dbx 20 Series User manual

OPERATION MANUAL
MODE D’EMPLOI
BEDIENUNGSANLEITUNG
MODO DE EMPLEO
20 SERIES
EQUALIZER/LIMITER
with TYPE III NR

WARNINGFORYOURPROTECTION
READTHESEINSTRUCTIONS:
KEEPTHESEINSTRUCTIONS
HEEDALLWARNINGS
FOLLOWALLINSTRUCTIONS
DONOTUSETHISAPPARATUSNEARWATER
CLEANONLYWITHADRYCLOTH.
DONOT BLOCKANYOF THEVENTILATION OPENINGS. INSTALL IN ACCORDANCEWITH THEMANU-
FACTURER’SINSTRUCTIONS.
DO NOT INSTALL NEAR ANY HEAT SOURCES SUCH AS RADIATORS, HEAT REGISTERS, STOVES, OR
OTHERAPPARATUS(INCLUDINGAMPLIFIERS)THATPRODUCEHEAT.
ONLYUSEATTACHMENTS/ACCESSORIESSPECIFIEDBYTHEMANUFACTURER.
UNPLUG THIS APPARATUS DURING LIGHTNING STORMS OR WHEN UNUSED FOR LONG PERIODS OF
TIME.
Donot defeatthe safetypurpose ofthepolarized orgrounding-type plug. Apolarized plughas
two blades with one wider than the other. A grounding type plug has two blades and a third
groundingprong. Thewide bladeorthirdprong areprovidedforyour safety. Iftheprovided
plugdoesnotfityouroutlet,consultanelectricianforreplacementoftheobsoleteoutlet.
Protect the power cord from being walked on or pinched particularly at plugs, convenience
receptacles,andthepointwheretheyexitfromtheapparatus.
Use only with the cart stand, tripod bracket, or table specified by the manufacture, or sold
withthe apparatus. Whenacart isused, use cautionwhen movingthecart/apparatus combi-
nationtoavoidinjuryfromtip-over.
Refer all servicing to to qualified service personnel. Servicing is required when the appara-
tus 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
ormoisture,doesnotoperatenormally,orhasbeendropped.
POWER ON/OFF SWITCH: For products provided with a power switch, the power switch DOES
NOTbreaktheconnectionfromthemains.
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
mmineachpoleshallbeincorporatedintotheelectricalinstallationoftherackorbuilding.
FOR UNITS EQUIPPED WITH EXTERNALLY ACCESSIBLE FUSE RECEPTACLE: Replace fuse with
sametypeandratingonly.
MULTIPLE-INPUTVOLTAGE: Thisequipmentmay requiretheuse ofadifferent linecord,attach-
mentplug,orboth,dependingon the availablepowersourceatinstallation.Connectthisequip-
ment only to the power source indicated on the equipment rear panel. To reduce the risk of
fireorelectricshock,referservicingtoqualifiedservicepersonnelorequivalent.
ThisEquipmentisintendedforrackmountuseonly.
SAFETYINSTRUCTIONS
NOTICEFORCUSTOMERSIFYOURUNITISEQUIPPEDWITHAPOWERCORD.
WARNING:THISAPPLIANCEMUSTBEEARTHED.
Thecoresinthemainsleadarecolouredinaccordancewiththefollowingcode:
GREENandYELLOW-Earth BLUE-Neutral BROWN-Live
As colours of the cores in the mains lead of this appliance may not correspond with the coloured mark-
ingsidentifyingtheterminalsinyourplug,proceedasfollows:
•The core which is coloured green and yellow must be connected to the terminal in the plug
markedwiththeletterE,orwiththeearthsymbol,orcolouredgreen,orgreenandyellow.
•ThecorewhichiscolouredbluemustbeconnectedtotheterminalmarkedNorcolouredblack.
•ThecorewhichiscolouredbrownmustbeconnectedtotheterminalmarkedLorcolouredred.
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
qualifiedservice personnel whoshouldrefer tothetable below. Thegreen/yellowwireshall beconnect-
eddirectlytotheunitschassis.
WARNING:Ifthe ground isdefeated,certainfault conditions intheunitor in thesystemto which itiscon-
nected can result in full line voltage between chassis and earth ground. Severe injury or death can then
resultifthechassisandearthgroundaretouchedsimultaneously.
Thesymbolsshownaboveareinternationallyacceptedsymbolsthatwarn of potential hazards with
electricalproducts. The lightning flashwitharrowpoint in anequilateral triangle means thatthere
are dangerous voltages present within the unit. The exclamation point in an equilateral triangle
indicatesthatitisnecessaryfortheusertorefertotheowner’smanual.
Thesesymbolswarn that there arenouserserviceableparts inside the unit. Donotopentheunit.
Do not attempt to service the unit yourself. Refer all servicing to qualified personnel. Opening the
chassisfor any reasonwillvoid the manufacturer’swarranty. Donot get theunitwet. If liquid is
spilled on the unit, shut it off immediately and take it to a dealer for service. Disconnect the unit
duringstormstopreventdamage.
IMPORTANT SAFETY INSTRUCTIONS

