dbx 231S Dual 31-Band Graphic Equalizer

Shape your venue's sound and cut out feedback with this dual 31-band graphic EQ. A serious value, the 231S equalizer offers dbx quality -- in 2 rack spaces.


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dbx 2231 Dual 31-Band Graphic Equalizer

No longer available at zZounds
This dual graphic EQ keeps your sound clean with built-in Type III noise reduction and PeakPlus limiting. Get connected with XLR, TRS and barrier strip I/O.

With a prestigious heritage extending back to dbx's heralded 30 Series equalizers, the dbx 2231 easily lives up to the revered dbx reputation. Besides including two 31-band channels of 1/3-octave equalization, the 2231 empowers you with flexible features like the PeakPlus limiter circuit, and the amazing Type IIITM Noise Reduction system. It also includes +12 dB input gain range; switchable +6 or +15 dB boost/cut range; XLR, Barrier strip, and TRS 1/4" inputs; nonconductive nylon sliders; and an intuitive user interface with comprehensive output and gain reduction metering. As always, the inevitable result of the meticulous attention to detail and top-quality componentry is exceptional sound, performance, and reliability.

The Graphic EQ with Built-in Type III Noise Reduction

The most revolutionary feature of the 2231 is the proprietary Type III Noise Reduction system, which enables you to boost signal-to-noise ratios by up to an incredible 20 dB. The result of this instant encode/decode process is that you're no longer forced to employ drastic EQ settings in effort to reduce system noise. Instead, you're freed to dedicate all 2 EQ bands to the most important thing, the music.

Peak Limiting Included

PeakPlus limiter technology allows you to easily safeguard your gear against hazardous dynamic surges in program material. In addition to these formidable tools, the 2231's front panel provides at-a-glance insight as to gain reduction and output level status via its read more four-stage LED ladders. With such power and finesse built into such a reasonably priced package, it's easy to see why dbx 20 Series equalizers are relied upon by studio and touring professionals the world over. With such affordable quality, there's no longer any excuse for compromising your sound.


- dbx's revolutionary Type IIITM Noise Reduction system, which increases S/N ratio by up to 20dB
- PeakPlus limiting technology with threshold range from 0dBu to +24dBu (off)
- Two 31-band, 1/3-octave channels with switchable boost/cut ranges of +6 or +15 dB
- +12 dB input gain range
- XLR, Barrier strip, and 1/4" inputs
- 4-segment LED ladders for monitoring of gain reduction and output levels -- the most comprehensive visual feedback available
- Exceptional sound quality
- dbx's unmatched engineering and construction standard
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- Connectors: 1/4" TRS, female XLR (pin 2 hot), and barrier terminal strip
- Type: Electronically balanced/unbalanced, RF filtered
- Impedance: Balanced 40kS, unbalanced 20kS
- Max Input Level: >+21dBu balanced or unbalanced
- CMRR: >40dB, typically >55dB at 1kHz

- Connectors: 1/4 in. TRS, male XLR (pin 2 hot), and barrier terminal strip
- Type: Impedance-balanced/unbalanced, RF filtered
- Impedance: Balanced 200S, unbalanced 100S
- Max Output Level: >+21dBu balanced/unbalanced into 2kS or greater

System Performance
- Bandwidth: 20Hz to 20kHz, +/-0.5dB
- Frequency Response: <10Hz to >50kHz, +0.5/-3dB
- Noise Reduction In (+/-6 and +/-12dB range):
- Signal-to-Noise: >102dB, unweighted, ref: +4dBu, 22kHz measurement bandwidth
- Dynamic Range: >120dB, unweighted
- Noise Reduction Out: (+/-6dB range):
- Signal-to-Noise: >94dB, unweighted, ref: +4dBu, 22kHz measurment bandwidth
- Dynamic Range: >112dB, unweighted
- Noise Reduction Out: (+/-12dB range):
- Signal-to-Noise: >90dB, unweighted, ref: +4dBu, 22kHz measurement bandwidth
- Dynamic Range: >108dB, unweighted
- THD+Noise: <0.04%, 0.02% typical at +4dBu, 1kHz
- Interchannel Crosstalk: <-80dB, 20Hz to 20kHz (2215/2231)
- Noise Reduction: Up to 20dB of dynamic broadband noise reduction

Function Switches
- Type III NR: Activates dbx Type III' Noise Reduction
- 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

- Output Level Meter: 4-LED bar graph (Green, Green, Yellow, Red) at -10, 0, +10, and +18dBu
- Gain Reduction Meter: 4-LED bar graph (all Red) at 0, 3, 6, and 10dB
- Type III NR Active: Yellow LED
- EQ Bypass: Red LED
- Clip: Red LED
- Low Cut Active: Red LED
- +/-6dB range: Red LED
- +/-12dB range: Red LED

Power Supply
- Operating Voltage: 100VAC 50/60Hz, 120VAC 60Hz, 230VAC 50/60Hz
- Power Consumption: 23W
- Mains Connection: IEC receptacle

Physical Dimensions: 5.25" H X 19" W X 7.9" D (13.335cm x 48.3cm x 20.1cm)

For support or warranty questions, please contact the manufacturer:
Phone: 844-776-4899
Web: https://www.dbxpro.com/en/support

dbx 2231 Dual 31-Band Graphic EQ

You used to have to settle for second best in a reasonably priced EQ, but not anymore. With the dbx 2231 Dual 31-Band Graphic Equalizer you get a great EQ circuit, a graceful yet powerful limiter and the revolutionary design of the Type III Noise Reduction.

Type III Noise Reduction

It's amazing. One little button. It has so much effect. The Type III Noise Reduction is a cool concept -- virtually instantaneous encode/decode within the circuitry of the box. dbx started out to build the finest EQ's possible, boxes with the heritage and performance to rival our famous 30 Series EQ's. And to no one's surprise they came out awfully darn good. But then, Roger (dbx's chief engineer, a nice guy, as far as engineers go) got the crazy idea of putting this noise reduction stuff in the box. They listened to it and were amazed. The EQ's sounded great without it but with it the performance was nothing short of incredible. Check it out yourself and see.

PeakPlus Limiter

Who knows more about limiting than the folks at dbx; nobody, that's who. So when the guys were developing this series of EQ's they wanted something that would be unique to these EQ's. That's when Roger got another one of his bright ideas and said "I bet they'll work a lot better if there's a cool limiter built in." Next thing you know, all the guys are in the studio amazed at the limiter Roger had designed specially for the 20 Series. Once again, hearing is believing.

With a threshold range of 0 to +20dbu, the PeakPlus limiter is designed to tame your program material from the subtlest nuances to the rowdiest hits. Also, the four stage LED ladder gives you a great visual indication as to what the limiter is doing.


- Revolutionary patent-pending instant encode/decode Type III Noise Reduction increases S/N ratio by up to 20dB.
- PeakPlus Limiter (also patent pending) threshold range from 0dBu to +20dBu
- Four segment LED bargraph for both Gain Reduction and Output Level.
- Status LEDs offer visual feedback for all settings on the front panel.