Discontinued Products
Dual 31 band Graphic Equalizer

The HD-231 is dual, 31 band, 1/3 octave graphic equalizer ideal for live sound systems, PA systems, permanent or fixed Installations, church systems, nightclub systems, practice PA systems, DJ sound systems, as well as home and project studios. With so many useful features and rugged construction, the HD-231 EQ will prove its value with every gig and live performance.

  • Accurate Constant Q Precision Center Frequencies
  • Exceptional Frequency Response at 20-20KHz, +/-0.5dB
  • Equipped with XLR, 1/4" Phone and Euroblock Barrier Strip Connectors
  • Independent Variable Hi and Low Pass Filtering deliver optimum control
  • Automatic Bypass Relays provided in case power is lost to the unit
  • Extremely Quiet Operation
  • Rugged Chassis Design

Please click here for a .pdf version of the spec sheet.

Controls Overall Gain Range: / Off to +6dB (Unbal. out) Sliders Centered / Off to +12dB (Bal. out) Sliders centered
Filter Type Constant Q, 3% Center Frequency
Input/Output Connections INPUTS
  • Input Type: Active Balanced/Unbalanced
  • Connectors: 3-Pin XLR, 1/4" TRS (Bal.), Euroblock
  • Impedance: 24k Ω (Balanced); 12k Ω (Unbal.)
  • Maximum: Level +22dBm (Level Control at Center)
  • Type: Active Balanced / Unbalanced
  • Connectors: 3-Pin XLR, 1/4" TRS (Balanced), Euroblock
  • Impedance: Typical
  • Max Level: +22dBm (Bal., 600 Ω load) +16dBm (Unbal., 2k Ω load)
  • RFI filters: Yes
  • Bypass Switches: Yes, Passive
  • Overload: LED Threshold 6 dB below clipping, (all filters set to flat)
  • High Pass Filter: 10-250Hz, 12dB/Oct
  • Low Pass Filter: 3k-40kHz, 12dB/Oct
  • Frequency Response: 20-20kHz, +/-0.5dB
  • THD + Noise: less than 0.01% (20Hz-20KHz, 0dBu)
  • IM Distortion (SMPTE): 0.005%
  • S/N Ratio: >98dB, Ref: 0dBu, (Bal.) 20Hz - 20KHz, unweighted.
  • Headroom: +22dB, Ref, 0dBu, (Bal.) (+/-6dB and +/-12dB range)
  • Dynamic Range: >117dB, (Bal.)
  • Channel Separation: >60dB
  • Common Mode Rejection: 50dB typical
Power 95-125VAC, 50/60Hz, 190-250VAC, 50/60 Hz
Power Requirements Input AC Power: 14 W, typical
Range +/-6dB or +/-12dB (Selectable)
Size 3.5"H x 19"W x 7.0"D
Slider Travel 20mm (Positive Center Detent)
Weight 12 Ibs (5.4 kg)
This is beta software, use at your own risk!
HD-231 - Dual 31 band Graphic Equalizer