Balanced / Unbalanced

An audio wiring scheme referring to an electrical (audio) signal having two "legs" independent of ground. One leg is generally considered positive (+) with reference to ground, and the other negative (-). A third conductor, the shield, is an outer wrap of conductive metal encircling the two inner, signal-carrying conductors. In balanced wiring, when the signal reaches the destination, the negative copy of the audio signal is polarity-reversed and added to the positive signal. Any noise induced into the signal on its travels is also reversed; when combined with the non-reversed noise, the two noise signals cancel each other out. This phenomenon is called "Common Mode Rejection." Balanced lines are thus used for lengthy cable runs in which unbalanced wiring schemes would be susceptible to induced inteference. The shield functions as a true shield, sending any waste-material noise to ground.Unbalanced lines have only a positive (+) signal, and the negative signal is carried on the shield of the cable. Any noise induced into the cable will make its way into the audio signal.Another use of a balanced wiring scheme is coming into popularity: balanced power systems. The concept remains the same- instead of an AC scheme wherein there is a positive signal which carries 120V with respect to ground (US), a neutral which carries 0V with respect to ground (ideally), and a ground, the positive and neutral legs both carry inverted copies of 60V with respect to ground. In this case, again, the power supplies can cancel any noise induced into the AC line and produce cleaner audio. Theoretically.