dbx 30 Series User manual

GRAPHIC
EQUALIZERS
30 SERIES
OPERATION MANUAL
®

A Harman International Company
CAUTION
ATTENTION: RISQUE DE CHOC ELECTRIQUE - NE PAS OUVRIR
WARNING: TO REDUCE THE RISK OF FIRE OR ELECTRIC SHOCK, DO NOT EXPOSE THIS
EQUIPMENT TO RAIN OR MOISTURE.
CAUTION: TO REDUCE THE RISK OF FIRE OR ELECTRICAL SHOCK, DO NOT REMOVE COVER
(OR BACK). NO USER SERVICABLE PARTS INSIDE. REFER SERVICING TO QUALIFIED SERVICE
PERSONNEL.
RISK OF ELECTRIC SHOCK
DO NOT OPEN
This symbol, where ever it appears, alerts
you to the presence of uninsulated dangerous
voltage inside the enclosure - voltage that
may be sufficient to constitute a risk of
shock.
This symbol, wherever it appears,
alerts you to important operating and
maintenance instructions in the
accompanying literature. Read the
manual.
dbx Professional Products
8760 South Sandy Parkway
Sandy, Utah 84070
Telephone [phone]
FAX [phone]
All trademarks are property of their respective companies.
This manual is part number 18-0521-A
© Copyright 1995 by dbx Professional Products
®

MANUAL CONTENTS
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
QUICK SET-UP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
INSPECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
WARRANTY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
OPERATING CONTROLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
CONNECTING THE EQ TO THE SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . 6
REAR PANEL DESCRIPTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
INSTALLATION CONSIDERATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
OPERATION AND APPLICATION NOTES . . . . . . . . . . . . . . . . . . . . . . . . . . 12
TECHNICAL SUPPORT / FACTORY SERVICE . . . . . . . . . . . . . . . . . . . . . . 13
SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
MANUAL CONTENTS
30 SERIES GRAPHIC EQs

INTRODUCTION
Congratulations for your purchase of a dbx equalization component. The dbx Graphic Equalizers are
high performance multifunctional units designed to deliver all the flexibility and power that professional
users demand. We recommend 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 30 Series features include:
❍31 ISO standard center 1/3 octave constant Q frequency bands per channel (or 15 ISO standard
center 2/3 octave constant Q frequency bands per channel on model 3215)
❍Low phase shift circuit design
❍Variable high pass and switchable low pass 12dB/octave filters
❍Electronically balanced inputs with superior common mode rejection
❍Servo balanced outputs
❍XLR, barrier strip, and TRS connectors
❍-12dB/+15dB of input gain
❍Chassis ground lift capability
❍Toroidal power supply transformer
❍Relay bypass on power-down
QUICK SET-UP
To get the equalizer up and running as quickly as possible, do the following:
❍Unpack and inspect the equalizer and contents (pg. 3).
❍Connect the equalizer to the system (pg. 6).
❍Set levels and controls as needed (pg. 4).
For more detailed information about these steps, refer to the specified pages.
®
PROFESSIONAL PRODUCTS
INTRODUCTION, QUICK SET-UP

INSPECTION
Verify that the equalizer's package contains the following:
❍Equalizer Unit (according to Model number marked on package)
❍AC Power Cord
❍ Operation Manual
❍Registration Card
❍4 Rack Mount Screws and Washers
If any of these items are missing, please contact dbx customer service at the number provided on the
inside cover.
WARRANTY
This warranty is valid only for the original purchaser and only in the United States. We warrant dbx prod-
ucts against defects in material or workmanship for a period of two years from the date of original pur-
chase for use, and agree to repair or, at our option, replace any defective item, except external power
transformers, without charge for either parts or labor.
IMPORTANT: This warranty does not cover damage resulting from accident, misuse or abuse, lack of
reasonable care, the affixing of any attachment not provided with the product, loss of parts, or connecting
the product to any but the specified receptacles. This warranty is void unless service or repairs are per-
formed by an authorized service center. No responsibility is assumed for any special, incidental or conse-
quential damages. However, the limitation of any right or remedy shall not be effective where such is pro-
hibited or restricted by law.
Simply take or ship your dbx product prepaid to our service department. Be sure to include your sales slip
as proof of purchase date. (We will not repair transit damage under the no-charge terms of this warranty.)
dbx will pay return shipping.
NOTE: No other warranty, written or oral is authorized for dbx products.
This warranty gives you specific legal rights, and you may also have other rights which vary from state to
state. Some states do not allow the exclusion of limitations of incidental or consequential damages or lim-
itations on how long an implied warranty lasts, so the above exclusion and limitations may not apply to
you.
INSPECTION, WARRANTY
30 SERIES GRAPHIC EQs

