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What Is Aux in Car Stereo? Everything You Need to Know.

Aux in car stereos allow you to connect your portable music players, smartphones, and other aux-enabled devices to play music through your car stereo system.

Although aux ports are not required to use these devices, they can provide a higher quality sound than other connection methods. So, what is AUX in car stereo? Let’s find out.

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AUX (auxiliary) is a 3.5mm jack that allows you to connect an AUX-enabled device, such as a portable music player or smartphone, to your car stereo system. This connection provides a higher quality sound than other connections, such as Bluetooth or FM transmitters.

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Tip: There is a large selection of the AUX wires available on the market, but to be honest, there is not much difference between them when it comes to the simple analog signal transfer.

Therefore, there is no need for overpaying, but if you are looking for several options with fancy designs or waterproof shielding, check this large selection of AUX wires at Amazon.

In the article below, I will explain everything you need to know about aux in car stereos, including how to choose the right aux cord and how to connect aux-enabled devices to your car stereo.

The Importance of Auxiliary Ports in Car Stereos

If you are using the car stereo but do not want to be limited to radio stations, it is good to have an AUX connection in the car.

It sends sound to the multimedia system, enabling you to ‘stream’ music from a device through the car’s speakers.

It is a simple and effective way to enjoy your music while on the move, without worrying about losing stations as you travel out of range.

What Does AUX Mean on a Stereo?

The AUX connection is commonly used to connect digital music players and speakers that receive sound from external sources. Auxiliary ports are frequently called jacks or plugs.

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An AUX in the car stereo means an additional port, usually on the front radio panel.

There are four main types of AUX ports known in the music industry. Most AUX cords for car audio are made with a standard 3.5mm aux connector, but some older radios may have a different, such as a 2.5mm or 6.35mm, and those models may require an RCA adapter.

How to Use AUX in Car Stereo?

Using AUX on the car stereo means that you have to plug the jack into the AUX port on the car radio, and that is it.

The AUX in car stereo will accept the signal from the AUX cord and play it through the car speakers.

Some stereos may have a button that says “AUX” or “Mode.” Once you have plugged the aux cord into the AUX port, you may need to press this button to switch from radio mode to AUX mode.

How to Get the Most Out of Your AUX Port?

You can get the best signal quality through the AUX connection if the aux cord is short. This way, there is no interference from other electromagnetic fields that can reduce the sound quality.

Another thing to keep in mind is that aux ports are usually located on the front of the car stereo, so you do not have to reach around to the back of the stereo to plug in your aux cord.

When choosing an aux cord, make sure you get one made with high-quality materials, which is the correct length for your needs.

Important in the AUX wire is also shielding that should be thick and robust to prevent any mechanical damage.

How to Connect Your Device to an Aux Port in Your Car Stereo

To connect any device to the car radio’s AUX port, you need to plug an AUX cable into the AUX port. The other end of the aux cord should be plugged into your device.

Once you have connected the aux cord and switched to AUX mode, you should be able to play music from your device through your car stereo system.

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If you’re having trouble connecting the wire or getting sound from your aux cord, make sure the aux cord is plugged in and that you have switched to AUX mode on your car stereo.

You may also need to adjust the volume on both your car stereo and your device.

What Are the Benefits of Using an AUX Port in Your Car Stereo?

Although AUX ports transfer only analog signals, they can still deliver high-quality sound.

Another great thing about aux ports is that you can use them to connect any device with a headphone jack, so you’re not limited to just digital music players.

You can also use aux ports to connect GPS units, tablets, and smartphones to your car stereo system.

AUX Ports vs. Other Methods of Connection: Which Is Best for You?

Other connection types, such as Bluetooth or FM transmitters, may also be used but may not provide the same audio quality.

Ultimately, it is up to your preference and the system you use to decide which type of connection best suits your needs.

FM Transmitters:

An FM transmitter (link to Amazon) is a device that uses the aux port to connect to your car stereo and broadcasts an FM signal.

