[sdiy] Midi opto isolation

[Scott Gravenhorst]

"Sean Ellis" <tensiontype at hotmail.com> wrote:
>> MIDI uses a current loop serial interface.  As such, it is very much noise 
>> immune.  The
>> optoisolator ensures that you can't have ground loops due to synth 
>> interconnection because
>> the ground is not part of the current loop.  I don't see how "isolation 
>> lowers the quality
>> of the signal", and the benefit is the noise immunity and absence of 
>> required ground
>> connection.
>
>That's what I was unsure about. The lower quality is from the led/ldr delay 
>times, but obviously that only applies to certain hardware units.

I think that if you look at opto specs, you'll see that any delay due to LED and
_phototransistor_ (LDRs are not used for this) is insignificant compared to the delay of a
single byte of serial data being transmitted.  In my view and experience, this delay is on
the order of humanly imperceptible even when several are daisychained.

-- ScottG

-------------------------------------------------------------

-- Scott Gravenhorst
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