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L-1 Microcompressor Stereo

MICROCOMPRESSOR STEREO – compact stereo VC compressor

This is compact but hi-quality compressor, using the THAT4301 dynamics processor.

THAT 4301 Dynamics Processor, dubbed “THAT Analog Engine®”, combines in a single IC all the active circuitry needed to construct a wide range of dynamics processors. The 4301 includes a high-performance, exponentially-controlled Blackmer® VCA, a log-responding RMS-level sensor and three general-purpose opamps.

Design is based on THAT Corp. design notes – Fully Adjustable Compressor / Limiter. This is a feedforward VCA compressor.


  • Adjustable by potentiometers Treshold, Ratio, Attack, Release, Makeup gain.
  • Reduction LED which lights when signal level exceeds treshold.
  • Treshold, Makeup, Attack and Release can be controlled by CV.
  • Hard/soft knee switch.
  • Two timing modes are available — auto and manual. In auto mode attack and release rates are linked, and depend on the non-linear capacitor circuit. In manual mode, variable, independent adjustments of the attack and release dynamics are possible.
  • Peak or Automatic timing detector options.
  • Sidechain in to external sidechain processing.
  • Envelope out allows to patch any VCA as compressor.
  • Full reverse polarity protection.


Power consumption: V+ 43mA, V- 30mA.


Soundsample. Tube VCA works as compressor modulated from envelope out of Microcompressor. Filter – Mutant vactrol VCF. No effects.


Sample made by Jim Sutherland 
Distorted drums in punk style are heavy compressed. Jim modulated Makeup from Envelope Out to have extremally strong compression.



Other modules by L-1 | L-1 Tube VCA | L-1 Quad VC Equalizer | L-1 VC Stereo Mixer | L-1 Digital Tuner | L-1 Mutant Vactrol VCF | L-1 Quad VCA-Mixer | L-1 Basic VCO | L-1 2180VCF