Re: [LAU] Galvanic isolation (was: Re: pianos with built in recorders?)

On Wed, 23 Dec 2015 17:42:29 -0600, Jonathan E. Brickman wrote:
>> USB MIDI has got the risk to cause noticeable MIDI jitter.
>>
>> Does USB MIDI provide galvanic isolation? Several times I read claims
>> that USB MIDI connections aren't galvanically isolated.
>>
>> Standard MIDI connectors make usage of opto-couplers and shield of
>> the MIDI DIN connectors is open.
>Certainly all of the USB MIDI connections I have ever tested, are not
>galvanically isolated; I always get trouble with USB signals bleeding
>over where they don't belong. USB-to-DIN adapters I have used have
>been better, but not perfect. Is there a make/model of USB-to-DIN (or
>even PCI-to-DIN if it exists anymore) which you know for sure has
>opto-coupling? That would be a great boon to me. Sooner or later I'm
>going to do optocoupling for audio too, probably using a TOSLink setup.

You can solder yourself or buy cables for serial port, resp. PCI
sound card output with such a connector, that have build in
opto-couplers. I remember this very good, because years back, when I
started needing reading glasses, but didn't own them, I tried to
resolder a a self made parallel port cable. I tried to add
opto-couplers and due to the missing reading glasses, resp. a missing
magnifier, I damaged the jack. The cable worked without opto-couplers
for my serial port, but didn't work for my Envy24 sound cards. I then
ordered a cable for around 10,- € with build in opto-couplers.
I own USB port to MIDI DIN, but never measured if shield is open and
can't take a look inside, but I didn't experience electric noise caused
by the USB to MIDI DIN cable, just jitter. My RME PCIe card has got
break through MIDI DIN. I don't know if inside the connector or on the
board are opto-couplers, but there are no noise issues caused by MIDI
connections and there are no level issues.

Discounter keyboards don't provide MIDI DIN connectors anymore, they
provide USB MIDI only

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