unit. Connection to an inap-
propriate power source may result in extensive
damage which is not covered by the warranty.
•
7

8
Connecting The l60XTToYour System
SystemConnections
FROM
LINE LEVEL
SOURCE 160XT
IN OUT
LINE 0 0 0
INPUT 0 0
0 0 0
© © ©
© © 0
© 0 ©
0
. 0 0
0
. © 0
© ©
. ©
0
0
0
©
0
©
®
0
0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 ©
. © © 0
0 © © 0 0 0
.
@ © 0 0 © 0
© 0 © 0 0 ©
© 0
. © 0 G 0
0 0 © 0 © ®
160XT
IN OUT
INSERT
0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 © © © 0 0 B B
© 0 0 © 0 ©
. .
© 0 0 © 0 ©
.
0 0 0 0 © 0 D D D D
.
0
. 0 0 G 0 0 . 0 0 0 0
© 0 0 © ® 0 0 0 0 0
Figure 4: Connecting a 160XTto a Mixing Board
The 160XT has balanced inputs and outputs,
and can be used with any line-level device. Some
common examples include: mixing consoles, n1usi-
cal instruments, patch bays, and other signal pro-
cessors.
A. Mixing Board:
If you wish to compress a particular track of a
multi-track recording or one channel of a live
performance mix, the 160XToutput can be di-
rectly connected 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.
Connecting The l 60XTToYour System dbx 160XT
160XT
IN our
P1lEAMP OUT POWERAMP
IN
OR
160XT
OUTP\/1
POWERAMP
IN
Figure 5: Connecting a 160XT to a Guitar
B. Musical Instruments (i.e., Electric Guitar,
Bass, Keyboards):
The output of an electric guitar is not usually
"hot" enough to drive the 160XT's input. There-
fore you must 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 input s (including various
stomp boxes and rack mount audio products,
like the dbx Performer Series processing units).
Such sources can be balanced or unbalanced,
but this is no problem for the 160XT(see Figure
5).
Microphones and bass guitars, like guitars, also
typica lly have low-level outputs.
Instruments like keyboards typically produce a
line-level signal and can be connected directly
from the instrument's output to the 160XT's
input (see Figure 6). 9

Connecting The l 60XTToYour System
POWER AMP IN
I 160XT I
._I_N_--=0--=U_T___ -'
Figure 6: Connecting a 160XTto a Keyboard
C. Patch bay:
In the studio, the 160XTmay 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 XL-type output connector (distortion can re-
sult). If your stu dio is not fully balanced , you
should leave pin 2 disconnected or use the ¼"
ph one jack output, which is single-€nded. An-
other option is to install an output tran sformer,
which will allow grounding of either pin 2 or 3
of the XL-type output (see page 28).
Connecting The l 60XTToYour System dbx 160XT
IIOXT PWR
-AMP
._.
..-·-
I
1(10)(1 PWRI-
-AMP
"' our KMID
X OVER I
MIX OUT
IIOXT e-
..--
' KBASS
/ /
Figure 7: Connecting 160XTsfor Sound Reinforcement
D. Sound reinforcement:
To compress a live mix or to protect loudspeak-
ers, connect the 160XTbetween the source (mix-
ing 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). Fig-
ure 7 shows three 160XTsused in a tri-amped
(multi-way) setup. For a stereo system, you can
separately stereo couple the two high band
crossovers, low band crossovers, etc. (see next
page). If limitations require that you use a sin-
gle 160XTbeforea crossover, adding an equal-
izer to the side chain may provide some
additional protection to your high frequency
component (see "Specific Applications," page
21).
11

12
Connecting The l60XTToYour System
Multi-ChannelConnections
"MASTER" "SLAVE"
160XT 160XT
IN OUT IN OUT
STEREO I STEREO
STRAPPING STRAPPING
L IN R IN
LOU T ROUT
TRS'STEREO'CABlE
(Shield pl1.11two conductor1)
Figure 8: Multi Channel Connections
The 160XTcan be "strapped" to another 160XT
for 2-channel stereo operation. This will force one
of the units (SLAVE) to track the other (MASTER)
to preserve proper stereo imaging. A ¼" stereo
phone cable is required to connect the two 160XTs
together.
Tooperate in stereo, designate one of the two
units to be a "MASTER" (SLAVEbutton OUT) and
switch the other unit to "SLAVE" mode (SLAVE
button IN, SLAVELED ON).
The master 160XTwill now respond to the com-
bined inputs of the 160XTs.The master's controls
will adjust the amount and nature of the compres-
sion and the slave will track accurately.
When the SLAVEswitches on both units are not
depressed, the 160XTsoperate completely indepen-
dently.
The 1/4"strapping cable may be left in place
when both 160XTsare to be used independently
(i.e., both as MASTER).
Special Connections (OPTIONAL) dbx l60XT
UsingExternalLevelDetectorInputs
To control the compressor by signals other than the audio input (via an auxiliary device), connect the aux -
iliary device 's output to the 160XT's Detector Ir.put jack, and feed the auxiliary device's input with the same
signal fed to the 160XT's Signal Input (for example, using a delay to create "negative" attack times) (Figure
16).
In certain situation s, 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 input of that device, and also to the detector input, and the auxiliary
device's output is fed to the 160XTsigna l input (Figure 9).
SAMPLER t tit tll l 160XT
IN OUT DET IN
EQ or DELAY AUDIO
INPUT
A UDIO OUTPUT
Figure 9: Using the 160XTwith a Sampler
13

