1 Scope

1.1 Purpose

The Eurorack Interface Specification (EIS) defines the mechanical and electrical interface between Eurorack modules, enclosures, bus boards, power supplies, and the cables that join them.

A requirement is a shall only where, without it, a conforming product from one maker could fail to fit, power up, or work with a conforming product from another: mechanical fit, power entry and distribution, published supply figures, and declared signal classes. Construction choices that do not change interoperability, such as board material, module depth, rail section, or screw finish, are described and recommended, not required.

1.2 Applicability

EIS applies to five product types (Conformance):

• A module: front panel, board clearance, patch jacks and their safety, power entries and header current, and the port list with signal classes and the formats of its rear video sync ports. A DC entry panel or a video sync distributor in module form keeps the rules of what it carries (5.1, 5.2, 6.1, 6.3, 6.4, 6.6, 7.1, 7.2, 7.3, 8.1, 8.2, 8.3).
• An enclosure: rack frame, rails, inserts, mounting screws, and the published width and depth of each row. A built-in supply plays the power supply role and a built-in bus board the bus board role; a case DC entry keeps the PWR-DC12 entry rules (5.1, 5.2, 5.3, 5.4, 6.1, 6.3, 6.5, 7.1, 8.1, 8.2, 8.3).
• A bus board: headers, links, published capacity, one 0 V, and row wiring terminals, and the rules of anything else it carries behind the panel: a DC rail or the video sync tree (6.1, 6.3, 6.4, 6.5, 7.1, 8.1, 8.2, 8.3).
• A power supply: rails, output connector, protection, published ratings and ripple, the earth bond of 0 V, and row wiring terminals, for a row or for the one product it is mounted on. A supply may also make the 12 V DC rail (6.1, 6.2, 6.3, 6.4, 6.5, 7.1, 8.1).
• A cable: the interface it mates: power ribbon, video, or DC (6.4, 6.5, 8.1, 8.2).

Every product meets Core (Part 2), which is never claimed: the rack, the panel, and the rail; power on the bus; and patch jacks with their signal classes, AUDIO, CV, and VIDEO among them. A product may also have the optional interfaces of Part 3, the 12 V DC rail and the video sync behind the panel. A requirement about a power header, a DC entry, or a video sync port applies to a product that has one, and its claim file lists them. Distributing a rail or the video sync is a capability of whatever product has the outlets or ports, not a product type. Chapter 9 binds the person who assembles a system, not a product.

1.3 Exclusions

EIS does not specify:

• product catalogs, mains wiring or earthing, or the safety or EMC certification of a product;
• the internal protocol of digital video or data streams;
• ports other than patch jacks, video sync ports, and power entries, such as coaxial picture video, line and microphone audio, MIDI, DMX512, word clock, and the ILDA connector; EIS asks nothing of them beyond SIG-001 and SIG-017, and Annex C gives an informative vocabulary for naming them;
• power rails outside the power interfaces of 6.1, such as a maker's own entry at other rails;
• a precision control-voltage class beyond PITCH pitch tracking; the stability of a DC reference and the accuracy of a quantizer are product figures;
• factory test procedures (4.3).

1U in EIS is the Intellijel 1U format: a 39.65 mm panel with a 33.65 mm hole span. Pulp Logic 1U tiles, 43.18 mm high, are a different format, physically incompatible with it, and outside EIS.

1.4 Where the values come from

Every requirement records the origin of its value, its provenance (Terms):

• Quoted from a dated publication. Rack geometry comes from IEC 60297-3-101:2004 and IEC 60297-3-100:2008: the HP and the rack unit (RACK-001, RACK-002), and the frame dimensions a rack-mount enclosure meets (RACK-003). The M3 thread pitch and major diameter come from ISO 261:1998 (RAIL-006, RAIL-007).
• Inherited from the Doepfer A-100 and restated in EIS words: the 3U panel height, the hole inset and drill, the patch jack, the panel width and thickness ceilings, the power header pinout, marking, and keying, the ±12 V and +5 V rails, the gate thresholds, and the bus CV and gate levels, regions, and links. The 1U panel height is inherited from the Intellijel 1U format, and the 5 mΩ limit of a row wiring conductor and the 2 mΩ 0 V link from Hinton Instruments' power distribution.
• Calculated from other EIS figures: the hole spans and offset (PANEL-009, PANEL-011), and the insert pitch, thread, and thickness and the screw length window that follow from them (RAIL-001 to RAIL-004, RAIL-009).
• Set by EIS: the M3 mounting screw, board edge clearance, the published width, depth, and current of a module, the power header form and its current limit, the signal classes and their ranges, patch safety, the 0 V reference and its earth bond, bus-board capacity, supply protection, published ripple and the ripple limit, the rest of the rail and enclosure geometry.

The patch levels are EIS figures, not inherited ones. Doepfer publishes typical ranges (audio 10 Vpp, LFOs ±2.5 V, envelopes 0 to +8 V) and no impedance. Modules in use exceed those ranges, and an input has to accept what an output may send, so EIS sets audio at ±10 V peak (B10) and control CV by the range a port claims: B5 when none is named, up to B10 (Annex J).

Where EIS states a value, that value governs a conformance claim. Annex J lists every difference from what Doepfer publishes, and the tests compare EIS with the published A-100 figures.