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.

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.

• BUS-CV is 1 V/octave pitch CV, with the scale of PITCH, from one transmitter, such as a MIDI interface or a keyboard controller, to the oscillators that listen. It is not general control CV: an LFO or an envelope on it would detune every listening oscillator. The transmitter drives from an op-amp output through at most 100 Ω and holds 1.00 V/octave within ±0.3 % of scale at the header into 10 kΩ, ten listeners; each listener presents at least 100 kΩ.
• BUS-GATE is a 0 / +5 V gate that keeps the 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 transmitter drives through at most 2 kΩ, high at +4 V or more at the header into 4.7 kΩ, ten listeners; each listener presents at least 47 kΩ.

The lines are multi-drop, so the source impedance matters: ten listeners at 100 kΩ each load a line with 10 kΩ, and a 1 kΩ source into that load loses 9 % of scale, nearly an octave at the top of a 10 V range. Even 100 Ω loses 1 % into that load, so a transmitter meets ±0.3 % only by taking its feedback after the resistor or by using a smaller one; EIS recommends at most ten listeners on a line (9.2).

Class table