[sdiy] Caution with DIY MIDI cabling

[Michael E Caloroso]

Only true for the ports in the devices, not for the cabling.  If you
think about it, it makes sense.

I am not using a generic OTS MIDI panel, I built my own MIDI panel
using raw materials.

MC

On 12/26/18, rsdio at audiobanshee.com <rsdio at audiobanshee.com> wrote:
> Hmm, I think the reason that this is happening is that MIDI In and MIDI Out
> jacks should be wired differently. MIDI Out should connect the shield
> ground, while MIDI In should not. It’s easy to manage in a synth, where
> there is only one of each (well, two MIDI “out” if you count MIDI Thru).
>
> I assume that your DIY MIDI I/O panel was perhaps generic? … so that the
> panel does not distinguish between In and Out, but depends upon which port
> you connect internally to the rack gear?
>
> It might work if you had one row dedicated to MIDI In, with isolated ground,
> and another row dedicated to MIDI Out, where you wouldn’t need to worry
> about grounding issues. Seems like that would be the only way for a generic
> panel to work, although you would be limited by the dedicate Input versus
> Output/Thru designations.
>
> Brian
>
>
> On Dec 26, 2018, at 6:14 PM, Michael E Caloroso <mec.forumreader at gmail.com>
> wrote:
>> I build my own I/O panels for my racks, and my own MIDI cables.  I
>> recently uncovered a nasty bug that has perplexed me for years:
>>
>> If you use metal shell MIDI plugs on your DIY MIDI cables, DO NOT
>> ALLOW MIDI GROUND TO COME IN CONTACT WITH THE SHELL.
>>
>> I was gigging my road system and was experiencing intermittent MIDI
>> errors.  After finally being able to reproduce it at home, I figured
>> out that the metal shell of the MIDI plug shorted to earth ground via
>> the metal DIN jacks I was using on my DIY I/O panels.  Stray shield
>> wires from the cable had contacted the cable clamp of the plug
>> (despite my best attempts at trimming the stray wires), completing the
>> short circuit of MIDI ground to earth ground.  MIDI gets very upset
>> under this condition.
>>
>> I use an EBTech cable tester after I build all my DIY cables, and it
>> does not have the capacity to detect a short from the shell to any of
>> the pins - it's not supposed to.  Even with my diligent testing after
>> completing a cable, this bug had eluded me for YEARS in my studio
>> system.  Yes I was well aware that the MIDI specification grounding
>> system is designed that way FOR A REASON.
>>
>> The only way to guarantee complete isolation of MIDI ground from earth
>> on the metal shell of the plug was to disassemble the plug and add
>> shrink tubing over the trimmed end of the cable.  This separates any
>> stray shield wires from the metal clamp of the plug.  Once I fixed my
>> cabling for the stage rig, it behaved MUCH better.
>>
>> Nasty bug, this.
>>
>> For years I had wondered why my SYSEX dumps were never 100% reliable,
>> now I know why.
>>
>> That's just the STAGE rig.  Now I have to make the cable corrections
>> to my STUDIO system, which has easily over 30 DIY cables that I built.
>> Guess how I am spending my holiday break...
>>
>> Sent from my iGroundingCanBiteYou,
>> MC
>
>