OPERATING CONTROLS
dbx 3031
dbx 3031C
dbx 3231L
dbx 3215
DUAL 2/3 OCTAVE
GRAPHIC EQ
3215
Hz
LO CUT
63
125
200
25
32
OUT
IN
EQ
6 dB
12 dB
RANGE
OUT
IN
HI CUT
OUT
IN
LO CUT
dB
GAIN
dB +15
+7-6
-12
0
Power
42
36
30
24
18
12
6
3
25 40 63 100 160 250 400CHANNEL 1 630 1k 1.6k 2.5k 4k 6.3k 10k 16k
Hz
LO CUT
63
125
200
25
32
OUT
IN
EQ
6 dB
12 dB
RANGE
OUT
IN
HI CUT
OUT
IN
LO CUT
dB
GAIN
dB +15
+7-6
-12
0
Power
42
36
30
24
18
12
6
3
25 40 63 100 160 250 400CHANNEL 2 630 1k 1.6k 2.5k 4k 6.3k 10k 16k
0
+12
-12
0
+6
-6
0
+12
-12
0
+6
-6
Headroom (dB)Headroom (dB)
GRAPHIC EQ
3231L
DUAL 1/3 OCTAVE
OUT
IN
EQ
6 dB
12 dB
RANGE
OUT
IN
HI CUT
OUT
IN
LO CUT
dB
GAIN
dB +15
+7-6
-12
0
OUT
IN
EQ
6 dB
12 dB
RANGE
OUT
IN
HI CUT
OUT
IN
LO CUT
dB
GAIN
dB +15
+7-6
-12
0
42
36
30
24
18
12
6
3
42
36
30
24
18
12
6
3
0
+12
-12
0
+6
-6
0
+12
-12
0
+6
-6
20 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
20 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
CHANNEL 1
CHANNEL 2
Power
Headroom (dB)
Power
Headroom (dB)
Hz
LO CUT
63
200
25
32
125
Hz
LO CUT
63
200
25
32
125
42
36
30
24
18
12
6
3
OUT
IN
EQ
6 dB
12 dB
RANGE
OUT
IN
HI CUT
OUT
IN
LO CUT
dB
GAIN
dB +15
+7-6
-12
0
20 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
1/3 OCTAVE
CUT ONLY
GRAPHIC EQ
3031C
-10
0
-20
-5
0
-10
Power
Headroom (dB)
Hz
LO CUT
63
200
25
32
125
0
+12
-12
0
+6
-6
42
36
30
24
18
12
6
3
OUT
IN
EQ
6 dB
12 dB
RANGE
OUT
IN
HI CUT
OUT
IN
LO CUT
dB
GAIN
dB +15
+7-6
-12
0
20 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
1/3 OCTAVE
GRAPHIC EQ
3031
Power
Headroom (dB)
Hz
LO CUT
63
200
25
32
125
®
PROFESSIONAL PRODUCTS
OPERATING CONTROLS

POWER SWITCH:Turns the equalizer's power ON or OFF. Power ON is indicated by the lighted power
LED.
POWER LED: Lights to indicate that the equalizer is turned on.
EQ IN/OUT:This switch removes the equalizer's input gain and individual slider controls from the signal
path. This does not, however, affect the HI CUT and LOW CUT filters. The entire equalizer is
enabled when the switch is in.
BOOST/CUT RANGE SELECTION SWITCH:The switch selects which of the two boost/cut ranges the
equalizer will use, either ±6dB or ±12dB (3031C: -10dB or -20dB)
HEADROOM BAR GRAPH:The eight LEDÕs indicate peak levels within the equalizer. The top LED is
3dB below clipping and indicates overload at the post-input gain, pre-EQ and post-EQ points in the
signal path.. Overload at the input amplifier is indicated by the entire LED bar graph getting brighter
when the signal is 3dB below clipping.
INPUT GAIN CONTROL:This control sets the signal level to the equalizer. It is capable of -12dB to
+15dB of gain. Its effect is indicated on the HEADROOM BAR GRAPH.
FREQUENCY BAND SLIDER CONTROL:Each one of these slider potentiometers will boost or cut its
noted frequency by ±6 dB or ±12dB depending upon the position of the BOOST/CUT RANGE
SWITCH (3031C is cut only: -10db or -20db). When all of the sliders are in the center detented posi-
tion, the output of the equalizer is flat (3031C: sliders placed at top position is flat). The frequency
band centers of the 3215 are marked at 2/3rds of an octave ISO spacings. The frequency band cen-
ters of the 3031,3031C, and 3231 are marked at 1/3rd of an octave ISO spacing.
LOCUT FREQUENCY CONTROL AND LOCUT IN/OUT SWITCH:This control varies the cutoff
frequency of the LO-CUT filter. It is variable from 25 Hz to 200 Hz. The roll-off of this filter is 12dB
per octave. The LO CUT IN/OUT switch to the left of this control inserts or removes the LO CUT filter
from the signal path. When the LO CUT IN/OUT switch is pushed IN, the LO CUT filter is IN the cir-
cuit.
HICUT IN/OUT SWITCH:This switch inserts or removes the HI-CUT filter from the signal path. When
the HI-CUT IN/OUT switch is pushed IN, the HI-CUT filter is IN in the circuit.
OPERATING CONTROLS
30 SERIES GRAPHIC EQs

