What’s the Difference Between Balanced and Unbalanced Audio?

Questions about balanced and unbalanced audio come up frequently and it is an important concept to understand when hooking up pro audio equipment. Before you start plugging things in, check if your devices use balanced or unbalanced audio so that you may purchase the correct cables only once.

Analog audio cables consist of a shield and one or more conductors. Corresponding connectors must then have at least two points of contact. Cables that only have a contact point for the shield and one signal are unbalanced. An example of this would be a guitar cable, as it uses 1/4” TS connectors. In this example the sleeve of the connectors is the shield and the tip is used for the signal. The problem with unbalanced cables is that if any noise enters the signal as it passes from one end to the other, that noise is added to the sound when it reaches its destination. This is precisely the reason balanced audio was created.

In balanced audio the signal is duplicated and carried on two separate conductors. The trick is that one of the signals is flipped, or inverted, to be the polar opposite of the other; one is positive and the other negative. At their destination, the negative signal is changed back to positive and combined with the original. At the same time, the noise traveling on the negative signal is also flipped and becomes the polar opposite of the noise on the positive signal. The result is any noise equally picked up by both conductors is rejected at the destination. Microphone cables, like the Hosa Edge CMK-010AU, are examples of balanced cables. Microphone levels are very low and the best way to keep them noise-free is to use balanced audio. Microphone cables with 3-pin XLR connectors, audio interconnects with 1/4” TRS connectors, and even interconnects with 3.5mm TRS connectors are examples of balanced audio cables if they are interconnecting devices using balanced audio.

It seems pretty easy when it comes to cables, right? If the cable has two points of contact, it’s unbalanced; and if it has three, it’s balanced. Well, not quite. A 2-conductor cable is not strictly a balanced cable. It’s the devices in use that determine the function of the cable. The Hosa CSS-110 is a 1/4” TRS interconnect. If you use this cable to go from the balanced left output of a mixer to the balanced input of a powered monitor, it is a balanced audio cable. Take the same cable and use it to hook up the stereo headphone output of a mixer to a headphone amp, and you’ve got an unbalanced stereo cable. In the second example, one conductor is carrying the left output of the mixer and the other, the right output. This cable is not carrying the same signal along both conductors and is therefore, not passing a balanced audio signal.

It’s important to always verify the type of cable you will need for the equipment you plan on connecting. Take the time to understand the connector types and the signal transfer formats before you begin researching the cable you wish to buy. Knowing this information before you go shopping for cables will save you time, which is better spent putting your new pro audio equipment to use.

- Jose
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