dbx 162SL User Manual
User Manual
Compressor/Limiter
®
162SL
WARNING FOR YOUR PROTECTION
READ THE FOLLOWING:
KEEP THESE INSTRUCTIONS
HEED ALL WARNINGS
FOLLOW ALL INSTRUCTIONS
DO NOT USE THIS APPARATUS NEAR WATER
CLEAN ONLY WITH A DRY CLOTH.
DO NOT BLOCK ANY OF THE VENTILATION OPENINGS. INSTALL IN ACCORDANCE WITH
THE MANUFACTURER’S INSTRUCTIONS.
DO NOT INST
ALL NEAR ANY HEAT SOURCES SUCH AS RADIATORS, HEAT REGISTERS,
STOVES, OR OTHER APPARATUS (INCLUDING AMPLIFIERS) THAT PRODUCE HEAT.
ONLY USE ATTACHMENTS/ACCESSORIES SPECIFIED BY THE MANUFACTURER.
UNPLUG THIS APPARATUS DURING LIGHTNING STORMS OR WHEN UNUSED FOR LONG
PERIODS OF TIME.
Do not defeat the safety purpose of the polarized or grounding-type plug. A polarized plug has two blades with one wider than the other. A grounding type plug has
two blades and a third grounding prong. The wide blade or third prong are provided for your safety. If the provided plug does not fit your outlet, consult an electrician for replacement of the obsolete outlet.
Protect the power cord from being walked on or pinched particularly at plugs, convenience receptacles, and the point where they exit from the apparatus.
Use only with the cart stand, tripod bracket, or table specified by the manufacture,
or sold with the apparatus. When a cart is used, use caution when moving the
cart/apparatus combination to avoid injury from tip-over.
Refer all servicing to to qualified service personnel. Servicing is required when
the apparatus has been damaged in any way, such as power-supply cord or plug is
damaged, liquid has been spilled or objects have fallen into the apparatus, the apparatus has been exposed to rain or moisture, does not operate normally, or has been
dropped.
POWER ON/OFF SWITCH: For products provided with a power switch, the power
switch DOES NOT break the connection from the mains.
MAINS DISCONNECT: The plug shall remain readily operable. For rack-mount or
installation where plug is not accessible, an all-pole mains switch with a contact
separation of at least 3 mm in each pole shall be incorporated into the electrical
installation of the rack or building.
FOR UNITS EQUIPPED WITH EXTERNALLY ACCESSIBLE FUSE RECEPTACLE: Replace fuse
with same type and rating only.
MULTIPLE-INPUT VOLTAGE: This equipment may require the use of a different line
cord, attachment plug, or both, depending on the available power source at installation. Connect this equipment only to the power source indicated on the equipment
rear panel. To reduce the risk of fire or electric shock, refer servicing to qualified
service personnel or equivalent.
This Equipment is intended for rack mount use only.
SAFETY INSTR
UCTIONS
NOTICE FOR CUSTOMERS IF YOUR UNIT IS EQUIPPED
WITH A POWER CORD.
WARNING: THIS APPLIANCE MUST BE EARTHED.
The cores in the mains lead are coloured in accordance with
the following code:
GREEN and YELLOW - Earth BLUE - Neutral BROWN - Live
As colours of the cores in the mains lead of this appliance may
not correspond with the coloured markings identifying the terminals in your plug, proceed as follows:
• The core which is coloured green and yellow must
be connected to the terminal in the plug marked
with the letter E, or with the earth symbol, or
coloured green, or green and yellow.
• The core which is coloured blue must be connected to the terminal marked N or coloured black.
• The core which is coloured brown must be connected to the terminal marked L or coloured red.
This equipment may require the use of a different line cord,
attachment plug, or both, depending on the available power
source at installation. If the attachment plug needs to be
changed, refer servicing to qualified service personnel who
should refer to the table below. The green/yellow wire shall be
connected directly to the units chassis.
WARNING:If the ground is defeated, certain fault conditions in
the unit or in the system to which it is connected can result in
full line voltage between chassis and earth ground. Severe injury
or death can then result if the chassis and earth ground are
touched simultaneously.
The symbols shown above are internationally accepted
symbols that warn of potential hazards with electrical
products. The lightning flash with arrowpoint in an equilateral triangle means that there are dangerous voltages
present within the unit. The exclamation point in an equilateral triangle indicates that it is necessary for the user to
refer to the owner’s manual.
