Frac rack

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Frac rack, FracRak or Frac, from Fractional Rack, is the modular synthesizer format designed by John Simonton of PAiA. It has a mainly USA following largely through the popularity of Blacet modules.[1][2][3]

Panel format

Like the Eurorack format, Frac is considered a 3U format. The height of most modern modular synthesizer modules is measured by the number of vertical units it consumes in a standard 19" equipment rack. Modules conforming to the 3U format will take up three vertical units in a 19" equipment rack. Each vertical rack unit is 1+3/4", so a 3U module is 5+3/4" (133.35 mm) tall. The Frac format has a standard width unit of 1+1/2". So 3" (76.2 mm) and 4+1/2" (114.3) wide modules are common in this format.[1]

Difference between Frac rack and Eurorack

Although both Frac and Euro modules are 3U, use V/octave and have similar signal levels the modules aren't interchangeable. Frac modules are deeper and have a different mounting system. The module power connectors are different and so are the voltages; Frac modules are powered with ±15V and Eurorack with ±12V. Check the specs of individual modules for CV compatibility. To patch between a banana Frac system and a Euro system a common ground connection will need to be made.[2][4][5][6][7]


Frac format modules typically use 3.5 mm connectors and plugs for patching, although there are companies that offer modules with banana jacks e.g. BugBrand, Metalbox.[8][9]


Power requirements for Frac modules are typically ±15VDC. Current draw depends on the module. The power connectors are 4 way AMP MTA-156 headers. The control voltage is 1V/octave.[1][2][4] PAiA P9700S modules are designed for an ±18V unregulated power with on module regulation where necessary, although ±15V regulated supplies can be used.[10]

Frac brands

See also


This page uses Creative Commons Licensed content from Mod Wiggler Wiki:Frac (View authors).

  1. ^ a b c Standard measurements in front panels, forum, April 2006
  2. ^ a b c Analog Notes
  3. ^ List of Frac module manufacturers, Mod Wiggler forum, August 2008
  4. ^ a b "Blacet FAQ". Archived from the original on 2015-02-12. Retrieved 2015-06-11.
  5. ^ Tech Notes, Blacet Research
  6. ^ Difference between Frac rack and Euro, Vintage Synth Explorer forum, May 2013
  7. ^ EuroSynth – FracRak Comparisons by Laurie Biddulph, 2015
  8. ^ Banana Frac: The Definitive Guide, Mod Wiggler forum, August 2009
  9. ^ Metalbox Info
  10. ^ P9700S Series Analog Synthesizer Modules
  11. ^ which frac filter?, Mod Wiggler forum, Dec 2008
  12. ^ Modular Addict has MFOS PCB's!, Mod Wiggler forum, Sep 2016
  13. ^ a b Source for MOTM Frac DIY, Mod Wiggler forum, Sep 2011

External links