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 cov-
ers can be obtained from your local retailer. Replacement fuses are
13 amps and MUST be ASTA approved to BS1362.
LITHIUM BATTERY
WARNING
CAUTION!
This product may contain a lithium battery. There is danger of
explosion if the battery is incorrectly replaced. Replace only
with an Eveready CR 2032 or equivalent. Make sure the bat-
tery is installed with the correct polarity. Discard used batter-
ies according to manufacturer’s instructions.
ADVARSEL!
Lithiumbatteri - Eksplosjonsfare. Ved utskifting benyttes kun
batteri som anbefalt av apparatfabrikanten. Brukt batteri
returneres apparatleverandøren.
ADVARSEL!
Lithiumbatteri - Eksplosionsfare ved fejlagtig håndtering.
Udskiftning må kun ske med batteri av samme fabrikat og
type. Levér det brugte batteri tilbage til leverandøren.
VAROITUS!
Paristo voi räjähtää, jos se on virheellisesti asennettu. Vaihda
paristo ainoastaan laitevalmistajan suosittelemaan tyyppin.
Hävitä käytetty paristo valmistajan ohjeiden mukaisesti.
VARNING!
Explosionsfara vid felaktigt batteribyte. Använd samma batteri-
typ eller en ekvivalent typ som rekommenderas av apparattil-
lverkaren. Kassera använt batteri enligt fabrikantens instruk-
tion.
IMPORTANT SAFETY INSTRUCTIONS
ELECTROMAGNETIC
COMPATIBILITY
This unit conforms to the Product
Specifications noted on the Declaration of
Conformity. Operation is subject to the fol-
lowing two conditions:
• this device may not cause harmful inter-
ference, and
• this device must accept any interference
received, including interference that may
cause undesired operation.
Operation of this unit within significant elec-
tromagnetic 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 2031, dbx2215 and dbx2231
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 73/23/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: July 1, 2003
European Contact: Your local dbx Sales and Service Office
or
Harman Music Group
8760 South Sandy Parkway
Sandy, Utah
84070 USA Ph: [phone]
Fax: [phone]

MANUAL CONTENTS
ENGLISH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
FRANÇAIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
DEUTSCH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
ESPAÑOL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
ENGLISH CONTENTS
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
INSPECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
OPERATING CONTROLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
CONNECTING THE EQ TO YOUR SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
REAR PANEL DESCRIPTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
INSTALLATION CONSIDERATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
OPERATION AND APPLICATIONS NOTES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
TECHNICAL SUPPORT / FACTORY SERVICE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
BLOCK DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
OPERATION MANUAL
1
20 SERIES GRAPHIC EQUALIZERS

