Balanced
audio
A way of sending sound down a cable on two wires: the signal on one and an upside-down copy on the other. Noise picked up on the way hits both alike and cancels when the receiver subtracts them.
See also · Unbalanced See also · XLR See also · ¼″ TRS See also · Phase
Each wire picks up the same hum and buzz on its way, because both run side by side through the same cable and shield. The receiver takes the difference between the two wires. The signal, sent in opposite polarity, survives the subtraction and adds up; the noise, the same on both, cancels. That is why microphone and studio line cables can run for many metres, while a long unbalanced cable is far more likely to pick up hum.
Strictly, what makes a line balanced is that both wires present the same impedance to ground. Many outputs also drive the two wires in opposite polarity, as drawn above; some drive only one, and the noise still cancels, because the cancellation comes from the matched impedances, not from the symmetry of the signal.
Source: Bill Whitlock, Design of High-Performance Balanced Audio Interfaces ↗, Jensen Transformers · checked 8 Oct 2026