From: ttl@aura.cs.wisc.edu (Tony Laundrie)
Subject: Re: Radio Shack Secret? (Midi cables)
Date: 8 Aug 91 17:38:55 GMT

> (From Bob McQueer's MIDI Spec Primer)
> 
> The standard connectors used for MIDI are 5 pin DIN.  Separate sockets
> are used for input and output, clearly marked on a given device.  The
> spec. gives 50 feet as the maximum cable length.  Cables are to be
> shielded twisted pair, with the shield connecting pin 2 at both ends.
> The pair is pins 4 and 5, pins 1 and 3 being unconnected:
> 
>                             2
>                         5       4
>                       3           1

If you buy a generic cable, it probably looks like:

      /\    #################    /\
  1 -|------#################---|------ 1
     |  |   #################   |  |
  2 -|------#################---|------ 2
     |  |   #################   |  |
  3 -|------#################---|------ 3
     |  |   #################   |  |
  4 -|------#################---|------ 4
     |  |   #################   |  |
  5 -|------#################---|----- 5
     |  |   #################   |  |
      \/    #################    \/ 
       \___/     SHIELD      \___/ Metal Shell of DIN Connector

This probably works, but it might be electrically noisy, and perhaps not
reliable for long distances.  If you make your own cables with 2-conductor
shielded wire as described in the SPEC, do it as shown below:

              /\                 /\
      /\     /  #################  \     /\
  1 -|- |   |   #################   |   | ----- 1
     |  |   |   #################   |   |  |
  2 -|-----/    #################    \--|------ 2
     |  |       #################       |  |
  3 -|- |       #################       | ----- 3
     |  |       #################       |  |
  4 -|----------#################-------|------ 4
     |  |       #################       |  |
  5 -|----------#################-------|----- 5
     |  |       #################       |  |
      \/        #################        \/ 
       \_            SHIELD             _/ Metal shell of DIN Connector

Connect the wire shield to pin 2, and connect pins 4 and 5 with the other
wires.  Do NOT connect the metal shell of the DIN connector to the wire
shield (pin 2) -- I had pin 2 shorted with the shell at first and that
didn't work with my setup.

						ttl@cs.wisc.edu

From: janin@v785.stanley.co.jp (chan" Janin)
Subject: Re: MIDI DIN connector pin-out needed
Date: 7 Jan 92 10:18:06 GMT

************************************************************************
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************************************************************************

In article <311@ittc.wec.com> simmons@ittc.wec.com (Gary Simmons) writes:
>A friend got a Soundblaster for Xmas and wants to make his own cable
>to go between the 15 pin connector on the SB card to a MIDI connector
>on the other. What pins do what on the MIDI end? I remember a bit of
>discussion on this a while back, but didn't save any of it...
>
>Thanks,
>
>Garry Simmons
>simmons@ittc.wec.com

I hope nodoby replied you before me...

This is the TRUE pin assignment for MIDI plugs.
I know it "by heart" because I used to make my own interfaces
for my computers...

MIDI IN :	1- n.c.
		4- anode of optocoupler
		2- n.c. <<<--- !!!! Different for MIDI OUT
		5- cathode of optocoupler
		3- n.c.

MIDI OUT/THRU:	1- n.c.
		4- +5v thru resistor
		2- local ground
		5- TTL open collector ouput
		3- n.c.

The pin numbers are usually printed into the plastic of the plug,
in that order (or the reversed one).

Don't connect MIDI IN pin 2... it preserves OPTOISOLATION from
MIDI OUT device to MIDI IN device.

To make your own MIDI cable, wire pin 4 to 4, pin 5 to 5, pin 2 to 2
and to the shield of your cable.

------------------------------------------------------------------------
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< STANLEY ELECTRIC CO. LTD,  R&D LAB 71G > |     // My 1st computer: DAI
< Fax: 81+ 45-9110007 (045-... from Japan> | \  //  My current 2nd:Amiga
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------------------------------------------------------------------------

From: smill@polari.online.com
Subject: Re: Now what? (MIDI)

As stated in the MIDI 1.0 Spec:

	"The cable shall be twisted pair, with the shield connected to
pin 2 at both ends."
      ^^^^^^^^^^^^

	The ground loop problem is dealt with in the fact that MIDI
jacks on instruments are specified as pin 2 (ground) being connected
only at the transmitting ends, not at receiving end.  This allows cables
to be used in any situation, with the ground connection taken care of
in the hardware specification.

-- 
Steven M. Miller		"The history of music evolution is
smill@polari.online.com		 not the history of nice guys"
					-- Anthony Braxton
Electronic Music Coordinator - Cornish College of the Arts, Seattle WA
