Page 1 of 2

physical MIDI cable specs

Posted: Wed Dec 15, 2010 2:53 pm
by cartesia
OK so I am making a 'double adaptor' midi plug because I have 2 devices with only a midi IN port on them... I know it is not 'recommended' but it works when I dont need to send different data to them and the distance is less than 20cm.


Anyhow after I spent all the time soldering up the wires to the 5 pins + ground for each 5-pin DIN plug I remembered something..

I only have to use 2 pins + the ground when I send MIDI out of my Arduino... it works fine.

But then I cut open a dead midi cable I had, and it has all 5 lines.

So that leaves me with 2 questions:

1) Do I only have to use the 2 pins + ground to make my own midi cables? Or do some devices send midi down all 5 cables therefore need them?

1) If I only need 2 + ground, then why the h**l did they choose FIVE pin din sockets to be the midi standard? expandability? lack of foresight?

Re: physical MIDI cable specs

Posted: Wed Dec 15, 2010 6:07 pm
by b3groover

Re: physical MIDI cable specs

Posted: Wed Dec 15, 2010 6:08 pm
by madtheory
Two pins and the ground is the correct wiring for a MIDI cable, anything else can cause problems. A lot of MIDI cables are not actually MIDI cables at all, but DIN audio cables rebadged.

Re: physical MIDI cable specs

Posted: Wed Dec 15, 2010 6:08 pm
by schmidtc
All midi I'm aware of only uses 3 of the 5 pins.

Re: physical MIDI cable specs

Posted: Wed Dec 15, 2010 6:15 pm
by meatballfulton
The actual cabling spec indicates that pins 1 and 3 are never connected.

Why did they choose 5 pins? At the time of MIDI 1.0 it was thought that future extension of the spec would make use of the extra pins. This has not happened yet.

Re: physical MIDI cable specs

Posted: Wed Dec 15, 2010 9:27 pm
by Synthaholic
Another interesting tidbit about the 5-pin DIN connectors used for MIDI: they are the same connectors that the original IBM PC and PC/AT used for the keyboard. Many "clone" PCs even into the mid 90s used this same "AT" keyboard connector. Why is this relevant? Well, one time years ago I needed a longer MIDI cable for something, and I was able to use an AT keyboard extension cable to do the trick.

Re: physical MIDI cable specs

Posted: Thu Dec 16, 2010 4:45 am
by cartesia
thanks guys!

Funny how such a simple thing can have quite a complicated background.

Re: physical MIDI cable specs

Posted: Thu Dec 16, 2010 5:57 pm
by Altitude
madtheory wrote:Two pins and the ground is the correct wiring for a MIDI cable, anything else can cause problems. A lot of MIDI cables are not actually MIDI cables at all, but DIN audio cables rebadged.

Also worth mentioning that the ground is only connected on the midi output, never on a midi input (It's just for shielding so its open on one end)

Re: physical MIDI cable specs

Posted: Thu Dec 16, 2010 7:43 pm
by cornutt
madtheory wrote:Two pins and the ground is the correct wiring for a MIDI cable, anything else can cause problems. A lot of MIDI cables are not actually MIDI cables at all, but DIN audio cables rebadged.
Also, DIN sync a la the Roland X0X drum boxes use the two pins that MIDI doesn't use. So some MIDI cables are also sold as DIN sync cables.

Re: physical MIDI cable specs

Posted: Mon Dec 20, 2010 1:20 am
by Shreddie
If you're planning on making your own midi cables, just use 2 core mic cable... It's of a higher standard than most off the shelf midi cable so is useable for surprisingly long runs, I've read that upto 70m is possible.

Re: physical MIDI cable specs

Posted: Mon Dec 20, 2010 8:21 am
by Hybrid88
Personally I'd rather get something like this for splitting purposes;

http://cgi.ebay.com.au/Touchprone-1x3-M ... 2554d7632b

Re: physical MIDI cable specs

Posted: Wed Dec 22, 2010 1:06 pm
by cartesia
wow.. There is no way I would ever pay $55 for that thing.. or even $25 for that matter. That box doesn't even seem to be powered (meaning it's doing exactly the same thing my device is.. but costs 10x as much)

Re: physical MIDI cable specs

Posted: Wed Dec 22, 2010 2:30 pm
by madtheory
Actually it does claim to be powered, it draws power from the MIDI line. That's entirely possible, there's 5V there to play with. In fact it's not possible to split the MIDI signal 3 ways without power.

Your passive splitter will work, but not with every piece of gear.

Re: physical MIDI cable specs

Posted: Wed Dec 22, 2010 2:50 pm
by Hybrid88
Fair enough, it's really not much to outlay though for what your getting. Difference is the $55 one is designed to work, plug and go. Whereas your solution is a bodge solution, that's not to critisise sure it might work sometimes, but I cant see it being very reliable... YMMV tho :)
cartesia wrote:wow.. There is no way I would ever pay $55 for that thing.. or even $25 for that matter. That box doesn't even seem to be powered (meaning it's doing exactly the same thing my device is.. but costs 10x as much)

Re: physical MIDI cable specs

Posted: Thu Dec 23, 2010 2:30 pm
by cartesia
there may be a few old devices it wont work with, but it's not gonna be like a half the time it works, half the time it doesnt thing, so yeah.. for me, it is perfect (more than 1 device that only has a midi IN port)