Basic Operation (Control Descriptions)
A 8
dbx .,o THRESHOLD 4:1 1:1 0 ...,,.
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160XT -40dlm •-
1:1 •1:1 .eo., -
B'l'PASS SI.AVE COMPRE!ISION OUTPUT OISPl.AY
THRESHOLD OVEREASY RATIO GAN COMPAESSOR/UMlltR
C
Figure 10: Front Panel
db:~ I INPUT- BAI.ANceo - OUTPUTI lNIALANCBl OET£CT0A BittEO =1
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AN). TIP• -· cc CXINTROI.
~ &HO ~GINO a.EEIIEClN) 110LTAGBI
Figure 11:Rear Panel
Basic Operation (Control Descriptions) dbx 160XT
+20
+15 2:1
1D
-o +10 RED 4:1
-..., Above threshold
-'
LU +S
~
20:1
-'
5 0 • \ co:
ci.
,- -5 Rotation Point Threshold
::::>
0 -10 GREEN
-15 Below thre,hold
-15 -10 ·S O +5 +10 +15 +20
INPUTLEVEL(dB)
Figure 12:Hard-Knee Compression Curve
A. THRESHOLD control (and LED indicators):
In hard-knee mode this control sets a reference
level above which input signals will be pro-
cessed by the 160XT's gain change circuitry in
the manner defined by the setting of the RATIO
control. Input signals which fall below this
level will pass through the 160XT unprocessed
(except for fixed gain changes directed by the
output control). See Figure 12.
+20
+15
~
O'.l
"O +10
-...,
-'
w +5
(0
_,
5 0
ci.
5 -5
0 -10
-15
4:1
=·
, RED
#~ •
~ Above Threshold
'
#~ • Over Easy Range
0 Below Threshold
-15 -10 -5 0 +S +10 +1S +20
INPUTLEVEL(dB)
Figure 13: Threshold LEDs and Over Easy
Compression Curve
In Over Easy Mode, signals begin to gradually
activate the 160XT's gain change circuitry as
they approach the THRESHOLD referenc_e
level and they do not get fully processed 1~ the
manner defined by the RATIO control until
they have passed somewhat above the
THRESHOLD reference level. In Over Easy
mode there is no distinct point at which pro-
cessing begins, and the THRESHOLD setting
corresponds to a point on the input/output 15

16
Basic Operation (Control Descriptions)
transfer curve midway between the onset of
processing and that point at which the transfer
curve corresponds to the setting of the RATIO
control (Figure 13.13.). Figure 13. also shows
how the 160XT's THRESHOLD indicator 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
input 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 160XTprocesses the signal coming
into its SIGNAL INPUT.
B. COMPRESSION RATIO control:
When an input signal is above the THRESH-
OLD reference level, the setting of this control
determines the number of decibels by which
the input signal must change in level to pro-
duce a ldB 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 ldB in-
crease in output signal. A setting of oo:1indi-
cates that an infinite increase in input level
would be required to raise the output level by
ldB.
The 160XT's RATIO control covers the entire
range from 1:1 to oo:1and, in addition, goes to
Infinity+ (negative) ratios. At a setting of -1:1,
the above threshold input signal must increase
by ldB in level to decrease the signal at the out-
put of the 160XT by ldB. See Figure 14.
The control curve of the RATIO potentiometer
has been designed to provide total operator
control, with scale expansion at the subtle
lower ratios for easy, repeatable settings.
+20
+15
$
:g,+10
_,
~ +5
5 0
5 -5
0 -10
-15
4 1 6 1
l 1 10 1
·• 1
COMP1ll;SSION
RATIO
\
£--- lhreshold
1:1
4:1
•l:1
-15 -10 -5 0 +5 + 10 +15 +20
INPUTLEVEL(dB)
Figure 14: Ratio Control and Infinity+ (Negative)
Ratios
Basic Operation (Control Descriptions) dbx 160XT
C. SLAVE button (Stereo Operation):
Two channels of program material do not neces-
sarily constitute a stereo program. A stereo pro-
gram is one where the two channels are
recorded and/or mixed to create the illusion of
a single unified "panorama" of sound. The sta-
bility of the psychoacoustic "image" of each
sound source within the stereo program de-
pends 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 pro~ram, a loud _sound o~cur-
ring in one channel will _cau~ea gain ~educhon
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 mo_mentarily sotter
in the compressed charinel. This can be avoided
by linking the two compressors in such a way
that both channels receiv e the same amount of
compression. On the 160XT,this is acc?m-
plished by means of the STRAPPING ,acks; a
cable between these jacks permits the RMS de-
tectors of both units to "talk" to one another -
but only when one of the u~ts' SLAVE b~ttoi:'s
is depressed. The SLAVE unit then sends its sig-
nal to the MASTER, where the RMS power of
the MASTER and SLAVE signals are combined
to generate a control voltage. This control volt-
age is then used to compress both the MASTER
and SLAVE units equally.
When compressing a stereo program_ with a
pair of 160XTs,only the MASTER urut controls
need to be adjusted.
D. METER CALIBRATION control:
The INPUT /OUTPUT LEVEL DISPLAY in the
160XT is factory-calibrated to indicate "O"when
the signal is +4dBu (1.23Vrms) at eith~r the
input or output of the_160XT,?~pending on the
DISPLAYfunction switch position. (The
METER CALIBRATION control does not affect
the GAIN CHANGE LEDs.)
To recalibrate the LEVEL DISPLAY,depress the
DISPLAYbutton to meter the INPUT LEVEL,
and feed a lkHz signal at the selected nominal
operating level (the level desired for a "OdB"
meter indication) to the 160XT's SIGNAL
INPUT. Then adjust the rear panel METER
CALIBRATION control until the meter indi-
cates "OdB."
17

