I think what I did was I followed this convention for the colors:
Source Plug end = shielding + black + clear/copper soldered to ground (sleeve) , red soldered to right+ (ring) , blue soldered to left+ (tip)
I was going to solder the spiral shield to the shield part of the plug only on one side, the source side.. for you the 3.5mm.. but I got lazy and I only soldered the black and clear conductors to the shield. it works fine but I think technically you'r;e supposed to attach the spiral shield to that side too.. I was going to cut off like 3/4 of the spiral and then twist the rest to make it small enough to fit on the shield.. but like I said I got lazy.. you should try it though..
and then for the two 3 pin mini xlr male plugs I think you'd just use red for R+ on the plug for the right headphone cup, then L+ for the left headphone cup.. and then R- and L- can be the other two conductors, I don't think it matters what colors you use but here's the convention I used:
Headphone end = red soldered to right + (positive) , black soldered to right - (negative) , Blue soldered to left + (positive) , clear/copper soldered to left - (negative)
and on the headphone side I don't think you connect the spiral shield at all...
here's a pic of the 3 pin xlr pins, note I think the top two numbers would be reversed when looking at the plugs from the back?
Warning: Spoiler! (Click to show)
Edited by uncola - 7/15/14 at 3:08am
Pin # 1 does not need to be connected to ground for headphone use, just leave it disconnected.
Many headphone amps have a pair of 3-Pin XLR connectors. For the Left XLR connector you connect the L+ to Pin 2, L- to Pin 3 and the cable shield to the XLR connector's ground lug. Connecting the cable shield to the ground lug will provide RFI noise protection for the cable. Pin 1 does not need to be connected to ground for a headphone cable (it's there for microphones and other audio gear). The Right XLR connectorwould be R+ to Pin 2, R- to Pin 3 and the cable shield to the ground lug.
If you wish to use one headphone cable and Y the cable to the XLR connectors and/or the ear cups I recommend using Canare Star Quad or Gotham Mini Quad cable. Remove the rubber outside layer and shield for the cable Y, you'll need about 17 inches for the ear cup Y and around 6 inches for the XLR Y. Unravel the 4 conductor wires and then twist them into right and left pairs going to the ear cups and/or XLR connectors. You can cover the cable split with a couple inches of heat-shrink tube to dress up the cable. I also recommend heat-shrink for the XLR end of the cable Y to enhance the grip of the XLR connector's strain relief clamp.