MOTU.com – What is the difference between balanced or unbalanced?

Balanced audio uses three conductors to carry the audio signal.
Two of the conductors carry negative and positive signals (audio is an AC signal), and the third is used for grounding.
With an unbalanced signal, there are only two conductors.
One carries positive, the carries negative and is also used for ground.
The advantage of a balanced signal is that because the ground is seperate from the negative conductor, there is less chance that radio frequency interferance will get into the audio signal.

Generally, +4 db, balanced signal are the way to go for long cable runs.
The high gain and isolated ground make for a cleaner, noise-free signal.
If cable runs are shorter, there should be no problem with RF interferance or noise on unbalanced, -10 db signals.
If you have RF problems in your studio, you probably have some kind of ground fault, and it’s a good idea to have it checked out by an electrician.
Typical studios have both +4 and -10 db gear, so the important thing there is to make sure gain stages match all the way through the signal chain.
The biggest cause of noise and distortion in audio is mismatched gain.