Important Safety Information
Warnings and Precautions
[Caution Symbol: Risk of Electric Shock - Do Not Open]
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
The symbols shown above warn of potential hazards with electrical products. The lightning flash with arrowpoint in an equilateral triangle indicates dangerous voltages within the unit [Electrical Hazard Symbol]. The exclamation point in an equilateral triangle indicates the need to refer to the owner's manual [Refer to Manual Symbol].
There are no user-serviceable parts inside. Do not open the unit or attempt to service it yourself. Refer all servicing to qualified personnel. Opening the chassis will void the manufacturer's warranty. Do not get the unit wet. If liquid is spilled, shut off immediately and take to a dealer. Disconnect the unit during storms to prevent damage.
Safety Instructions
Mains Connection: This appliance must be connected to a mains socket outlet with a protective earthing connection.
Wire Colour Coding: The mains lead cores are coloured as follows: BROWN - Live, BLUE - Neutral, GREEN and YELLOW - Earth. If colours do not match your plug, connect green/yellow to the terminal marked E (earth symbol), blue to N (black), and brown to L (red).
Grounding: If the ground is defeated, fault conditions can result in full line voltage between chassis and earth ground, causing severe injury or death if touched.
Power Switch: If present, the power switch does not break the connection from the mains.
Mains Disconnect: The plug must remain readily operable. For inaccessible plugs, an all-pole mains switch with at least 3mm contact separation is required.
Fuse Replacement: Use only fuses of the same type and rating.
Multiple-Input Voltage: Connect only to the power source indicated on the rear panel. Refer servicing to qualified personnel for line cord or plug changes.
Rack Mount Use: This equipment is intended for rack mount use only.
U.K. Mains Plug Warning
A molded mains plug cut from the cord is unsafe. Discard it properly. Never insert a damaged or cut mains plug into a 13 AMP power socket. Do not use the plug without the fuse cover in place. Replacement fuses are 13 amps and must be ASTA approved to BS1362.
Electromagnetic Compatibility
This unit conforms to Product Specifications and is subject to two conditions: it may not cause harmful interference, and it must accept any interference received. Avoid operation in significant electromagnetic fields; use only shielded interconnecting cables.
Lithium Battery Warning
CAUTION! This product may contain a lithium battery. Danger of explosion if incorrectly replaced. Replace only with an Eveready CR 2032 or equivalent, ensuring correct polarity. Discard used batteries according to manufacturer's instructions.
Multilingual warnings are provided for: ADVARSEL (Norwegian/Danish), VAROITUS (Finnish), VARNING (Swedish).
Warranty
Valid for original purchaser in the U.S. only. Register within 30 days of purchase online at www.dbxpro.com. Proof of purchase is required for warranty service. dbx warrants this product against defects in materials and workmanship under normal use for two years. Repair or replacement is at dbx's discretion. A Return Authorization number is required for factory returns. dbx is not liable for consequential damage. dbx reserves the right to make design changes. This warranty is in lieu of all other warranties.
Disposal: Do not mix with household waste. Use separate collection systems for electronic products for proper treatment, recovery, and recycling. Contact local authorities for disposal methods in your region.
Declaration of Conformity
Manufacturer: dbx Professional Products, 8760 S. Sandy Parkway, Sandy, Utah 84070, USA.
Product Name: dbx 1215 and dbx 1231.
Conforms to Product Specifications: Safety (IEC 60065), EMC (EN 55022), RoHS Directive, WEEE Directive. Exempt from Directive 2005/32/EC as Professional Audio Equipment.
Date: November 19, 2010. Signed by Roger Johnsen, Director, Engineering, Signal Processing.
European Contact: Local dbx Sales and Service Office or Harman Music Group.
Introduction
Congratulations on your purchase of a dbx graphic equalizer. The dbx 12 Series Equalizers are high-performance, multi-functional units designed for professional users, offering flexibility and power. This manual provides information for system set-up and EQ applications.
Visionary Design
The dbx 12 Series was designed to meet the demands of sound reinforcement environments, offering straightforward controls. The 1231 model features dual channels, 31 1/3 octave bands, ISO frequency centers, +/-12dB input gain, and switchable 40Hz/18dB per octave low-cut filters. Additional features include 45mm faders, selectable +/-6dB or +/-15dB boost/cut ranges, XLR, barrier strip, and 1/4" TRS connectors, balanced I/O, and chassis/signal ground lift capabilities for hum isolation.
Revolutionary Engineering
The dbx 12 Series Equalizers are precision-engineered for years of maintenance-free operation. They feature magnetically isolated transformers, electronically balanced/unbalanced inputs, servo balanced/unbalanced outputs, RF-filtered I/O, and power-off hard-wire relay bypass with a 2-second power-up delay. These units utilize high-quality components, offering a 10Hz to 50kHz frequency response, >90dB SNR, <0.005% THD+Noise, and < -80dB interchannel crosstalk. The robust 3U steel/aluminum chassis ensures durability.
Features
- 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
Operating Controls
The front panels of the dbx 1231 (dual channel 31 band) and 1215 (dual channel 15 band) graphic equalizers feature intuitive controls.
Input Gain Control
Adjusts the signal level to the equalizer, with a range of -12dB to +12dB. The effect is visible on the OUTPUT LEVEL BAR GRAPH.
EQ Bypass
This switch removes the graphic equalizer section from the signal path. The bypass mode only affects the graphic equalizer section; Input Gain and Low Cut controls remain unaffected.
EQ Bypass LED
A red LED illuminates when the EQ is in bypass mode.
Boost/Cut Range Selection Switch and LEDs
This switch selects the boost/cut range: ±6dB or ±15dB. A red LED lights for ±15dB, and a yellow LED lights for ±6dB. The switch is recessed to prevent accidental activation.
