What is the difference between a balanced and an unbalanced line?
A balanced (or directionally balanced) line is a circuit that uses two conductors and a shield for connection, in which first conductor carries the standard audio signal and the second conductor carriers an inverted signal, which is re-inverted and added to the first signal at the destination. This inversion also inverts any line noise which is picked up by the cable, so that the line noise is cancelled out. Compare to the illustration of an unbalanced line, such as a mono microphone cable, shown below.
