Part 3 — Power

EIS power comes in power domains, each with its own connectors, distribution, and limits (6.1). PWR-BUS is the bus every Eurorack row has: ±12 V and optional +5 V from a supply through bus boards and ribbons to each module's power header (6.4 to 6.6); it is EIS Core. Three more domains are features a product adds.

PWR-DC12 (6.7) carries nominal 12 V DC from an external adapter into a product at a DC entry. It exists for two cases the bus does not serve: a product whose draw exceeds what one power header carries, and a product meant to run on a desk, or in a case with no bus, from a wall adapter. A DC rail is filtered or regulated in each product, so the rail's own noise does not reach a signal.

PWR-A6 (6.8) carries ±6 V to the analog circuits of a module. Video and other wideband analog circuits run from ±5 V regulated locally; a ±6 V rail gives a low-dropout regulator per circuit block the headroom it needs, while a ±12 V rail would turn the difference into heat on every module. A supply or a power converter makes it, and the module finishes the regulation.

PWR-A15 (6.9) carries ±15 V to analog circuits that run at the full rail: the op-amp stages of an analog computing module, a display amplifier, or a video output stage with ±10 V of swing. Its connector and pin map are the LZX Deflect series' Mini-Fit Jr entry.

What is common to every domain is in 6.1 to 6.3: the currents a product publishes, the protection and ripple of a source, and the one 0 V that a row's signals are measured from.

Contents

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

EIS · Power domains: where each is made, how it is distributed, where it enters The bus +12 V, −12 V; +5 V optional PWR-BUS-IN / PWR-BUS-OUT made by power supply distributed by bus board and power ribbon enters at power header 2 × 5 or 2 × 8 12 V DC 12 V: one +V and −V pair PWR-DC12-IN / PWR-DC12-OUT made by external adapter outside EIS, or a power supply with PWR-DC12 outlets (6.2) distributed by PWR-DC12 outlets of a bus board a module, or a supply, and DC cables enters at DC entry DC-BAR21 to DC-MF8 ±6 V analog +6 V, −6 V PWR-A6-IN / PWR-A6-OUT made by power supply or power converter distributed by A6-VH3 outlets of a supply a converter, or a bus board, and PWR-A6 cables enters at PWR-A6 entry A6-VH3 ±15 V analog +15 V, −15 V PWR-A15-IN / PWR-A15-OUT made by power supply or power converter distributed by A15-MF4 outlets of a supply a converter, or a bus board, and PWR-A15 cables enters at PWR-A15 entry A15-MF4 In every domain a product publishes the current at each power entry (PWR-001) and at each outlet (PWR-002); it needs only one of its alternative entries connected (PWR-003) and never drives current back into one (PWR-004). Every entry's 0 V, and the −V of a DC entry, is the product's one 0 V (GND-001).

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.

6.2 Power supplies and power converters

A power supply is the source of a power domain for a row, and a power converter the source of one for a single product, such as ±6 V made on the back of a module from the bus (6.1). A bus supply feeds the row's bus board with the rails of 6.4: +12 V and −12 V, and +5 V if it provides one. It may be built into an enclosure or sold on its own. The rules below bind every outlet of a supply or a converter, whatever its domain; the limits that differ by domain are in the table at the end of the clause. The 12 V of PWR-DC12 comes from an external adapter, which is outside EIS; a supply that takes it at a DC entry is also a PWR-DC12 product (6.7).

Supplies in the other domains

A power supply may make the 12 V DC rail of 6.7 or the ±6 V rails of 6.8, beside or instead of the bus; it then claims PWR-DC12-OUT or PWR-A6-OUT, publishes the current of each outlet, and meets that domain's outlet rules (SUP-009): PWR-DC12 outlets are DC-BAR21 jacks or DC-VH2 headers, each protected separately (DC-009, DC-012), and PWR-A6 outlets are A6-VH3 within the window of 6.8 (A6-001, A6-002). A claim names each domain the supply gives, power supply (PWR-DC12-OUT) or power supply (PWR-A6-OUT), and each it takes, PWR-DC12-IN for a supply fed from a brick; the direction is in the name, and the claim file carries the figures.

What a supply publishes

A power supply publishes the current it delivers on each rail, in total and at each outlet (PWR-002). It shall publish its ripple and noise on each rail it provides, peak-to-peak, measured as stated below (SUP-001).

Output connector and protection

An output on a plug-and-socket connector, such as a keyed header, a wire-to-board housing, or a DC plug, shall not mate with reversed polarity (SUP-002). An output on individual ¼ in quick-connect tabs or screw terminals cannot be keyed and is exempt; each such terminal shall be marked with its rail (SUP-003).

Each rail shall survive an indefinite short to 0 V without damage (SUP-004). During power-up, power-down, or a fault, no rail shall swing more than one diode drop toward the opposite polarity (SUP-005). At start-up, no rail shall overshoot its nominal voltage by more than 10 % (SUP-006).

