"The DP-1 is a one knob compressor with additional features for dynamic treatment of music material in standard and some unique ways. The module consist of three main parts:Compressor
The compressor is build around a high performance VCA circuit with low distortion and low noise floor. Instead of two controllers it has only one RATIO controller which compensate the signal loss at increased compression. It means that the low level signal is boosted and the high level signal is attenuated. The incoming signal passes the LEVEL INPUT controller and the outgoing signal is controlled by the OUTPUT GAIN. All parameters, such as the envelope follower (output ENV) with ATTACK and RELEASE, RATIO and OUTPUT GAIN are controllable manually by knobs and by CV inputs. The switch SOFT KNEE activates the function for gradual compression action.
Mute
The Mute (or squelch) circuit allow amplitude re-shaping in many ways for compressed or uncompressed audio signal. The muting circuit has four controllable parameters, TRESHOLD for activating the circuits at variable signal level, DEPTH for the muting process, from 0 to 72 dB deep, ATTACK and RELEASE controls for the muting process derived from the Gate. The Mute allows a complete re-shaping the dynamics for the audio signal. You can remove the unwanted and high spikes from heavy compressed signal due the compressor attack time which prevent overload the outgoing signal. The result is a compressed signal with short attack time and with no overshoots of the signal. Another example is treatment of beats, drum sounds or other sounds with variable accents or dips, variable fade in and out, also called as “push, pull”, “breathing”, or “suction” sounds. Just two examples and all four parameters are CV controllable, as well.
Side Chain Filter
The side chain is the circuit which determinate the compression and mute action related to the frequency characteristic of the side chain filtering. A side chain with equalization controls can be used to reduce the volume of signals that have a strong spectral content within a certain frequency range: it can act as a de-esser, reducing the level of vocal sibilance in the range of 6–10 kHz using the high pass filter or "de-bumper", as I called, for reduction of strong bass or sub bass signals by using the low pass filter in the sidechain path. The build in side chain filter is a 12 dB/octave multi mode filter with low pass and high pass outputs for mentioned duties and others since the corner frequency is controllable by external CV signal."
via http://www.cwejman.net/dp-1.htm
