Disting Mk4 MIDI breakout kit - possible wiring issue?

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StutzJr
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Disting Mk4 MIDI breakout kit - possible wiring issue?

Post by StutzJr » Thu Apr 25, 2019 8:16 am

I just did a DIY build today of the MIDI breakout board for my Disting Mk4.
Initially I could not get it to function at all in my setup, until I realised that the module required a power connector for the ground return. I do note that this module is listed as passive, and the kit is only provided with a connector cable to the Disting, not with a power cable. Still it seems to only function with the power cable connected. Perhaps it's "default" design assumes the mechanical connection to the mounting rails will provide ground return?

Anyway during my faultfinding I noticed something that seemed odd: When I was checking continuity with my multimeter probes, I noticed that pin "2" of the MIDI out socket (the middle pin) was a short circuit to ground.. Is this correct? I checked the board and there does not appear to be any issues with the soldering. The reason I ask is when I connect a Volca Keys to the MIDI out socket and "play" it with the modular rig, the Volca is very quiet unless I press "play" on the Volca. However when I connect another MIDI controller to the Volca, I do not have to press "play" first to hear the output at normal volume.
I was wondering if this "short circuit" at Pin 2 on the Disting MIDI kit is affecting the Volca in some way? Should I attempt to desolder or cut "Pin 2" on the output socket of the Disting MIDI kit?

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os
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Post by os » Thu Apr 25, 2019 8:21 am

MIDI doesn't require a 'ground return' - it's an opto-isolated current loop. The power connector is there for if you want to ground the shield of the cable, which is different. It's optional and generally not required.

The MIDI spec says to ground pin 2 on the output, but not the input.
https://www.midi.org/specifications-old ... cification

From my experience the Volcas' MIDI ports are wired in a weird way.

StutzJr
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Post by StutzJr » Sat Apr 27, 2019 1:22 am

Thanks os for your reply, I appreciate your answers.

It seems to be all working correctly now, I'm not entirely sure if I just did something wrong or created an unrelated issue with external audio in my initial attempts. I've now tried the MIDI out with both a Meeblip Anode and a Microbrute and found the setup to be much more reliable than with the Volca.

Also glad to hear I didn't do anything wrong with the DIY build for the output pin 2 to be grounded. Cheers!

cooljules1
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Post by cooljules1 » Mon Jun 17, 2019 8:32 am

I also added a DIY breakout to my Disting Mk4.

CV clock -> X port -> Midi out works fine
Midi in - > A port does not work

Any idea what could be wrong?

Currently testing with an Octatrack MKII.

Sorry to HJ thread, but it was the topic closest i could find.

JH

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os
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Post by os » Mon Jun 17, 2019 8:37 am

Are you using the most recent disting firmware?

cooljules1
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Post by cooljules1 » Mon Jun 17, 2019 1:52 pm

I was not! :despair:

Works as intended now. Thank you.

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