CONNECTING THE EQ TO THE SYSTEM
The 30 Series equalizers have balanced inputs and outputs that can be used with any line-level device.
For more specific information about cabling possibilities, please refer to INSTALLATION CONSIDERATIONS
(pg. 9).
To connect the equalizer to the system, refer to the following steps:
❍Turn off all equipment before making any connections.
❍Mount equalizer in rack mount.
Install the EQs in a rack with the rack screws provided. It can be mounted above or below any-
thing that does not generate excessive heat. Ambient temperatures should not exceed 113°F
(45°C) when equipment is in use. Although the units chassis are shielded against radio frequen-
cy and electromagnetic interference, extremely high fields of RF and EMI should also be avoided.
❍Make audio connections via XLR, barrier strip or 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 input/output pair could unbal-
ance balanced lines, cause phase cancellation, short a conductor to ground, or cause damage to
the other equipment connected to the equalizer.
❍Select the operating range with the BOOST/CUT RANGE SELECTION SWITCH
❍Apply power to the equalizer
Connect the the AC power cord to the AC power receptacle on the back of the equalizer. Route
the A.C. power cord to a convenient power outlet away from audio lines. The unit may be turned
on and off from the front panel power switch or a master equipment power switch. Since they
draw a relatively small amount of current during idle, the units may be left on continuously.
®
PROFESSIONAL PRODUCTS
CONNECTING THE EQ TO THE SYSTEM

REAR PANEL DESCRIPTIONS
dbx 3031
dbx 3031C
dbx 3231L
dbx 3215
OUTPUT
-GND +INPUT -GND +
OUTPUT INPUT
INPUT
GROUND
OUTPUT
-GND +INPUT -GND +
OUTPUT INPUT
INPUT
GROUND
GROUND LIFT
CHANNEL 2 CHANNEL 1
LIFT LIFT
PROFESSIONAL PRODUCTS
A HARMAN INTERNATIONAL COMPANY
SALT LAKE CITY, UTAH
MADE IN USA

®
CAUTION
WARNING: TO REDUCE THE RISK OF FIRE OR ELECTRIC
SHOCK DO NOT EXPOSE THIS EQUIPMENT TO RAIN OR MOISTURE
CAUTION: TO REDUCE
THE RISK OF FIRE REPLACE
ONLY WITH SAME TYPE FUSE. RISK OF ELECTRIC SHOCK
DO NOT OPEN
ATTENTION: UTILISER
UN FUSIBLE DE RECHANGE DE
MEME TYPE.
ATTENTION: RISQUE DE CHOC ELECTRIQUE - NE PAS OUVRIR
PHONE:
TIP
RING
SLEEVE
XLR:
PIN 1
PIN 2
PIN 3
CONNECTOR POLARITY
INPUTOUTPUTINPUTOUTPUT
PUSH PUSH
OUTPUT
-GND +INPUT -GND +
OUTPUT INPUT
INPUT
GROUND
CHANNEL 2
OUTPUT
-GND +INPUT -GND +
OUTPUT INPUT
INPUT
INPUTOUTPUT
OUTPUT
INPUT
GROUND
LIFT
CHANNEL 1
PROFESSIONAL PRODUCTS
A HARMAN INTERNATIONAL COMPANY
SALT LAKE CITY, UTAH
MADE IN USA