Specific Applications
Smoothing out variations in microphone levels
When the distance between a vocalist and a mi-
crophone changes, variations in signal level occur.
To smooth out these variations, start with the
160XTadjusted 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 Over Easy
characteristic of your 160XTyou will find that even
fairly high ratios are handled transparently .
Smoothing out variations in musical instrument
levels
To achieve a smoother electric bass sound, com-
press the instrument's output with a ratio of about
4:1 (the COMPRESSION RATIO control set at ap-
proximately 12:00).Compression lessens the loud -
ness variations among the strings and increase s the
sustain. Other instruments, such as horn s, vary in
loudness depending on the not e being played, and
benefit similarly.
NOTE: When compressing a stereo program
with a pair of 160XTs,the factors affecting a com-
pression curve and the actual compression ratio
and threshold settings, are like those previously
covered with reference to single channels of pro-
gram material. However, it will generally be found
that large amounts of compress ion are more audi-
ble in a mixed stereo program than they might be
Specific Applications
Preventing tape saturation
With programs of widely varying levels, com-
pression can prevent recording levels from saturat-
ing tape tracks (see Frequency-weighted
compression, page 20).
Speaker protection
Compressors are frequently used to prevent ex-
cessive 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 vol-
ume. In a musical performance, this provides addi-
tional intimacy as the vocalist's whispers are heard
clearly at every seat in the house. The Over Easy
curve available with the 160XTpermits a very high
amount of COMPRESSION (10:1or greater) to be
used in many situations. Vocalists and musicians
don't get the sense of being held back, but high av-
erage levels can be maintained without speaker
damage due to excessive heat buildup.
In circumstances where the 160XTis expected to
cause no change in gain unless an emergency
arises (wildly excessive levels) some operators set
the COMPRESSION RATIO to 00 :l, the THRESH-
OLD to the highest permissible level, and operate
the unit in hard-knee mode. As a general rule, the
compressors should be asclosetotheamplifiersas
possiblein the signal chain. If the 160XT is placed
before the EQ, for example, a potentially damaging
on the separate tracks that were mixed to create the
program.
Raising a signal out of a mix
Since reducing dynamic range increases the aver-
agesignal 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 possi-
ble to separate certain vocals or instruments from a
mono program already mixed by frequency-
weighted compression (see page 20).
Using your EQ to reduce feedback in live settings.
You can use your 160XTand EQ to reduce feed-
back in clubs or halls by placing the 160XTat oo:l,
Hard Knee, and a low threshold. Increase control
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 minimze it. Continue
to increase your console gain and set your EQ until
the 3 or 4 "ring" frequencies have been compen-
sated for.
dbx 160XT
boost in EQ won't be seen by the 160XTand the
speakers may be damaged. (see Multi-way speaker
systems, page 12). For maximum sound pressure
levels, large sound reinforcement systems fre-
quently use a separate compressor on each output
of the electronic crossover(s). For a stereo sound-re-
inforcement system, stereo strapping cables should
be run between the 160XTsin each band (low-low,
mid-mid, etc.).
The 160XTas a line amplifier
To use the 160XTas a line amplifier, adjust the
COMPRESSION ratio control to fully counterclock-
wise (1:1position), THRESHOLD to full clockwise
position(+ 10) and OUTPUT GAIN to whatever set-
ting is required for the application. Remember that,
as with any amplifier, excessive gain may lead to
output clipping of high level signals. Toadd com-
pression, adjust the COMPRESSION ratio and the
THRESHOLD controls to the desired settings.
79

