Some of Car DVD players have iPod support, you can easily connect your it to your Car DVD unit by an iPod cable through the iPod input. . But Eonon would like to remind you, if your car doesn't have an iPod dock or iPod support audio system, rather than scrapping your mp3 player for burned cds, (or scrapping your car, for that matter) owners of dockless vehicles can patch together a method for streaming their MP3s through the built-in stereo. Effort and expense will vary, and some setups will sound much better than others. Here are five options to connect your iPod to your car.

Option 1: Wireless FM Transmitter
INSTALLATION: Easy
SOUND QUALITY: Poor
FM transmitters are the most popular and convenient way of playing an MP3 device through a car stereo. They typically plug into an iPod’s dock or headphone jack to create what is essentially a low-wattage pirate radio station—powerful enough to be picked up by your car radio inches away, but not strong enough to interfere with neighboring car radios. Unfortunately, these transmitters need to compete with real (and far more powerful) radio stations and are easily swamped by 6000 watts of classic rock. When this happens, the sound that comes out of the speakers can be a cacophonous mix of static, local radio stations and whatever your iPod is playing. This problem is exacerbated by FCC regulations, which prohibit FM transmitters from broadcasting at greater than 18.75 nanowatts, essentially ensuring that they won’t work well. And while this problem is particularly pronounced in cities with crowded airwaves, the issue exists nearly everywhere in the country. There’s another downside to FM transmitters: Even under ideal conditions, FM radio just can’t deliver excellent sound quality.

That being said, FM transmitters are extremely convenient and, with many models selling for as little as $15, affordable. If you decide to use one, choose a model that lets you pick any FM frequency (some restrict you to a few stations on the top or bottom of the spectrum). This will increase your odds of finding an open channel.

Option 2: Cassette Adapter
INSTALLATION: Easy
SOUND QUALITY: Good
Audio cassette adapters take advantage of an increasingly rare feature: a car’s tape player. These adapters are shaped exactly like a cassette tape. They are cheap (around $15), commonplace and deliver decent sound quality. To use one, simply plug one end into the MP3 player’s headphone jack and the other into the tape deck. If your automobile has a cassette player, there is no easier way to get interference-free listening.

Option 3: Wired FM Modulator
INSTALLATION: Moderate
SOUND QUALITY: Good
With wireless FM transmitters, the signal has to travel through high-traffic airwaves on its way to your car antenna. Wired FM modulators, which usually come as small boxes with a few cords running out from them, intercept the connection between the car’s antenna and radio, allowing you to inject your iPod’s signal directly into this wired pathway. The result is dramatically improved sound quality—although the final result is still hampered by the limitations of FM radio, which is far from audiophile-friendly.

These modulators are inexpensive (they can be found online for as little as $15) and relatively easy to put in, as long as you are comfortable fiddling with your car stereo’s wires. To install one, position yourself underneath the dash. Reach up and unplug the antenna from the back of the stereo and plug it into the modulator’s antenna input. Take the modulator’s output cord and connect it to the stereo’s antenna input. You can then set the modulator to run at any FM frequency. Pick one with weak competing signals (usually at the very top or bottom of the spectrum), and plug the modulator’s audio output cord into your iPod’s headphone jack.

Option 4: Stereo With Line-In Port
INSTALLATION: Moderate
SOUND QUALITY: Very Good
If you’re lucky, your car stereo has a headphone-size line-in port right on the front. If so, all you have to do is jack your MP3 player into this hole, tune your stereo source to “Auxiliary,” and crank some tunes. Unfortunately, most car stereos lack this port. Installing a new car stereo that has one is one method for getting excellent sound using your iPod. New stereos with the port can be purchased for under $100 and installed either by you or a professional. (Some shops offer free installation with purchase.)

Option 5: RCA Port
INSTALLATION: Moderate
SOUND QUALITY: Very Good
Some car stereos—primarily ones with CD players—include an RCA jack in the back. Hijacking this audio connection from the CD player will provide excellent sound quality for music coming off an iPod. First step: Remove the stereo. If there is an RCA port, you will see dual jacks—one with a red and one with a white input (similar to the RCA jacks on home stereos). RCA-to-headphone cords can be bought for a few dollars at just about any electronics store. Plug the red and white ends of this cord into the stereo’s RCA jack and the other end into your MP3 player’s headphone jack. Finally, tune your stereo to either “CD” or “Auxiliary” (the exact setting depends on your stereo).