EIS · A supply's rails at power-up -12 V -6 V 0 V +6 V +12 V +13.2 V: 10 % overshoot −13.2 V: 10 % overshoot ±one diode drop toward the opposite polarity +12 V rail −12 V rail time from power-on At start-up no rail overshoots its nominal voltage by more than 10 % (SUP-006). During power-up, power-down, or a fault, no rail swings more than one diode drop toward the opposite polarity (SUP-005). Each rail survives an indefinite short to 0 V (SUP-004). The traces are illustrative.

EIS recommends constant-current or hiccup current limiting rather than foldback: a row is a large capacitive load, and a foldback limiter can fail to start into it. EIS recommends bringing the rails up in an order that avoids reverse stress on modules; SUP-005 bounds the reverse swing whatever the order.

Output quality

EIS requires no particular topology. EIS recommends a setpoint within ±1 % and load regulation within ±1 % from 10 % to 100 % load.

Each rail shall have ripple and noise below the limit of its domain (SUP-007):

Domain Ripple and noise, peak-to-peak
The bus below 150 mV Most open-frame switching supplies meet it.
12 V DC — Not set: the adapter that makes it is outside EIS.
±6 V analog below 20 mV For the analog rails a module regulates locally; a linear source is typically under 5 mV.
±15 V analog below 20 mV For the ±15 V analog rails of op-amp circuits that run at the full rail; a linear source is typically under 5 mV.

A linear or post-regulated supply is typically under 10 mV, which suits a row of MOD-VIDEO modules.

Ripple and noise are measured peak-to-peak on each rail at the supply's output terminals, or at test points the product publishes, with each rail loaded at the maker's stated test current, at 20 MHz oscilloscope bandwidth, with a 0.1 µF ceramic capacitor in parallel with a 47 µF electrolytic across the measurement point and a 300 mm (12 in) twisted pair from there to the probe. This is the method common supply datasheets use, so one maker's figure is comparable with another's.

EIS · Measuring ripple and noise supply one rail +12 V 0 V load 0.1 µF ceramic 47 µF at the output terminals 300 mm (12 in) twisted pair oscilloscope, 20 MHz bandwidth peak-to-peak Each rail is loaded at the maker's stated test current and measured at the supply's output terminals, or at test points the product publishes, with 0.1 µF in parallel with 47 µF across the measurement point and a 300 mm (12 in) twisted pair to a 20 MHz oscilloscope. The supply publishes the peak-to-peak figure for each rail (SUP-001); every rail stays below 150 mV (SUP-007). A linear or post-regulated supply, typically under 10 mV, suits a row of MOD-VIDEO modules.

Power converters

A power converter shall publish the heat it dissipates at its rated output and how far it extends behind the product it is mounted on (SUP-008). It publishes the current it takes at its input as every power entry does (PWR-001): for a linear converter on the bus, the output current plus its own. A module sold with an adapter publishes the currents and the depth of the pair. The PWR-A6 converters are in 6.8.

EIS recommends that a power converter's board fit the outline of a 1U module board (5.2.2): a parallel board no taller than 21.10 mm, with the 1U mounting-hole span of 33.65 mm (PANEL-009) behind a 1U panel, so that the same converter can be mounted as a 1U module in a row that has one, or behind the product it feeds.

6.3 Grounding and 0 V

Where the 0 V reference of a row runs, across its power domains, and how it meets protective earth and the next case. Every patch cable and every coaxial cable joins the 0 V of the two products it connects, so the products in a system share one 0 V whether or not anyone planned it; this clause makes that shared reference predictable.

EIS · Grounding: one 0 V for the bus, the DC rail, and the jacks; one bond to earth supply 0 V terminal one earth bond bus board: every header's 0 V on one 0 V (GND-002) module 0 V module 0 V module dual-source DC adapter floating −V = 0 V Every 0 V pin of a module's header is tied to its 0 V (GND-001). With a DC entry, the DC rail's −V is the product's 0 V (GND-001). A supply publishes where its 0 V meets protective earth (GND-003). Patch sleeves and coax shells join the 0 V of the products they connect. A second earth bond makes a loop: hum on audio, slow bars on a picture.

In a row

A product shall connect every 0 V pin of its power headers and PWR-A6 entries, and the −V of its DC entry, to its 0 V (GND-001). The header's 0 V pins share the return current of all three bus rails, and a module that uses only some of them puts that current through fewer contacts. A module that runs from either of two power entries has one reference for its signals whichever is connected, and a supply that takes PWR-DC12 and delivers the bus keeps both domains on one 0 V. A bus board shall join the 0 V pins of every header to one 0 V that runs to the supply's 0 V terminal (GND-002).

EIS recommends keeping any panel-mounted part whose body touches the panel free of a connection to the module's 0 V; an insulated jack (7.1) meets that.

Protective earth

A power supply shall publish whether its 0 V output is connected to protective earth, and where (GND-003). A built-in supply publishes the same in the enclosure's documentation. Mains safety, including the bonding of a metal case to protective earth, follows the safety standard the supply or case is certified to, not EIS.