20
Specific Applications
Side-chain applications
Frequency-weighted com pression
It is possible to separate certain vocals and in-
struments from a mix by frequency-weighted com-
pression. With an equalizer inserted ahead of the
detector input (but not in the audio path), the
equalization settings do not shift the timbre or fre-
quency response of the audio signal. They merely
alter the threshold response of the compressor on a
"frequency-weighted" basis (see Figure 15).
/; EQ IN DETECTOR
•
SOURCE ,7 ' IN AUDIO OUT
.
160XT
Figure 15: Frequen cy-Weighted Compression
With this arrangement, raising certain frequen-
cies 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
Specific Applications
De-Essing
To apply de-essing to vocals (i.e., a reduction of
sibilance), use a param etric 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 (generally in the 4-6kHz re-
gion). This pre-emphasizes the al~ady ~'hissy"
vocal input to the detector. Used 1nconJunct1on
with a moderate to high threshold and compres-
sion ratio, this arrangement greatly attenuates the
"essing" without affecting the basic sound quality
or balance of the voice. While it is true that all fre-
quencies are lowered in level when the compressor
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 equ~lizer in th<:level
detector circuit and boost the EQ 1n the dorrunant
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 leve l detec-
tor circuit are basically the same as ob tained with
an equalizer, as previou~ly descri~. Those fre-
quencies passed by the f1lte~are subJec~to compres-
sion (or at least they are subiect to cons iderably
harmonics will not cause compression, and the pro-
gram is not subject to the phase shift normally
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 equalizer can
be adjusted for boost with a peak of about 5kHz,
causing the cymbal to be compressed on a very
loud crash, stopping tape saturation at high fre-
quencies , 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 detector cir-
cuit 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 equalizer bands causes any
sound with dominant energy in the affected regis-
ter to pull the level up because the 160XT will de-
tect a need for less compression.
dbx 160XT
more compression than those frequencies outside
the passband). Because a passive filter can have in-
sertion loss, it may be necessary to lower the
160XT's THRESHOLD setting to maintain a given
amount of gain reduction wi~hin the filter _ .
passband; this can be determined by mon1tonng
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 pr?blem
of keeping levels below the point of destruction of
the most sensitive part of the system. If, for exam-
ple, 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 de-
tector path to the 160XT,it can be made more sensi-
tive to frequencies in the range handled by the
sensitive driv ers. The system can then be run at
higher levels and will only be dropped back when
damaging signals are present.
Pre-emphasis for broadcast applications
By inserting a pre-emphasis filter network in the
detector path of a 160XTproces sing p~-ei:npha-
sized audio, higher levels can be run withi~ the
headroom limitations of the broadcast chain.
21

22
Specific Applications
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 "an ticipate" the need for a gain change.
See Figure 16. With some experimentation the ef-
fect can be that of "zero" attack time at a given fre-
quency. Additional signal delays beyond this
"zero" time will then cause the compressor to fin-
ish reducing the gain before the leading edge of the
loud passage even enters the signal input. This will
suppress the program material preceding this loud
passage. The 160XTwill then begin to release (re-
cover from compression) before the loud passage
has dropped back down toward the set threshold.
This will cause the output level to surge higher as
the note or passage should be decaying. The pro-
duced effect sounds like reverse playback of a tape
recording. When coupled with Infinity+ compres-
sion, highly unusual effects can be achieved.
Installation Considerations
Power Considerations
Connect Power
A. Check the line voltage.
The 160XTis shipped for 115or 230V,50 or 60Hz
operation. Refer to the unit's rear panel to verify
your unit's precise line voltage.
SOURCE I! IN DETECTOR
, I DEIAY IN AUDIO OUT
'
160XT
Figure 16:Anticipated Compression
dbx 160XT
B. Connect the 160XT's power cord to an appropriate AC power source.
Mounting the 160XT in a Rack (OPTIONAL)
Mount the 160XT in a lU 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 shor ten componen t life and is not recommended. Ambient temperatures should not exceed 113°F (45°C)
when equipment is powered.
23

24
InstallationConsiderations
Input Cable Configurations
FAOM llOIJllCE DEVlCE TO leoxt
---------- FllOM SOUl!a DEVlCE TO leoxt
• <:Di [) f O-----0 f(] i II:>
>
CONNECTF NEEDEDTO !!EDUCEHUM
FEMALE XL-TYPETO STEREOPHONE PLUG STEREOPHONE PLUG TO STEREOPHONE PLUG
FROM9:>Ul!a DEVlCE TO leoxt FAOM llOIJllCE DEVICE TO 160XI
2 I ----------• r l 2
3 I 3
• I, I
JQ.•M'E MALE Xl·TVl'EFEMAlf Xl-M>E !Ml£
STEREOPHONE PLUG TO MALE XL-TYPE FEMALE XL-TYPETO MA LE XL-TYPE
Figure 17:Input Connections (Balanced Lines)
Connect Audio Inputs
The 160XThas an actual input impedance of 100kn in balanced configuration or SOkn if unbalanced. This
makes the 160XTaudio input suitable for use with virtually any source impedanc e, low or high.The 160XT's
input connectors are wired in parallel. That is, the phone jack TIP(+) connection is internally wired to the XL-
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 ").
InstallationConsiderations
FROM9:>UllCEDEVICE TO leoxt
<:11 OP!:e··--01 i{] in:>
..,.. __ -l ....
CONN(Cl IF NEEDED 10 REDUCE HIJM
MONO PHONE PLUG TO STEREOPHONE PLUG
FAOM SOURCE DEVCE TO 160XI
<_::it.__-D~:o-------·o:;{].____.r.......t>
MONO PHONE PLUG TO MONO PHONE PLUG
FllOM SOUl!a DEVICE TO 160XI
• -------- I 2
---lJ:i;Ja::::====::u.::µ"t°3o-t-"'
lO.-TVl'EMALE
MONO PHONE PLUG TO MALE XL-TYPE
dbx 160XT
FROM9:>UllCE DEVICE TO 160XI
C Q:b+ e--------a r{] I It)
-.....
~
CONNECTIF NEEDED10 l!EDUa HUM
PHONO PLUG TO STEREO PHONE PLUG
FAOMSOURCEDEVICE TO 160XI
, [J:b:e-----·o,:;{]...._ ....1.....C>
PHONO PLUG TO MONO PHONE PLUG
FAOM 9:>UllCE DEVlCE 10 160XI
Xl-Tl'l'EW. lE
PHONO PLUG TO MALE XL-TYPE
Figure 18:Input Connections (Unbalanced Lines)
Reversing the input wires to the input terminals will result in the output signal polarity being the oppo-
site of the input signal ("180°out of phase ").
The 160XThas a rear-panel GROUND LIFTswitch. This switch disconnect s the in~ut XL-type pin Jfrom
the 160XT'scircuit 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 LIFTposition (shield disconnected at
the 160XTinput). 25

