What Is The Difference Between Balanced And Unbalanced Audio Cables?
While working with your recording equipment in your home studio and doing some research, or looking to solve a problem online, you will often read about balanced and unbalanced cables. You will be forgiven for wondering what on earth "balance" has to do to do with sound quality and a recording studio. We take a look at what exactly the difference between the two types of cables are and why it is so important.
Simply explained, a balanced audio cable uses three wires (conductors) within the cable to provide a clear signal with a much reduced noise level. The unbalanced cable on the other hand, use just two wires (conductors) in the cable, which simply carries the signal without actively reducing noise that might be picked up by the cable.
Obviously this is a very simplistic explanation. To understand exactly how it works and why you would choose to use one over the other, we need to take a much more detailed look at each and its function.
The Difference Between Balanced & Unbalanced
From the quick explanation given in the previous section, it will be easy to make the conclusion that the balanced cable is clearly the better choice. Although mostly true, it is not always that simple or absolutely necessary.
It is best to have a closer look at how each cable function to better understand why one may be preferably over the other, depending on the situation.
The Unbalanced Cable
As I already mentioned, the unbalanced cable consists of two wires. The first is the ground wire while the other wire carries the actual audio signal.
As the signal travels through the cable it starts to pick up some noise (from various external sources like electromagnetic fields generated by nearby electronics). As the length of the cable increases, so does the amount of noise it will pick up.
This last point is important and we will come back to it a bit later on.
The Balanced Cable
A balanced cables consists of three wires. The first is the ground wire, the same as the unbalanced cable.
The second and third cable though, carries the exact same audio signal. There is a catch though. The polarities of these cables are reversed, with one cable being positive (hot) and the other negative (cold). This means these two signals are basically cancelling each other out as the signal travels down the cable.
This may sound very confusing and not make sense at first. There is a reason for this though, so just bear with me as it will soon clear why this is done.
As the with the unbalanced cable, noise is also picked up as the signal travels down the cable. This noise however, is picked up in the same direction on both the positive and negative signal. (Remember, the two signals are already reversed at this point.)
Now this is the important part. At the end of the cable the the negative signal gets flipped back again, so that the two signals are in phase and audible. (If they were still reversed/polarized, they would have cancelled each other out producing no sound where the signal exists the cable.)
The resulting sound is slightly amplified as the two signals are combined (about six to ten decibels). This not the the important result though.
The noise that was picked up along the way in the same direction by both signals, also got flipped/reversed at the end of the cable. This means the noise signals are now polarized and are cancelling each other out, removing almost all noise in the process.
This may still be confusing. Take a look at the diagram below that will help you to better understand exactly how the whole process works.
Why Is This Important?
So does this mean that the balanced cable should always be used and are superior in all instances? Not at all.
Like I mentioned on earlier, the impact of noise in a cable becomes more pronounced as the length of the cable increases. And this is why unbalanced cables are preferable and used in many applications.
Audio components standing right next to (or on top of) each other, are normally connected to each other via unbalanced cables. As the length of the cables is too short for any noise to have any impact, there is no need for a balanced cable.
(A simple example of these commonly used unbalanced connections, is the RCA cables you find at the back of audio equipment in the recording studio and home audio equipment.)
When the signal travels through a long cable though (several feet), noise becomes a factor. This is especially applicable to microphones which produces a weak signal to start with and the least amount of noise can have an impact. As a result almost all quality microphones make use of balanced cables.
The Right Connector For The Right Cable
Needless to say, the connectors at the end of a cable, balanced or unbalanced, should have the appropriate amount of connections in order for the cable to function correctly.
The typical microphone cable uses and XLR connection with three connection points to accommodate the three signals required by the balanced cable. So does the 1/4" TRS (Tip, Ring, Sleeve) connection at the end of a long speaker cable.
Without these 3 connection points, a balanced cable will not be able to function. The same rule applies to unbalanced cable connections. In this case we however we are looking at a connector with two connection points.
Examples of unbalanced connections include the RCA connectors, as I already mentioned. Another unbalanced connector is the 1/4" TS connection.
The TS connection looks deceptively similar to the TRS connection, with the only difference being the extra "ring" not present, turning this connection into one with two connection points, not three.
The reason for mentioning the different types of connections, is to emphasize the importance of paying attention to your connectors and making sure you are using the correct ones. Many, like the TRS and TS cable, also look very similar but function very differently and will not work when connected to the wrong interface.
(Don't worry, you will not blow up any equipment if you get it wrong. It simply will not function correctly or worse case scenario, not work at all.)
Conclusion
So that is the difference between balanced and unbalanced cables in a nutshell. The fact that balanced cables are carrying three wires instead of two (unbalanced cable), enable them to produce a stronger and noise-free signal especially in longer cables.
This is crucial for instruments like microphones who generally produce a weak signal and use longer cables, making it especially prone to any noise interference. You will have to look long and hard to find a microphone in any studio not using balanced cables.
An added benefit for balanced cables, is the fact that it is able to carry a small electrical current. Again, this is essential for microphones where it enable condenser microphones to operate, or supply power to mic activators which are used to boost the weak signal of a dynamic microphone. This is done via phantom power supplied by an audio interface.
(I will explain what exactly phantom power is and how it works in a future article. I will them provide a direct link from this article to make things easier for you. Stay tuned!)
But, as mentioned in the article, this does not mean you have to try and use balanced cables for all audio equipment in your home recording studio. Most audio components in close proximity to each other happily communicate to each other and other components using unbalanced cables.
The signals created by the vast majority of audio equipment are strong enough (normally at line level strength) and the distance of the cables too short for noise have any impact. (In fact, you will battle to find any balanced cable at the back of any piece of equipment connected to another nearby component.)
I hope this seemingly confusing, but relatively easy to understand differences between these two type of cables are a lot less confusing to you after reading this article.
As always, feel free to leave me any comments or suggestions you may have, and I will respond and try and get to them as soon as I can.
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Catch you in the next article and happy recording!
Wessel
