DMX wiring VS Xlr 3 Pin sound

[Gaurav]

Could you please share why the number 3 pin in XLR connector is positive in DMX connection and negative in Sound connectors

 

Thanks

[timsabre]

I was always told that it followed the US audio convention which also has pin 3 positive.

But 3 pin DMX is not a standard anyway, so really it is just because a major manufacturer (Martin Professional) started making product like that and everyone else followed.

Actually Martin originally started with Pin 2 positive, which other products followed, then they changed to pin 3 positive. Hence why you still get some products with pin 2 positive and need to use pin swapper cables.

 

[Brian]

Could you please share why the number 3 pin in XLR connector is positive in DMX connection and negative in Sound connectors

 

 

Because. Just because.

 

(In other words, they had to pick a pinout and went with that one for no good reason.)

[sunray]

Actually Martin originally started with Pin 2 positive, which other products followed, then they changed to pin 3 positive. Hence why you still get some products with pin 2 positive and need to use pin swapper cables.

Interesting, when did they swap to pin 3 positive? I did a fair bit in mid 90's and we used their 'special' software to allow Martin and DMX in the same universe which involved remaking loads of their IDC plugs.

 

Anyway not all audio uses the same standards, some of the early Shure dual impedance mics used strange connexions.

[timsabre]

Interesting, when did they swap to pin 3 positive? I did a fair bit in mid 90's and we used their 'special' software to allow Martin and DMX in the same universe which involved remaking loads of their IDC plugs.

I'm not sure when they swapped it. Their original "Martin" protocol used pin 2 hot, it was standard RS-485 wiring so could also be used to receive DMX. So they modified their firmware to receive either Martin protocol or DMX, but still with pin 2 hot (there was no "standard" wiring at that point, people were using stereo jacks for DMX and all sorts).I had a load of Roboscans which had pin 2 hot. The Mac500/600s had pin 3 hot so I guess it was sometime around then.

 

[DrV]

It is also useful that the pin NUMBERING matches that of a 5 pin XLR even though the physical layout is different.

[Jivemaster]

Also the connector gender is reversed, a mic has pins on the back a desk has sockets -beware any cable with mains and signal for audio or DMX.

[sunray]

Interesting, when did they swap to pin 3 positive? I did a fair bit in mid 90's and we used their 'special' software to allow Martin and DMX  in the same universe which involved remaking loads of their IDC plugs.

I'm not sure when they swapped it. Their original 'Martin' protocol used pin 2 hot, it was standard RS-485 wiring so could also be used to receive DMX. So they modified their firmware to receive either Martin protocol or DMX, but still with pin 2 hot (there was no 'standard' wiring at that point, people were using stereo jacks for DMX and all sorts).I had a load of Roboscans which had pin 2 hot. The Mac500/600s had pin 3 hot so I guess it was sometime around then.

We installed the first 4 moving head fixtures in a club in 1995 and several more the same year, At the time I believe they were made using standard existing parts and I have it in my head from 518's so the connexions were pin 2+ but this was 1995 and they turned out to be prototypes. I think they must have been introduced about 1997 in a blaze of publicity as I was called a liar by the guys at another install company when I said we'd installed some 2 years before.

As they hadn't 'been invented yet' they didn't have a number but went on to be 500's and lot of XLR's have been terminated and scrapped since so exact details may be a bit hazy.

We were one of the 3 'Martin Houses' to trial the combined Martin & DMX combination PC cards and software which I believe didn't go on general release until much later.

[indyld]

In the mid to late - 90's, it was common to have to distinguish between the 'new' standard pinout (including Mac500s etc), Robocolors that had pin 2 hot and Robocolors etc. that had been since been converted by their owners to pin 3 hot.

 

There was a short point in time when many control issues where solved with judicious use of hot/cold swap adaptors at various places in the rig. It didn't last that long though and that particular issue wandered off as the old pinout either got converted or fell out of use.

 

Edit to add: There was also a convention in some large rental houses, where the Mac500 and Mac600s were flooded onto the market, to zip tie 3-5 and 5-3 pin adaptors to the unit handle to allow for 5pin cabling to be used throughout the rig. I'm not sure of the details of these jumpers, which in the early days may have also been hot/cold swapped.