Ecler QEM.30

The QEM Constant Q Equalizer series have general slide output level controls, level indicators and flat switches, electronically balanced in- and outputs. And for perfect result: a radiofrequency filter and a switchable subsonic filter. Constant shape, or constant Q system means filter bandwith independant from the selected gain. This system provides a better selectivity and accuracy in the equalization. 
QEM 30-1
  § One channel, 30 bands one third octave equalizer (ISO)
  § Two rack unit height
  § Boost/cutrange ± 12 dB.
  § General slide output level control, level indicators and FLAT switch.
  § Electronically balanced input and output by using XLR-3 connectors.
  § High and low cut filter controls, providing the ability to set the upper and lower cutoff
          frequencies of the unit from between 2.2 kHz to 30 kHz on the high end and 15 Hz to 300
          Hz on the low.
  § A relay switch the unit to bypass mode when the power switch is off.