EIS recommends one bond between the bus 0 V and protective earth in a system, at the supply, so that the 0 V of a row cannot carry mains-frequency current between two earth points. A DC adapter whose output floats, the usual Class II desktop adapter, adds no second bond.

EIS recommends that chassis ground carry only metalwork and screens and bond to 0 V at one point: at the supply or at the bus board, not independently at both. The bond itself is a ring terminal on bare metal under a toothed lock washer, 14 AWG or a bus bar (PWR-008, 6.1).

The front panels and rails of a case are bonded to each other by the mounting screws. With insulated jacks (7.1), the panel carries no signal return, and bonding the case metal to the supply's earth terminal, where it has one, is a shielding choice rather than a signal path.

Between cases

A patch cable or a VID-75 cable between two cases joins their 0 V through its sleeve or shell (V75-002). EIS recommends that the cases of one system take their 0 V from supplies that are all bonded to protective earth at the same outlet strip, or all floating, and that a system spread over several cases join their 0 V with one short, heavy conductor rather than through signal cables alone. A loop through two earth bonds shows as hum on audio and as slow-moving horizontal bars on a picture.

Annex O covers the heat a row's current becomes; the currents published under 6.1 are the same figures.

6.4 The bus

The bus is the power domain every Eurorack row has: +12 V and −12 V, and optionally +5 V, made by a power supply, carried by bus boards and power ribbons, and taken by each module at its power header. This clause defines the rails, the power header, its pinout, marking, and keying once, and what a module owes at its header; 6.5 adds the bus board and the ribbon, and 6.6 the CV and gate lines.

EIS · From the supply to the module: what each part owes power supply +12 V −12 V +5 V tabs or a keyed connector bus board power ribbon module draws from the bus Power supply Publishes each rail's rating (PWR-002) and its ripple and noise (SUP-001), below 150 mV (SUP-007). Survives a short (SUP-004); no reverse swing (SUP-005); overshoot ≤ 10 % (SUP-006). Keyed connector (SUP-002), or terminals marked with their rail (SUP-003). Bus board +12 V and −12 V, and optionally +5 V, at every header (BUS-001). Publishes its rail totals and the limit per header (PWR-002), at most 2 A per rail (BUS-012). A link joins CV to CV and gate to gate (BUS-014). Ribbon At most 400 mm, at least 28 AWG (BUS-015). Marked conductor on −12 V (BUS-004); keyed (BUS-005). Module Draws only ±12 V, and +5 V if it needs it (BUS-006). Publishes its maximum current on each rail (PWR-001). At most 2 A per rail through one header (BUS-008); never feeds a rail (PWR-004). Survives a reversed ribbon (BUS-009). The installer adds a module only while each rail's sum fits the bus board and the supply (ASM-001).

Rails

The bus shall provide +12 V and −12 V, and may provide +5 V, at every power header (BUS-001).

Header and pinout

A power header on a module or a bus board shall be a 2 × 5 or 2 × 8 pin header on a 2.54 mm grid, and a power cable shall end in IDC ribbon sockets that mate it (BUS-002). It shall follow this pinout (BUS-003):

Pins 10-pin header 16-pin header
1, 2 −12 V −12 V
3 to 8 0 V 0 V
9, 10 +12 V +12 V
11, 12 — +5 V
13, 14 — CV
15, 16 — Gate

Some community tables give a different order, with +12 V on pins 7 and 8 and +5 V on pins 15 and 16. A cable or bus board made to such a table puts +12 V on a module's 0 V pins.

On a 16-pin header, pins 13 and 14 carry one CV line and pins 15 and 16 one gate line. Using them is optional; their levels and the rules for a module on them are in 6.6.

Marking and keying

On a module, a bus board, and a power ribbon cable, the marked conductor shall be −12 V and shall point to the −12 V end of the header (BUS-004). A module and a bus board shall mark the −12 V end of each power header on the board (BUS-019), so that an unshrouded header can be oriented by eye at both ends.

A shrouded power header on a module or a bus board shall be keyed so that, viewed from the mating side with the −12 V end at the bottom, the key gap is on the right, and a keyed cable socket shall match it (BUS-005). The figure below is the reference view: pins 1 and 2 at the bottom, the gap centered in the right-hand wall; a drawing of a header shows the same view. Shrouded headers in the field are keyed both ways, so a keyed cable from a conforming product enters a conforming bus board and may not enter another.

EIS · Power header, 16-pin, from the mating side key gap on the right −12 V 1–2 0 V 3–4 0 V 5–6 0 V 7–8 +12 V 9–10 +5 V 11–12 CV 13–14 Gate 15–16 odd even 10-pin header marked conductor = −12 V (BUS-004) Viewed looking into the pins with the −12 V end at the bottom: the shroud key gap is on the right (BUS-005). Pinout: BUS-003.

