The DPR-901 II is a four-band parametric Dynamic Equaliser which allows frequency-selective compression (-3OdB) and expansion (+16dB). 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.

The DPR-901ii is a new class of audio equaliser. Both subtle and powerful, it builds on the established problem solving capabilities of parametric equalisers. It’s uses range from processing and sweetening speech, instruments and composite music, through SPL control, to loudspeaker system and room tuning. The DPR-901ii refines the EQ process, makes it more specific - and expands it too. For the first time, changes in EQ and signal dynamics at the EQ’d frequency can be created which are triggered either above or below the individual threshold levels in four adjustable frequency bands. The changes in tonality can range from the subtle and highly specific, up to the extremes of instrument effects. Either way, the DPR-901ii’s unique subtractive process coupled with state-variable equalisation ensures uncoloured, low distortion sound. Group delay in particular is low and uniform, maintaining vital accuracy in the time/transient domain that is lacking in the majority of conventional equalisers with ‘Bell’ response envelopes.

Each band features:

  • A frequency sweep.
  • A bell width.
  • An IN/OUT switch.
  • Compress/expand control.
  • Compress/expand metering.
  • Threshold metering.
  • Time constants which are automatically controlled by dynamic and harmonic content of signal with selectable FAST RELEASE.

Some possible uses for the DPR-901ii  can be: 

  • To selectively compress and/or expand, broad or narrow-band segments of program. 
  • To de-ess and de-pop. 
  • To add dynamic loudness control (eg. bass boost at low SPLs). 
  • To control SPL in a dynamic and frequency conscious manner. 
  • To enhance or 'sweeten' mixed programme. 
  • To improve voice intelligibility (without risking howlround or feed-back). 
  • To enhance low level vocals. 
  • To correct for and/or guard against, bad microphone technique (by unskilled performers). 

Frequency response +/- 0.5dB, 20Hz to 20kHz with all sections bypassed.
Noise < -86dBu, all controls set flat (CCIR 468-2)
Distortion THD < 0.05% 20Hz-20kHz at +15dBu, all controls set flat.
Frequency Band 1 LF Sweepable from 40Hz to 320Hz.
Band 2 LM Sweepable from 150Hz to 1600Hz.
Band 3 HM Sweepable from 800Hz to 9kHz.
Band 4 HF Sweepable from 1.6kHz to 18kHz.
Width Variable from narrow (0.5Oct) to wide (3Oct)
Width control is inoperative in SHELF mode.
Filter Shelf Selects shelving EQ response (Bands 1 & 4)
Filter Defeat Selects broadband operation (Bands 2 & 3).
A bell-shaped EQ response is the norm for all bands if these switches are ‘out’.
Threshold Variable from +20dBu to -30dBu.
Comp/Exp Variable from -30dB compression to +16dB
expansion. Soft knee at low settings.
Below Switched in for below threshold processing.
Fast Release Switched out to prevent pumping on composite music mixes.
Switched in to respond to highly dynamic signals.
Metering - per channel:
8 horizontal green LEDs indicate compression activity.
8 horizontal red LEDs indicate expansion activity.
Note: The 1-8 scaling is for convenience
only. It is not a decibel scale.
6 vertical LEDs display signal level (in dB) relative to the threshold control’s setting.
Band In Switches each band into circuit.
EQ In Enables or bypasses the whole system.
Output Headroom indicating 4 LED display, indicates CLIP (overload =+20dBu), +15dBu, +10dBu, as well as signal present (-20dBu).

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