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You tune your car stereo to an unused FM frequency, and the FM transmitter broadcasts the audio signal from your aux cord to that frequency.

One advantage of using an FM transmitter is that you can still use your car stereo’s controls to skip tracks, adjust the volume, or pause your music.

However, there are some disadvantages to using an FM transmitter. For example, the sound quality may not be as good as a direct aux connection, and you may also experience interference from other radio stations.


Bluetooth is a wireless technology that allows devices to connect with each other, meaning you can connect your phone to your car stereo and stream audio wirelessly.

The main advantage of using Bluetooth is that you don’t have to worry about tangled wires or aux cords, but not all devices can support Bluetooth connections. If your stereo does not support Bluetooth connections, you can install a Bluetooth adapter (link to Amazon).

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However, there are some disadvantages to using Bluetooth. The sound quality may not be as good as a direct aux connection, and you may experience signal loss.

What Is the Difference Between the AUX and USB?

The main difference between an AUX and a USB is that an AUX connection transfers analog signals, while a USB transfers digital signals.

In other words, USBs are more popular to transfer data to a computer, but AUX transmits the analog signals to/from the amplifier or headphones.

AUX connections are more useful when there is no USB or digital interface, for example, in an older car. Still, on the other hand, USBs are more convenient and deliver better sound but are only available on digital systems.

In some cases, USB connections also control playback from the device you’re connected to, and in the case of the car audio, this is a stereo. However, since AUX only transfer analog audio signals, they do not offer the same flexibility of two-way functionality.

Another drawback of the AUX is that these connections tend to wear out faster than USB, and AUX cords also introduce more audible noise due to shorts in the electrical flow.

There are many types of AUX connections, with the most common 3.5 mm jack, that is known in two configurations:

  • tip-ring-sleeve (TRS)
  • tip-ring-ring-sleeve (TRRS) connector many use to connect headphones. 

What Is DAC?

DAC stands for Digital-to-Analog Converter. A DAC changes digital data into an analog signal that can then drive speakers or headphones.

The car radios use DAC (Digital Audio Converter) to convert the data into an audio signal, creating a more precise sound with no loss of information.

Because auxiliary inputs and USB connect a phone to a stereo in different ways, there can also be a difference in signal quality based on how the DACs are used:

  • AUX connection utilizes the DAC in a phone.
  • A USB connection allows the DAC on a car stereo or audio interface to process the data.

Is AUX better than USB?

According to most audiophiles, an optical line improves sound clarity, channel separation, and spatial quality.

Many say that difference isn’t considerable, pointing out that speaker quality, time spent connecting to speakers, the recording source, and even your hearing contribute.

When consumers listen to an uncompressed FLAC recording on a high-end sound system, they are more likely to notice the difference between AUX and optical connections than when listening to a 128kbps mp3 on their cell phones.

What Can I Use if My Car Doesn’t Have an AUX Input?

If your car or car radio does not have an aux connection, you can still play music using an FM transmitter.

There are no cables needed because they send out signals over the air, which means there’s not as much chance of interference from other electronics around you and provides easy access for charging devices with built-in USB ports.

Can you add an AUX port to a car?

When either car or the stereo is not equipped with an aux port, you can add it by installing an aux kit. An aux kit comes with a car aux adapter and an aux cord.

You need to connect the aux adapter to the car’s cigarette lighter port. Once it is done, play music from your phone using the aux cord.

If you’re looking for a more permanent solution, you can install a new car stereo with an aux port.


AUX outputs in car stereos allow for the connection of portable music players, smartphones, and other devices to play music through the car stereo system.

Although AUX ports are not required to use these devices, they can provide a higher quality sound than other connection methods.

Other connection types, such as Bluetooth or FM transmitters, may also be used but may not provide the same audio quality. Ultimately, it is up to you to decide which type of connection is the best for your needs.