Frac rack

Frac is a modular synthesizer format. Frac is sometimes referred to as "Frac Rack".

Like the Euro 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, for example, will take up three vertical units in a 19" equipment rack. Each vertical rack unit is 1.75", so a 3U module is 5.25" tall.

The Frac format has a standard width unit of 1.5". So 3" and 4.5" wide modules are common in this format. Frac-Rac is an American format designed by John Simonton of PAIA, which has found a wide following largely through the popularity of Blacet modules. (Excerpted from Randall's excellent post at the Electro-Music modular forum.)

Frac format modules typically use 3.5mm connectors and plugs for patching, although there are several companies that offer banana jacks (BugBrand, Metalbox).

Power requirements for Frac modules are typically +/-15VDC.

Refer to the List of Modular Synth Equipment Manufacturers page for a list of Frac module manufacturers.