Gyraf GSSL Buss Compressor

Projects > Gyraf GSSL Buss Compressor

The GSSL is a clone of the stereo buss compressor found in SSL4000-series desks.  Because of it’s affordability and relatively low difficulty, the GSSL has become a very popular project with many PCBs and mods available.

Images courtesy of Gyraf Audio and FiveFish Studios

Notable Features:

  • Designed for DBX202x or THAT2180/2181 VCAs
  • Uses all modern easily sourceable components
  • Ratio, attack, and release pots

Possible Modifications:

  • Turbo Mod
    • Changes the sidechain from summed (mono) to stereo.  This makes the GSSL behave more like the original SSL.
  • CRC Filter Mod
    • Fixes power hum problems inherent in the original GSSL design.
  • VU Meter Mod
    • Usually GSSL builders use a peak meter.  The VU meter makes the “feel” of the compressor closer to, say, the 1176.
  • Super Sidechain
    • Adds adjustable 60, 90, 130 & 200hz high-pass filters, Tilt-Medium and Tilt-Loud sidechain eq curves, and the option for an external sidechain input.
  • Crush’n’Blend
    • Adds wet/dry mix control



  • $9.95 for Turbo PCB from Expat Audio
  • $30 for Turbo kit from DIY Parts Supply
  • 12€ for Super Sidechain PCB from Gustav
  • $9.95 for VU Meter PCB from Expat Audio
  • $6.95 for CRC PCB from Expat Audio
  • $16 for CRC kit from DIY Parts Supply

More information:

  • A blog about building a GSSL.
  • Five Fish’s GSSL build blog with sound clips.