EQ Series
CAUTION
RISK OF ELECTRIC SHOCK
DO NOT OPEN
ATTENTION:
WARNING:
SHOCK DO NOT EXPOSE THIS EQUIPMENT TO RAIN OR MOISTURE
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.
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 A13 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 ASTAapproved to BS1362.
RISQUE DE CHOC ELECTRIQUE - NE PAS OUVRIR
TO REDUCE THE RISK OF FIRE OR ELECTRIC
1
SAFETY INSTRUCTIONS (EUROPEAN)
NOTICE FOR CUSTOMERS IF YOUR UNIT IS EQUIPPED WITH APOWER
CORD.
WARNING: THIS APPLIANCE MUST BE EARTHED.
The cores in the mains lead are colored in accordance with the following code:
GREEN and YELLOW - Earth BLUE - Neutral BROWN - Live
As colors of the cores in the mains lead of this appliance may not correspond with
the colored markings identifying the terminals in your plug, proceed as follows:
• The core which is colored green and yellow must be connected to the terminal in the plug marked with the letter E, or with the earth symbol, or colored green, or green and yellow.
• The core which is colored blue must be connected to the terminal marked
N or colored black.
• The core which is colored brown must be connected to the terminal marked
L or colored red.
EQ Series
These units comply with the European “EMC Directive” for emissions and suscept-
2
ability
The power cord is terminated in a CEE7/7 plug (Continental Europe). The
green/yellow wire is connected directly to the unit's chassis. If you need to change
the plug, and if you are qualified to do so, refer to the table below.
CONDUCTOR
L
N
E
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.
LIVE
NEUTRAL
EARTH GND
WIRE COLOR
Normal Alt
BROWN
BLUE
GREEN/YEL
BLACK
WHITE
GREEN
IMPORTANT!
FOR YOUR PROTECTION, PLEASE READ THE FOLLOWING:
WATER AND MOISTURE: Appliance should not be used near water (e.g. near a
bathtub, washbowl, kitchen sink, laundry tub, in a wet basement, or near a swimming pool, etc). Care should be taken so that objects do not fall and liquids are not
spilled into the enclosure through openings.
POWER SOURCES: The appliance should be connected to a power supply only of
the type described in the operating instructions or as marked on the appliance.
GROUNDING OR POLARIZATION: Precautions should be taken so that the
grounding or polarization means of an appliance is not defeated.
POWER CORD PROTECTION: Power supply cords should be routed so that they
are not likely to be walked on or pinched by items placed upon or against them,
paying particular attention to cords at plugs, convenience receptacles, and the point
where they exit from the appliance.
SERVICING: The user should not attempt to service the appliance beyond that
described in the operating instructions. All other servicing should be referred to
qualified service personnel.
EQ Series
INTRODUCTION
Congratulations, and thank you for your purchase of DOD equalization
components. DOD equalizers are versatile, cost-effective equalization
tools for the musician, performer, studio engineer, and sound contractor.
Each equalizer allows the user to see a graphic representation of the equalization applied to the audio spectrum, and offers the flexibility to provide
solutions to many EQ problems. The units offer up to 12 dB of cut or
boost per band with a switchable low cut filter for each channel. Electronic
switching of these functions minimizes switching transients (loud pops or
clicks when the switch is depressed), and up to ±12 dB of level control is
available to compensate for gain changes due to equalization. This feature
makes A/B comparisons of the equalized signal to the original signal quick
and easy. Connection to the equalizer may be either balanced with a 1/4"
tip-ring-sleeve phone plug or unbalanced with a mono 1/4" phone plug or
RCA phono connector (XLR connectors are available as an option), making the units readily interfaceable to any system. Dual channel units may
be used as a stereo equalizer or as two independent equalizers. The units
offer either 1/3rd octave or 2/3rds octave resolution, depending on the unit
chosen. All DOD equalizers are solidly built with steel chassis and militarygrade circuit boards for years of reliable service.
