The difference between balanced vs. unbalanced audio comes up frequently and is an important concept to understand when hooking up pro audio equipment. Before you start plugging things in, check if your devices use balanced audio or unbalanced audio so that you may purchase the correct cables only once.
What are Unbalanced Cables?
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.
Unbalanced Cable Connectors
Some connector types are inherently unbalanced, so any time you see them present, you know that particular connection is one half of a balanced signal, or a single unbalanced input. RCA (or phono) connectors are always unbalanced, as are TS ¼” jacks.
TS stands for “tip/sleeve,” which refers to the points of the cables that are soldered. A TS cable will feature a ¼” or 3.5mm connector and are easily identified by having a single band near the tip. This band is often black, though a clear band is also used, and its purpose is to separate the two contact points. Most commonly these are used for instrument cables or modular patch cables.
RCA connectors, or phono connectors because of their original use with phonograph players, are used in a lot of audio equipment. It’s rare to see a single RCA cable, as they will usually come in pairs, or sometimes in triples for component video cables. Like TS connectors, these have two contact points. The placement of the contacts on RCA connectors is different from TS connectors. The RCA connector shield is a circular surface around the center pin contact. When connected, the pin makes contact inside the device RCA jack and the shield makes its contact around the jack.
What are Balanced Cables?
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.
Balanced Cable Connectors
Just like unbalanced cables, sometimes you can tell which cables are balanced just by the connectors that are used. TRS and XLR would be the most common connectors used for balanced connections.
TRS stands for “tip/ring/sleeve,” which refers to the points of the cables that are soldered. A TRS cable will feature a ¼” or 3.5mm connector and are easily identified by having two bands near the tip. These are more commonly used for single-cable stereo signals. It is important to note that an analog stereo signal traveling along a single cable with TRS connectors is not balanced. More on that in the next section. In a typical balanced application, the original signal is wired to the tip and the inverted signal is soldered to the ring contact.
XLR cables most commonly feature three pins, though they can be found with four or five pins in some applications. The three pins will carry a positive charge, negative charge, and ground. Most pro audio equipment uses XLR connections, which are sturdy and feature a locking mechanism. When using 3-pin XLR, pin 2 has the original, or positive, signal while pin 3 gets the inverted signal. Pin 1 of the XLR connector is the shield contact.
When Balanced Cables Become Unbalanced
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. The devices in use 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.
Pros and Cons of Balanced vs. Unbalanced Audio
The biggest weakness of unbalanced cables is their susceptibility to picking up noise, so the longer a cable is run, the more interference it will pick up and the more the signal strength will diminish.
Balanced audio solves that issue with a design based on reversing the polarity of any noise generated along its run. Ideally, you want to use balanced audio when possible but the use of balanced audio is determined by the devices generating the signal, not the cable. You cannot connect a balanced TRS cable to a device with an unbalanced TS output and get a balanced signal. Lots of audio equipment still uses unbalanced audio. Best practice when using unbalanced signals is to keep your cable runs short.
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