Aux vs. Bluetooth: What's the Difference?

The key difference between Aux and Bluetooth is that one is wireless and the other is wired. An Aux (auxiliary) connection refers to any secondary wired connection but is commonly associated with the 3.5 mm headphone jack. Bluetooth is a wireless technology standard that connects keyboards, headsets, speakers, controllers, and other peripheral devices to a host computer like a laptop, phone, or tablet.

Apart from the wired vs. wireless distinction, what else separates an Aux connection from a Bluetooth connection? When it comes to convenience, compatibility, and sound quality, which one is better? Here we cover the similarities and differences between Aux and Bluetooth.

Overall Findings

While Aux may refer to any auxiliary or secondary input, it is commonly associated with the 3.5 mm headphone jack, which has been around since the 1950s. Aux inputs are also referred to as phone plugs, stereo plugs, headphone jacks, audio jacks, 1/8-inch cords, or any iteration of these terms.

Bluetooth, meanwhile, refers to a wireless connectivity standard for computers and peripheral devices. While not as universal as Aux inputs, Bluetooth is increasingly common.

Convenience: Aux Is Faster, Universal, and Wired

It's easy and perhaps faster to connect a phone to a speaker system with an Aux cable, but the presence of a cord limits the range between a device and its host. There's no need to digitally set up an Aux connection. You only need a headphone jack that runs from the audio source to an Aux input on a speaker or receiver. Unlike Bluetooth audio, however, Aux connections require a physical cord, which can get lost or damaged.

Bluetooth is a wireless standard, which allows for more freedom of movement between a device and its host. Most connections are effective at distances of up to 33 feet. Some industrial use cases range up to 300 feet or more. For car audio, Bluetooth connections allow for hands-free control through virtual assistants like Siri. This also allows you to make hands-free calls, which you cannot do with an Aux connection.

Bluetooth connections can be finicky. To connect a phone or media-playing device to a speaker system, you must place the speaker on a discovery mode and use a phone to locate the speaker. This process is not always as easy as advertised. If two devices don't pair, repeat the process until it works. Because software is always updated, old or outdated devices can be a challenge to connect. Some pairings also require a passcode to complete a connection. All this can make the process of playing audio more of a startup hassle than an Aux cord.

Sound Quality: Aux Delivers Superior Sound Without Data Loss

Bluetooth audio is generally considered inferior to most wired audio connections, including 3.5 mm Aux connections. This is because sending audio over a wireless Bluetooth connection involves compressing digital audio into an analog signal at one end and decompressing it into a digital signal on the other. This conversion results in a minor loss of sound fidelity.

While most people will not notice the difference, the process contrasts with Aux connections, which are analog from end to end. Digital-to-analog conversion is performed by the computer or phone hosting the audio.

Although the sound quality is theoretically superior, Aux does have drawbacks. Because it is a physical connection, Aux cords tend to wear out over time. The repeated plugging and unplugging of the cord can slowly erode the metal, creating poor connections that distort audio. Shorts in the electrical flow also introduce audible noise. For wired connections, digital USB connections generally provide better sound quality, but not everyone will notice a difference.

On high-end sound systems, those differences become clear—be it through Aux, Bluetooth, or USB. As such, an Aux connection provides higher quality audio than Bluetooth. A digital connection (like USB) provides better sound. The differences in fidelity between each source must be weighed against the differences in convenience.

Compatibility: Aux Is Ubiquitous, but Only for Audio

Because Aux connections are analog, there's a wider range of compatible sound systems. Almost every audio-playing device has a wired Aux input, including CD players, head units, portable speakers, record players, home theater receivers, some musical instruments, and most smartphones and tablets. The biggest exception is every iPhone made since 2016.

Bluetooth connections are completely wireless and work with an array of peripheral devices, not just sound systems. Bluetooth can be used to connect keyboards, printers, headsets, drawing tablets, and hard drives to a host device. However, because Bluetooth connections are wireless, Bluetooth is less compatible with old or archaic sound systems.

Final Verdict

Aux describes any secondary audio connection, but most commonly refers to the 3.5 mm headphone jack. The technical term for this type of Aux connection is TRS (Tip, Ring, Sleeve) or TRRS (Tip, Ring, Ring, Sleeve). These names, in turn, refer to the physical metal contacts in the plug head.

It's because Aux cords are time-tested that they remain so common. Aux cords are not without drawbacks, but the simple analog convenience is one reason these cords are popular. That said, Bluetooth is catching up.

The motivation behind Bluetooth was to come up with a faster, wireless alternative to the RS-232 serial port connection for personal computers in the 1990s. The serial port was largely replaced by USB by the end of that decade, but Bluetooth eventually found its way into the mainstream.

Since Bluetooth allows for the creation of mostly secure, local, wireless networks, the technology can be used for more than listening to audio. Bluetooth is not a one-to-one stand-in for a 3.5 mm headphone jack. Each standard has its core use cases, but as media becomes more wireless and digital, the case for Bluetooth becomes more compelling.