I'm planning to add a Male 4 Pin Mini XLR socket to my T50RP for a balanced cable and just want to confirm the pin numbers and layout. Here's the pinout of a Female 4 Pin Mini XLR socket:
(I'm a new guy so I can't post pics yet)
I was planning to leave the standard 3.5mm connector in place for flexibility and solder the 4 new balanced wires to the 3.5mm jack inside the ear cup but after doing some research I realized the 3.5mm jack combines the two grounds which would cause a problem for the balanced line. I could possibly install a microswitch to disconnect the two grounds and switch between the single ended and balanced jacks but I'll probably just take the easy route and disconnect the 3.5mm jack and build 4 Pin Mini XLR single ended and balanced cables. I'm using balanced line in star quad format for the headphone cables pairing the quad's opposing conductors for each channel.
I found 10 feet of CANARE L-4E6S STAR QUAD BALANCED MICROPHONE CABLE BULK 21 AWG 4 conductor cable for $11 on ebay. It has 2 blue wires and 2 white wires. I'll have to use a multi-meter to identify one of each color wire and mark it. I used the marked wire as the negative conductor.
Classic 4-pin XLR pinout (pin - signal - wire color):
1 - Left + Blue
2 - Left - Blue with mark
3 - Right + White
4 - Right - White with mark
Since it's a shielded cable I'm going to ground only the amp end of the shield to the connector barrel so the shield will provide interference protection and yet keep the signal lines balanced.
Edited by robrob - 7/22/13 at 7:05pm