[sdiy] midi and DIN sync in the one connector

[rsdio at audiobanshee.com]

On Apr 28, 2015, at 9:53 PM, Adam Inglis <21pointy at tpg.com.au> wrote:
> I'm retrofitting my old Roland CR-8000 drum machine with a midi-to-trigger board.
> To minimise cosmetic disfiguration, I thought I might make the DIN sync jack do double duty for midi.
> That way I could run a simple preset pattern and spice it up with some extra notes/fills here and there.
> Does anyone know if there is likely to be any problems doing this, say, caused by stray capacitance or crosstalk? The ground wire would have to be shared.

MIDI does not use ground. MIDI is a current loop. The ground connection is only for the shield, and it is only supposed to be connected on the MIDI OUT, not the MIDI IN.

If you're adding MIDI-to-trigger, then I assume you only have a MIDI IN jack, in which case there is no ground connection anyway.

There shouldn't be much crosstalk with the MIDI current loop. Maybe your best bet is a cable that has isolated pairs inside, and then you can dedicate one pair to MIDI, and another pair to Clock and GND. The Start-Stop signal can be on it's own or just connect GND a second time if there are three pairs in the cable.

I assume you're not using the optional DIN Sync Reset-Start or Fill-In signals - those would conflict with the MIDI pinout.

Brian Willoughby
Sound Consulting