dbx 1231 Installation and operation manual

8760 S. Sandy Pkwy.
Sandy, Utah 84070
Phone [phone]
Fax [phone]
Int’l Fax [phone]
[email protected]
http://www.dbxpro.com
A Harman International Company
®
1231
Graphic Equalizer
20 25 31.5 40 50 63 80 500400315250 1.6k1.25k1k800 5k4k3.15k2.5k 16k12.5k10k8k6.3k 20k2k630100 125 160 200
RANGE
OUTPUT
LEVEL (dBu)
LOW
CUT
EQ
BYPASS INPUT
GAIN
dB
-12
0
+12
+/-6
+/-15
CLIP
+18+100-10
RANGE
OUTPUT
LEVEL (dBu)
LOW
CUT
EQ
BYPASS INPUT
GAIN
dB
-12
0
+12
+/-6
+/-15
CLIP
+18+100-10
0
-15
+15
0
-15
+15
0
-6
+6
0
-6
+6
The dbx 12 Series were designed to meet the needs of the most demanding sound
reinforcement environments, while offering the simplicity of straightforward controls.
The 1231 provides standard features like dual-channels, 31 1/3 octave bands, ISO
frequency centers, +/- 12 dB input gain range, and switchable 40Hz/18 dB per octave low-
cut filters, but also includes other insightful features. These include 45 mm faders;
selectable +/-6dB or +/-15dB boost/cut range for precise gain adjustments; XLR, barrier
strip, and 1/4” TRS connectors for installation ease; balanced inputs and outputs for quiet
operation; and chassis/signal ground lift capabilities for quick hum isolation. The
visionary design of the dbx 12 Series makes your job easier.
The dbx 12 Series Equalizers were precision engineered to provide years of maintenance-
free operation in any application. The magnetically isolated transformer, electronically
balanced/unbalanced inputs and servo balanced/unbalanced outputs, RF-filtered inputs
and outputs, and power-off hard-wire relay bypass with 2 second power up delay were
steps our engineers took to ensure compatibility for all installations. Only the best
components were utilized, yielding a 10Hz to 50kHz frequency response, greater than
90dB SNR (ref +4dBu), less than 0.005% THD +Noise (1kHz at +4dBu), and
interchannel crosstalk of less than -80dB from 20Hz to 20kHz. All this attention to detail
is contained in a 3U steel/aluminum chassis. It’s no wonder that dbx has been a leader in
the industry for over 25 years.
18-1779-A 07/99
• Switchable Boost/Cut range between ±6dB and ±15dB
• Electronically balanced/unbalanced inputs
• Servo balanced/unbalanced outputs
• RF filtered 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 hardwire relay bypass with 2-second power-up delay

DUAL CHANNEL 31 BAND EQUALIZER
1231
The graphic equalizer shall be a dual 31-band type with frequency centers on standard ISO
one-third octave frequencies ranging from 20Hz to 20kHz. The boost/cut ranges shall be
switchable via recessed front panel switches to either +/-6dB or +/-15dB and the selected
range shall be indicated on the front panel by either of two LEDs per channel. Low-noise
equalization sliders having a 45mm travel shall be utilized having center detents at 0dB.
The equalizer shall have front panel 41-detent rotary input gain controls having a +/-12dB
range. Bypassing the equalizer sections of the signal path shall be accomplished via front-
panel switches having corresponding LEDs to indicate when each channel is bypassed. A
40Hz low-cut Bessel filter per channel with 18dB/octave slope shall be insertable in the
signal path via front panel recessed switches with an LED to indicate when the filter is
active. Output levels shall be monitored on four-LED peak-reading bar graphs calibrated to
read -10, 0, +10, and +18dBu.
Electronically balanced/unbalanced inputs shall include 1/4" TRS, female XLR, and screw
terminal barrier strip, while servo-balanced/unbalanced outputs shall include 1/4" TRS,
male XLR, and screw terminal barrier strip shared with the input. A circuit/chassis ground
lift jumper per channel shall be strapped across circuit ground and chassis ground screw
terminals and shall be removable by the user. Inputs shall be electronically
balanced/unbalanced and RF filtered having a nominal input impedance not less than 40kΩ
balanced and 20kΩunbalanced, and shall accept maximum signal levels of not less than
+21dBu. Outputs shall be servo-balanced/unbalanced and RF filtered having a nominal
output impedance of not more than 200Ωbalanced and 100Ωunbalanced, and shall be
capable of driving not less than +21dBu into 2kΩor greater and not less than +20dBm (into
600Ω) continuously.
Frequency response shall be better than 10Hz to 50kHz, +0.5/-3dB. Signal-to-noise ratio
shall be greater than 90dB, referenced to +4dBu. THD+Noise shall be less than 0.005%
with a 1kHz signal at +4dBu, while interchannel crosstalk shall be lower than -80dB from
20Hz to 20kHz.
