Found this around....may be of some use.
Check your wiring standardse
Probably the single most common mistake for beginners is the wiring of an XLR plug. You'd be amazed at how often beginning technicians confuse the numbering and wiring of a simple XLR connector. For who knows why, it does not go from one to three or three to one. Rather, pin 2 is designated to be the hot or in-phase pin, pin 3 to be the cold or out-of-phase pin and pin 1 is ground. Years ago, there was no agreed-upon standard, and you may still find equipment with pin 3 wired hot. This is especially true with older, non-U.S. equipment and even some old Ampex VTRs. Check the operating manual for the pin configurations.
For 1/4-inch TRS (stereo plugs), military-style, bantam or tiny telephone connectors and jacks, the tip becomes pin 2 (hot), the ring pin 3 (cold), and the sleeve connects to the shield.
If you're dealing strictly with monaural signals, you can get away with a few phase reversals in your connectors and you probably won't notice it. However, connect two mics out of phase and try mixing them together and it's a completely different matter. The signals will cancel and create moving acoustic phase errors, resulting in havoc for the audience (and engineer). The fix is to swap the hot pin wire with the cold pin wire inside the XLR plug on one side of the offending XLR connecting cable. If you use this alternately wired cable to connect the two units, they will now be hooked up in-phase with each other. Be sure to label that cable as phase-reversed so that if it is unplugged and used again, it will be designated for use only when you need to reverse a phase. It's better to use commercially built phase-reverse adapters. They provide a quick and easy solution to phase problems. You can even paint them a special color so you'll know where they are and when they are in use.
Have a few phase-reversed cables and patch-bay jacks available in your studio, especially for use with rental or guest equipment that may have alternate pin configurations being brought in. This can save time and trouble if someone wants you to interface a special device.
If you need to make a cable with a 1/4-inch, unbalanced, mono connector on one end, and an XLR on the other, you must combine two methods of wiring. The hot connection goes to the 1/4-inch plug's tip on one end, and to the XLR connector's pin 2 on the other. The shield goes to the 1/4-inch plug's sleeve, and pin 1 on the XLR connector. If you are using single-conductor, shielded cable, you are done on the 1/4-inch side. For the XLR side, make the wire bridge between pin 1, which currently has the shield connected to it, and pin 3.
When wiring a 1/4-inch, unbalanced plug using balanced cable you have to combine methods. Connect the hot wire to the plug's tip and both the shield and old wire to the plug's sleeve.
Now that you know all you need to know about wiring XLR connectors, stop. All this becomes even more critical if you're dealing with powered microphones. When using phantom power for condenser microphones or direct boxes requiring power, you cannot connect the low side of the cable to ground. You cannot use unbalanced cables in these applications. If you do, you're going to ground or short the power supply. Not good.
