Dynamic Equalizer The DPR-901 is a four-band parametric Dynamic Equaliser which allows frequency-selective compression (-3OdB) and expansion (+16dB). It has a filter switch on bands 1&4 which changes bell filter response to a shelving response and on bands 2 & 3 cancels the filter for wide band operation. Electronically balanced input and output. The unit may be set up as a 1 input/4band or 2 input / 2 bands per channel device, and the filter side chain may be monitored to allow precise tuning of the audio spectrum to be effected.