How to Use an MP3 Player in Your Car

There are more ways than one to play music from your mobile device

What to Know

  • Use CarPlay for iOS devices or Driving Mode in Google Maps in Android. If your head unit lacks built-in support, use a USB or Bluetooth connection.
  • For older head units, use an AUX input, which works just like headphone jacks. For very old radios, try using a cassette adapter.
  • Another option is to use an FM transmitter or modulator. Most FM transmitters plug into an MP3 player like a cassette adapter or aux input.

This article explains several ways to listen to music in your car, whether you have an iPhone, Android, or MP3 player. Options depend on the type of head unit you have, as well as the compatibility of your mobile device.

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Best for iOS Devices: Carplay

iPod in a car
Some head units are specifically designed for use with iPods.

osaMu /Flickr (Creative Commons 2.0)

What We Like
  • Connects with any iPhone, iPad, or iPod.

  • Access your entire music or podcast library on the road.

  • Control on phone from the interface on your head unit.

What We Don't Like
  • Only works with iOS devices.

  • Not available on a lot of head units.

The ideal connection for an iOS device is through a compatible head unit with Apple CarPlay. Built-in iOS controls are also available on a number of aftermarket head units. You can use a USB cord or Bluetooth pairing to interface with your head unit, though USB provides superior sound quality.

Once connected, you can view and select songs through the head unit controls. This is one of the most streamlined ways to listen to an iOS device in your car—be it an iPhone, iPad, or iPod.

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Best Sound for All Digital Media Players: USB

usb connection car mp3
USB connections in cars work with most phones and MP3 players.

knape / Getty Images

What We Like
  • Better sound quality than wired connections.

  • Easy to plug in when you start driving and unplug when you've arrived.

What We Don't Like
  • Compatibility far from universal.

  • Older vehicles may require additional accessories.

If your head unit lacks built-in support for your mobile device or MP3 player, the next best option is a USB connection. USB allows for an all-digital pathway between your device and your head unit, which makes for superior sound quality because the media does not have to be compressed and converted to a wired analog signal.

Some head units can even read media from a USB flash drive, but most simply have a standard USB output. You will need to supply the cord that works with your device.

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Best Option Without a USB Cord: Bluetooth

iPhone's Bluetooth Setting
Many head units can be paired with mobile devices via Bluetooth.
What We Like
  • Hands-free control

  • Interfaces with head unit without need for USB cord.

What We Don't Like
  • Pairing is finicky.

  • Sound quality not as great as USB.

Bluetooth can deliver the same head unit interface and functionality as a USB connection but without the wires. However, the sound quality is not as good, and it can sometimes be a hassle to pair your device with your head unit.

Bluetooth is increasingly common in vehicle head units. However, because most of these interfaces also have USB outputs, most people opt for the latter. Bluetooth is generally preferable to Aux inputs because they allow for hands-free control.

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Best Sound for Older Head Units: Aux Input

mp3 car aux
Plugging in an MP3 player or phone via an auxiliary input is one way to go, but it may not provide the best sound.

PraxisPhotography / Getty Images

What We Like
  • Offers decent sound with greater compatibility than USB.

  • Easy to connect.

What We Don't Like
  • Sound quality generally inferior to USB connections.

  • Can't be controlled from the head unit.

Some head units don't have USB outputs, neither do some (very old) MP3 players. Thankfully, Aux inputs are nearly universal. These inputs work just like headphone jacks, in that you can use any 3.5mm aux cord to connect your media player to the car stereo.

You will need a cable with two 3.5mm male ends. Make the connection and select the Aux audio source on the head unit. Because the line-in is an analog input, you will need to use your MP3 player to select and play songs. Audiophiles may also notice inferior sound due to the lossy compression of digital-to-analog audio.

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Best Option for Very Old Car Radios: Cassette Adapters

cassette tape in car with mp3
Cassette tape adapters weren't meant for use with MP3 players, but they'll do in a pinch.

Baturay Tungur / Getty Images

What We Like
  • Works with old cars that lack a digital interface.

  • Easy to set up.

What We Don't Like
  • Sound quality is not great.

  • Cluttered presentation with wire hanging out of the tape player.

Cassette decks are no longer available as original equipment in new cars, but they're still prevalent in a lot of old cars. If your car has a cassette deck and lacks direct smartphone controls, USB, or Aux, then you may be able to use a cassette adapter with your MP3 player.

These adapters were originally used with portable CD players, but they work just as well with MP3 players. They look like cassette tapes, except they don't actually contain any tape. Audio is transferred via a cable to the adapter and then passed through the tape heads.

Cassette adapters don't provide the best sound quality, but they're a lot cheaper and easier than a brand new head unit.

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Most Universal Solution: FM Transmitter

fm broadcaster mp3 player
An FM broadcaster or modulator is a sure-fire way to listen to MP3s on any car radio, but there are drawbacks.

Kyu Oh / Getty Images

What We Like
  • Works with any FM car radio.

  • Bluetooth options available.

What We Don't Like
  • Sound quality is not great.

  • Does not work well in areas with a lot of FM radio traffic.

The last way to connect an MP3 player to a car is with an FM transmitter or modulator. FM transmitters broadcast very weak FM signals that your head unit can pick up. Due to the strict regulation of radio broadcasting in most countries, these signals can't be picked up very far away from the transmitting device.

Most FM transmitters plug into an MP3 player just like a cassette adapter or auxiliary input. The best sound quality is typically achieved by selecting a frequency that does not have much or any idle reception.

Some FM transmitters use Bluetooth technology. These devices can be paired with MP3 players or phone that are also Bluetooth-compatible. This allows for a wireless interface between your media player and stereo. If your radio does not have an auxiliary input, an FM modulator is likely the next best thing.

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How to Connect a Phone or MP3 Player to Your Car Stereo

Some head units are designed to work only with certain devices. To determine which systems are compatible with your device, consider these options:

  • USB: Many cars have built-in USB inputs, allowing you to plug your phone directly into the head unit as you would a phone charger or external hard drive.
  • Auxiliary (Aux): Some head units include a 3.5mm auxiliary input that you can use with any phone, MP3 player or audio device with a standard headphone jack.
  • Bluetooth: Increasingly common in car head units, Bluetooth allows for hands-free wireless control of your MP3 player or smartphone.
  • Apple CarPlay: Some head units have built-in compatibility with iOS devices. Carplay allows your iPhone, iPad, or iPod to take over the infotainment system, replacing the original vehicle interface with something more Apple-friendly.

You will get the best sound quality with a USB or Lightning connection. This is because, with USB, the digital media on your mobile device does not have to be compressed into an analog signal, as it does with an aux connection.

An aux input is still better than an FM transmitter or a cassette tape adapter, although both of those options may still be better than having no access to digital audio at all.

Just thinking about buying an MP3 player? Here are our picks for the best budget MP3 players on the market.

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