Balanced Vs. Unbalanced: Audio for Video Production

Audio for Video Production: Balanced Vs. Unbalanced


I know this is an old arti

dennmill's picture
I know this is an old article but maybe someone is just now reading it like myself and is interested in a little more accuracy. Balanced does NOT mean that a signal goes above and below the zero volt ground. Similarly Unbalanced does not mean that the signal stays above the zero volt ground. Unbalanced simply means there is one signal and one ground. If the signal wire picks up interference, well, you've got interference. Balanced means that there are two signals and one ground. One signal is an inverted or negative version of the other. At the receiving end one of the balanced signals is subtracted from the other to get the actual audio signal. And herein lies the great noise rejection of balanced cables. Think about it. When interference happens, both audio signals pick it up. However, since the receiving end subtracts one signal from the other, then the interference on the one signal is subtracted from the other and is cancelled out. Pretty clever if you ask me.

Dennmill is 99% correct. T

man0utside's picture
Dennmill is 99% correct. The unbalanced lines use something called 'common mode rejection'. That means since noise is introduced in both signal lines, the common mode rejection circuitry cancels out identical signals (whihch would be the noise) and passes the clean audio which is out of phase.

try this explanation

Jilly's picture

balanced audio is sent along a pair of wires and the signal in each is identical except that one is 180 degrees out of phase with the other. Any interference picked up will be induced in to both wires equally and in phase. At the other end the signal is unbalanced using a transformer or differential amplifier where one of the signals is phase inverted so that now both are in phase and can be added together, at the same time the interference will be made out of phase in the two wires and when added will cancel out.

note that two signals 180 degrees out of phase when added will result in zero.