balanced line and unbalanced line
Audio Lab

What is balanced cable?

The balanced cable is an audio signal cable with an ideal transmission effect. Although it transmits analog audio signals, its structure and transmission principle are different from the traditioan cables. The balance cable can effectively eliminate all kinds of external interference to achieve the purpose of high-fidelity transmission of audio signals. A typical balance line is XLR cable.

From the perspective of transmission, the balanced cable has a strong anti-interference ability and is suitable for long-line transmission. If the wire is short, it has no advantage. Its most significant advantage is that its anti-noise ability is outstanding, which is very suitable for long-distance transmission of low-level signals.

Distance transmission, because there are quite a lot of other electronic equipment interferences. In this case, the balanced transmission is very advantageous. The disadvantage is that the cost is relatively high. In the HIFI field where short-distance transmission is dominant, the anti-noise advantage is not very obvious compared with unbalanced transmission.

The difference between analog and digital signal audio cables

One thing to understand first, what is the difference between analog and digital signal audio cables? They all transmit audio signals. The only difference is that the analog signal cable transmits electrical audio signals. In contrast, the digital signal cable carries digital information based on binary code (0 and 1, a language that computers can understand).

The balanced cable and unbalanced cable

Now we start with the most common problems with analog signal cables. What is the difference between balanced cable and unbalanced cable?

Unbalanced cable is more likely to introduce noise and interference. If you cut an unbalanced cable,you can see inside there are two lines inside: 1 signal line and one ground line.

However, the ground wire itself also functions as an antenna, picking up unwanted noise in the environment along the way during the transmission of the signal wire. That is one of the reasons why electric guitars have some background noise.

Because unbalanced cables can pick up noise along the way during signal transmission, they are best used for short distances. That minimizes unnecessary noise. Besides, some high-end and professional guitar connecting wires will also wrap a densely woven shield layer on the outermost layer to reduce the noise of the wire.

Where does the noise come from? The noise may come from various electronic devices and radio interference. If they are close to unbalanced wires, they will generate hum noise. For example, when your mobile phone is close to some cheap speakers or headphone cables, as long as someone calls you, you can hear noticeable noise. Also, on the stage, spotlights and dimmers may increase signal interference.

unbalanced cable

The balance cable is just the opposite. It is designed to eliminate noise and interference. It is realized by adding an extra line: there are two signal lines and one ground line. With the additional second signal line, the noise on both signal lines is eliminated, sometimes called “Hot” and “Cold” signals.

What is the difference between the “hot” signal and the “cold” signal?

The polarities of the two signals are opposite, so when they propagate along the wire, they cancel each other out.

As we said before, the wire will pick up noise along the way. When the polarity of the “cold” signal is reversed to match the polarity of the “hot” signal, the noise carried along with both the two signals cancel each other out.

This “cancellation” process is called “common-mode rejection”, where noise is the “common” signal between the two.

balanced cable

Since the balanced signal sends two “in-phase” signals, they also provide a louder sound (about 6 to 10db stronger) than the unbalanced signal under the same conditions.

Typical unbalanced line vs balanced line interface

Unbalanced line interface: RCA interface

RCA interfaces are very common in our daily lives, such as speakers, TVs, power amplifiers, and other devices are available. The RCA interface is named after the English abbreviation of Radio Corporation of America. In the 1940s, Radio Corporation of America introduced the interface to the market and used it to connect devices such as phonographs and speakers. Therefore, the RCA interface is also called the PHONO interface in Europe and America.

Balance line interface: XLR interface

The XLR interface is also known as the “Cannon”. That is because Cannon Electric, founded by James H. Cannon, was its original producer. Their earliest product was the “cannon X” series. Later, the improved product added a locking device (Latch), so an “L” was added after the “X”. Later, a rubber compound was added around the connector’s metal contacts, so an “R” was added after the “L”. Therefore, people later put these three capital letters together and named it the XLR interface.

rca connector
*RCA connector
xlr connector
*XLR connector

Can a balanced cable ensure a balanced connection (transmit balanced signals)?

The answer is no! Please keep in mind here: if you want to maintain a balanced connection, you must ensure that the entire circuit is balanced. The summary is as follows:

  • Output on your device should be balanced
  • cable for connecting should be balanced
  • Inputs (such as your mixer or microphone) should be balanced

As long as one of the above is an unbalanced signal, then your connection is unbalanced.

How do you make sure that your device supports a balanced signal?

If your device is like this, your device is a balanced signal:

  • It has XLR output or input.
  • There is a written on your device or manual.

For example, a microphone, some mixers, sound reinforcement system, some professional equipment and synthesizer with XLR output 

In the following cases, your device is unbalanced:

  • It is a guitar or bass
  • It is 3.5 mono or dual channel output
  • It is RCA input or Output

Conclusion

Knowing the difference between balanced and unbalanced signal cables plays a crucial role in choosing the right cable. That will prevent signal loss and noise introduction during recording or performance. Using the wrong cable can even damage your device. 

If you have a balanced-signal device and a balanced-signal mixer, only balanced-signal cables can guarantee an excellent balanced-signal connection.

But if you can’t use balanced signal connections, make sure the cables are as short as possible. 

Tips: If you want to use an unbalanced connection, please ensure that your unbalanced cable is less than 1.8 meters to reduce signal interference.

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