INTRODUCTION
Congratulations on your purchase of a dbx graphic equalizer. All dbx graphic equalizers are high performance multi-
functional units designed to deliver all the flexibility and power that professional users demand. We recommend that
you take a moment to read through this operation manual. It provides information that will assist you from system set-
up to EQ applications. The 20 Series Equalizers include the following features:
• Revolutionary dbx TYPE III™ Noise Reduction capable of restoring up to 20dB S/N ratio
• Proprietary patent-pending PeakPlus™ Limiter for system protection
• Switchable range between ±6dB and ±15dB
• Balanced inputs and outputs
• XLR, Barrier Strip, and 1/4” TRS connectors
• -12dB/+12dB input gain range
• 18dB/octave 40Hz Bessel Low-Cut filter
• Chassis/signal ground lift capability
• Internal power supply transformer
• Power-off hard-wire relay bypass with 2-second power-up delay
INSPECTION
Verify that the equalizer’s package contains the following:
• Equalizer unit matching serial number marked on package
• AC power cord
• Operation Manual
• Registration Card
• Four rack mount screws and washers
If any of these items are missing please contact dbx customer service at the number provided on the back cover of this
manual.
OPERATING CONTROLS Front Panels
2031 - single channel 31 band graphic equalizer
2231 - dual channel 31 band graphic equalizer
2
OPERATION MANUAL
RANGE
GAIN
REDUCTION (dB)
OUTPUT
LEVEL (dBu)
LOW
CUT
EQ
BYPASS
TYPE III
NR INPUT GAIN
dB
-12
0
+12
PeakPlus
THRESHOLD
dBu
0 OFF
+20+5
+15+10 +/-6
+/-15
CLIP
1
0
-6
+6
20 25 31.5 40 50 63 80 500400315250 1.6k1.25k1k800 5k4k3.15k2.5k 16k12.5k10k8k6.3k 20k2k630100 125 160 200
0
-15
+15
3610+18+100-10
2031
Equalizer/Limiter
with TYPE III NR
2231
Equalizer/Limiter
with TYPE III NR
20 25 31.5 40 50 63 80 500400315250 1.6k1.25k1k800 5k4k3.15k2.5k 16k12.5k10k8k6.3k 20k2k630100 125 160 200
RANGE
GAIN
REDUCTION (dB)
OUTPUT
LEVEL (dBu)
LOW
CUT
EQ
BYPASS
TYPE III
NR INPUT GAIN
dB
-12
0
+12
PeakPlus
THRESHOLD
dBu
0 OFF
+20+5
+15+10 +/-6
+/-15
CLIP
13610+18+100-10
RANGE
GAIN
REDUCTION (dB)
OUTPUT
LEVEL (dBu)
LOW
CUT
EQ
BYPASS
TYPE III
NR INPUT GAIN
dB
-12
0
+12
PeakPlus
THRESHOLD
dBu
0 OFF
+20+5
+15+10 +/-6
+/-15
CLIP
13610+18+100-10
0
-15
+15
0
-15
+15
0
-6
+6
0
-6
+6

2215 - dual channel 15 band graphic equalizer
Input Gain Control: This control sets the signal level to the equalizer. It is capable of -12dB to +12dB of gain. Its
effect is apparent by viewing the OUTPUT LEVEL BAR GRAPH.
EQ Bypass: This switch removes the graphic equalizer section from the signal path. (See Block diagram on Page
32.) The BYPASS switch does not, however, affect the INPUT GAIN, or LOW CUT filters.
EQ Bypass LED: This red LED lights when the EQ is in bypass mode. Note that bypass mode only effects the
graphic equalizer section of the 20 Series EQs. The INPUT GAIN and and LOW CUT controls remain unaffected
when the EQ is bypassed.
Boost/Cut Range Selection Switch and LEDs: This switch selects which of the two boost/cut ranges the equalizer
will use, either ±6dB or ±15dB. The red LED lights when the ±15dB range is selected, and the yellow LED lights
when the ±6dB range is selected. Note that the BOOST/CUT switch is slightly recessed. This is to prevent acciden-
tal activation of the switch, possibly causing damage to other sound system components.
Output Level Bar Graph: These four LEDs indicate output level of the equalizer. The red LED is 3dB below clip-
ping and is marked as +18dBu. It monitors the level at the output of the equalizer after all other processing, includ-
ing the limiter.
Clip LED: This LED lights whenever any internal signal level reaches 3dB below clipping which may occur when
any of the following happen: 1) the input signal is “hotter” than +22dBu, 2) excessive gain is applied by the input
gain control, or 3) excessive boost is applied using the frequency sliders.
Gain Reduction Meter: These four LEDs indicate the amount of gain reduction being induced by the setting of the
PeakPlus™ LIMITER THRESHOLD control as the signal level from the graphic EQ section exceeds this limiter
threshold setting.
PeakPlus™ Limiter Threshold Control: This control engages the PeakPlus™ limiter. It sets the threshold level at
which ∞:1 gain reduction will begin to occur. Its design is borrowed from the patent-pending PeakStopPlus™
Limiter found on the popular dbx 1066 and 1046 compressor/limiters. It is capable of a range of 0dBu through
“OFF” (+24dBu). When the threshold control is set to “OFF”, the limiter is effectively disabled, and no gain reduc-
tion will occur.
dbx Type III™ Noise Reduction Switch: The switch engages the dbx Type III™ Noise Reduction circuit within
the EQ.
dbx Type III™ Noise Reduction LED: The yellow LED lights when the dbx Type III™ Noise Reduction circuit is
activated via the NOISE REDUCTION Switch.
Frequency Band Slider Controls: Each one of these slider potentiometers will boost or cut at its noted frequency
by ±6dB or ±15dB, depending upon the position of the BOOST/CUT RANGE switch. When all the sliders are in
the center detented position the output of the equalizer is flat. The frequency band centers of the 2031 and the 2231
are marked at 1/3rd of an octave intervals on ISO standard spacings, while the frequency band centers of the 2215
are marked at 2/3rds of an octave intervals on ISO standard spacings.
Low Cut Enable Switch: The LOW-CUT switch inserts or removes the 18dB/octave 40Hz Bessel low-cut filter
from the signal path. When the LOW-CUT switch is pushed in, the LOW-CUT filter is IN the audio path.
OPERATION MANUAL
3
20 SERIES GRAPHIC EQUALIZERS
RANGE
GAIN
REDUCTION (dB)
OUTPUT
LEVEL (dBu)
LOW
CUT
EQ
BYPASS
TYPE III
NR INPUT GAIN
dB
-12
0
+12
PeakPlus
THRESHOLD
dBu
0 OFF
+20+5
+15+10 +/-6
+/-15
CLIP
1
0
-6
+6
25 40 63 100 160 250 400 16k10k6.3k4k630 1k 1.6k 2.5k
3610+18+100-10
2215
Equalizer/Limiter
with TYPE III NR
0
-15
+15
RANGE
GAIN
REDUCTION (dB)
OUTPUT
LEVEL (dBu)
LOW
CUT
EQ
BYPASS
TYPE III
NR INPUT GAIN
dB
-12
0
+12
PeakPlus
THRESHOLD
dBu
0 OFF
+20+5
+15+10 +/-6
+/-15
CLIP
1
0
-6
+6
25 40 63 100 160 250 400 16k10k6.3k4k630 1k 1.6k 2.5k
3610+18+100-10
0
-15
+15

