Comparison Table

If certain features are important to, you may find the below comparison table helpful in deciding which connection option is right for you.

Connection Connection Type Likely Sound Quality Charging Supported? How is media device controlled? Additional Functionality (beyond playing music) Key Advantages
AUX Inputs (3.5mm and RCA) Analogue
(requires cable)
Good No3 Media device itself Can transfer audio from phone calls and apps5 Simple, easy to use and compatible with most devices. Widely fitted to cars
USB Inputs Digital
(media devices require cable)
Excellent Yes Media device or car controls4 Display track information. Can be used simultaneously with Bluetooth for calls Can select and play music files from USB memory sticks. Will charge devices (with cable)
Bluetooth® Digital
Very Good2 No3 Media device or car controls Will display track information. Can often transfer audio from phone calls and apps Widely compatible, wireless solution, which can support phone calls and music streaming
Mobile Operating Systems Digital
(requires cable)1
Excellent Yes Car Controls Promises full integration for phone calls, maps and many other apps Fully integrates many of your phone's features with your car's display, stereo and controls
SD Card Inputs Digital Excellent N/A Car Controls Will display track information. SD cards can also store maps for navigation systems Can play music files from SD Cards, so no need for expensive media players
Manufacturer Media Ports Depends
(requires cable)
Depends Yes Media device or car controls4 Will display track information. May work with apps Allows you to connect and control your device, display track information and support charging
FM Transmitter Analogue
(requires FM transmitter)
Can suffer from interference Potentially Media device itself Can transfer audio from phone and apps5 Allows connections to older stereos, will work with most cars and devices
Tape Adapters Analogue
(requires tape adapter)
Can suffer from interference No3 Media device itself Can transfer audio from phone calls and apps5 Allow connection to older stereo
Aftermarket Solutions Depends Depends Potentially Depends Potentially much of the above depending on solution Can bring the latest connection methods to older cars

1 Although wireless integration with mobile operating systems may become available at a later date
2 The quality of Bluetooth connections can vary depending on the transfer rates / versions supported by your device and car.
3 Although they will not charge devices Aux inputs, Bluetooth and Tape Adapters generally leave your charging socket free to plug in separate charges simultaneously.
4 Sometimes you will be able to control through both device and car, however sometimes control may be restricted to just the car controls.
5 This connection method plugs into the headphone socket of your device. As a result if you can hear audio from an app via headphones you will also be able to transfer that same audio to your car stereo.

Connection Types and Cables

Many of the options available require hardwired connections between your device and car. Often this means you will need a cable compatible with your device and car. For example with AUX inputs you will need an AUX-IN cable and with USB inputs you will need a USB cable. Whilst cables generally provide a reliable connection, the cables and sockets can wear and will sometimes need replacing. Also bear in mind that with some cable designs, cases will have to be removed to allow access to the connector.

Other methods such as Bluetooth® have the advantage of being wireless. These means you can connect your device without taking it out of your pocket! Whilst this is clearly more convenient, there are occasionally issues with range and connections being unreliable. Also without a hardwired connection you will be unable to charge your device and there may be some limitations on functionality.

Sound Quality

All of the modern methods for playing audio through your car give reasonable sound quality and, given the background noise in cars, you probably wont notice much difference between them. If you are a complete audiophile however, you may find that digital connections are slightly better.

This is because all modern media devices store your music in a digital file formats (such as mp3, wmv or AAC), but the speakers in your car require analogue audio signals. This means that at some point the signal has to be converted from digital to analogue using a digital-analogue converter (DAC). Some connections provide the sound to your car stereo in digital formats (such as USB, Bluetooth, SD Cards.) When this happens the conversion will be done by a DAC in your stereo. In comparison, with methods like AUX inputs and 3.5mm FM transmitters (which accept analogue audio signals), this conversion will be done by your smartphone / mp3 player. The DACs in phones and other portable devices are sometimes not as good as they could be (they are optimised for headphones). As a result the sound quality may be clearer with digital connections. Of course don't forget many other things can also affect audio quality, not least the format and quality of your music files on your device!

Charging Devices

Some connection methods (USB inputs, Media Ports, Mobile Operating System Ports) plug into your devices' charging port and can provide power. Other methods won't charge your devices (like AUX inputs or Bluetooth) but normally leave the charging port free, allowing you to connect a charger simultaneously.

Controlling your Media Device

The way you control your media device (how to select music, playlists or apps) differs greatly across the various connection methods.

Some connections (USB) are bi-directional and will let you to control your media device through your car's buttons and screens, allowing you to safely use your device on the move. The latest mobile operating systems for cars are taking this a step further, by fully integrating your phone's features into your car. For example you can view, select and control applications through touchscreens in your vehicle, as well as using buttons and technologies like voice recognition. This makes the user experience easier and more intuitive, whilst avoiding distracting drivers.

Other methods (AUX inputs) will only allow control via the media device itself (although you will be able to alter the volume using the car). This may be preferable if say a passenger is selecting songs to play. It also means you will be able to use any app that works with headphones (so Spotify, Audible & Podcasts should all work).

By contrast some methods support both. Bluetooth connections normally allow you to control playback through your device and offer limited control through the car. For example you can normally select the next or previous song using your car's controls, but can't select a new playlist (you would have to do this on the device itself).

Seeing Phone Display / Track Information

The types of information that can be transferred to your car also differs between methods.

Some more sophisticated methods can transfer information to your car's display. This might include song titles, artists or albums. Mobile operating systems for cars will be able to display a whole lot more, including menu systems and applications like maps.

Meanwhile, simple analogue audio connections, like AUX inputs, FM transmitters and cassette adapters, generally can only transfer audio signals. They won't be able to transfer any track information. Some customers get around this problem by using phone mounts, which allow you to place your phone on the dashboard so you can see the display handsfree.

Additional Functionality

All of the methods discussed can let you listen to music and often other forms of audio (like podcasts and audiobooks) from compatible devices. The analogue audio connections will also let you transfer audio from phone calls, or apps like maps or Spotify. Sometimes digital methods can do this as well.

The latest mobile operating systems in cars promise a wider set of functionality. This includes integration of many of your phone's features (phone calls, maps, audio streaming and third party applications) with your vehicle's display, stereo and controls. Development and innovation is growing rapidly in this area. For example Volkswagen are making a dedicated Android™ app, which you will be able to use in the new Polo with MirrorLink™.