EIS · The marked conductor and the shroud key Socket the right way round Socket reversed Gate CV +5 V +12 V 0 V 0 V 0 V −12 V the tab enters the gap Gate CV +5 V +12 V 0 V 0 V 0 V −12 V the tab meets the wall marked conductor on −12 V marked conductor on gate Seen from the mating side with the −12 V end at the bottom, the shroud's key gap is on the right (BUS-005). On a module, a bus board, and a ribbon, the marked conductor is −12 V and points to the −12 V end of the header (BUS-004). A cable that comes with a module is keyed, so it enters a shrouded header only the right way round (BUS-010). An unshrouded header cannot stop a reversed socket, so every module also survives one (BUS-009).

Any voltage on these pins other than the pinout and a reversed ribbon is outside EIS.

A module on the bus

A module powered from the bus shall draw only +12 V and −12 V, and may also draw +5 V (BUS-006). A module that uses neither +5 V nor bus CV or gate may use the 10-pin header (BUS-007). It publishes its current on each rail as every power entry does (PWR-001).

A module shall not draw more than 2 A on any rail through one power header (BUS-008): an IDC contact is rated about 1 A, and each rail has two. A module that needs more uses a second header or a DC entry.

EIS · Module power entry: what a module may draw, and through which header 1 −12 V 2 −12 V 3 0 V 4 0 V 5 0 V 6 0 V 7 0 V 8 0 V 9 +12 V 10 +12 V 10-pin no +5 V, CV, or gate 1 −12 V 2 −12 V 3 0 V 4 0 V 5 0 V 6 0 V 7 0 V 8 0 V 9 +12 V 10 +12 V 11 +5 V 12 +5 V 13 CV 14 CV 15 gate 16 gate 16-pin the full bus pin 1 at the marked conductor Draws only +12 V and −12 V, and may draw +5 V (BUS-006). The 10-pin header is enough when the module uses neither +5 V nor bus CV or gate (BUS-007). At most 2 A on any rail through one header: two IDC contacts of about 1 A each (BUS-008). A module that needs more takes a second header or a DC entry. Never sources current into a bus rail (PWR-004). Survives a reversed ribbon (BUS-009); its every 0 V pin is tied to its 0 V (GND-001). Another header on the module does not mate a power ribbon, or survives one (BUS-011).

A module shall tolerate reverse polarity at its power header without damage (BUS-009): a ribbon fitted backwards is the commonest field fault. A bus cable supplied with a module shall be keyed so that it enters a shrouded header only with the marked conductor on −12 V (BUS-010). On a bus board whose shroud is keyed the other way, outside EIS, the installer fits an unkeyed cable with the marked conductor on −12 V.

Other headers

A header on a module that is not its power header shall either not mate a Eurorack power ribbon socket or tolerate one fitted to it, either way round, without damage (BUS-011). A 2 × 7 header mates a 2 × 5 socket as readily as a 2 × 5 header does, so a module that takes its video sync on a rear ribbon header is one this rule reaches. Expander and link headers are often 2 × 5 or 2 × 8 pin headers on the same grid, and a power ribbon fitted to one puts ±12 V on its signal pins. A shrouded header keyed differently, a different pin count, or a different connector family meets this; Annex N covers expanders and links.

EIS · An expander header beside the power header power header, 2 × 5 expander, 2 × 5, same key a power ribbon fits expander, 2 × 4 a power ribbon does not fit expander, 2 × 6, unshrouded fits only if it survives ±12 V A header that is not the power header either does not mate a power ribbon socket or survives one fitted to it, either way round (BUS-011). A different pin count, a different key, or another connector family meets the first; protection on every pin meets the second. Annex N lists expanders and digital links on the port list as unclassified, named by what they connect to.

Wiring

EIS recommends blue for −12 V, black for 0 V, and red for +12 V in the distribution wiring of bus boards and supplies, and names no color for +5 V. Chassis ground is in 6.3.

6.5 Bus boards

The board in a row that carries power from the supply to every module. An enclosure row has one or more, behind the panels. Every header on a bus board is an outlet of the bus (6.4): the rails, the header form, the pinout, the marked conductor on −12 V, and the shroud key.

Capacity

A bus board publishes its maximum current on each rail, in total and at each header (PWR-002). The per-header limit it publishes shall not exceed 2 A per rail (BUS-012), the module limit of BUS-008.

EIS · Bus boards: published totals, the per-header limit, regions, and links region A region B CV and gate split here (BUS-013) linked board link module ≤ 400 mm, ≥ 28 AWG (BUS-015) Publishes its maximum current on +12 V, −12 V, and +5 V, in total and per header (PWR-002), never more than 2 A per rail (BUS-012). A link joins CV to CV and gate to gate (BUS-014); every header's 0 V runs to the supply's 0 V (GND-002).

A bus board may split CV and gate into two regions (BUS-013). A link between two bus boards shall join CV to CV and gate to gate (BUS-014). How many modules may transmit on a line is a rule for assembling a system.

The supply-to-bus-board and bus-board-to-bus-board connections are row wiring (6.1): the board's terminals are quick-connect tabs, ring-terminal studs, or a wire-clamp block, published with the conductor sizes they take (PWR-005), and EIS recommends the 6.3 mm quick-connect tab for them.