WHY A 1/3RD OCTAVE OR A 2/3RD OCTAVE EQUALIZER?
Most graphic equalizers divide up the audio frequency range into 1/3rd
octave or 2/3rds octave pieces. One octave covers a 2-to-1 range of frequencies. For example, the frequency range form 50 to 100 Hertz is one
octave. The audio frequency range covers 10 octaves from 20 Hz to 20
kilo (thousand) Hz. If each of the ten octaves is divided into thirds, you
get 30 pieces, or bands, of frequency. (The 31 bands on DOD equalizers
result from including both 20 Hz and 20 kHz bands on the ends of the
audio frequency range). A 1/3 octave equalizer means that 3 bands span
1 octave, while a 2/3 octave equalizer means that 3 bands span 2 octaves.
Therefore, one band on a 2/3 octave equalizer is twice as wide as one band
on a 1/3 octave equalizer. So, boosting or cutting any band will affect a
wider range of frequencies on the 2/3 octave equalizer.
3
A 1/3rd octave equalizer is the most precise because you're working with
a narrower frequency range per band or slider on the equalizer. To cover
the entire audio range, you need 31 bands or sliders, which normally take
up the entire width of a rack panel, and take some time to adjust properly.
EQ Series
A high-resolution real time audio spectrum analyzer (such as DOD's RTA
4
Series II) is a very useful tool when setting up a 1/3rd octave graphic
equalizer to compensate for poor room acoustics, poor speaker response,
or the deficiencies of an audio system.
While the 2/3rds octave is not as precise as a 1/3rd, it takes far less time
to equalize a signal with this unit, and allows more channels of EQ to be
reached. The 2/3rds octave EQ allows you to quickly and easily modify a
sound for use in music, recording, or sound reinforcement.
DOD graphic equalizers offer both 1/3rd and 2/3rds octave models in
stereo and 1/3 octave models in mono to meet any need.
INSTALLATION
Install the equalizer in a rack with the provided rack screws. Route the AC
power cord to a convenient power outlet away from audio lines. The unit
may be turned on and off using the front panel power switch. Since the
units draw a relatively small amount of current during idle, they can be left
on continuously.
DOD equalizers generate very little heat during operation and thus do not
need to be specially ventilated or cooled. The units should not, however,
be subjected to high temperatures for extended periods. Although the
unit's chassis is shielded against radio frequency and electromagnetic
interference, extremely high RF and EMI fields should be avoided.
Only the 1/4" phone plug and the optional XLR connector inputs and outputs can be used for balanced or unbalanced connections. The RCA
phono plugs are for unbalanced connections only. Use only one
input/output connector pair at a time. Using more than one input/output
connector pair at a time can unbalance balanced lines, cause phase cancellation, short a conductor to ground, or cause damage to other equipment connected to the equalizer.
EQ Series
FOR BALANCED 1/4 “ TSR PHONE PLUG CONNECTION - Wire the connectors as follows:
Phone Plug Connection
tip : high
ring : low
sleeve : ground
FOR 1/4" MONO PHONE PLUG OR RCA PHONO PLUG CONNECTION:
Phone plug Connection
tip : high
sleeve : ground
OPTIONAL XLR CONNECTORS - Optional XLR type connectors may be
ordered installed in the units at the factory. These connectors allow both
balanced and unbalanced connection to the equalizers, and are wired as
follows:
XLR Balanced Unbalanced
Connector Connection Connection
pin 1: ground ground
pin 2: high high or hot
pin 3: low ground
5
Once the graphic equalizer has been installed and adjusted for the
required equalization and level, an optional security panel can be installed
to keep unauthorized persons from changing settings.
EQ Series
6
APPLICATIONS
DOD graphic equalizers can be used wherever modification of the frequency contour of a sound or sound system is needed. A graphic equalizer offers a solution to many common sound problems, both large and
small. Also, creative experimentation on the part of the user can produce
some nice results.
