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 contract, an output high at +4 V to +12 V and low at +0.5 V or less, and a listener that reads +3 V or more as high and +1 V or less as low.

The bus lines are multi-drop: ten listening modules at 100 kΩ each load a line with 10 kΩ, and a 1 kΩ source into that load loses 9 %, nearly an octave of pitch error. A BUS-CV transmitter therefore drives from an op-amp output through at most 100 Ω, holds 1.00 V/octave within ±0.3 % of scale at the header, and each listener presents at least 100 kΩ; a BUS-GATE transmitter drives through at most 2 kΩ into listeners of at least 47 kΩ.

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 Thresholds Class ceiling Source Z Load Z
BUS-CV 16-pin Eurorack bus (CV net) DC 1.00 V/octave pitch CV (bus CV), ±0.3 % of scale, from one transmitter — ±12 V ≤ 100 Ω ≥ 100 kΩ per listener
BUS-GATE 16-pin Eurorack bus (Gate net) DC 0 / +5 V gate (bus gate): output high +4 V to +12 V, low ≤ +0.5 V, from one transmitter Listener reads high at ≥ +3 V, low at ≤ +1 V ±12 V ≤ 2 kΩ ≥ 47 kΩ per listener