Distribution on a bus board

A bus board may also distribute a DC rail, the ±6 V analog rails, or the video reference behind the panel, or be the case's CTRL-USB-HOST; it then claims the matching feature, PWR-DC12, PWR-A6, the VID-REF ports, or CTRL-USB-HOST, beside PWR-BUS and meets its requirements (BUS-020). Its PWR-DC12 outlets are those of 6.7, each protected (DC-009, DC-012); its PWR-A6 outlets are A6-VH3 outlets fed from a PWR-A6 supply or a converter on the board (6.8); as a video reference distributor it takes the reference at a VID-REF-IN and gives each module a buffered copy at a VID-REF-PASSTHRU (7.4); as a case host it has the downstream ports and limits of 8.1. The claim line names each feature, bus board (PWR-BUS-OUT, VID-REF-IN, VID-REF-PASSTHRU) or bus board (PWR-BUS-OUT, CTRL-USB-HOST) (4.2). A board that carries no bus at all, only a DC rail or the reference tree, is still a bus board: it claims the features it carries and not PWR-BUS. The board's one 0 V is shared by every domain on it (6.3).

Power ribbon cables

A power ribbon from a bus header to a module shall be no longer than 400 mm and shall use conductors of at least 28 AWG (BUS-015), the conductor of standard 1.27 mm pitch ribbon: the voltage drop of a longer or thinner ribbon at the header limit eats into the module's rails. At 28 AWG (0.21 Ω/m) a 400 mm ribbon drops about 85 mV on a rail carrying 2 A over its two conductors, and a third of that on the 0 V return over its six. A power ribbon cable sold on its own meets the marking and keying of 6.4 (BUS-004, BUS-005). The figures are in data/power_ribbon.json.

6.6 Bus CV and gate

The CV and gate lines of the 16-pin power header (6.4): when a module may use them, and their levels. Both follow A-100 practice.

The bus CV line carries 1 V/octave pitch CV from one transmitter, such as a MIDI interface or a keyboard controller, to the oscillators that listen to it. BUS-CV is therefore pitch CV, with the scale of MOD-CV-1VOCT, not general control CV: a module that put an LFO or an envelope on it would detune every listening oscillator. The bus gate line carries a 0 / +5 V gate; BUS-GATE keeps the MOD-GATE receiver thresholds, high at +3 V or more and low at +1 V or less.

A module shall listen to or transmit bus CV or gate only when a jumper or switch on the module is set to do so (BUS-016). A module that drives or receives bus CV shall meet the BUS-CV limits below (BUS-017), and one that drives or receives bus gate shall meet the BUS-GATE limits (BUS-018). At most one module transmits on each line, across linked bus boards (ASM-002). The patch classes are in 7.2.

EIS · Bus CV and gate: one transmitter, many listeners CV gate CV gate bus board second bus board link MIDI interface jumper on transmits VCO jumper on listens VCO jumper on listens VCO jumper off ignores VCO jumper on listens At most one module transmits on each CV line and one on each gate line, across linked bus boards (ASM-002); a link joins CV to CV and gate to gate (BUS-014), so linked boards share one transmitter. A module listens or transmits only when its jumper or switch says so (BUS-016). Bus CV is 1 V/octave pitch CV (BUS-017); bus gate is 0 / +5 V, high at +3 V or more (BUS-018).

Class table

Class Connector Coupling Nominal Class ceiling Source Z Load Z
BUS-CV 16-pin Eurorack bus (CV net) DC 1.00 V/octave pitch CV (bus CV) ±12 V 1 kΩ 100 kΩ
BUS-GATE 16-pin Eurorack bus (Gate net) DC 0 / +5 V gate (bus gate); high ≥ +3 V, low ≤ +1 V at the receiver ±12 V 1 kΩ 100 kΩ

6.7 12 V DC power (PWR-DC12)

PWR-DC12 is the power domain of nominal 12 V DC, and an optional feature for the products in it: a module with a rear DC entry, a DC entry panel or a bus board with PWR-DC12 outlets that feeds several modules from one entry, a case DC entry on an enclosure, a power supply that takes 12 V DC and delivers the bus, and the cables between them. The 12 V DC comes from an external adapter, the domain's source, enters at a DC entry, and feeds a DC rail, one +V and −V pair that each product filters or regulates locally (Terms). The DC rail is separate from the bus (6.4); the rules common to both domains are in 6.1 to 6.3.

Filtering, output connectors, ripple at PWR-DC12 outlets, and the adapter a product ships with are product documentation, not EIS. The connection rules for the person fitting it are in 9.3. The tables are in data/dc_12.json.