SOUND REINFORCEMENT APPLICATIONS
By routing the signal from the mixer to the main power amplifiers (or
crossover), the overall frequency of the mix can be altered to do a number of things.
A. Using a real time audio spectrum analyzer (such as DOD's RTA Series
II), a calibrated microphone, and a pink noise generator, the audio system
can be tuned to make the overall audio spectrum response of the sound
system and the room environment flatter in frequency response.
B. Greater gain-before-feedback characteristics can be achieved by turning up the sound system to the feedback point and attenuating the oscillating (ringing) frequency. 1/3rd octave resolution is best for this application. Turn the system up to feedback again and attenuate the second
oscillating frequency. Repeat the process again for the third oscillating
frequency.
C. Protection of amplifiers and speakers can be accomplished using the
LOW CUT feature of the equalizer. Wind noise or dropped microphones
can cause damage to the amps and/or speakers. However, by rolling off
the extreme low frequencies, a measure of protection is added to the system without severely affecting the overall sound quality.
D. In noisy environments, the audio signal can be tailored for better intelligibility and penetration. This is particularly useful for annunciation systems.
E. Creative use of the equalizer allows shaping of the signal for a more
pleasing sound or for special effects. The only limits are those of taste
and imagination.
EQ Series
MUSICAL INSTRUMENT APPLICATIONS
7
A. Putting an equalizer in line with a musical instrument allows you to
modify the sound of the instrument. You can brighten the sound, add
body to a thin sounding instrument, or you can give the sound a totally
different character.
B. An equalizer allows you to eliminate unwanted sounds, such as the 60
cycle hum from a badly grounded sound source.
STUDIO APPLICATIONS
A graphic equalizer is one of the most useful tools in the sound engineer's
bag. DOD equalizers offer the features and the flexibility to deliver
uncompromising quality in the studio.
A. Fix a track that doesn't sound quite right. Put the equalizer in an
effects send and return it to the mix bus.
B. Create an artificial stereo image by splitting a monaural signal and
equalizing the split signals differently. Pan one signal to the right and the
equalized signal to the left.
C. Shape the sound by changing the frequency response of the track.
D. Special effects like telephone sounds are done by cutting off the low
end to 200 Hz and the high end to 6 kHz.
Also, when used with other pieces of equipment, you can do some real
signal processing magic. Emphasizing the high frequencies of a signal
and feeding the modified signal to the side chain of a compressor makes
the compressor a de-esser. By emphasizing the low frequencies and
feeding the signal to the side chain makes the compressor a de-thumper.
You can also reduce unwanted frequency-dependent noise in a signal by
cutting the offending frequencies with an equalizer and letting a noise gate
"key" on the modified signal while letting the original signal pass, gating
the unwanted sounds.
EQ Series
8
OPERATION
FRONT PANEL FUNCTIONS DESCRIPTION
POWER SWITCH: Turns the power to the equalizer on or off.
EQUALIZER SLIDERS: Each one of these linear potentiometers will boost
or cut its noted frequency by +/- 12 dB. When all the sliders are in the
center detented position, the output of the equalizer is said to be flat. The
numbers marked over the top of each slider represent the center of frequency that each band will control.
INPUT LEVEL CONTROL: This control sets the signal level to the equalizer. It is capable of +/- 12 dB of gain. Its effect is indicated on the INPUT
LEVEL BAR GRAPH. This control is used to adjust for variations in input
level to the equalizer channel, and to compensate for the equalization
applied to the input signal.
LOW CUT FILTER SWITCH: This switch electronically inserts a filter into
the signal path, which cuts the low frequencies at 12 dB per octave (-3dB
@50 Hz). The LED indicator lights when the switch is depressed and the
filter is in the circuit.
IN/OUT BYPASS SWITCH: This switch inserts or removes the equalizer
channel from the signal path. An LED indicator lights when the switch is
depressed and the equalizer channel is in the circuit path. The bypass
function is FET switched to prevent switching transients when inserting
the equalizer into the circuit.
LED LEVEL INDICATOR: The LED level indicator shows the signal level to
the unit.
