What are balanced connections and the benefits of balanced cable?

What are balanced connections and the benefits of balanced cable?
Q. Some expensive A/V preamp-processors and power amplifiers offer ““balanced connections.”” And the new Axiom EP600 and EP500 subs also have them. What are they, and are ““unbalanced”” connections inferior to balanced? What would I gain in performance using balanced cable? –– J.C.
Balanced Connector

Used almost universally in the world of recording studios and professional broadcasters, balanced cable use a three-wire cable fitted with very secure and solid ““XLR”” connectors (sometimes called ““Cannon”” connectors). The three-wire balanced configuration is composed of an outer shield surrounding two out-of-phase inner wires that carry the positive and negative portions of the signal. This enables running very long cables–hundreds of feet if necessary– between amplifiers and preamps or between microphones and a mixing console without picking up hum or interference and without significant signal loss.

Since long cable runs aren't required by most consumer audio/video installations, the simpler 2-wire ““unbalanced”” design and connectors are used——an outer shield that carries the ground (negative) portion of the signal plus a single inner positive (““hot””) wire. This design is much less costly and, so long as cable runs remain relatively short, offers ample shielding and resistance to interference and signal loss. From a performance standpoint, an unbalanced amplifier or receiver is capable of excellent performance but may be more vulnerable to RF (radio frequency) interference as well as AC hum problems from ““ground loops”” and component interconnection. To the electronics engineer, a ““balanced”” system of inter-component connection is a technically more elegant design but considerably more expensive.

To find out more about balanced cable and other connections click here.