DC entries

A product shall publish its DC entry variant: DC-BAR21, DC-BAR25, DC-VH2, DC-DIN4, DC-MF6, or DC-MF8 (DC-001), and the minimum and maximum DC input voltage its DC entry accepts (DC-002). Two kinds of DC entry share the domain. A module DC entry, DC-BAR21 or DC-VH2, takes the rail for one module from a PWR-DC12 outlet. A case DC entry, DC-BAR25, DC-DIN4, DC-MF6, or DC-MF8, takes a brick's output for a row: it sits on an enclosure, which then claims PWR-DC12-IN, or on a DC entry panel, a module that claims PWR-DC12-IN and feeds the supply, the bus board, or its own PWR-DC12 outlets, for which it claims PWR-DC12-OUT too. The wires from a case DC entry to what it feeds are row wiring (6.1). A DC entry shall be marked beside it with its polarity symbol, its nominal voltage, and its maximum current (DC-011), as the trade marks every DC inlet. The current it takes at its DC entry, or delivers at each distribution output, is published at 12 V like every domain's (PWR-001, PWR-002). A DC entry shall not use the pinout of a Eurorack 10-pin or 16-pin power header (DC-003).

A barrel DC entry, DC-BAR21 or DC-BAR25, shall be center positive (DC-004).

Variant Pin × barrel (mm) Typical continuous (A) Notes
DC-BAR21 2.1 × 5.5 2.5 Also a PWR-DC12 outlet to a module (DC-009).
DC-BAR25 2.5 × 5.5 5 Higher current, from an adapter; never an output to a module (DC-009). A DC-BAR25 plug enters a DC-BAR21 DC entry but makes unreliable contact (ASM-004).

DC-VH2 is a 2-pin JST VH wire-to-board header, rated 10 A, that takes power from a PWR-DC12 outlet. Above 5 A, EIS recommends DC-VH2, DC-DIN4, DC-MF6, or DC-MF8 rather than a barrel: a through-hole 2.1 mm jack is rated about 2.5 A and a 2.5 mm jack about 5 A, and the product publishes its own figure (PWR-001). A product with a DC-VH2, DC-DIN4, DC-MF6, or DC-MF8 DC entry shall implement the pin functions tabulated for that variant (DC-005). The receptacle and plug named are reference parts; an interchangeable part rated for the published current may be used.

Variant Receptacle (reference) Mating plug (reference) Rated continuous (A) Rating basis
DC-VH2 JST B2P-VH or B2PS-VH JST VHR-2N 10 1 contact per pole × 10 A (JST VH)
DC-DIN4 Kycon KPJX-4S-S Kycon KPPX-4P 15 2 contacts per pole × 7.5 A (Kycon KPJX-4S-S)
DC-MF6 Molex 39-30-1060 Molex 39-01-2060 24 3 circuits per pole × 8 A at 18 AWG (Molex PS-5556-001, 4 to 6 circuits)
DC-MF8 Molex 39-30-1080 Molex 39-01-2080 28 4 circuits per pole × 7 A at 18 AWG (Molex PS-5556-001, 7 to 10 circuits)

DC-VH2 pins

Pin Function
1 +V
2 −V

DC-DIN4 pins

Pin Function
1 +V
2 −V
3 −V
4 +V
5 shell (optional)

DC-MF6 pins

Pin Function
1 +V
2 +V
3 +V
4 −V
5 −V
6 −V

DC-MF8 pins

Pin Function
1 +V
2 +V
3 +V
4 +V
5 −V
6 −V
7 −V
8 −V

EIS · PWR-DC12 power entry: barrel polarity and multi-pin pin functions + − center positive DC-004 DC-BAR21 2.1 × 5.5 mm about 2.5 A DC-BAR25 2.5 × 5.5 mm about 5 A Pin × barrel. A DC-BAR25 plug fits a DC-BAR21 DC entry loosely and is never inserted (ASM-004). Multi-pin variants and their pin functions DC-VH2 10 A pin 1 +V pin 2 −V DC-DIN4 15 A pin 1 +V pin 2 −V pin 3 −V pin 4 +V pin 5 shell DC-MF6 24 A pin 1 +V pin 2 +V pin 3 +V pin 4 −V pin 5 −V pin 6 −V DC-MF8 28 A pin 1 +V pin 2 +V pin 3 +V pin 4 +V pin 5 −V pin 6 −V pin 7 −V pin 8 −V A product with a multi-pin variant implements these pin functions (DC-005); its cables connect each pin to the same pin (DC-008). Modules take power from a PWR-DC12 outlet on DC-BAR21 or DC-VH2, never DC-BAR25 (DC-009).

Modules with a DC entry

A module may have both a power header and a DC entry. Such a module does not require both sources to be connected at the same time (PWR-003), and the installer connects only one (ASM-003). When the DC entry carries the load, the module's published bus currents (PWR-001) state what it draws from the bus, which may be nothing. It does not feed its DC rail back onto the bus (PWR-004), and the DC rail's −V is its 0 V (GND-001).

A module's barrel DC entry shall tolerate reverse polarity without damage (DC-006).

Cables

A straight DC barrel cable shall connect tip to tip and sleeve to sleeve at both ends (DC-007). A cable for a DC-VH2, DC-DIN4, DC-MF6, or DC-MF8 DC entry shall connect each pin to the same pin and function at both ends (DC-008).