26
Installation Considerations
Output Cable Considerations
FROM 160)(! TO NEXTDEVICE FROM 160Xl TO NEXTDEVICE
2 i' , ----------~ ' 1 2
3 I 3 -----------
II I
.71
lQ..JWE FOM U CONNECTF NE!lltD TO 111:DUCEHUM Xl•M'E MALE lQ..J\'PEFOMU /I
CONNECTF NE!lltD 10 REDUCE~ M
FEMALE XL-TYPETO MALE XL-TYPE FEMALE XL-TYPETO STEREOPHONE PLUG
Figure 19:Output Connections (Balanced Lines)
Connect Audio Outputs
The model 160XThas two seperate outputs: one single-ended amplifier driving the 1/4"stereo phone jack,
and a separate active-balanced amplifier driving the XL-type output connecto r.Each is capable of driving a
600 ohm load to +24dBu. The XL-type output (balanced) can be transformer-coupled by installing an op-
tional output transformer inside your 160XT(see page 28).
Installation Considerations
FAO" 160(1 10 NEXTDev>C!
<._..]._I_.....,(} :: 0--------o::{]1-_ _,1.._.lt>
MONO PHONE PLUG TO MONO PHONE PLUG
FAOM 160)(1 TO NOO OEVO
I ID
CONNEC1 IF NEElltD TO AEOUCEHUM
MONO PHONE PLUG TO STEREOPHONE PLUG
FROM 161>CT 10 NEXT DEVICE
<.,,..:I....1__ (}:: -o------D:cf[],
MONO PHONE PLUG TO PHONO PLUG
dbx l60XT
FROM 101 10 NOO DEVICE
<JI1 [}ii IO----0::{]1-_ _,1.._.t>
STEREOPHONE PLUG TO MONO PHONE PLUG
fQOM lt:OXT
<::11I
10 NEXTOEVICt
[}! 0------0 !i{] I ID
'
,l'
00NNEC1 F NEEDED10 q(OUC( HUM
STEREO PHONE PLUG TO STEREOPHONE PLUG
FqQM 160)(1 10 NOO OEVQ
<)I I
STEREOPHONE PLUG TO PHONO PLUG
Figure 20:Output Connectio ns (Unbalanced Lines)
27

28
InstallationConsiderations
TransformerBalanced (OPTIONAL)
POWER
IRANSfOllMER
-- ------1
,,-o0-0 0- ,
t ' ' I
t I I
:,,;; S!,•
I I I t
I 1.().0.().0 t I
------- -·
Figure 21:Transformer Mounting Area on 160XTBoard
The 160XTmain circuit board is drilled to accept an output transformer to provide a balanced, floating
output stage. dbx recommends installing transformers only when an isolated output is needed. Compatable
transformers are currently available from two sources:
Bauer Communications, Inc.
6887 Farmdale Ave., Bldg 12
North Hollywood, CA91605
TEL [phone]
or [phone]
A. Unplug the 160XTfrom the AC Mains.
Jensen Transformers
10735Burbank Boulevard
North Hollywood, CA 91601
TEL [phone]
B. Toopen the unit for access to the main circuit board, first remove the screws securing both rack ears,
and set them aside.
C. Next, remove the remaining screws, which secure the top cover to the chassis.
InstallationConsiderations dbx 160XT
D. Referring to Figure 21, note the mounting location of the transformer on the 160XTcircuit board.
Within tne transformer mounting area are two jumpers (YSand Y7).Cut or unsolder these jumper s.
E. Insert the transformer from the top side of the board, pressing its pins firmly into the socket cup s pro-
vided .These transformers are symmetr ical (primary and secondary windings are identical ), so onen-
tation on the 160XTcircuit board is not critical; if the pins line up, they are correctly installed .
F. Reverse the disassembly procedure (Steps A and B)to attach the top cover and rack ears.
G. The 160XToutput is now balanced and floating, since there is no ground reference. We recommend
you label the rear panel accordingly, indicating that a balanced , floating out put is installed .
Grounding
160XT
SIGNAL FLOW
Figure 22: Signal Flow (Balanced Connection)
NOTE: For maximum hum rejection, avo id common ground ing at the 160XT's input and output. The best
start ing point is to ground the shield of the input cable at the source dev ice (leaving it unconnected at the
160XT)and to ground the shield of the output cable to the ground terminal of the 160XT(leaving it uncon-
nected at the receiving device). 29

