6.1 Power architecture

EIS power comes in power domains. A domain is a set of rails with its own connectors, its own way of reaching a module, and its own limits. EIS has four: PWR-BUS, the +12 V and −12 V (and optional +5 V) that a power supply feeds through bus boards and power ribbons to each module's power header; PWR-DC12, nominal 12 V DC from an external adapter that enters a product at a DC entry; PWR-A6, ±6 V for analog circuits from a supply or a power converter to a module's A6-VH3 entry; and PWR-A15, ±15 V for analog circuits that run at the full rail, at an A15-MF4 entry. Each domain is two features, one per direction: a product claims the IN feature for an entry of the domain and the OUT feature for its outlets (4.1).

The designators follow one rule. The word after PWR names the domain's topology and the number its rail voltage: BUS is the Eurorack bus, defined by its header pinout rather than by one voltage, so it carries no number; DCnn is a single-rail nn V DC domain fed from an adapter, the DC jack of the trade; Ann is a bipolar ±nn V analog domain. A later single-rail domain would be PWR-DCnn and a later bipolar one PWR-Ann; the bus stays the bus.

This clause and the next two hold what is common to every domain: the published currents, sources (6.2), and 0 V (6.3). Each domain then has its own clauses: the bus in 6.4 to 6.6, PWR-DC12 in 6.7, PWR-A6 in 6.8, PWR-A15 in 6.9. Mains voltage, safety certification, and the internal construction of a supply are outside EIS.

Domains

Domain	Rails	Feature	Made by	Distributed by	Enters a product at	Clauses
The bus	+12 V, −12 V; +5 V optional	PWR-BUS-IN, PWR-BUS-OUT	power supply	bus board and power ribbon	power header, 2 × 5 or 2 × 8	6.4, 6.5, 6.6
12 V DC	12 V: one +V and −V pair	PWR-DC12-IN, PWR-DC12-OUT	external adapter, outside EIS, or a power supply with PWR-DC12 outlets (6.2)	PWR-DC12 outlets of a bus board, a module, or a supply, and DC cables	DC entry, DC-BAR21 to DC-MF8	6.7
±6 V analog	+6 V, −6 V	PWR-A6-IN, PWR-A6-OUT	power supply or power converter	A6-VH3 outlets of a supply, a converter, or a bus board, and PWR-A6 cables	PWR-A6 entry, A6-VH3	6.8
±15 V analog	+15 V, −15 V	PWR-A15-IN, PWR-A15-OUT	power supply or power converter	A15-MF4 outlets of a supply, a converter, or a bus board, and PWR-A15 cables	PWR-A15 entry, A15-MF4	6.9

Sources, distribution, and entries

In each domain, a source, a power supply for a row or a power converter for one product, makes the power, distribution passes it on without converting it, and a product takes it at a power entry. A source or a distribution product delivers at outlets: a supply's output terminals, a bus board's headers, the PWR-DC12 outlets of a bus board, a module, or a supply, DC-BAR21 jacks or DC-VH2 headers. A module's power header, its DC entry, and its PWR-A6 entry are all power entries.

One product can sit in two domains. A power supply that takes PWR-DC12 at a DC entry and delivers the bus is a PWR-DC12 entry and a bus source; a dual-source module has a power header and a DC entry; a power converter is an entry of the domain it takes and a source of the one it makes.

Rules for every domain

A product shall publish, for each power entry, the maximum current it takes on each rail at the entry's nominal voltage, stating 0 for a rail it does not draw (PWR-001). A power supply, a power converter, a bus board, and any product with outlets of a power domain shall publish the maximum current it delivers on each rail, in total and at each outlet (PWR-002). These published figures are what the person assembling a system budgets a row with.

A product whose power entries are alternatives, each able to power it alone, shall not require more than one of them to be connected at the same time (PWR-003); the installer connects one (ASM-003). Entries that feed different circuits, such as PWR-A6 for a module's analog rails and the bus for its logic, are not alternatives, and the claim file says which the product needs. A module shall not source current into a rail of any of its power entries (PWR-004): a module with its own +5 V regulator leaves pins 11 and 12 of its power header undriven, and a module with a DC entry does not feed its DC rail onto the bus.

