[sdiy] MIDI specifications

[Scott Gravenhorst]

Plus it would overly complicate things.  You'd have to 
make sure that all of the outputs have a device connected.
One device failing to pass current causes the whole chain
to fail.  (reminds me of IBM's Smoken-Ring)  5 pin DINs 
don't normalize well AFAIK.  

The best method seems to be a single buffered input 
driving N separately buffered outputs.  Yes, that does 
require a power supply, but precious little in electronics 
does not.  The parts required for such a box are pretty 
cheap and commonly available.

harrybissell at prodigy.net wrote:
>Though it is very non-standard, you could run MIDI ports
>in series.  I'd consider a current loop drive... otoh that would
>require power AND be a freak as well...
>
>H^) harry
>
>--------Original Message--------  
>
>From: debus at cityweb.de
>To: synth-diy at dropmix.xs4all.nl
>Sent: Apr 18 2003 15:47
>Subject: Re: [sdiy] MIDI specifications
>
>>Magnus Danielson wrote:
>>>>what would this do or prevent? it seems to work as it is.. a small wooden
>>>>teabox with some holes for the midi ports i've just soldered wires from the
>>>>input-pins to each output pin.
>>> 
>>> 
>>>>From the output you have a current, it's going to drive 5 inputs now, which
>>> means that the opto-coupler runs at the fifth of the current it is supposed to
>>> run at, meaning less emitted signal and all that. If it works it works, but you
>>> have just moved from one case of a limit into another. Also, all of a sudden you
>>> want to run another pair of boxes in the same time, so you hang them in too...
>>The biggest problem here seems to me is that there are now several 
>>LEDs in parallel with a common current limiting resistor. Those with 
>>just a slightly higher voltage drop won't light up well.
>>> By using a single chip and a small handfull resistors and a opto-coupler, you
>>> have built yourself a propper MIDI-splitter. My point is that it isn't as far
>>> away, so why not do it properly? As it is now you survive over the weekend, but
>>> is it the long-time solution?
>>Well, it would need a power supply...
>>Ingo
>
>
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