Monthly Archives: November 2017

Audio: Balanced and Unbalanced

Below is what an unbalanced audio signal looks like. The Y axis is volts, the X axis is time. The red line is the + signal, the black horizontal line is the – signal. The + signal carries the music, the – signal is ground. This is sometimes called “single-ended” because only one wire carries the musical signal.

audioSignal-unbalanced

Below is what the same audio signal looks like when balanced. The red line is the + signal, the blue line is the – signal. Here, neither wire carries ground. Each wire carries the same signal, but they have reverse polarity. The difference between them is a signal having twice the amplitude. At every instant in time, the voltage sum of the + and – wires is zero, so the cable (containing both + and – wires) has a net field of zero, which makes it immune to interference.

audioSignal-balanced

This gives balanced signals 2 advantages: S/N ratio is 6 dB higher (twice the voltage = 6 dB), and immunity from interference.

Balanced audio was designed for microphones, which have low level signals carried on long wires. In this application, noise isolation is important and you need all the S/N you can get. Consumer audio analog line levels are in the range of 1-2 Volts, about 1,000 times or 60 dB stronger than microphones. And cable runs tend to be shorter.

Thus, balanced audio doesn’t make much if any difference in consumer audio applications. It’s a superior engineering design, but it doesn’t necessarily make any audible difference especially in top notch gear that already has S/N ratios well over 100 dB. It’s nice to have, but I would not pay extra, or chose one piece of equipment over another, for this feature alone.