CV over AC coupled interface

Expert sleepers (silentway ) encode DC CV signal on to a AC signal, so it can be output via an AC coupled interface, and then on the modular side use a ‘adapter cable’ or something like disting to decode it back to DC.

my understanding is it uses a carrier wave, which the DC signal modulates.

but does anyone have a reference to the specifics e.g. is it a fixed frequency carrier?, what frequency? phase modulate? amp modulate?

Ive now only ES, but also Bitwig and Ableton are supporting it, so i guess there is some kind of ‘standard’?

(I’d like to add it as an option to Orac’s CV tools for those without DC couple audio interfaces etc)

i looked at this briefly a while ago, and figured the “decoding” is a simple smoothing+rectification scheme:

https://www.expert-sleepers.co.uk/siwaacencoder.html#es1

(JP1 is for AC-coupled channels)

IOW: encoding as amplitude of AC, but lowpassed so that the exact carrier frequency would not be critical. (“fast”)

someone with access to es-1 and scope could measure DC encoding and give the right answer very easily

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being able to send CV and gate out of a stereo headphone jack would be pretty exciting - it’d be wild if this is possible and no one has done it yet

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