REAR PANEL FUNCTIONS
BALANCED INput: Accepts a 1/4" tip-ring-sleeve phone plug or a 1/4"
mono phone plug (or optional XLR connectors) [see section on installation for wiring connections]. Connections can be either balanced or
unbalanced. Maximum allowable input level is +18 dBµ (ref.: 0.775
Vrms). Input impedance for a balanced connection is 80 kOhms, and 40
kOhms for an unbalanced connection.
UNBALANCED INput: Accepts an RCA phono plug (see section on instal-
EQ Series
lation for wiring connections). Connections are unbalanced. Maximum allowable
input is +18 dBu. Input impedance for the unbalanced connection is 40 kOhms.
BALANCED OUTput: Accepts a 1/4" tip-ring-sleeve or 1/4" mono phone plug (or
optional XLR connectors)[see section on installation for wiring connections].
Connections can be either balanced or unbalanced. Maximum balanced output
level is 18 dBm into 600 Ohms (ref.: 1mW/600 Ohms) or higher impedance .
Maximum unbalanced output level is 18 dBm (ref.: 1mW/600 ohms). Output
impedance is 51 Ohms balanced and 120 Ohms unbalanced.
UNBALANCED OUTput: Accepts an RCA Phono plug (see section on installation
for wiring connections). Connections are unbalanced. Maximum unbalanced
output level is 18 dBu. Output impedance is 51 Ohms unbalanced.
ATTENTION: DO NOT USE BOTH THE BALANCED AND UNBALANCED
INput/OUTput JACKS TO A CHANNEL AT THE SAME TIME. Using more than one
connector at a time for the input/output pair can unbalance balanced lines, cause
phase cancellation, short a conductor to ground, or cause damage to other equipment connected to the equalizer.
9
MAINTENANCE AND SERVICE
Other than keeping the unit clean and occasionally checking the connectors and
cables to the unit for integrity, there is no maintenance necessary for DOD equalizers.
There are NO user serviceable parts inside the units. Opening the chassis will
void the warranty. All service and repair must be performed by the factory for the
warranty to remain in service.
Should a problem arise with the equalizer, please contact your authorized DOD
Electronics dealer for return/repair procedures.
EQ Series
10
SPECIFICATIONS
Frequency Response: 20Hz to 20kHz, =0/-0.5 dB
Low Cut Filter: 12 dB/ octave roll-off, 3 dB down at 50 Hz switch-
able in or out.
Frequency Center Tolerance: 5%
Control Range: 12 dB cut/ boost
Recommended Operating Level: -10 dBV to +4 dBu
Input Impedance: 40k Ohms balanced, 20k Ohms unbalanced
Maximum Output Level: +21 dBu (balanced or unbalanced)
Input Level Control: +/-12 dB
Input Level Indicator: LED bar graph; -10,0,+10, and +17
Harmonic Distortion: .006% @ 1 kHz
S/N Ratio: Greater than 90 dB (ref. 0.0775Vrms)
Electronic Switching: In/Out and Filter switches (FET type)
Power Requirements: 100/120/220-230/240 VAC, 50/60 Hz @ 18
watts
Dimensions 430 and 431: 1.75”x6”x19”
Dimensions 231, 830, and 831: 3.5”x6”x19”
All EQs available in XLR format
DOD WARRANTY
1. The warranty registration card must be mailed within ten days after
purchase date to validate this warranty.
2. DOD warrants this product, when used solely within the U.S., to be free
from defects in material and workmanship under normal use and service.
3. DOD Electronics liability under this warranty is limited to repairing or
replacing defective materials that show evidence of defect, provided the
product is returned through the original dealer, where all parts and labor
will be covered up to a period of one year. The company shall not be
responsible for any consequential damage as a result of the products use
in any circuit or assembly.
4. Proof of date of purchase is considered tobe the burden of the consumer.
5. DOD reserves the right to make changes in design or make improve-
EQ Series
ments upon this product without incurring any obligation to install the
same on PRODUCTS PREVIOUSLY MANUFACTURED.
