Combining Balanced Cables
The standard connector for balanced audio is the 3-pin XLR. For details on wiring various configurations and connectors see Audio Connections.
Unfortunately there is no official standard for wiring balanced audio cables, but the most common configuration is:
Pin 1: Shield (Ground)
Pin 2: Hot
Pin 3: Cold
Mixing Wiring Configurations
Using cables or equipment with different wiring configurations in the same system is a recipe for trouble. You may well find that audio signals start canceling each other out and leave you with nothing.
Many sound mixers have a "phase invert" switch on each channel. This swaps the phasing of the hot and cold pins to solve the mismatch problem.
Obviously the best plan is to keep your wiring consistent. Use the configuration above and you shouldn't experience too many problems.
The rule of thumb for audio systems is: Connect all shields, ground everything, balance wherever possible.
That's the end of this tutorial. If you have any questions, please ask in the Audio Forum.