30
Maintenance and Technical Support
Maintenance and Troubleshooting
The 160XTis an all-solid-state product with components chosen for high performance and excellent reli-
ability. Each 160XT is tested, burned in and calibrated at the factory and should require no adjustment of any
type throughout the life of the unit. We recommend that your 160XTbe returned to the factory should cir-
cumstances arise which necessitate repair or recalibration. The 160XTrequires no specia l preventive mainte-
nance .
Technical Support
If you require technical support, contact dbx customer service. Be prepared to accurately describe the
problem. Know the serial number of your 160XT- this is printed on a sticker attached to the rear panel.
Telephone: [phone] or Write: Customer Service
or Fax: [phone] dbx Professional Products
or Telex: 17-1480 a division of AKG Acoustics Inc.
1525 Alvarado Street
San Leandro, CA 94577 USA
FactoryService
Always contact Customer Service before returning a product to the factory for service. Often, a problem is
relatively simple and can be quickly fixed after telephone consultation.
Products can be returned to the factory for service onlyafter Customer Service has issued a Return Autho-
rization number. This number flags the returned unit for priority treatment when it arrives on our dock, and
ties it to the appropriate information file.
Please refer to the term s of your Limited Two-Year Standard Warranty , which extends to the first end-user.
After expiration of the warranty, a reasonable charge will be made for parts, labor, and packing if you choose
to use the factory service facility. In all cases, you are responsible for transportation charges to the factory.
dbx will pay return shipping if the unit is still under warranty.
Maintenance and Technical Support dbx 160XT
ShippingInstructions
Use the original packing material if it is available or a sturdy, double-walled carton no smaller than 22 x
1_2 ~ 5 inches (55.~5_x 31 x 13 cm). ~lace the unit i!l a plastic bag to protect it from moisture and to protect the
firush, then pack it in the carton with at least 1.5 inches (3.75 cm) of cushioning on all sides of the unit. Use
enough packing to prevent the module from moving during shipment. Seal the carton with 3-inch (7.6 cm)
reinforced fiberglass or polyester sealing tape .
Mark the package with the name of the shipper, and with these words in red:
DELICATEINSTRUMENT,FRAGILE!
Insure the package properly. Ship prepaid, not collect. Do not ship parcel post.
31

32
Specifications
Input Characteristics
Rear Panel Input Impedance:
Balanced =1()()k.Q/ Unbala nced =SOk.Q
Maximum Input Level:
+24dBu (12.3Vrms)
Rear Panel Connector Type:
1/4"TRS Phone Jack and XL-type Connector
Detector Input Impedance:
Balanced =4601<.Q/Unbalanced =2301<.Q
Maximum Detector Input Level:
+28dBu (19.SVrms)
Detector Connector Type:
1/4"TRS Phone Jack
Output Characteristics
Output Source Impedance:
Balanced, 22.Q,XL / Unbalanced = 440, Phone
Minimum Load Impedance:
Greater than or equal to 600Q
Maximum Output Level:
Balanced and Unbalanced, +24dBu (12.3Vrms)
into 6000
Connector Type:
¼" TR5 Phone Jack and XL-type Connector
Specifications
Controls,Indicators,Meters
Controls:
Threshold Knob, Ratio Knob, Output Gain
Knob, Over Easy/Hard Knee Switch, Slave
Switch, Bypass Switch, Input/Output Switch
Indicators:
Below: Green; Threshold: Yellow; Above: Red;
Slave: Yellow; Bypass: Red; In/Output: Red
Metering:
19 Segment LED Bargraph Disp lay indicating
Input/Output Level; 13 Segment LED Bar-
graph Display indicating Gain Reduction
Calibration: Factory preset at OVU= +4d8u
(1.23Vrms); rear panel potentiometer sets
OVUfor any level from - lOdBu (7.8mVrms) to
+lOdBu (2.45Vrms).
Stereo Coupling:
True Power Summing; l/4" TR5 Phone Jack
PerformanceCharacteristics
Frequency Response:
20Hz-20kHz (+O.SdB)
THO Distortion:
<0.2%, Any amount of compression@ lkHz
IMO Distortion:
<0.2% SMPTE
Equivalent Input Noise:
-89dBu
Dynamic Range:
113dB
Output Gain:
Variable from - 20dB to +20dB
Threshold:
Compressor -40dBu to +20dBu
Threshold Characteriitics
Selectable Over Easy or Hard Knee
Compression Ratio:
Variable 1:1 - oo:1thru to - 1:1; >60dB Maximum
Compression
Attack Time:
Program-Dependent; 1Sms for lOdB, Sms for
20dB, 3ms for 30dB
Release Time:
Program-Dependent; 8ms for ldB , 80ms for
lOdB, 400ms for SOdB;125dB/sec Rate
dbx 160XT
General
Power Line Requirements:
90-130VAC, 50/60Hz, Switchable to 220-
240VAC
Power Consumption:
12W
Dimensions:
1.75" (H) x 19" (W) x 9.25" (D)
Rack Space:
1 Rack Unit
Weight:
6.Slbs/9lbs shipping weight
Warranty:
Two-yea r, parts and labor: Subject to limita-
tions set forth in our Standard Warranty. Fac-
tory assistance and service will beavailable
throughout the life of the product.
Specifications are subject to change. 33

