[sdiy] Optoisolator for MIDI

[James Patchell]

Personally, I prefer the Sharp PC900 opto....although, it is kind of hard 
to get now.

I think there is an equive part number, but haven't looked for it yet.

At 12:26 AM 5/15/2004 -0400, R. D. Davis wrote:
>While looking over various circuits for a MIDI interface that connects
>to a PC's sound card, I see that most of them use the 6N138
>optoisolator.  A few of the earlier schematics that I've seen used a
>4N35 optoisolator; does anyone see any problems with still using the
>4N35 (along with appropriate resistors values, etc.)?  Also, any
>problems with using a 4N35 in a MIDI ckt for an older Power Mac's
>serial port?  I'm planning on building ckts for both the PC and Mac.
>
>If I get these to work, perhaps I'll then go for adding MIDI to a Sun
>workstation serial port, my PDP-11/73 and VAX ...might turn out to be
>useful for something or other, so why not?  It would be fun to try out
>John Wilson's (IIRC) circuit for a PDP-11 MIDI interface. :-)
>
>Also, I read somewhere that some of the newer sound cards won't work
>properly with some of the circuits used with the old Soundblaster
>cards, and that one has to add either an IC buffer or a transistor
>ckt.  between the sound card and the optoisolator; seems to me that
>newer cards would require less, not more, current, however.
>
>Any thoughts or advice on this?
>
>--
>Copyright (C) 2004 R. D. Davis The difference between humans & other animals:
>All Rights Reserved | My VAX | an unnatural belief that we're above Nature &
>www.rddavis.org | runs VMS & | her other creatures, using dogma to justify 
>such
>410-744-4900 | doesn't crash!| beliefs and to justify much human cruelty.

         -Jim
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