CONNECTING THE EQ TOYOUR SYSTEM
The 20 Series Equalizers have balanced inputs and outputs that can be used with any balanced or unbalanced line-
level device. For more specific information about cabling possibilities, please refer to the section entitled
Installation Considerations, Page 5.
To connect the equalizer to your sound system refer to the following steps:
• Turn off all equipment before making connections.
• Mount equalizer in a standard-width rack.
Install the EQs in a rack with the rack screws provided. It can be mounted above or below anything that does
not generate excessive heat. Ambient temperatures should not exceed 113° F (45°C) when equipment is in use.
Although the unit’s chassis is shielded against radio frequency and electromagnetic interference, extremely
high fields of RF and EMI should be avoided.
• Make audio connections via XLR, barrier strip, or 1/4” TRS jacks (according to application needs)
All three types of connectors for the inputs and outputs can be used for balanced or unbalanced connections.
The use of more than one connector at a time for the inputs could unbalance balanced lines, cause phase cancel-
lation, short a conductor to ground, or cause damage to other equipment connected to the equalizer. More than
one output may be used simultaneously as long as the combined parallel load is greater than 600Ω.
• Select the operating range with the BOOST/CUT RANGE SELECTION switch
Note: Be sure to reduce audio levels at the power amplifiers when changing the setting of this switch as it may generate an audible transient.
• Apply power to the equalizer
Connect the AC power cord to the AC power receptacle on the back of the equalizer. Route the AC power cord
to a convenient power outlet away from audio lines. The unit may be turned on and off from the rear panel
power switch or a master equipment power switch. Since the 20 Series Equalizers consume a relatively small
amount of power, the units may be left on continuously.
REAR PANEL DESCRIPTIONS Rear Panels
2031 - single channel 31 band graphic equalizer
2231 - dual channel 31 band graphic equalizer
4
OPERATION MANUAL

