The dbx 231s is a professional dual-channel 31-band graphic equalizer designed to provide precise frequency control in live sound reinforcement, recording studios, broadcast facilities, and permanent installation environments. Each channel features 31 individual bands of 1/3-octave Constant Q filtering covering the 20 Hz to 20 kHz frequency spectrum, allowing engineers to make detailed tonal adjustments without affecting adjacent frequencies. The Constant Q design ensures that each filter maintains a consistent bandwidth regardless of the amount of boost or cut applied, resulting in more predictable and musical equalization than cheaper designs where filters narrow or widen unpredictably.

The front panel features 20mm non-conductive sliders that provide smooth, precise control with excellent tactile feedback. A Range switch allows the operator to select either ±6 dB or ±12 dB of maximum boost or cut per band, providing flexibility for both subtle tone shaping and aggressive corrective equalization. A dedicated low-cut switch engages a 50 Hz 12 dB/octave high-pass filter, effectively removing unwanted subsonic rumble and stage noise that can rob amplifier headroom and damage loudspeakers. The front panel bypass switch instantly removes the graphic equalizer section from the signal path for A/B comparison or troubleshooting, while ±12 dB of input gain adjustment accommodates a wide range of source signal levels.

Connectivity is comprehensive, with both electronically balanced XLR and 1/4-inch TRS connectors for inputs and outputs, all RF filtered to prevent radio frequency interference from contaminating the audio path. Input impedance measures 40 kΩ balanced and 20 kΩ unbalanced, while output impedance is 100 Ω balanced and 50 Ω unbalanced. The unit delivers a maximum input and output level exceeding +21 dBu, with a typical dynamic range of 112 dB, signal-to-noise ratio of 95 dB, and total harmonic distortion plus noise below 0.003 percent. The interchannel crosstalk is better than -90 dB from 20 Hz to 20 kHz, ensuring excellent stereo separation. The 231s is housed in a rugged 2U steel chassis measuring 19 inches wide, 3.5 inches high, and 6 inches deep, weighing 6.2 pounds (2.82 kg). A universal power supply accepts 100 to 240 VAC at 50 or 60 Hz, consuming just 15 watts.