The cables used in an audio system have a large impact on the quality of the sound. Every cable can potentially add noise or compromise the sound quality of the components it connects. Understanding how the signal is carried through the cable is helpful in minimizing the risk for noise. One important consideration when hooking up the audio system is whether to use balanced or unbalanced connections. Here, we will briefly cover some of the differences between these two types of connections.
Unbalanced connections use a two conductor, unshielded cable. The cable consists of a signal wire and ground wire. A standard TS instrument cable is the unbalanced cable you will run into most often. The red and white RCA cable used with many AV components is another common example of an unbalanced
Inside the cable, the ground wire is wound around an internal wire that carries the signal. The ground wire serves two functions in this design: it carries the negative part of the audio signal and helps to shield the main positive signal wire from external interference. The downside is that the ground wire itself also acts like an antenna and can pick up noise. Unbalanced cables are generally only good for running signal up to 15 feet. This is not acceptable in most professional applications because of these limitations.
A balanced cable, by contrast, has two signal wires as well as a separate ground wire. Just like the unbalanced cable, the ground wire wraps around the signal wires serving as a shield against interference. XLR mic cables and 1/4” TRS are the most commonly found types of balanced connectors in live sound. On a balanced cable, the pair of signal wires carries identical copies of the signal on each, except that one of the wires is 180 degrees out of phase with the other. This creates what is called a differential. Any noise that is induced will be so equally on both connections. The receiving equipment will bring the two signals back into phase with one another. This flips the noise 180 degrees out of phase between the two signals serving to cancel out the induced noise. This is known as “Common Mode Rejection”.
Remember, the audio quality that a sound system produces is only as good as the weakest component in the signal path. Do you need to go out and spend hundreds of dollars on a mic cable? No, but the cables do have a significant impact on the overall quality and choosing the option that reduces the potential for noise will always yield better results