Finally The Truth About Balanced and Unbalanced Audio Signals

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The issue of balanced and unbalanced audio signals is one of the most misunderstood technical issues in our industry. Conflicting theories can be troublesome when you are designing a system where the choices become important. For the purposes of this discussion, we will deal with line level signals. Microphone level signals will be addressed at another time.

Line level signals are typical of your home stereo system. The output of a CD player, for instance, is line level. Most consumer-grade CD players output an unbalanced line level audio signal. This is best identified by the use of a simple RCA (phono) connector on the back panel of the product. RCA connectors are the most common unbalanced connector used. These signals are designed to interface over short cable lengths between compatible equipment, like your CD player to your amplifier. The physical make up of the cable is a single ‘hot’ conductor and a ‘shield,’ or ground, encasing the hot conductor. This is the kind of cable that usually comes with the product, and has a red and white color RCA plug end.

Unbalanced signals are NOT designed to travel over long distances, as they become vulnerable to hum and noise due to the limited physics of the cable. Most system engineers will limit unbalanced cables to 15 feet. For any audio cable run over 15 feet, the solution is balanced cable. Balanced audio signals are typically associated with two types of connectors. The first type, and the most popular in the professional world, is the XLR connector which has three pins, and TRS (tip-ring-sleeve) phone jacks. The XLR or TRS connector was chosen by the industry to accommodate the special means by which balanced signals are created.

Balanced audio signals feature a positive (+) phase signal match to a negative (-) phase signal of the same information. These ‘out of phase’ signals are surrounded by a shield (ground) weave to provide proper shielding. The use of ‘out of phase’ signals are part of the physical method which allows long distance cable to run hundreds of feet to occur with minimal noise and ingress hum. The negative and positive signal conductors are twisted around each other so that any noise on the positive cable is cancelled by the equal noise on the negative cable. Because they are in such close proximity to each other, the sum noise is close to zero. In other words, the cable is designed to cancel noise.

Equipment designed for balanced audio can drive signals as far as 500 feet easily without any noise problems. What if you needed to send an unbalanced signal over a long distance? Or you want to feed such a device into a professional audio device such as a studio mixer which may only feature balanced audio inputs? Not to worry. There is equipment available that easily converts unbalanced-to-balanced and the other way as well. These converters can allow a CD player to be run room to room without any problems. Simply feed the unbalanced output into the UB-BAL converter, and then run balanced cable the distance required. On the receive end, you can either plug the cable directly into the balanced equipped product, or you convert back to unbalanced, if that is your requirement.