Hook up your iPod up to your Car Stereo

Lots of us spend too much time in our car. But driving does have its small perks. The best one is that your car is a great place to listen to your tunes. Catching up on new releases, listening to old favorites, all have a great way of making commutes or jaunts around town more enjoyable.

But how do you hook up your iPod to your Car Stereo for the best possible sound? There are loads of articles on the web that talk about this very concept, but many are filled with both technical errors and just plain bad advice.

So let's look at the Ipod/Car connection from the hi-fi perspective.

Connection Time

There are various ways to connect an external sound source to your car stereo. Here they are from worst to best:

Using an FM Transmitter

This is the easiest way to connect  an audio device to your car stereo if you don't have an auxiliary input (or Line In).

It is unfortunately also the worst sounding solution.

An FM transmitter works by taking the audio input from your iPod and converting it FM radio signals. It accomplishes this by being an actual mini-FM radio station. It compresses the signal heavily, does the nasty FM conversion, and then sends it out as radio waves. There are several reasons FM transmission sounds like ass:

• FM Radio sounds like ass anyway. It is heavily compressed to fit within the narrow bandwidth allowed by the FCC and has very bad specs for noise, distortion and dynamic range.
• In urban areas, there will be a lot of crosstalk within the heavily laden FM band.
• In urban areas with loads of stations, it can be damn near impossible to find a usable spot in the FM frequency range to tune to.
• Since you are converting your sound to a radio signal, any noise that your FM radio picks up from outside RFI will be amplified.

In summary, the FM Transmitter should be your last resort.

The Cassette Adaptor

The next level up in sound quality is the cassette adaptor. This device is light years better than the FM transmitter route because it provides a semi-protected signal path for your audio. How does it do this? To understand the principle, let's first look at how sounds are recorded on to tape:

The audio signal is fed to a recording signal which converts the signal to a series of magnetic pulses which are recorded on the tape as it moves over the record head. Pretty cool stuff. Now lets look at the playback process the enables us to hear the recorded tape:

So if a record head will imprint an audio signal and the record head will pick it up and play it back, why not just take the tape out of the equation and have the record head directly talk the playback head? That's the genius of the cassette adaptor design:

If you pry a cassette adaptor open, you'll see that it is simply a recording head with wires running to it. When you stick the cassette adaptor in your cassette deck, the recording head butts up against the playback head and directly transfers signals to it.  Pretty clever stuff!

Sound quality out of a cassette adaptor, while certainly not audiophile-grade, is light-years ahead of an FM transmitter. There is very little noise, and you can get a good signal regardless of the outside world's continuous beam of bad FM and RFI.

Of course, if your car stereo doesn't have a cassette player, this option won't work.

Headphone Jack to Car Stereo Line In

Now  we are talkin'!

If your car stereo has an input jack, life suddenly gets a lot better. On newer cars, there is often a dedicated line-in/iPod jack located somewhere in the passenger compartment. Sometimes it is in the glove compartment, often it is right on the front of the stereo. Similarly, most newer after-market car stereo units have a line-in jack, either directly on the front of the unit or behind the moving faceplate.

These jacks are 3.5mm female stereo types that use the exact same type of connector that is on the end of your iPod headphones.

So to use this connection method, simply run a cable from the headphone jack of your iPod to the line-in on your car stereo. This method beats both the FM transmitter and the Cassette Adaptor, hands-down in terms of audio quality.

You have a direct, shielded, connection between the iPod's output signal and your car stereo's input preamplifier. This results in a dramatic decrease in noise and a dramatic increase in frequency response and dynamic range. Good stuff!

But wait, for a few dollars more, you can get the best possible solution:

iPod Line Out to Car Stereo Line In

If you read my article about/against headphone jacks, you already know this:

Here's a quick recap: headphones are low-impedance devices that expect a fairly low-level signal. When you connect your iPod to a stereo (whether it's in your car or in your home), using the headphone jack will cause a couple of things. First, volume drop is prevalent. You have to jack up the volume on your iPod all the way and then probably turn up your stereo too. Because of the impedance mismatch, you will also likely hear a lack of bass response.

These two factors make the headphone jack less than ideal as a sound source for your car stereo.