The internal power supply shall be constructed using a thermally-fused transformer
mounted in a low hum orientation and shall be magnetically isolated from equalizer
circuitry by means of a mu-metal shield. The power cord shall be detachable from an
international standard IEC 320 power inlet receptacle. Unit shall be constructed to meet or
exceed all applicable international safety and regulatory agencies. Domestic unit shall be
powered from 100VAC 50/60Hz, 120VAC 60Hz, while international unit shall be powered
from 230VAC 50/60Hz. Unit shall consume no more than 24W. Housing shall be of all
steel/aluminum construction and shall be rack-mountable in an IEC standard 19" rack and shall occupy a 3U (5.25") rack space. The unit shall be a dbx 1231
Equalizer.
dbx engineers are constantly working to improve the quality of our products. Specifications are, therefore subject to change without notice.
®
FOR MORE INFORMATION CONTACT:
dbx Professional Products
8760 S. Sandy Pkwy.
Sandy, Utah 84070
Phone [phone]
Fax [phone]
Int’l Fax [phone]
[email protected]
http://www.dbxpro.com
A Harman International Company
20 25 31.5 40 50 63 80 500400315250 1.6k1.25k1k800 5k4k3.15k2.5k 16k12.5k10k8k6.3k 20k2k630100 125 160 200
RANGE
OUTPUT
LEVEL (dBu)
LOW
CUT
EQ
BYPASS INPUT GAIN
dB
-12
0
+12
+/-6
+/-15
CLIP
13610+18+100-10
0
-6
+6
RANGE
OUTPUT
LEVEL (dBu)
LOW
CUT
EQ
BYPASS INPUT GAIN
dB
-12
0
+12
+/-6
+/-15
CLIP
+18+100-10
0
-6
+6
0
-15
+15
0
-15
+15
1231
Graphic Equalizer
24 WATTS
OUTPUT
- +INPUT - +
OUTPUT INPUT
PHONE:
TIP
RING
SLEEVE
XLR:
PIN 1
PIN 2
PIN 3
CONNECTOR POLARITY
INPUTOUTPUT
OUTPUT
- +INPUT - +
OUTPUT INPUT
INPUTOUTPUT
100V 50/60Hz
120V 60Hz
PROFESSIONAL PRODUCTS
A HARMAN INTERNATIONAL
COMPANY
MODEL 1231
GRAPHIC EQUALIZER
WARNING:TOREDUCETHERISKOFFIREORELECTRIC
SHOCKDONOTEXPOSETHISEQUIPMENTTORAINORMOISTURE
RISKOFELECTRICSHOCK
DONOTOPEN
ATTENTION:RISQUEDECHOCELECTRIQUE-NEPASOUVRIR
CAUTION:TOREDUCE
THERISKOFFIREREPLACE
ONLYWITH SAME TYPEFUSE.
ATTENTION:UTILISER
UNFUSIBLEDERECHANGEDE
MEMETYPE.
POWER
MANUFACTURED UNDER ONE OR MORE OF THE FOLLOWING
U.S. PATENTS: 4,234,804 4,316,107 4,329,598 4,331,931 4,377,792
4,403,199 4,409,500 4,425,551 4,434,380 4,454,433 4,471,324
4,473,793 OTHER PATENTS PENDING
586 Dual Vacuum Tube Preamp
TYPE IV™ Conversion System
704
Inputs
Connectors: 1/4" TRS, female XLR (pin 2
hot), and barrier terminal strip
Type: Electronically
balanced/unbalanced, RF
filtered
Impedance: Balanced 40kΩ, unbalanced
20kΩ
Max Input Level: >+21dBu balanced or
unbalanced
CMRR: >40dB, typically >55dB at
1kHz
Outputs
Connectors: 1/4" TRS, male XLR (pin 2
hot), and barrier terminal strip
Type: Impedance-
balanced/unbalanced, RF
filtered
Impedance: Balanced 200Ω, unbalanced
100Ω
Max Output Level: >+21dBu balanced/unbalanced
into 2kΩor greater
>+18dBm
balanced/unbalanced (into
600Ω)
System Performance
Bandwidth: 20Hz to 20kHz, +0.5/-1dB
Frequency Response: <10Hz to >50kHz, +0.5/-3dB
+/-15dB range +/-6dB range
Dynamic Range: 109db 115db
Signal-to-Noise: 90db 97db
THD+Noise: <0.005%
Interchannel Crosstalk: <-80dB, 20Hz to 20kHz
Function Switches
EQ Bypass: Bypasses the graphic equalizer
section in the signal path
Low Cut (recessed): Activates the 40Hz
18dB/octave Bessel high-pass
filter
Range (recessed): Selects either +/- 6dB or +/-
15dB slider boost/cut range
Indicators
Output Level: 4-LED bar graph (Green,
Green, Yellow, Red) at -10, 0,
+10, and +18dBu
EQ Bypass: 1 LED: red
Clip: 1 LED: red
Low Cut: 1 LED: red
+/-6dB: 1 LED: yellow
+/-15dB: 1 LED: red
Power Supply
Operating Voltage: 100VAC 50/60Hz, 120VAC
60Hz, 230VAC 50/60Hz
Power Consumption: 1215 24W; 1231 24W
Mains Connection: IEC receptacle
Physical
Dimensions: 1215: 3.5" H X 19" W X 7.9" D
(8.9cm x 48.3cm x 20.1cm)
1231: 5.25" H X 19" W X 7.9"
D (13.4cm x 48.3cm x 20.1cm)
Weight: 1215: 8.5 lbs.
1231: 10.6 lbs.
Shipping Weight: 1215: 9.5 lbs.