Connecting A Mp3 Player To A Car Stereo

You can take your tunes with you and play your MP3 player through your car stereo.

Just about everyone who has an MP3 player of any kind at some point has thought it would be really neat if they could take their tunes - or audiobooks - or lecture notes - or podcasts with them in the car. And they can.

It's not a good idea to pop on the headphones and just get in the car and go, at least not if you're driving. In many places it's illegal, and it is dangerous, since you won't be able to hear traffic sounds, and hearing a horn or a bicycle or screeching brakes could be a life and death thing.

You can, however, add some small speakers to the sun visor or near the head restraint of the seat back, and plug the player into that. Not especially convenient but it's simple, cheap and works, though it won't be very loud. You could get an add-on amplifier as well, but that means another box with wires for audio in and out and cables for power.

With the popularity of MP3 players, plus the popularity of other portable devices such as satellite radio receivers and DVD players, there's a choice of off-the-shelf methods for playing audio through the car's speakers.

An MP3 player has an earphone jack and in some cases a "line output" jack, both of which put out audio. A cord can be plugged into either jack and run to any amplifier and speaker setup, whether in your home or your car or on the beach. The difference between the two jacks is that the headphone jack is at a higher level than the line output jack, and its level is adjustable via the volume control on the MP3 player. The line output's level is fixed.

The main point here is that if you plug something into the headphone jack, it must be made for headphone-level signals. If it is designed for line level inputs, the sound will be horribly distorted as the headphone levels are just too high unless you turn the headphone level way down, in which case you have a hair trigger adjustment that can damage your ears with a noise burst. So check whatever you plug into your MP3 player as to what it expects to see.

The simple way to fit an MP3 player to a car stereo is to use a small FM transmitter. The transmitter has an audio input that plugs into the MP3 player, and an antenna a few inches long. It has a control to set its frequency, and so you adjust it to an empty spot on the FM dial - a spot where there are no local stations. It transmits a very low power FM stereo signal, just like the transmitter on a real broadcast station, except it has a range of maybe 10 or 15 feet. You tune the FM radio in your dashboard to the frequency to which you've set the transmitter, and there you are - the sound from the MP3 player comes in just like a radio station"¦because the little FM transmitter plus the MP3 device is, as far as the radio is concerned, a radio station.

This is a very popular solution, and it's easy and inexpensive. The transmitters can be purchased for between $25 and $100 US, and require no installation. They just hook to the player and perhaps the cigar lighter socket for power, although some use batteries.

However, for anyone who is an audiophile, this is an absolutely revolting solution. And for anyone who doesn't like to tinker, it's a big pain in the neck. Here's why.



No matter how good your transmitter might be, even if you took a $50,000 FM broadcast transmitter a radio station would use and set it in your car, the fidelity you'd get wouldn't be as good as in your headphones. That's because the FM broadcast standards call for lower fidelity - that is, a restricted frequency range compared to a high quality MP3 encoding. Plus there is the added processing of the transmitter, reducing the dynamic volume range of the signal and adding various noises.

Not interested in super fidelity? Well the big problem with these car FM transmitters is that there aren't many empty spots on the FM dial. And what's empty in your driveway won't be a few miles away. You'll either find your MP3 audio disappearing under a radio station or annoying "splash" pulse-type noises in time with the music from a station on a nearby channel. So you have to fiddle with the transmitter AND your in-dash radio to find another spot.

There's also a difficulty with picking enough signal strength from the small antenna on the transmitter, since the in-dash radio is designed to pick up signals from outside the car.

If the transmitter is an analog type, it will tend to drift off the frequency to which you've set it, leading to progressively increasing distortion on your sound and finally no sound at all as it's drifted to another channel. If you want to avoid this fiddling, you can buy a digital transmitter. These are digitally controlled - they don't process the sound digitally - but they will be far more stable and are at the higher end of the price range quoted above.

A better alternative, if harder to find, is a "direct connect" FM transmitter. It takes a little more work, as it plugs into the antenna input of the in-dash radio, so you'll have to crawl under the dashboard or pull the radio. However it interrupts the path between the regular FM broadcast antenna and the radio so the problem of interference from real radio stations is reduced and the signal strength from the FM transmitter is increased. Of course, the device can be switched off so as not to interfere with your regular broadcast listening.

Some folks have a cassette player in their car. It's possible to buy a cassette adapter from an electronics store. It looks like a regular cassette, but it has a wire coming out that plugs into the MP3 player. You pop the cassette adapter into the slot on the dashboard and the stereo thinks it's playing a cassette. This sound quality is pretty good, and it requires no batteries or other power source, so you only have the one cord.

Major problem is that some cassette players don't like fake cassettes, and will reject them, or shut the audio off and reverse direction every minutes If it does work properly, the cassette mechanism will be running the entire time you're listening, and that means a lot of extra wear and some extra noise.

From a technical standpoint, the best solution to using an MP3 player - or any other portable audio thing - is a car stereo with an auxiliary input socket. Then all you need is a $5 or $10 US patch cord available anywhere to plug the MP3 player into the stereo in full fidelity and without extraneous noises and needing no tinkering whatever.

Auxiliary inputs are commonly available on car radios, but not on the low end ones and not on ones generally installed by the factory as standard equipment. If you want a nice installation, and don't mind spending in the order of $300 US for a new radio, get one with an auxiliary input.

If your existing car radio has a CD changer, or if it has a socket for a CD changer on its rear panel, there's another simple solution. From auto stereo installation suppliers it's possible to buy a wiring harness setup called an "auxiliary audio input interface" that uses the CD input to give you an auxiliary input for the MP3 player without impairing the CD operation. This does require access to the rear of the radio but otherwise is an easy job and sounds great.

It's certainly possible to enjoy your MP3's as you drive, you'll just have to pick the solution that's best for you.

© High Speed Ventures 2011