These symbols warn that there are no user serviceable
parts inside the unit. Do not open the unit. Do not
attempt to service the unit yourself. Refer all servicing to
qualified personnel. Opening the chassis for any reason
will void the manufacturer’s warranty. Do not get the unit
wet. If liquid is spilled on the unit, shut it off immediately
and take it to a dealer for service. Disconnect the unit
during storms to prevent damage.
IMPORTANT SAFETY INSTRUCTIONS
CAUTION
RISK OF ELECTRIC SHOCK
DO NOT OPEN
ATTENTION:
WARNING:
SHOCK DO NOT EXPOSE THIS EQUIPMENT TO RAIN OR MOISTURE
RISQUE DE CHOC ELECTRIQUE - NE PAS OUVRIR
TO REDUCE THE RISK OF FIRE OR ELECTRIC
CONDUCTOR
LIVE
L
NEUTRAL
N
E
EARTH GND
WIRE COLOR
Normal Alt
BROWN
BLUE
GREEN/YEL
BLACK
WHITE
GREEN
U.K. MAINS PLUG WARNING
A molded mains plug that has been cut off from the cord is unsafe.
Discard the mains plug at a suitable disposal facility. NEVER UNDER
ANY CIRCUMSTANCES SHOULD YOU INSERT A DAMAGED OR CUT
MAINS PLUG INTO A 13 AMP POWER SOCKET. Do not use the
mains plug without the fuse cover in place. Replacement fuse covers
can be obtained from your local retailer. Replacement fuses are 13
amps and MUST be ASTA approved
to BS1362.
IMPORTANT SAFETY INSTRUCTIONS
ELECTROMAGNETIC
COMPATIBILITY
This unit conforms to the Product
Specifications noted on the Declaration
of Conformity. Operation is subject to
the following two conditions:
• this device may not cause harmful
interference, and
• this device must accept any interfer-
ence received, including interference
that may cause undesired operation.
Operation of this unit within significant
electromagnetic fields should be avoided.
• use only shielded interconnecting
cables.
DECLARATION OF
CONFORMITY
Manufacturer’s Name: dbx Professional Products
Manufacturer’s Address: 8760 S. Sandy Parkway
Sandy, Utah 84070, USA
declares that the product:
Product name: dbx 162SL
Note: Product name may be suffixed by the
letters-EU.
Product option: None
conforms to the following Product Specifications:
Safety: IEC 60065 (1998)
EMC: EN 55013 (1990)
EN 55020 (1991)
Supplementary Information:
The product herewith complies with the requirements
of the Low Voltage Directive 72/23/EEC and the EMC
Directive 89/336/EEC as amended by Directive
93/68/EEC.
Vice-President of Engineering
8760 S. Sandy Parkway
Sandy, Utah 84070, USA
Date: January 30, 2004
European Contact:
Your local dbx Sales and Service
Office or
Harman Music Group
8760 South Sandy Parkway
Sandy, Utah 84070 USA
Ph: (801) 566-8800
Fax: (801) 568-7583
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
Why you need compression
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
The difference between compressors and limiters
. . . . . . . . . . . . . . . . . . . . . .4
The compression and limiting effects
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Limiters and PeakStopPlus™
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6
Features
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
Connection To Your System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
Operating Controls
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
Front Panel Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
Rear Panel Description
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
Operating Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17
OverEasy® and hard knee
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
Using the Compression Control
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
Using the Stereo Couple Switch
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
Using the Auto Switch
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
Setting the Attack and Release Controls
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
Using PeakStop®/PeakStopPlus
®
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
Specific Applications
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
Sidechain Applications
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
Te chnical Support/Factory Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
Warranty
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
Block Diagram
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26
Specifications
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27
Why You Need A Compressor
A remarkable feature of the human ear is that it can detect an extremely wide range of amplitude
changes - from the slightest whisper to a deafening clap of thunder. If one tries to record or reproduce
this wide spectrum of sound with the help of amplifiers, cassette recorders, records, or even digital
recorders, one is immediately restricted by the physical limitations of electronic and acoustic sound
reproduction technology.
The useable dynamic range of electronic audio equipment is limited as much at low levels as at high
levels. The thermal noise of electrons in the components results in an audible noise floor and thus represents the bottom limit of the transmission range.