2215 - dual channel 15 band graphic equalizer
Power Cord Receptacle: Connects AC power to the equalizer.
Power Switch: Switches the power on and off. Always make audio connections with the power switch in the OFF
position.
Input Connectors: Three types of input connectors are provided for input connections: female locking XLR type
connectors, 1/4” tip-ring-sleeve phone jack connectors, and a barrier strip. The maximum input level that the equal-
izer can accept is +22dBu (ref: 0.775Vrms).
Output Connectors: Three types of output connectors are provided for output connections: male XLR type con-
nectors, 1/4” tip-ring-sleeve phone jack connectors and a barrier strip.
Chassis Ground Lift Strap: By removing the jumper connecting the two screws on the barrier strip, the chassis
ground is separated from the circuit ground of the equalizer. This is sometimes necessary to prevent “ground loops”
in a sound system. When lifting the ground strap, you must make a connection from the circuit ground ( ) terminal
to some other ground point in your audio system in order for the equalizer to function properly.
INSTALLATION CONSIDERATIONS
Hookups and Cabling: The 20 Series Equalizers are designed for nominal +4dBu levels. The equalizers can be
used with either balanced or unbalanced sources, and the outputs can be used with either balanced or unbalanced
loads, provided the proper cabling is used.
A balanced line is defined as two-conductor shielded cable with the two center conductors carrying the same signal
but of opposite polarity when referenced 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.
Input Cable Configurations: The equalizer has an input impedance of 40kΩbalanced and 20kΩunbalanced. This
makes the 20 Series Equalizers’ audio inputs suitable for use with virtually any low source impedance (under 2kΩ).
Output Cable Configurations: The equalizer’s output is capable of driving a 600Ωload to +18dBu. For maximum
hum rejection with a balanced source, avoid common grounding at the equalizer’s inputs and outputs. Most bal-
anced (3-conductor) cables have the shield connected at both ends. This can result in ground loops which cause
hum. If hum persists try disconnecting the shield on one or more of the cables in the system, preferably at the input
of a device, not at the output.
OPERATION MANUAL
5
20 SERIES GRAPHIC EQUALIZERS
++
+
++ +
++
Without Jumper in Place With Jumper in Place
jumper
optional
circuit
ground chassis ground
circuit
ground chassis ground
to system
ground
optional
WIRING CONNECTIONS WITH GROUND
Input
Cable
Output
Cable
Input
Cable
Output
Cable
Wiring Connections With Ground

OPERATION AND APPLICATION NOTES
The dbx 20 Series Graphic Equalizers are useful audio signal processing tools in situations where precise frequency
control is required across the audible frequency spectrum.
When used with an audio spectrum analyzer the EQs can tune any acoustical environment -- from the studio to the
concert hall -- to stop ringing, increase clarity, and flatten the overall frequency response of the environment. A
real-time spectrum analyzer or other types of audio environment analyzers are very useful in determining the
amount of equalization needed.
Insert the graphic equalizer between the signal source (usually a mixer) and the power amplifiers (or the crossover if
there is one). Adjust the level and equalization as required to yield the desired system response. The long throw
faders of the EQs allow very precise settings of the equalization for accurate equalization curves.
For optimum signal-to-noise response, the gain structure of the sound system must be properly set up. Each compo-
nent of the sound system should be set at its nominal operating level, starting with the first element in the system,
usually a mixing console. Each element should be run at its nominal operating level in order to take advantage of
the maximum signal-to-noise properties of that element. Loudspeaker amplifiers, as the last element in the chain,
should be set only as loud as necessary, in order to avoid inducing unnecessary noise into the system.
All active equalizers, by nature of design, add noise when boosting or cutting that can easily degrade the otherwise
acceptable signal-to-noise ratio of a sound system. Drastic equalization can result in a loss of 20dB or more signal-
to-noise. dbx Type III™ Noise Reduction was engineered specifically for applications such as this. It provides up to
20dB of noise reduction, thus restoring the dynamic range necessary for even the most demanding professional
sound systems. The combination of proper wiring, proper gain structure and TYPE III™ Noise Reduction should
render your sound system virtually noise free.
TECHNICAL SUPPORT / FACTORY SERVICE
The dbx 20 Series EQs are all solid-state products with components chosen for high performance and excellent reli-
ability. Each unit has been tested and burned-in at the factory. No adjustment of any type should be required
throughout the life of the unit.
If circumstances arise which necessitate repair, we recommend that your EQ be returned to the factory. This can
only be done by receiving a RETURN AUTHORIZATION number from dbx customer service.
If you require technical support contact Customer Service. Be prepared to accurately describe the problem. Know
the serial number of your unit (printed on a sticker attached to the chassis of the unit).
Contact information is printed on the back cover of this manual.
6
OPERATION MANUAL