Why Do XLR Cables Have 3 Pins? The Facts Explained

If you’ve seen professional audio setups, you may have noticed that the engineers often use XLR cables and that these cables have three pins. So why three pins, and not more or less? Also, what are each of the pins for?

XLR cables have 3 pins because they can carry balanced audio signals and also protect the signal chain from electrical surges. Two pins connect to the positive and negative wires, which carry audio signals, while the third connects to the cable shield, providing the protective ground connection.

In the rest of this article, I’ll take a closer look at the XLR cable. I’ll explain its different parts, how it functions, its advantages and disadvantages, and how it compares to other alternatives.

Table of Contents

Why Do XLR Cables Have 3 Pins? The Facts Explained

Facts About XLR Cables Explained

XLR (Extended Line Return) cables are designed with two ends — male connector and female connector — that plug into each other. While XLR cables can have up to 7 pins, those used for audio have three pins. 

Here are the three pins and how they work.

  • First pin: This connects to the protective cable shield around professional audio cables. The first pin protects the other two pins from electromagnetic waves (external noise) while also adding a ground connection that prevents electrical damage to the audio device it’s connected to.
  • Second pin: Often referred to as the “hot” terminal by an audio engineer, it’s the positive channel because it carries the positive phase of the audio signal.
  • Third pin: This is also known as the cold terminal or negative pin. Like the hot terminal, it carries audio signals — albeit only the negative phase.

How an XLR Cable Functions

I mentioned earlier that XLR cables deliver balanced audio signals.

This is possible because of the way a balanced audio cable functions. When the three pins I discussed above work together, you get the balanced audio signals that have made XLR cables preferable for modern microphones (and most microphones) and some other audio applications.

When the original audio signal enters an XLR cable, both the positive and negative pins carry that signal into their respective wires.

The signal on the negative wire is inverted completely, putting it out of phase with the signal carried by the positive pin. Theoretically, these two signals cancel out each other.

As the audio signal travels from one end of the XLR cable to the other, it’s likely to pick up some other noise carried by both the positive and negative wires. However, the noise signals on both the negative and positive wires are in phase.

At the end of the XLR cable, when the receiving audio device gets the audio signal, it will flip the signal from the negative pin (which was out of phase), putting it back in phase with the audio signal from the positive pin.

As a result of the above, a couple of things will happen:

  • The merging of the two audio signals from both the negative and positive pins boosts the audio level since they are now both in phase.
  • The noise signals in both the positive and negative pins cancel out. When the signals (noise and audio) from the negative pin were flipped, the audio signal came into phase with the audio signal in the positive pin. In contrast, the noise signal went out of phase with the noise signal in the positive pin resulting in a canceling out of the noise signal after the two are combined.

The first pin plays no active role in carrying audio signals.

Instead, as I’ve mentioned earlier, it protects the other two pins from electromagnetic interferences while providing a power ground wire connection for the cable and connected audio devices. The result is an audio signal free from noise interference.

Advantages and Disadvantages of an Three Pin XLR Cable

The advantages of XLR cables include:

  • Ability to remove noise from the signal path and deliver balanced audio
  • Shielding of electromagnetic interference
  • Providing a power ground pin that protects the connected devices from electrical surge or damage

On the other hand, the major disadvantage of XLR cables is that the benefits listed above are only possible when both the XLR output and XLR input devices utilize the same balanced connection.

If you’re looking for a decent XLR cable, you can start with the Amazon Basics XLR Male to Female Microphone Cable – 6 Feet, Black (available on Amazon.com). You can make this no-frills XLR cable work with most compatible audio equipment and can help you create studio-quality sound.

If you need more than one XLR cable, no worries: The Cable Matters 2-Pack Premium XLR to XLR Microphone Cable 6 Feet (available on Amazon.com) has you covered. The PVC jacket is made of oxygen-free copper, meaning the copper is purer and is less likely to suffer damage due to corrosion. 

Other Types of XLR Connectors

Aside from the three pin XLR connectors used in the audio industry, there are other types with more than 3 pins. 

Other XLR Connector Types:

  • 4-Pin XL: 4-pin XLR connectors have several applications. One of these is powering video cameras and other equipment. In this case, they’re used for delivering DC power (phantom power). You can also find them used in intercom headsets. The four pins are split between the headphone and the microphone.
  • 5-Pin XLR: You’ll usually find this type of XLR cable in the lighting field, where they’re used for connecting digital light control boxes. They’re also used for stereo intercom headsets.
  • 6-Pin XLR: 6-pin XLR connectors are used for two-channel intercom systems, as well as some lighting control setups.
  • 7-Pin XLR: 7-pin XLR connectors are the other type of XLR cable found in a professional audio setup. Studios with tube microphones usually have this type of XLR cable connecting the microphone to its power pack. It’s also used to connect the remote control of some fog machines.

Final Thoughts on XLR Connectors

The reason XLR connectors have three pins — not more or less — is that two of them carry the audio signal, while the third (ground wire) protects the other two wires from interference and provides the power ground pin.

I hope that, after reading this article, you have a much better understanding of how XLR cables work than before. If you decide on using an XLR microphone, be sure that your audio interface device has and XLR input.

Juan Louder
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Juan Louder

I started SoundStudioMagic to learn how to record my own audiobook at home, and now I'm addicted to all the latest techniques and gear.

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