Schematic (160XTMain Board)
••
"
-··x
·y·.,, -.,.•
. ··r.;- Aj·•
.'. •.• .... -- • tit 11.. ..
,-;;;.-...;•::,..,• ., -
r······...-. .. - - , ,1 .. .... ··• 'l'I·' "ti' ... - .. . - "' ··!·
:I~ . ~ ....._........ .,,·- .•,. ·tr - - 1:,_-+-.,--'-~::c..,... ~ ..b-.. +-!+~·· .-
1 - ;~ ~- • ,.. ~ I~
:7==:-:::-~r,·i:-·ri;.:~- H"'~·,.:;.:~·~~ , - :r·"-i"r..,i;-~:--.:.~...tJ·1·,._~.. ~~ , •# - .;- i.., i :-~ .•
········-'' "'ill'--'!l'ili-f -:.f!~'.i, " .,,. f.:. ·w-.,.~.... ~ - .., -l:.: - ;~~I- Im-".~• _ :_
• • • ,... ::, • .,,_ ?llt h- lfiiirl -..,--~--- .:: ..:
,----8-~h-, ..,.~~s. . ' ~ .•.~,. , I .. '
I ' ·•"' r,._ """ .... U' ... !.- 1 . l
·: =· , .'ff. . .,.,...·s. ua: ~ -Yij;=,;=::ftt:E ,
: ..,. V 1:' ~ ••. --"" • -~ . , I ..... I
: I~ - • • Ill :~ :;1 '~=..- ~ ...- ..._ • ~--·-~ j
I. "" "" '' - · . ''
·-
-~ . NOTES: UNLESSOTl<ERWISESPECIFIED
I AllllESISTOASAREEXPRESSED1HOHMSAl«>ARE•1,w5'4
2 All CAJ'ACJTORSAREEXPESSEOIN.. CROFARADS
3. All OIOOESAAE1N4148
• 'INOICATl:SHEATSINKONDEVICE
5. All RAOlAlRECTAOLYTICCAJ'ACITOASAAE•f 10,,.
6 All MYlAACAJ'ACITOASARE•;5'1'.,
7 All CERAMICDISCCAPAC4TOASARE•f Hl'"·
8 All P0tYPAOCAPACITOASARE·/2 S%
9 All SWITCHESS>l()WNIN'Ol/l"POSm<JN
' ~- V . r- -~ __: i..,'E-, - ..._, • I.,. _ , :
- .------- ..... - ~ J.q ..•r.,1, J,.... •.. ..
I~·-~.. ~ ..::~-..;k~-~J-hr-+-.1:;i,,-~·••:C-i~ .__·_··--:-:"f- .....·~'---·..-:::E:•~~r:::----:- ----- ---·-- --- ----...!:!'. --,,_____,
~ • .. .,. I ' • _ ::;:,, .._ , ,. ., ., , "' .. ,
·;~ ;~..ltw-nlll-~ .• --~ ,~.: ~.. .!........P.:. *7,,;:;,... ·.,,j)l
tf'- "'° ..,. L...... ,, ~ !.,,-""-'-- ,-.. ~ ~•~.,_L;---"''-"-'"7" -<i'"' ......._fi..I I0:" ;•-.,..- ...-r: _:;_
- ... ... -· J ., .... "' .. .,. "!1 .L
~ ... .... ,.." • , !,r,- " :r• ,..,
,:,.ri!! ~ ....:,~ - .., " .,., '"' ;~ j"!I l1.. 7• S?' •• .r'.'f'i:. •., - .., 1:1. I.::;...
:::, a;_""-1' ,., - '"' 1_ • • IT • Uh. < .., - -. 'W I I l; ~ ~ - - ' - •-".
• n
~••...:·~•-~1-~~-c11J:-- .::'......~- ,\o .... .... ' "'' '!'!~• :51.L..J W,. •• J - I- "n .'..,.
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Glossary
This section offers a brief discussion of concepts
directly related to the 160XT's features and func-
tions (e.g., Dynamic Range, Compression, Limit-
ing, Threshold and Leveling) as well as other
common audio concepts (e.g., Noise Reduction).
Read this section if any of these concepts are new
or unclear. Understa _nding the concepts behind the
160XTand other audio equipment will help you to
get the most productivity for all your audio appli-
cations .
Asperity Noise
This is a swishing type of background noise
that occurs with tape recordings in the presence
of strong low frequency signals to mask the
hiss. Asperity noise is caused by minute imper-
fections in the surface of the tape, including
variations on the magnetic particle size in the
tape's oxide coating. The imperfections in-
crease or decrease the strength of the magnetic
field passing the play head in a random man-
ner, resulting in audible noise. Asperity noise
may be present even when no program is re-
corded. When a program is recorded, asperity
noise becomes superimposed on a signal, creat-
ing modulated asperity noise, or "modulation
noise." Using high-quality tape with a
calendered surface helps reduce asperity and
modulation noise (calendered tape is pressed
smooth by high-pressure rollers).
mu SCHEMATIC
MODEL180-Xl
COMPRESSOR,UWITEFI
dbx 160XT
Attack Time
Attack time has different meanings in different
contexts. In music, it is the time it takes for a
note to reach its full volume is the attack time
of the note. Percussive instruments usually
have short attack times (reaching maximum
volume quickly) and wind instruments tend to
have long attack times (reaching maximum vol-
ume more gradually).
A compressor or expander requires a finite time
to respond to changes in level. This time is
known as attack time. More precisely, the at-
tack time is the interval (usually measured in
milliseconds, or microseconds) during which
the compression or expander amplifier changes
its gain from the initial value to 90%of the final
value.
Aux Input (Aux Level)
Aux inputs, an abbreviation for auxiliary in-
puts, are low sensitivity jacks provided on most
hi-fi and semi-professional equipment. Aux in-
puts (also known as "aux level" or "line-level"
inputs) have "flat" frequency response and are
intended to be used with pre-amplified signals.
Aux-level (line-level) signals are medium-level,
higher than microphone levels, but not enough
power to drive a speaker. The advantage to
these levels is that they are less susceptible to
hum and noise than are microphone levels. Typ-
ical items that might be connected to aux in- 35
........
__...
-~.. ~
..

