Frac rack

Frac Rack, FracRak or Frac is the modular synthesizer format designed by John Simonton of PAiA. It has a wide 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 1¾", so a 3U module is 5¼" tall. The Frac format has a standard width unit of 1½". So 3" and 4½" wide modules are common in this format.

Note that even though the height of both Frac and Euro modules are 3U, differences exist in the mounting system. Paia, Blacet and some Wiard modules are Frac mounting compatible.

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.

Power requirements for Frac modules are typically ±15VDC. Current draw depends on the module.