Every power entry's 0 V, and the −V of a DC entry, is the product's one 0 V (6.3). An isolated converter joins its output 0 V to its input's 0 V.

EIS recommends limiting inrush current when a product's rails come up: a row of modules is a large capacitive load on its source.

Row wiring

Between a power supply and its bus boards, between linked bus boards, between a case DC entry and the supply, bus board, or PWR-DC12 outlets it feeds, and from a supply's 0 V to the chassis or earth, a row is wired with discrete conductors rather than a connector of a domain. Where a power supply, a bus board, or a product with PWR-DC12 outlets takes or gives a rail or 0 V on such wires, each terminal shall be a 6.3 mm × 0.8 mm quick-connect tab, a stud or screw that takes a ring terminal, or a wire-clamp terminal block, and the product shall publish the terminal type and the conductor sizes it accepts (PWR-005). Each terminal is marked with its rail (SUP-003).

A row wiring conductor between a power supply, a bus board, a product with PWR-DC12 outlets, or a DC entry shall be stranded copper, insulated and rated 105 °C or more, of at least 16 AWG, at least 14 AWG where it carries more than 5 A, and at least 12 AWG where it carries more than 8 A, terminated by a crimped terminal at each end (PWR-006); a joint shall not rely on solder alone (PWR-006). The 0 V conductor between a power supply and a bus board, and between linked bus boards, shall be of at least the gauge of the rail conductors beside it (PWR-007). Where a product bonds its 0 V to its chassis or to a protective-earth terminal, the bond shall be a conductor of at least 14 AWG with a ring terminal on a stud or screw through bare metal under a toothed lock washer, or a bus bar of equivalent section (PWR-008). An installer who joins a supply and bus boards from different makers wires them the same way (ASM-009, 9.1).

Terminal (PWR-005)	Size	Mates with	Rated	EIS recommends it for
quick-connect tab	6.3 mm × 0.8 mm (¼ in, the 250 series)	fully insulated receptacle, crimped	15 A	bus board inputs and links; supply outputs on a board
stud or screw for a ring terminal	M3 or M4 (ring terminal sized to the stud)	insulated ring terminal, crimped, under a toothed lock washer	20 A	0 V and earth bonds; bus bars; metal-case supplies
wire-clamp terminal block	screw or spring clamp for 12 to 16 AWG	bare stranded end with a crimped ferrule	15 A	the output block of a metal-case supply

Current in the conductor	Conductor (PWR-006)
up to 5 A	at least 16 AWG (1.3 mm²)	most rows: a 16 AWG rail conductor drops about 25 mV per metre at 3 A
up to 8 A	at least 14 AWG (2.1 mm²)	a large row, or several bus boards on one pair
up to 15 A	at least 12 AWG (3.3 mm²)	the limit of a 6.3 mm tab; above it, use a second pair

EIS recommends the quick-connect tab for bus board inputs and links and for supply outputs on a board, with a fully insulated receptacle crimped onto the wire and a double (piggyback) receptacle where one tab feeds two boards; the ring terminal, under a toothed lock washer, for every 0 V and earth bond and for a bus bar; and, on a metal-case supply's wire-clamp block, a crimped ferrule on each stranded end. EIS recommends 105 °C PVC wire (UL 1015 at 600 V or UL 1007 at 300 V), or silicone where the wire flexes, with tin-plated brass or phosphor-bronze terminals crimped with the terminal maker's tool, so that each joint stays under 5 mΩ; the rail conductors and their 0 V run together, bundled or twisted, to keep the loop small; the colors of 6.4: red +12 V, blue −12 V, black 0 V, and green-and-yellow only for an earth bond. A wire nut, an insulation-displacement splice, a soldered strand under a screw, and a bare wire wrapped around a tab are not row wiring.