The upper limit of useable dynamic range is determined by the levels of the internal operating voltages;
if they are exceeded, audible signal distortion is the result. Although in theory the useable dynamic range
sits between these two limits, it is considerably smaller in practice, since a certain reserve must be maintained to avoid distortion of the audio signal if sudden noise peaks occur. Technically speaking, we refer
to this reserve as headroom--usually about 10-20dB. A reduction of the operating level would allow for
greater headroom, i.e. the risk of signal distortion due to high level peaks would be reduced. However
at the same time, the basic signal to noise ratio of the program material would be increased significantly. It is therefore useful to keep the operating level as high as possible without risking signal distortion
in order to achieve optimum transmission quality. It is possible to further improve the transmission quality by constantly monitoring the program material with the aid of a volume fader, which manually
changes the level of the program material. During low passages the gain is increased, and during loud
passages the volume is decreased. Of course it is fairly obvious that this kind of manual control is rather
restrictive; it is difficult to detect signal peaks and almost impossible to level them out. Manual control
is simply not fast enough to be satisfactory.
The need therefore arises for a fast acting automatic gain control system which will constantly monitor
the signals and which will always adjust the gain to maximize the signal-to-noise ratio without incurring
signal distortion. This device is called a compressor or limiter.
3
The Difference Between Compressors and Limiters
By measuring the dynamic range of musical instruments in live recording situations, you will experience
extreme amplitudes which will often lead to overload in subsequent signal processing equipment.
Especially in broadcasting and digital recording, these signal peaks can lead to heavy distortion. To avoid
this kind of distortion or, to avoid loudspeakers being damaged by overload, compressors and limiters
are used.
The principle function of these devices is automatic gain control, as mentioned in the previous paragraphs, which reduces the the amplitude of loud passages and therefore restricts the original signal
dynamics within a desired range. This is useful, especially in conjunction with microphone recording
techniques, to compensate for level changes which are caused by inconsistent microphone techniques
on the part of the player, or to restrict the natural dynamic range of voices or instruments to achieve a
more even level.
Although compressors and limiters perform similar tasks, one essential point makes them different:
Limiters abruptly limit the signal above a certain level, while compressors control the signal “gently” over
a wide range. A limiter continuously monitors the signal and intervenes as soon as an adjustable level
is exceeded. This level is called the “threshold”. Any signal exceeding this threshold level will be immediately held below the set threshold level.
A compressor also monitors the program material continuously and also has a set threshold level.
However, in contrast to the limiter, signals exceeding the threshold are not reduced abruptly, but gradually. Above the threshold the signal is reduced in level relative to the amount the signal exceeds this
point.
Generally, threshold levels for compressors are set below the normal operating level to allow for the
upper dynamics to be musically compressed. For limiters, the threshold point is set above the normal
operating level in order to provide peak signal limiting and thus protects subsequent equipment.
4
Dynamic
Range
Clipping
Clipped signal heavily distorted
Headroom
Operating Level
Useable dynamic range
Noise Floor
Audio levels below here are not heard, because of noise
The Compression and Limiting Effects
On a compressor, there is a relationship between the input signal, and the threshold level, input, output, and ratio settings. Look at an input signal applied to the inputs of two compressors. The threshold
level of the second unit is set ten decibels higher than the threshold of the first unit. Since a compressor only affects signals that exceed the threshold level, it is obvious that the signal of the first compressor will be compressed more, because it exceeds the threshold level more than the level of the second
unit, because the second compressor’s threshold level is set higher.
The difference between compression and limiting is shown visually below. In the first diagram below,
compression “squashes” the signal. Its peaks are lowered, but the overall level of the signal is raised due
to applied make-up gain (Output Gain). In the second diagram, the peaks are lowered to the threshold
level, but the rest of the signal has not been altered.
Obviously, there is a large difference between these two signals in relation to their dynamic range and
the processed signal. In the third figure, it is shown to have been compressed, and in the fourth figure,
it has been limited.
5
Input of compressors at
different threshold settings.
= threshold
Difference in output of
compressors and limiters.
= threshold
input
dBu
input
dBu
input
dBu
+10
0
+10
+10
0
0
-10
-10
-10
-20
time
Figure 1
-20
time
-20
Figure 2 Figure 1
time
output
dBu
+10
0
output
dBu
+10
0
-10
-10
-20
time
Figure 3 Figure 4
-20
time
6
Furthermore, it is interesting to note that by comparing the input and output waveforms for the compressed mode, the quietest sections of the input signal have been effectively raised in level, whereas the loudest sections have been effectively decreased in level. The overall effect is that both ends
of the dynamic range have been pushed toward the middle. This squashing effect of compression is
important to remember and highlights the major difference between compressing and limiting.
