7.2 Patch signal classes

The signal classes a patch jack may claim, and the ranges a class may take. Every patch jack also follows the patch-safety rules of 7.1: its input withstands ±12 V and its output never exceeds it.

All classes but MOD-VIDEO share one interface: a source impedance of 1 kΩ typical and at most 2 kΩ, into loads of 100 kΩ typical and at least 47 kΩ; a 2 kΩ source into a 47 kΩ load loses 4 %, which is the most a conforming pair loses. Each class has a nominal level, what an output puts on the port, a full scale, the swing its range allows, a class ceiling, and a damage limit (Terms); the gate, trigger, and clock classes have thresholds as well, what an input reads. In the class table a cell marked typical is a guide and every other figure is a limit that SIG-005 to SIG-013 bind. The levels are EIS figures; the gate thresholds follow A-100 practice (Scope 1.4).

Audio

MOD-AUDIO (SIG-005) is Eurorack audio: nominally ±5 V on the patch tip, with a full scale of ±10 V peak at the default range B10, 7.07 V RMS for a full-scale sine. Coupling may be AC or DC; an AC-coupled input passes 20 Hz within 1 dB, and a DC-coupled output states its offset.

Control CV

MOD-CV (SIG-006) is control voltage: envelopes, LFOs, offsets, and any other control that is not calibrated for pitch. Its level is the range the port claims, bipolar or unipolar at 1, 5, or 10 V full scale; B5, −5 to +5 V, when the port list names none, since that is what most control inputs and outputs are built for, and a port built for ±10 V claims B10. A control port with a stated scaling that is not 1 V/octave, such as Hz/V, is MOD-CV and names the scaling in its port list.

Pitch CV

MOD-CV-1VOCT (SIG-007) is precision pitch CV: 1.00 V per octave within ±0.3 % of scale, 3.6 cents per octave, over the span the port's range names; B10 when the port list names none, U10 for a 0 to +10 V sequencer or MIDI-to-CV output, B5 or U5 for a narrower span. EIS recommends that 0 V correspond to C0 (16.35 Hz, MIDI note 12), that the tracking error of a pitch output be published in the manual, and that pitch ports be labeled 1 V/oct so that they are not mistaken for video ports; every oscillator has a tune control, so the absolute pitch at 0 V is a calibration figure, not a requirement.

Video

MOD-VIDEO (SIG-008) carries video on patch jacks, pictures, ramps, keys, and control at video rate, 0 to +1 V DC with the U1 ceiling of −0.1 to +1.2 V. A MOD-VIDEO input shall present 100 kΩ ±10 % to 0 V at the patch tip (SIG-009). A MOD-VIDEO output shall drive through a 75 Ω ±5 % total series source impedance at the patch tip (SIG-010). A 75 Ω source into a 100 kΩ load arrives at almost unity gain; the cable's capacitance and the input's set the bandwidth: the cable alone gives about 70 MHz over 300 mm of 100 pF/m patch cable and about 20 MHz over a metre, and an input of 20 pF takes the 300 mm figure down to about 42 MHz, so EIS recommends an input capacitance of 30 pF or less.

Video on a 75 Ω RCA, BNC, or SMA jack is not a patch jack: a rear video reference port is a VID-REF port of 7.4, and a front picture jack is an Annex I port (VID-CVBS, VID-YPBPR, VID-RGBS). A module's video reference is a rear coaxial port, never a patch jack (SIG-015, V75-010); the formats a VID-REF-IN or VID-REF-OUT port lists are in 7.3.

Black, bandwidth, and delay

EIS recommends that a picture signal on MOD-VIDEO place black at 0 V and full scale (white, or a color channel at full saturation) at +1 V, so that a mixer or keyer can treat any two picture sources alike.

Two figures decide whether video patched through several modules stays sharp and stays in place on the screen. A module shall publish, for each MOD-VIDEO path from an input jack to an output jack, its −3 dB bandwidth into 100 kΩ in parallel with 30 pF (SIG-016), as the claim-file field bandwidth_mhz on the output; EIS recommends that it publish the delay too (delay_ns):

A path may claim a bandwidth tier beside its figure, the highest whose minimum it meets, so that a port list says at a glance what the path carries: BW6, at least 6 MHz, carries the standard-definition formats, and BW30, at least 30 MHz, carries every listed format. The tiers are named by their figure, not by a timing format, since a format is what a reference port lists and a bandwidth is what a path does. A path below BW6, such as a filter, claims no tier and publishes its figure; a wider tier is not named because a patch cable of ordinary length does not carry it. A module with no MOD-VIDEO input, such as a ramp or shape generator, has no path to publish; EIS recommends that it publish the bandwidth of each MOD-VIDEO output into the same load all the same.

