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 separate from the negative conductor, there is less chance that radio frequency interference will get into the audio signal.