Distribution to modules

A product with PWR-DC12 outlets to modules, a bus board, a DC entry panel, or a power supply (SUP-009), shall feed them only through DC-BAR21 jacks or DC-VH2 headers, never DC-BAR25 (DC-009). It shall protect each output separately and shall publish the current at which the protection acts (DC-012), so that one shorted cable takes down one module and not the rail, and its own DC entry shall tolerate reverse polarity without damage (DC-013). A cable from a DC distribution output to a module shall end in DC-BAR21 plugs or DC-VH2 housings and connect +V to +V and −V to −V, tip and pin 1 being +V (DC-010). A DC-BAR25 DC entry takes power from an adapter, not from a distribution product.

EIS · PWR-DC12 distribution: from the adapter to the modules adapter 12 V DC PWR-DC12 outlets bus board or entry panel DC-DIN4 or DC-BAR25 DC-VH2 module DC entry DC-VH2 module DC entry DC-BAR21 module DC entry DC-BAR25 never pin 1 = +V tip = +V A product with PWR-DC12 outlets feeds modules only through DC-BAR21 jacks or DC-VH2 headers, never DC-BAR25 (DC-009); its cables keep +V to +V (DC-010). DC-BAR25 takes power from an adapter. A DC-BAR25 plug fits a DC-BAR21 entry loosely and is never inserted (ASM-004).

6.8 ±6 V analog power (PWR-A6)

PWR-A6 is the power domain of ±6 V for analog circuits, and an optional feature for the products in it: a module with an PWR-A6 entry, a power supply that makes ±6 V for a row, a power converter that makes it for one product from the bus or from PWR-DC12, and the cables between them. A module on PWR-A6 finishes its own regulation, typically ±5 V from a low-dropout regulator per circuit block, so that the drop and pickup of the cable land on the module's regulator headroom and not on its signals. PWR-A6 is separate from the bus (6.4) and from PWR-DC12 (6.7); the rules common to every domain are in 6.1 to 6.3, and the ripple limit of PWR-A6 is in the table of 6.2. The figures are in data/analog_6.json.

EIS · PWR-A6: the A6-VH3 entry and the voltage window polarizing rib 1 +6 V 2 0 V 3 −6 V A6-VH3 from the mating side, 3.96 mm pitch 10 A per circuit; 1 A per rail at an entry 5.0 V 5.5 V 6.0 V 6.5 V outlet 5.75–6.25 module entry 5.55–6.25 cable ≤ 0.2 V withstood 6.6 V a module's ±5 V LDO One connector for PWR-A6 only (A6-001). An outlet holds its window to its rating (A6-002); a module works across the entry window (A6-003), survives 6.6 V (A6-004), and draws at most 1 A per rail (A6-005).

Connector and pins

A PWR-A6 entry or outlet shall be an A6-VH3 connector, a JST VH 3-circuit header on a 3.96 mm pitch with its polarized housing, with the pin functions tabulated below (A6-001). No other EIS domain uses a 3-circuit VH; a DC-VH2 housing fits two of its pins, which is why the ±6 V mark beside the connector matters (A6-007) and why an entry withstands 6.6 V and no more (A6-004). A PWR-A6 entry or outlet shall be marked ±6 V beside it (A6-007). The header and housing named are reference parts; an interchangeable part rated for the published current may be used.

Variant Header (reference) Mating housing (reference) Rated per circuit (A)
A6-VH3 JST B3P-VH (straight) or B3PS-VH (right angle) 3-circuit header JST VHR-3N housing with SVH-21T-P1.1 crimp terminals 10

A6-VH3 pins

Pin Function
1 +6 V
2 0 V
3 −6 V

Voltage window

A PWR-A6 outlet shall hold each rail between 5.75 V and 6.25 V in magnitude, from no load to its published rating (A6-002). A module shall meet its published behavior with each rail anywhere from 5.55 V to 6.25 V in magnitude at its entry (A6-003); the 0.2 V between the two windows is the allowance for the cable and the connectors at the entry limit. A PWR-A6 entry shall withstand 6.6 V in magnitude on either rail without damage (A6-004), the start-up overshoot that SUP-006 allows a source.

Figure Value
Nominal ±6 V
At an outlet, no load to rating 5.75 V to 6.25 V
At an entry, where the module meets its behavior 5.55 V to 6.25 V
Withstood at an entry 6.6 V
Ripple and noise at an outlet below 20 mV p-p
Per rail through one entry 1 A
Cable at most 500 mm, at least 22 AWG

EIS recommends that a source clamp its outlet so that a failed pass element cannot put its input voltage on a module, and that a module's entry carry a resettable fuse and a clamp per rail.

Modules

A module shall not draw more than 1 A on either rail through one PWR-A6 entry (A6-005). It publishes its current on each rail as every power entry does (PWR-001). A module that takes its analog rails from PWR-A6 and its logic supply from the bus needs both connected; its entries are not alternatives, and its claim file says so.

Cables

A PWR-A6 cable shall connect each pin to the same pin at both ends, be no longer than 500 mm, and use conductors of at least 22 AWG (A6-006). A power converter mounted on the back of the module it powers connects to the module's entry by such a cable; EIS defines no board-to-board mate.

