Legacy Products

HD-131 – Single 31 Band Graphic Equalizer


The HD-131 is single, 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-131 EQ will prove it”s value with every gig and live performance.

Key Features


Controls Overall Gain Range: Sliders Centered / Off to +6dB (Unbal. out) / Off to +12dB (Bal. out)
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 <150 Ω
  • Max Level: +22dBm (Bal., 600 Ω load) +16dBm (Unbal., 2k Ω load)
  • RFI filters: Yes
  • Bypass Switches: Yes, Passive
  • Overload: LED Threshold
Low Pass Filter
  • 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: 9 W
Range +/-6dB or +/-12dB (Selectable)
Size 1.75″H x 19″W x 7.0″D
Slider Travel 20mm (Positive Center Detent)
Weight 7.5 Ibs (3.4 kg)