That stripboard project is more or less done, although there’s a bit of debugging still to do. It’s a sort of a mini-Roland OP8M – maybe an OP2M, effectively, allowing the MC-4 to control a MIDI synth.

I did a demo of it for a mate, I think he was a bit mystified. Here it is – I got slightly carried away, as usual.

It’s the usual MC-4 syncing a TR-606, with the out-of-tune big black modular bass synth being the System 100M clone, and the parpy MIDI’d up thing being a JX-3P.

It takes CV1, CV2, gate, and MPX from the MC-4. (MPX is a digital signal and is either on or off for the duration of the step).

One switch selects the octave for the base note, and the other switch is for selecting what happens when it receives an MPX signal from the MC-4.

Position one of the MPX switch selects sending CV1 to a different MIDI channel (so you might get a different sound), position three sends CV2 to the same channel (so you get a second note), and in the middle it’s effectively off and just uses CV2 for velocity.

My JX3P doesn’t do velocity, and is only responding on MIDI channel 1 in the video above, so we get this muting effect when switching to “cv1 diff ch”.

I fret about the timing, as always. I’d buffered the CV signal before it hits the ADC to get a low impedance, but it still takes a fair number of samples before I get something reliable. My Poly61M definitely seemed a bit late when triggered from it, but there’s every chance the MIDI in that is just slow.

Anyway it’s working well enough for now, although there’s a minor bug that needs sorting. It should give me different options when I do my long-winded MC-4 jams.