6. The foregoing is in lieu of all other warranties, either expressed or
implied, and DOD neither assumes nor authorizes any person to assume
for it any obligation or liability in connection with the sale of this product.
In no event shall DOD or its dealers be liable for special or consquenctial
damages or from any delay in the performance of this warranty due to
causes beyond their control.
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EQ Series
-3
-6
-12
+3
+6
+12
25
0
-3
-6
-12
+3
+6
+12
0
0
+12-12
-10
0
+10
+17
IN /
OUT
LOW
CUT
LEVEL
dB
-3
-6
-12
+3
+6
+12
0
-3
-6
-12
+3
+6
+12
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+12-12
-10
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+10
+17
IN /
OUT
LOW
CUT
LEVEL
dB
40 63 100 160 250 400 630 1K 1.6K 2.5K 4K 6.3K 10K 16K 25 40 63 100 160 250 400 630 1K 1.6K 2.5K 4K 6.3K 10K 16K
CHANNEL ONE CHANNEL TWO
430
series
II
graphic equalizer
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EQ-430 SE R I E S I I
+12
+6
+3
0
-3
-6
431
series
graphic equalizer
II
-12
EQ-431 SE R I E S I I
+12
+6
+3
0
-3
-6
-12
25 40 63 100 160 250 400 630 1K 1.6K 2.5K 4K 6.3K 10K 16K
830
series
II
graphic equalizer
EQ-830 SE R I E S I I
+12
+6
+3
0
-3
-6
-12
25 31.5 40 50 63 80 100 125 160 200 250 315 400 500 630 800 1K 1.25K 1.6K 2K 2.5K 3.15K 4K 5K 6.3K 8K 10K 12.5K 16K 20K
831
series
graphic equalizer
20
II
EQ-831 SE R I E S I I
+12
+6
+3
-3
-6
-12
+12
+6
+3
-3
-6
231
series
graphic equalizer
-12
II
5004003152502001601251008063504031.52520 16K12.5K10K8K6.3K5K4K3.15K2.5K2K1.6K1.25K1K800630 20K
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+12
+6
+6
+17
0
+3
+3
+10
0
0
0
-10
-3
-3
dB
+12-12
LOW
IN /
LEVEL
-6
-6
CUT
OUT
-12
-12
25 40 63 100 160 250 400 630 1K 1.6K 2.5K 4K 6.3K 10K 16K
5004003152502001601251008063504031.52520 16K12.5K10K8K6.3K5K4K3.15K2.5K2K1.6K1.25K1K800630 20K
+12
+17
0
+6
+10
+3
0
0
-3
-10
-6
dB
+12-12
-12
LOW
IN /
LEVEL
CUT
OUT
+12
+6
+17
0
+3
+10
0
0
-10
-3
dB
+12-12
LOW
IN /
LEVEL
-6
CUT
OUT
-12
+12
+6
+17
0
+3
+10
0
0
-10
-3
dB
+12-12
LOW
IN /
LEVEL
-6
CUT
OUT
-12
+12
+17
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+6
+10
+3
0
00
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-10
-6
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+12-12
-12
LOW
IN /
LEVEL
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+17
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DDOODD EELLEECCTTRROONNIICCSS CCOORRPPOORRAATTIIOON
A Harman International Compan
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DOD ELECTRONICS CORPORATION
8760 SOUTH SANDY PARKWAY
SANDY, UTAH 84107
INTERNATIONAL DISTRIBUTION
3 OVERLOOK DRIVE UNIT 4
AMHERST, NEW HAMPSHIRE 03031
U.S.A.
FAX (603) 672-4246
DOD IS A REGISTERED TRADEMARK OF
© 1995 DOD ELECTRONICS CORPORATION
PRINTED IN U.S.A. 7/95
MANUFACTURED IN THE U.S.A.
DOD 18-0120-B
DOD ELECTRONICS
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