Tier −3 dB bandwidth Carries
BW6 at least 6 MHz pictures with 5.5 MHz of luma bandwidth, the standard-definition formats
BW30 at least 30 MHz pictures with 30 MHz of luma bandwidth, every listed format

EIS · A MOD-VIDEO path: bandwidth and delay 1 MHz 10 MHz 100 MHz 0 -3 -6 -9 −3 dB at 45 MHz SD luma HD luma bandwidth: input jack to output jack, into 100 kΩ delay path A: 12 ns path B: 27 ns 15 ns Two copies of one picture through paths 15 ns apart land about one HD sample apart on the screen (13.5 ns at 74.25 MHz). EIS recommends publishing both figures for each MOD-VIDEO path in the claim file, and placing black at 0 V and full scale at +1 V.

Gate, trigger, and clock

MOD-GATE (SIG-011), MOD-TRIG (SIG-012), and MOD-CLK (SIG-013) share one contract. An output drives high at +4 V to +12 V into 100 kΩ and low at +0.5 V or less; an input reads +3 V or more as high and +1 V or less as low, and EIS recommends at least 0.5 V of hysteresis between the two. MOD-GATE is a sustained high or low level; a run, reset, or start signal is a MOD-GATE. MOD-TRIG is a pulse at least 1 ms high (5 ms recommended), and a MOD-TRIG input catches a 1 ms pulse. MOD-CLK is a repeating wave, high and low each at least 1 ms, at any duty; the product states the rate it accepts or produces and, for a tempo clock, the pulses per quarter note. The gate line on the 16-pin header is BUS-GATE (6.6).

Timing pulses on patch jacks

A video module's horizontal, vertical, field, burst-gate, or composite video sync pulses on patch jacks are patched signals like any other: a 0 / +5 V pulse train is MOD-GATE (a field or frame pulse) or MOD-CLK (a line-rate pulse), and a 0 to +1 V composite video sync waveform is MOD-VIDEO. A module may reset a ramp, key, or trigger from such a pulse. What SIG-015 keeps off the patch field is the video reference: the signal a module's own raster timing, the formats of 7.3, locks to. A module that derives its line and field timing from a patch jack locks to a patched signal and does not meet SIG-015; it lists that jack by its class and claims no VID-REF port for it.

EIS · Gate, trigger, and clock against the receiver thresholds 0 V +1 V +3 V +5 V high: +3 V or more neither low: +1 V or less MOD-GATE held high for as long as it lasts MOD-TRIG ≥ 1 ms high MOD-CLK a repeating square wave MOD-GATE (SIG-011), MOD-TRIG (SIG-012), and MOD-CLK (SIG-013) share the receiver thresholds, which follow A-100 practice: an input reads +3 V or more as high and +1 V or less as low. The bus gate line, BUS-GATE, keeps the same thresholds.

Ranges

A range is the full-scale swing a port is built for, named on the port list beside the class. A port claiming a range shall meet that range's limits as tabulated below: an output keeps its full-scale signal within the range's ceiling, and an input accepts the range's full swing without clipping (SIG-014).

EIS recommends that an output claim the smallest range that contains its full-scale signal, and an input the largest range whose full swing it accepts; an input accepts a swing when its gain at full scale is within 0.5 dB of its small-signal gain. A port that names no range has its class's default. A unipolar ceiling allows 20 % above full scale and 10 % below 0 V; a bipolar ceiling 20 % beyond full scale either way. Ranges do not relax patch safety. EIS recommends printing a range other than the default on the panel next to the jack.