®
CAUTION
WARNING: TO REDUCE THE RISK OF FIRE OR ELECTRIC
SHOCK DO NOT EXPOSE THIS EQUIPMENT TO RAIN OR MOISTURE
CAUTION: TO REDUCE
THE RISK OF FIRE REPLACE
ONLY WITH SAME TYPE FUSE. RISK OF ELECTRIC SHOCK
DO NOT OPEN
ATTENTION: UTILISER
UN FUSIBLE DE RECHANGE DE
MEME TYPE.
ATTENTION: RISQUE DE CHOC ELECTRIQUE - NE PAS OUVRIR
GROUND LIFT
PHONE:
TIP
RING
SLEEVE
XLR:
PIN 1
PIN 2
PIN 3
CONNECTOR POLARITY
LIFT
PUSH
-GND +-GND +
PUSH
OUTPUT
-GND +INPUT -GND +
GROUND LIFT
OUTPUT INPUT
INPUT
GROUND
LIFT
PROFESSIONAL PRODUCTS
A HARMAN INTERNATIONAL COMPANY
SALT LAKE CITY, UTAH
MADE IN USA

®
CAUTION
WARNING: TO REDUCE THE RISK OF FIRE OR ELECTRIC
SHOCK DO NOT EXPOSE THIS EQUIPMENT TO RAIN OR MOISTURE
CAUTION: TO REDUCE
THE RISK OF FIRE REPLACE
ONLY WITH SAME TYPE FUSE. RISK OF ELECTRIC SHOCK
DO NOT OPEN
ATTENTION: UTILISER
UN FUSIBLE DE RECHANGE DE
MEME TYPE.
ATTENTION: RISQUE DE CHOC ELECTRIQUE - NE PAS OUVRIR
PHONE:
TIP
RING
SLEEVE
XLR:
PIN 1
PIN 2
PIN 3
CONNECTOR POLARITY
INPUTOUTPUT
PUSH
OUTPUT
-GND +INPUT -GND +
GROUND LIFT
OUTPUT INPUT
INPUT
GROUND
LIFT
PROFESSIONAL PRODUCTS
A HARMAN INTERNATIONAL COMPANY
SALT LAKE CITY, UTAH
MADE IN USA

®
CAUTION
WARNING: TO REDUCE THE RISK OF FIRE OR ELECTRIC
SHOCK DO NOT EXPOSE THIS EQUIPMENT TO RAIN OR MOISTURE
CAUTION: TO REDUCE
THE RISK OF FIRE REPLACE
ONLY WITH SAME TYPE FUSE. RISK OF ELECTRIC SHOCK
DO NOT OPEN
ATTENTION: UTILISER
UN FUSIBLE DE RECHANGE DE
MEME TYPE.
ATTENTION: RISQUE DE CHOC ELECTRIQUE - NE PAS OUVRIR
PHONE:
TIP
RING
SLEEVE
XLR:
PIN 1
PIN 2
PIN 3
CONNECTOR POLARITY
INPUTOUTPUT
PUSH
REAR PANEL DESCRIPTIONS
30 SERIES GRAPHIC EQs

POWER CORD RECEPTACLE:Connects A.C. power to the equalizer.
INPUT CONNECTORS:Three types of input connectors are provided for input connections: female
locking XLR type connectors, 1/4-inch tip-ring-sleeve phone jack connectors, and a barrier strip.
The maximum input level that the equalizer can accept is +22dBu (ref: 0.775Vms).
OUTPUT CONNECTORS:Three types of output connectors are provided for output connections: male
XLR type connectors, 1/4 inch tip-ring-sleeve phone jack connectors and a barrier strip.
INPUT GROUND LIFT SWITCH:Disconnects the grounding of the input connector from the equalizer's
grounding system. This is sometimes helpful in preventing electronic "hum" in a sound system by
breaking the common ground connection between the equalizer and other products.
CHASSIS GROUND LIFT STRAP:By removing the jumper connecting the two screws on the barrier strip,
the chassis ground is separated from the electronic ground of the equalizer. This is sometimes nec-
essary to prevent Òground loopsÓ in a sound system.
FUSE:Should the fuse fail, be sure to determine and remove the cause of the problem before replacing
the fuse. Failure to do so could result in damage to the equalizer. The following is a list of fuse types
used for different AC voltage configurations:
100VAC T 250mA 250V
120VAC 200mA 250V Slow Blow
230VAC T 125mA 250V
240VAC T 125mA 250V
®
PROFESSIONAL PRODUCTS
REAR PANEL DESCRIPTIONS