36
Glossary
puts are tape machine "play" outputs, tuner
outputs, and dbx "play" outputs. Mic-level or
phono-level signals are considerably lower in
level than aux inputs (approx -60 to -40dBu), so
they will not produce adequate volume when
connected to an aux input: Moreover, phono
cartridge outputs require RIAA equalization
that is not provided by aux inputs.
Bandwidth
Bandwidth refers to the "space" between two
specific frequencies that are upper and lower
limits; alternately, bandwidth refers to the abso-
lute value of the range of frequencies between
t~ose limits. Thus, a filter that passes frequen-
oes from lkHz to lOkHz may be said to have a
bandwidth of lkHz- lOkHz, or it may be said
to have a 9kHz bandwidth (lOkHz minus lkHz
equals 9kHz).
Bandwidth is not necessarily the same as fre-
quency response. Bandwidth may be measured
at low levels, and frequency response at higher
level~. Mo~ver, bandwidth may refer only to
certain portions of the circuitry within a piece
of equipment, whereas frequency response
mar refer to the overall performance of the
equipment. Thus, while the overall input-to-
outpu_t frequency response of dbx Type II equip-
ment 1s20Hz to 20kHz, the bandwidth of the
RMS detection circuitry within that equipment
is 60Hz to lOkHz.
Glossary
The frequency of the bias signal is approxi-
mately 4 times the highest frequency of the
tape recorder's Record/Reproduce response.
The bias energy level has a direct effect on re-
corded level, background noise and the distor-
tion. For optimum _performance, it is
recommended that the tape recorder be cali-
brated each time a different tape type is used.
Most, if not all professional tape recorder manu-
facturers feature bias presets to accommodate
the different tape types. Many consumer tape
machines offer bias select swi tches to optimize
for most of the High bias cassette tapes avail-
able today.
Clipping
Clipping is a very distorted sound. It occurs
when the output capabilities of an amplifier are
exceeded, and the amplifier can no longer pro-
duce anymore voltage, regardless of how much
additional gain or how much more input signal
is present. Clipping is relatively easy to see on
an oscilloscope, and is sometimes audible as an
increase in harmonic distortion. In severe cases
of clipping (hard clippin g), sine waves begin to
resemb le square waves, and the sound quality
is very poor. Often, the maximum output level
of an amplifier is defined as that level where
clipping begins to occur. There is a phenome-
non known as input clipping, and this may
occur where the input signal is so high in level
that it exceeds the level-handling ability of the
Bass
The low audio frequency range below approxi-
mately SOOHz.For the purpose of discussion or
analysis, the bass range may be further divided
into upper bass (250 to SOOHz),mid bass (100 to
200Hz), low bass (50 to lOOHz)and ultra-low
bass (20 to SOHz).
Bass Boost
An accentuation of the lower audio frequencies
(bass frequencies), whereby they are made
louder than other frequencies.
Biamplified
Descriptive of a sound system that utilizes a
low level crossover network to divide the full-
spectrum audio signal into low and high fre-
quency ranges. These ranges are then fed to
separate power amplifiers, which in turn feed
low frequency speakers (woofers) and high fre-
quency speakers (tweeters).
Bias
Bias, as the term used in tape recording, is a
very high frequency signal (usually over
lOOkHz)that is mixed with the program being
recorded in order to achieve linear magnetiza-
tion of the tape. If only the audio program were
applied to the recording head, a very distorted
recording would result because lower-energy
portions of the program would not be able to
overcome the initial magnetization threshold of
the tape (known as hysteresis).
dbx 160XT
transformer and/ or of the input amplifier. Clip-
ping also occurs when tape is saturated by ex-
cessive record levels.
So-called "soft clipping" is usually the result of
transformer saturation, and it may be some-
what less objectionable than the "hard clip-
ping" that occurs when output voltage limits
are reached. Aside from degrading the sound
quality, clipping can damage loud speakers.
Output clipping can be avoided by reducing
the level of the input signal, reducing the gain
of the amplifier, or using a larger amplifier.
Input clipping may be avoided by reducing the
input level.
Clipping Level
This is the signal level at which clipping just be-
gins to occur. Clipping level is not always easy
to define. It may be a matter of visually judging
the waveform on an oscilloscope as the level is
increased; alternately, clipping may be defined
as the level at which harmonic distortion
reaches a given value. Tape clipping, or satura-
tion, is defined as the 3% harmonic distortion
level.
Compression
Compression is a process whereby the dynamic
range of program material is reduced . In other
words, the difference between the lowest and
highest audio levels is "squeezed" into a 37