Range Polarity Full scale Swing Ceiling
B1 bipolar 1 V −1 to +1 V ±1.2 V
U1 unipolar 1 V 0 to +1 V −0.1 to +1.2 V
B5 bipolar 5 V −5 to +5 V ±6 V
U5 unipolar 5 V 0 to +5 V −0.5 to +6 V
B10 bipolar 10 V −10 to +10 V ±12 V
U10 unipolar 10 V 0 to +10 V −1 to +12 V

EIS · The six ranges, on the ±12 V patch axis -12 -10 -8 -6 -4 -2 0 +2 +4 +6 +8 +10 +12 volts at the patch tip ±12 V: the damage limit of every patch input Classes that take it B1 bipolar MOD-AUDIO, MOD-CV U1 unipolar MOD-CV, MOD-VIDEO (default) B5 bipolar MOD-AUDIO, MOD-CV (default), MOD-CV-1VOCT U5 unipolar MOD-CV, MOD-CV-1VOCT B10 bipolar MOD-AUDIO (default), MOD-CV, MOD-CV-1VOCT (default) U10 unipolar MOD-CV, MOD-CV-1VOCT the full-scale swing a port is built for the ceiling an output stays within A port claiming a range meets its limits (SIG-014): an output keeps its full-scale signal within the ceiling, and an input accepts the full swing without clipping. Every input still withstands ±12 V.

The last column of the class table says which ranges each class takes, and a class with ranges has the claimed range's ceiling as its class ceiling. MOD-AUDIO at B5 or B1 is a quieter audio port. MOD-VIDEO takes U1 alone. A range on MOD-CV-1VOCT states the span of pitch CV a port accepts or produces; the scale stays 1.00 V per octave. Gate, trigger, and clock ports have thresholds, not ranges. For example, an envelope from 0 to +8 V is MOD-CV at U10, and an LFO at ±2.5 V is MOD-CV at B5.

Class table

Class Coupling Nominal Thresholds Full scale Class ceiling Source Z Load Z Ranges
MOD-AUDIO AC or DC ±5 V (10 V peak-to-peak) typical; full scale by range, ±10 V at B10 — ±10 V peak (B10) By range; ±12 V at B10 1 kΩ typical; ≤ 2 kΩ 100 kΩ typical; ≥ 47 kΩ B10 default; B5, B1
MOD-CV DC ±5 V or 0 to +5 V, typical control; by range — the claimed range; ±5 V at B5 By range; ±6 V at B5 1 kΩ typical; ≤ 2 kΩ 100 kΩ typical; ≥ 47 kΩ B5 default; U5, B10, U10, B1, U1
MOD-CV-1VOCT DC 1.00 V/octave pitch CV, ±0.3 % of scale over the claimed span — by range; ±10 V at B10 By range; ±12 V at B10 1 kΩ typical; ≤ 2 kΩ 100 kΩ typical; ≥ 47 kΩ B10 default; U10, B5, U5
MOD-GATE DC Output high +4 V to +12 V into 100 kΩ, low ≤ +0.5 V; a sustained level Input reads high at ≥ +3 V, low at ≤ +1 V; hysteresis ≥ 0.5 V recommended — ±12 V 1 kΩ typical; ≤ 2 kΩ 100 kΩ typical; ≥ 47 kΩ —
MOD-TRIG DC Output pulse high +4 V to +12 V into 100 kΩ, low ≤ +0.5 V, at least 1 ms high; 5 ms recommended Input reads a rising edge through +3 V and accepts a 1 ms pulse; hysteresis ≥ 0.5 V recommended — ±12 V 1 kΩ typical; ≤ 2 kΩ 100 kΩ typical; ≥ 47 kΩ —
MOD-CLK DC Output square wave high +4 V to +12 V into 100 kΩ, low ≤ +0.5 V, each state ≥ 1 ms; any duty Input reads high at ≥ +3 V, low at ≤ +1 V; hysteresis ≥ 0.5 V recommended — ±12 V 1 kΩ typical; ≤ 2 kΩ 100 kΩ typical; ≥ 47 kΩ —
MOD-VIDEO DC 0 to +1 V DC: black 0 V, full scale +1 V — +1 V (U1) −0.1 to +1.2 V (U1) 75 Ω ±5 % series 100 kΩ typical; 100 kΩ ±10 % U1 default

The table is generated from data/signals.json. Every class is on a 3.5 mm mono jack and withstands ±12 V (SIG-002); the requirement that binds each class is named beside it above. An impedance cell gives the typical figure and the limit; a MOD-VIDEO impedance is a limit alone (SIG-009, SIG-010).