Output Level Bar Graph
Four LEDs (Green, Green, Yellow, Red) indicate the output level at -10, 0, +10, and +18dBu, respectively. The red LED indicates a level 3dB below clipping.
Clip LED
Lights when any internal signal level reaches 3dB below clipping, which can occur due to a hot input signal (+22dBu), excessive input gain, or excessive boost from frequency sliders.
Frequency Band Slider Controls
Each slider boosts or cuts the signal at its noted frequency by ±6dB or ±15dB, depending on the Boost/Cut Range switch position. When all sliders are centered, the output is flat. The 1231 features 1/3 octave ISO spacing, while the 1215 features 2/3 octave ISO spacing.
Low Cut Enable Switch
Inserts or removes the 18dB/octave 40Hz Bessel low-cut filter from the signal path. The filter is active when the switch is pressed in, indicated by an LED.
Rear Panel Descriptions
The rear panels of the 1231 and 1215 models provide connection and control points.
- Power Switch: Switches the unit on and off. Make audio connections with the power switch OFF.
- Power Cord Receptacle: Standard IEC receptacle for AC power connection.
- Output Connectors: Male XLR, 1/4" Tip-Ring-Sleeve (TRS) phone jacks, and barrier strip terminals.
- Input Connectors: Female XLR, 1/4" TRS phone jacks, and barrier strip terminals. Maximum input level is +22dBu.
- Chassis Ground Lift Strap: A jumper connecting barrier strip screws. Removing this jumper separates chassis ground from circuit ground, which can prevent "ground loops." If lifted, a connection from circuit ground to another system ground point is required for proper function.
Installation Considerations
Hookups and Cabling
The 12 Series Equalizers are designed for nominal +4dBu levels and can be used with balanced or unbalanced sources and loads, provided proper cabling is used.
A balanced line uses two-conductor shielded cable with opposite polarity signals. An unbalanced line uses a single-conductor shielded cable with the shield at ground potential.
Input Cable Configurations
Input impedance is 40kΩ balanced and 20kΩ unbalanced, making them suitable for low source impedance (under 2kΩ).
Output Cable Configurations
Outputs can drive a 600Ω load to +18dBu. For best hum rejection with balanced sources, avoid common grounding at inputs and outputs. If hum persists, try disconnecting the shield on one or more cables, preferably at the input end.
Wiring Connections With Ground
The diagrams illustrate wiring with and without the chassis ground lift jumper. The jumper connects circuit ground to chassis ground. Removing it disconnects chassis ground from circuit ground to prevent ground loops.
Operation and Application Notes
dbx 12 Series Graphic Equalizers are valuable tools for precise frequency control across the audible spectrum. They can tune acoustical environments from studios to concert halls, reducing ringing, increasing clarity, and flattening frequency response. Using a real-time spectrum analyzer is recommended for determining equalization needs.
Insert the equalizer between the signal source (e.g., mixer) and the power amplifiers or crossover. Adjust levels and equalization for desired system response. The long-throw faders allow for precise settings.
For optimal signal-to-noise, establish a proper gain structure for the sound system, setting each component to its nominal operating level. Amplifiers, as the last element, should be set only as loud as necessary to avoid introducing noise.
Technical Support / Factory Service
The dbx 12 Series EQs are solid-state products with components selected for high performance and reliability. Units are factory tested and burned-in, requiring no user adjustments during their life.
For necessary repairs, return the unit to the factory with a RETURN AUTHORIZATION number obtained from dbx customer service. When contacting customer service for support, accurately describe the problem and know your unit's serial number.
Specifications
Specifications are provided in English, French, German, and Spanish.
Inputs
- Connectors: 1/4" TRS, female XLR (pin 2 hot), 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), barrier terminal strip.
- Type: Impedance-balanced/unbalanced, RF filtered.
- Impedance: Balanced 200Ω, unbalanced 100Ω.
- Max Output Level: >+21dBu balanced/unbalanced into 2kΩ or greater; >+18dBm balanced/unbalanced (into 600Ω).
System Performance
- Bandwidth: 20Hz to 20kHz, +0.5/-1dB.
- Frequency Response: <10Hz to >50kHz, +0.5/-3dB.
- Dynamic Range: ±15dB range: 109dB; ±6dB range: 115dB.
- Signal-to-Noise: ±15dB range: 90dB; ±6dB range: 97dB.
- THD+Noise: <0.005%.
- Interchannel Crosstalk: <-80dB, 20Hz to 20kHz.
Function Switches
- EQ Bypass: Bypasses the graphic equalizer section.
- Low Cut (recessed): Activates the 40Hz 18dB/octave Bessel high-pass filter.
- Range (recessed): Selects ±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 (H x W x D):
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 Net: 8.5 lbs. (3.9 kg)
1231 Net: 10.6 lbs. (4.8 kg)
1215 Shipping: 9.5 lbs. (4.3 kg)
1231 Shipping: 11.6 lbs. (5.3 kg)
Block Diagram
The dbx 1231 Graphic Equalizer features a signal path that includes an input stage with an RF filter and Input Gain control, followed by a switchable 40Hz Low Cut filter. The signal then enters the main Graphic EQ section, where the Boost/Cut range (±6dB or ±15dB) can be selected via a switch. An EQ Bypass switch allows the signal to bypass the graphic EQ. Output Level is monitored by a 4-LED bar graph, and a Clip LED warns of signal clipping. The processed signal passes through an output RF filter before exiting the unit.
Contact Information
dbx Professional Products
8760 South Sandy Parkway
Sandy, Utah 84070
Phone: (801) 568-7660
Fax: (801) 568-7662
Int'l Fax: (801) 568-7583
Email: customer@dbxpro.com
Website: http://www.dbxpro.com
