What is the difference between balanced and unbalanced cable?
All audio signal cable is screened, which means that an outer conductor wraps around the other conductor(s) to shield them from electromagnetic interference. The outer screen, which may be made of wire braid, metal foil or conductive plastic, is usually connected to ground so that any induced currents (due to interference) flow directly to ground rather than being allowed to modulate the audio signal. However, screening isn’t a perfect solution, which is why balancing was invented. In an unbalanced cable, there’s a single inner core that carries the signal while the outer screen also doubles as the signal return path. Any interference that results in induced currents flowing through the screen conductor will cause these currents to be added to the wanted signal, so some interference problems are still possible, especially with long cable lengths or where there are nearby sources of strong interference. Though it’s not often realised, screened cable offers very little protection against
