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

[Ralf Mardorf]

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Hi :)

On Thu, 24 Dec 2015, Len Ovens wrote:
> http://www.maxmidi.com/diy/serial/

A circuit with a processor is ridiculous.

>Actually, much simpler would be to just take the optocoupler and add
>an inverter (or two) after to feed the computer. (basically a thru
>box) Make sure power comes from the receiver (computer in this case).

;)

On Thu, 24 Dec 2015 11:48:07 -0700, Bob van der Poel wrote:
>I believe that the MIDI spec
>
>http://www.midi.org/techspecs/electrispec.php
>
>says that you must have a opto-isolator. Devices without one are
>probably not compliment ... don't know about direct usb connections.

MIDI does work if the level is correct, with or without opto-coupler.

The squares separating low and high levels are not that clear when
using an opto-coupler, this is not an issue per se, but it's the
cause that with an opto-coupler the signal is delayed and this becomes
an issue for MIDI thru. The only advantage of an opto-coupler and a one
side open shield is to avoid ground loops for audio signals, this is
why it's required by the MIDI specifications. However, if the levels
are ok, it works without opto-coupler too and without opt-coupler it's
quasi better for the data transfer and it doesn't necessarily cause
noise.

Marry Christmahanakwanzika!

Ralf
-- 
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