Many new car stereos are made with either a line-in jack or a universal serial bus (USB) port on the face of the deck to use with an MP3 player, a memory stick, or both devices. Decks with a line-in jack can interface with an music player by running a 5mm stereo cable from the headphones jack of the device to the line-in jack on the deck. Those with a USB port may be able to accept a memory stick plugged into it directly, although a USB cable may be needed in other cases.
Of the two types of decks, the model that features a line-in jack is usually less expensive. In this scenario, the MP3 player is tethered to the deck by the stereo cable, and must be turned on and used normally. Navigation, song selection, and partial volume control are done directly with the music device. The stereo simply acts as an amplifier and speaker system, with equalization filters and other audio controls affecting the sound.
The advantages to using a music player this way include the ability to take along a large library of music without having to burn a selection to CD to listen to in the car. Using the device in the vehicle also allows for hours of non-repeat listening of your favorite tunes for road trips or commutes. Assuming the MP3 player supports playlists, you can also listen to a different selection of music every day.
Disadvantages include the hassle of the player being tethered by a cable, and the difficulty in navigating a small device while driving. The latter point makes it safer to either create playlists ahead of time, use the “random play” feature, or simply allow the player to cycle through the music library normally. Another disadvantage is that the device must use its battery to play music through the vehicle’s stereo.
A car stereo with a USB port can also accept an MP3 player or memory stick, and these decks can typically read file folders and perform navigation. While the previously mentioned advantages apply, there are a few more pluses. Devices fitted with a USB-end do not require a tethering cable, nor do memory sticks. A memory stick doesn’t use batteries, either, and they are inexpensive enough that an extra one can be purchased to leave in the car with an entire mobile music library.
The main disadvantage to consider is the added expense of a USB-enabled stereo. Navigating a memory stick or music player using the stereo controls can also be awkward. Again, it might be easier to create folders ahead of time with pre-selected music, or let the deck cycle through the library using dash controls to skip undesired tunes.
If purchasing a car stereo with line-in or USB capability, be sure the interface is on the front of the deck and not at the rear. Car stereos made to interface with the Apple iPod™ typically feature a rear port that requires a proprietary adapter, though models vary.