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.
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/", so a 3U module is 5 3/" (133.35 mm) tall. The Frac format has a standard width unit of 1 1/". So 3" (76.2 mm) and 4 1/" (114.3) wide modules are common in this format.
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.
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. PAiA P9700S modules are designed for an ±18V unregulated power with on module regulation where necessary, although ±15V regulated supplies can be used.
- Ad Infinitum
- Analog Metropolis
- Bananalogue – Frac with banana jacks
- Blacet Research
- Encore Electronics
- Flight of Harmony
- Livewire Electronics
- Magic Smoke Electronics
- MFOS – not format specific and can be powered by +/-15V
- Oakley Sound Systems – some support for Frac and some 5U PCBs can fit behind a Frac panel.
- PAIA – pioneers of the Frac format
- STG Soundlabs
- Stroh Modular
- Synthesis Technology MOTM – never supported Frac but some 5U PCBs will fit behind a Frac panel.
- ^ a b c Standard measurements in front panels, Electro-music.com forum, April 2006
- ^ a b c Analog Notes
- ^ List of Frac module manufacturers, Muff's Modules & More forum, August 2008
- ^ a b Blacet FAQ
- ^ Tech Notes, Blacet Research
- ^ Difference between Frac rack and Euro, Vintage Synth Explorer forum, May 2013
- ^ EuroSynth – FracRak Comparisons by Laurie Biddulph, 2015
- ^ Banana Frac: The Definitive Guide, Muff Wiggler forum, August 2009
- ^ Metalbox Info
- ^ P9700S Series Analog Synthesizer Modules
- ^ which frac filter?, Muff Wiggler forum, Dec 2008
- ^ Modular Addict has MFOS PCB's!, Muff Wiggler forum, Sep 2016
- ^ a b Source for MOTM Frac DIY, Muff Wiggler forum, Sep 2011
- Fractional Rack Modules, Muff's Modules & More forum,
- Standard measurements in front panels, electro-music.com, DIY Hardware and Software forum, May 2007
- About Blacet Research
- Frac on ModularGrid
- EuroSynth – FracRak Comparisons by Laurie Biddulph, 2015
- 1978 PAIA catalog
- PAiA at Marvin Jones' website, also has some issues of Polyphony
- PAiA documents, Synth & Studio Docs Archive