Cable connectors for the NAD VISO HP-50 headphones
...reporting back, for the sake of Google and anybody might need to know someday.....
I got some plugs from eBay and they work:
The 'shoulder' is .202" in diameter by .075" in length.
I still have no idea if there is a standard, informal or otherwise, for the 'shoulder' dimensions.
They look bigger than they are. The Mogami 2893 mini-quad that I used looks like power mains cable on these things. Trust me, without getting too graphic or sexual, I'm pretty sure that we all will at some point in our lives experience something that is more fun than soldering them up. There are no real facilities for strain relief. I connected the unused fourth conductor pretty tight, made sure the cable fit tightly in the hole in the body, and potted the thing full of glue. Speaking of the hole in the body - for the Mogami, I had to drill it out to 3/16". The silver one's body was brass and the snazzy red one's was aluminum. Both drilled just fine.
Here is the eBay listing where I bought them:
http://www.ebay.com/itm/201075924663
Once again, connections are (3-pole to 4-pole) tip to tip, ring to the first ring, shaft to the second ring, and the shaft on the 4-pole isn't used.
It turned out that in addition to being long enough to reach from my amp to my head, the Mogami cable sounded better than the stock one. (I wasn't trying to be all audiophile about this. I had chosen the Mogami on the basis of cheap and I had some in my parts box.) On my Fiio X-3/ Pico rig the HP-50s just weren't cutting it, musically, for some subtle reason. The Mogami cable made just enough difference to bring them back in the zone. So I made a four-foot cable as well.
Kinda makes me wonder how a cable similar to the 2893 but not wonky in the top octave might sound.