Compressing and limiting differ in one more aspect: the dynamic settings for attack and release times.
Attack time is defined as the time taken to for a compressor to respond to program levels which have
exceeded the threshold point. Release time is the amount of time a compressor takes to return the
program level to its original level, after the last excursion over the threshold point. For compression,
a preferably longer attack and release time are generally the best in order to keep the overall output
signal within a specified dynamic range. For limiting applications, considerably shorter attack and
release times are necessary to control fast transient signals or to increase headroom.
To achieve inaudible compression, it is advisable to work with program dependent attack and release
times. The advantage of program dependent compression is most apparent when processing musical material that is varied.
The dbx 162SL Stereo Compressor is suitable for all applications because of the ability to manually
set both attack and release parameters.
Limiters and PeakStopPlus
®
Lower frequencies work best when compressed with slower attack times. When compressing a mix
that includes a wide range of frequencies, a compromise is made when setting the attack time. The
attack setting would generally suit the lowest frequency components of the material. For general
dynamic range control with a compressor, this is of no serious consequence.
However, in a “limiting” situation, where we are restricting the peaks of our signal to a maximum
operating level to avoid distortion in subsequent devices, a slow attack time is not acceptable. This
would result in very fast high frequency signal transients passing through unaffected by gain reduction. These transients could then cause distortion in the following equipment such as tape recorders
and radio transmitters. It is therefore necessary to choose an attack time which is as close to “zero”
attack as possible, independent of the frequency.
This makes the limiter necessary, and it’s why we include a peak limiter on almost all of our compression products. The dynamics of the dbx limiters are set to handle these fast transients through a
process called PeakStop and the newer, improved two-stage process called PeakStopPlus.
The first stage of PeakStopPlus is the Instantaneous Transient Clamp™ which clamps the signal with
a soft logarithmic clamp function. This logarithmic function assures that the signal will not exceed
the level set by the PeakStopPlus LEVEL control by more than 2 dB typically, and that it will not
introduce harsh artifacts. The second stage is a unique program limiter featuring Intelligent Predictive
Limiting™. Its function is to monitor the input signal and intelligently predict the amount of gain
reduction needed to keep the output signal below the ceiling set by the Instantaneous Transient
Clamp™. Note, since the PeakStopPlus limiter is a fail-safe limiter it must come after the OUTPUT
7
GAIN control. If the output gain is set too high as compared to the PeakStopPlus Level control, continuous limiting can occur. While PeakStopPlus is typically used as a protective function, creative
effects can be achieved by intentionally driving the signal into heavy PeakStopPlus limiting. Great
care has gone into the design of the PeakStopPlus limiter to keep it acoustically transparent.
Appropriate use of it can protect your gear while keeping the signal free of artifacts.
For best results the Limiter functions of your compressor should be used in conjunction with the
Compressor functions.
Features
When we at dbx decided to make a premium compressor that would perform to the industry’s highest standards, it became readily obvious that every component and design strategy had to be chosen
with high-performance foremost in mind. After the revolutionary process of engineering design and
implementation was complete, the result was stunning. Here is a partial list of the features found on
the 162SL. You won’t hear about most of them anywhere else, but they are
critical to the amazing specs, comprehensive functionality, and visionary
design of the 162SL Stereo Compressor.
• Precision 1% metal film resistors.
• Gold-palladium-nickel board-to-board connectors.
• Jensen
®
Output transformers.
• Gold-plated Neutrik
®
XLR connectors.
• Rare earth magnet relays with gold contacts in a hermetically
sealed nitrogen environment.
• Military-grade glass epoxy circuit boards.
• Toroid transformer.
• Custom-machined, 1/4” thick front panel.
• Hand-crafted, solid aluminum knobs.
• LEDs mounted in machined, stainless steel housings.
• Custom dbx VU meters with peak indicators.
• Switchable OverEasy
®
/hard knee characteristics enable the 162SL to
sound like the traditional 165A as well as the old and still popular 160.
• Program dependent Auto mode, or fully variable attack and
release.
• PeakStop/PeakStopPlus
®
switchable limiting topologies, the perfect
complement to the 162SL feature set.
• Sidechain capabilities, switchable from the front panel.
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