Sources

A power supply that makes PWR-A6 for a row publishes the current of each outlet and its total (PWR-002), and meets the rules of 6.2 at every outlet. A power converter makes PWR-A6 for one product: from the bus, by stepping each rail down, or from PWR-DC12, which needs an isolated or inverting converter for the negative rail. A linear converter on the bus draws the module's full current from the bus and turns the difference into heat; its published bus current and heat (PWR-001, SUP-008) are what the installer budgets.

EIS recommends a linear or post-regulated source for PWR-A6, typically under 5 mV of ripple and noise.

6.9 ±15 V analog power (PWR-A15)

PWR-A15 is the power domain of ±15 V for analog circuits that run at the full rail, and an optional feature for the products in it: a module with a PWR-A15 entry, a power supply that makes ±15 V for a row, a power converter that makes it for one product from PWR-DC12 or from the bus, and the cables between them. Where PWR-A6 feeds a module that finishes its own regulation to ±5 V, PWR-A15 feeds op-amp circuits directly: the ±10 V signal swing of an analog computing or display amplifier, the headroom a video output stage needs, and the ±15 V parts of the broadcast trade. The connector and pin map are those of the LZX Deflect series, whose every powered module takes ±15 V this way. The tables are in data/analog_15.json.

EIS · PWR-A15: the A15-MF4 entry and the voltage window latch 1 0 V 2 0 V 3 −15 V 4 +15 V A15-MF4 from the mating side, 4.20 mm pitch 9 A per circuit; 2 A per rail at an entry 13 V 14 V 15 V 16 V 17 V outlet 14.4–15.6 module entry 14.0–15.6 cable ≤ 0.4 V withstood 16.5 V One connector for PWR-A15 only (A15-001); the Deflect series' entry. An outlet holds its window to its rating (A15-002); a module works across the entry window (A15-003), survives 16.5 V (A15-004), and draws at most 2 A per rail (A15-005).

Connector and pins

A PWR-A15 entry or outlet shall be an A15-MF4 connector, a Molex Mini-Fit Jr 4-circuit header, two rows of two on a 4.20 mm pitch, with its latched polarized housing, with the pin functions tabulated below (A15-001). No other EIS domain uses a 4-circuit Mini-Fit Jr; the case DC entries DC-MF6 and DC-MF8 are the same family with six and eight circuits and do not mate it, which is why the ±15 V mark beside the connector matters (A15-007) and why an entry withstands 16.5 V and no more (A15-004). Pins 1 and 2 are both 0 V so that the return carries the same current as either rail; pin 3 is −15 V and pin 4 is +15 V.

Variant Header (reference) Mating housing (reference) Rated per circuit (A)
A15-MF4 Molex 39-30-1040 (vertical) or 39-30-1041 (right angle) 4-circuit header, 5569 series Molex 39-01-2040 receptacle housing with 5556 crimp terminals 9

A15-MF4 pins

Pin Function
1 0 V
2 0 V
3 −15 V
4 +15 V

Voltage window

A PWR-A15 outlet shall hold each rail between 14.4 V and 15.6 V in magnitude, from no load to its published rating (A15-002). A module shall meet its published behavior with each rail anywhere from 14.0 V to 15.6 V in magnitude at its entry (A15-003); the 0.4 V between the two windows is the allowance for the cable and the connectors at the entry limit. A PWR-A15 entry shall withstand 16.5 V in magnitude on either rail without damage (A15-004): a source that overshoots on start-up, or a supply set a volt high, does not take a module with it.

Figure Value
Nominal ±15 V
At an outlet, no load to rating 14.40 V to 15.60 V
At an entry, where the module meets its behavior 14.00 V to 15.60 V
Withstood at an entry 16.5 V
Ripple and noise at an outlet below 20 mV p-p
Per rail through one entry 2 A
Cable at most 500 mm, at least 20 AWG

EIS recommends that a source clamp its outlet so that a failed pass element cannot put its input voltage on a module, and that a module's entry carry a resettable fuse and a reverse-polarity element per rail.

Modules

A module shall not draw more than 2 A on either rail through one PWR-A15 entry (A15-005). It publishes its current on each rail as every power entry does (PWR-001). A module on PWR-A15 alone has no bus header and claims no PWR-BUS; one that also takes the bus for its logic needs both connected, and its claim file says so.

Cables

A PWR-A15 cable shall connect each pin to the same pin at both ends, be no longer than 500 mm, and use conductors of at least 20 AWG (A15-006). The Mini-Fit Jr housing latches; a cable is pulled by its latch, never by the wire.

Sources

A power supply that makes PWR-A15 for a row publishes the current of each outlet and its total (PWR-002), and meets the rules of 6.2 at every outlet. A power converter makes PWR-A15 for one product from PWR-DC12 by an isolated or boost converter, or from the bus by stepping each rail up; a linear source needs an input above the window, so a converter from the bus is a switching stage followed by a linear post-regulator.

EIS recommends a linear or post-regulated source for PWR-A15, typically under 5 mV of ripple and noise.