Balanced audio isn't very friendly. While most in society strive for harmony and agreement, the basics of balanced audio call for the exact opposite: a complete rejection of anything in common. But peace and harmony aren't what we want when we turn to a balanced approach to signal handling.
We're going to start our understanding of balanced audio by first separating tasks. This is important because the term
balanced audio has so many applications. For example, there are balanced outputs, balanced amplifiers, quasi-balanced, fully balanced, and balanced inputs. It is this last category we'll start with.
A single ended (SE) cable has only two conductors: one for the signal, the second for ground. Most are shielded, which means the ground conductor wraps around the outside, surrounding the inside signal wire, and is called the "shield".
Attach an RCA connector on each end and you have a single ended cable. Construction varies immensely (this is high-end audio, after all), but at its core this is what a single ended cable is all about. Two wires, each isolated from the other, one acting as an outer "shield".
A balanced cable is the same but with one addition. Instead of the SE's single wire in the center, a balanced cable has two, each with insulation so they don't electrically touch.
Going back to the SE cable, we understand the outer ground conductor (the shield) has an important role to play. Noise reduction. Think of this shield as a protective outer coat from nasties: cell phone signals, static, electrical garbage floating about. These unwanted electrical vermin never get past the outer shield and thus lower noise as they are swept away to the system's ground. The incoming amplifier now gets a relatively clean signal from which to amplify.
This is all nice and tidy until you look closer. Not all noise is the same, and some types are like deadly viruses worming through to infect both the shield and the signal conductor.
That's where a balanced cable comes to the rescue.