Fortunately, most iPods have a line out jack that is specifically designed to put out the type of signal that a stereo wants to hear. That's the good news. The bad news is that there is no physical jack on the iPod to get to the line out signal. Instead, it is hidden away inside the dock connector on pins 2,3 and 4. The good news? You can buy a very inexpensive device that connects the line out signal to a 3.5mm jack--just the kind of thing you can hook a cable into.

Wait a Minute you Doofus! My Car Stereo doesn't have a Line In!

Don't worry, there a ton of articles out there that talk about hacking a line in capability on to your existing stereo. Many articles, especially on car stereo forums and sites, will have how-to articles that even relate to specific vehicles and stereos.

Google Search

Practical Applications: Making it All Happen

Now that we've gone through the pantheon of fail -> win options, let's take a detailed look at how to get the optimum connection to your car stereo assuming you have a car stereo line in.

Solution	Pros	Cons
Line Out Dock to Car Stereo The easiest route is to use a Line Out Dock. This is a plug that inserts into your iPod's line dock connector (the multi-connector thingy on the bottom). The LOD provides a 3.5mm stereo jack. Connect one end of 3.5mm stereo cable to the LOD and the other to your car stereo line/aux input. Done!	Super Cheap and Easy	Provides no charging capability Cables laying about
Charger + Line Out Dock This solution involves a 12vDC cigarette plug adaptor that charges your iPod while also providing a line out connection. Some models also include rudimentary iPod navigation buttons like play, forward, stop, etc. These units do not provide a physical mount for your iPod--they assume that you either are just going to connect up the iPod and toss it on the passenger seat or already have a mounting solution.	Super cheap and easy	Some units do not filter the power supply resulting in hum. Cables laying about
Integrated Holder + Charger + Line Out Dock If you want a nice neat place to hold your iPod, you can find devices that will providing charging, a line out connection, and a way to affix the whole thing to your car. Most commonly found types use your cigarette lighter receptacle as the mounting mechanism. This is convenient, but be sure you actually have clearance in your ashtray area to plug the device in. Another problem with these devices is caused by the generally crappy construction of the cigarette lighter receptacle itself. It is usually made of some type of thin metal and over time will become loose, wiggly, and otherwise unsuitable as a mounting base. Other types of physical connectors are more durable. You can get devices that sit in cupholders, attach to the dash with adhesive tape, or use suction cups for attaching to the inside of the windscreen. Take your time to find the right solution for your needs and vehicle.	More expensive Can be tough to find the perfect mounting solution	Fewer wires laying about Looks more professional. Sturdy protection for your iPod

Caveats and Common Sense

There are a few things to be aware of that may trip you up in your quest for transportation-related iPod nirvana.

Power Supply Noise: Newer cars use loads of computing power. There are CPUs for engine management, accelerometers for managing airbags, and all sorts of other mechanical and electrical noise sources. Astonishingly enough, some commercial companies don't build in even rudimentary power supply filtering, so that noise will go directly from the cigarette lighter power adaptor into your iPod, and then be happily amplified by  your car stereo. Be sure that whatever you buy has an easy, no-hassle return policy. Some vehicles are noisier than others, be sure you can return a crappy unit that doesn't filter out noise.

Hey! Steal Me!: Often we'll mount our nice new iPod Touch so it is easy to see and reach, this means it is somewhere up on the dash. That's very tempting for smash and grab bastards who will have no qualms about smashing a car window to grab your hot iPhone or other player. If you have an "up front and prominent" mount, be sure to pop your iPod out of its slot when you leave the car. Best case is to take it with you, but at a minimum, stash it in the glove box or under a seat.

Screw-Mounting Stuff: If you drive a smoke belching rusty old hoopdie, then you probably won't care about damage to the dash or other interior parts when you drive big old machine screws in to hold your new iPod mount. Otherwise, I'd recommended against mounting solutions that require you screw stuff into the dash. Modern adhesives are, well, modern, and do a great job of holding stuff in place. Yet they are still easy to remove in most cases.

Conclusion

If you can get your car setup to use your iPod's Line Out connector, that's the best way to go. Other solutions are available, but as we've seen, they aren't as great. Hopefully you now have enough knowledge go forth and rock your car.