Eurorack

Euro is a modular synthesizer format, (sometimes called "Eurorack").

The height of Euro format synthesizer modules is 5.25" or 1.33.35mm, which is equal to three vertical units in a standard 19" equipment rack. (This standard height is called "3U".) Note also that the panels of the Euro format are often shorter than the 3U would suggest. This is not due to allowances for paint and fitting, (which is seen in many of the other formats), but rather due to the shape of the top and bottom mounting rails (produced by ProMA or Gie-Tec). These have a lip which uses some of the height. So Euro rack modules are often approximately 5mm shorter than the technically exact 3U height of 133.35mm (5.25"). Commonly 1/8" thick aluminium is used for the module panels.

The width of Euro modules is typically measured in "HP" (or "TE"); 1 TE/HP is equivalent to 5.08mm, or 1/5 inch. So a 24 TE/HP width is 24/5, or 4.8". In millimeters, it becomes 24 x 5.08, or 122mm.

Note that even though the height of both Frac and Euro modules are 3U, differences exist in the mounting hardware. So, each format requires its own mounting system (screws, rails, etc).

Power requirements for Euro modules are usually +/-12VDC and 5VDC. Current draw depends on the module.

Euro modules typically use 1/8" or 3.5mm connectors and plugs for patching.

Mounting Screws
Most companies use an M3 sized screw with a typical length of 6mm that will extend to 10mm. Analogue Systems use M2.5 for their cases. Doepfer specifications call for M3x6mm size screws. Elby racks call for M3x8mm size screws. Monorocket cabinets use sliding nuts in their rails, threaded to accept 4-40 screws.

Module Depth
Following is an alphabetic list of Euro module depths.

This information is important when purchasing or planning construction of a case or rack for your modules.

(courtesy of felix, from this thread)

Alyseum

 * MS-812 - 1.57" (40mm) maximum

Doepfer

 * A-126 Voltage Controlled Frequency Shifter (105mm)
 * A-112 Sampler/Wavetable Gen. (100mm)
 * A-190-1 MIDI-to-CV/Gate/Clock Interface (95mm)
 * A-113 Subharmonic Generator (90mm)
 * A-154 Enhanced Sequencer Controller (9Omm)
 * A-108 48dB Low Pass (75mm)
 * A-188-2 A-188-2 Tapped BBD Module (70mm)
 * A-101-3 Vactrol Modular Phaser (65mm)
 * A-111-1 H-VCO (65mm)
 * A-120 24dB Low Pass (Moog type) (65mm)
 * A-125 Voltage Controller Phaser (VCP) (65mm)
 * A-137-1 VC Wave Multiplier (65mm)
 * A-188-1? BBD Module (65mm)
 * A-102 Diode Low Pass (60mm)
 * A-128 Fixed Filter Bank (60mm)
 * A-129-1/2 Vocoder Analysis+Synthesis (60mm)
 * A-129-3 5xAttenuator/Offset/Slew Limiter (60mm)
 * A-141 VC ADSR (60mm)
 * A-149-1 Quantized/Stored Random Voltages (60mm)
 * A-189-1 VC Bit Modifier (60mm)
 * A-101-9 Universal Vactrol Module (55mm)
 * A-103 18dB Low Pass(TB303 type) (55mm)
 * A-106-5 SEM VCF (55mm)
 * A-109 Voltage Controlled Signal Processor (55mm)
 * A-110 VCO (55mm)
 * A-121 12dB Multimode Filter (55mm)
 * A-127 Triple Resonance VCF (55mm)
 * A-135-1 VC Mixer (55mm)
 * A-135 (/A-144) VC Mixer (with A144 order) (55mm)
 * A-145 Standard LFO (55mm)
 * A-146 Variable Waveform LFO (55mm)
 * A-147 Voltage Controlled LFO (55mm)
 * A-156 Dual Quantizer (55mm)

Livewire

 * Frequensteiner - 1.50" (38.1mm)
 * Dual Cyclotron - 2.25" (57.15mm)

Metasonix

 * All R modules: less than 1" (25.4 mm) behind panel

Plan B

 * Model 28 - 2.50" (63.5mm)
 * Model 15 - 1.75" (44.45mm) (MKII, MKI is much deeper)
 * Model 14 - 3.75" (95.25mm)

The Harvestman

 * Tyme Sefari - 2.00" (50.8mm)
 * Malgorithm - 1.50" (38.1mm)