Hacking Your Car: How to Get Clean Audio and Video Signals into Your Car
Pages: 1, 2, 3

Audio Inputs

The center controls of a car's audio system are usually called the head unit. Depending on the car, the amplifier will be either inside the head unit, or stashed somewhere else in the car, such as under a seat or in the trunk. But the head unit is the audio hub, and all the audio goes through it first to get out to the speakers.

Depending on the complexity of your factory stereo system, the head unit may be dealing with a half-dozen audio sources or more--AM, FM, satellite radio, CD player, external CD changer, DVD player, hands-free cellular, OnStar, and the navigation system. But for most cars, even the most basic stereo system is designed to connect to an external CD changer.

Figure 3. Auxiliary input box from Peripheral/AAMP

Now, don't even think about some sort of standard interface here. Every different head unit has its own proprietary CD changer interface--sometimes several per carmaker. These head units won't enable the audio input unless they actually sense the presence of a CD changer. But if you do have the CD changer installed in the trunk, you can simply splice in a pair of audio wires and voilà.

I don't know what your time is worth, but for my money there's an easier way. For less than $100, you can buy a plug-and-play version of these gadgets from several manufacturers for almost any car you own. (Since these are some of the same manufacturers that make video adapters, which we'll get into next, I'll list all of them in the Resources section at the end of this article.)

Figure 4. Simple Pioneer (IP-bus) input dongle

Now, there's another way. If you were already planning to upgrade to an aftermarket stereo (such as a Pioneer, Kenwood, Alpine, Sony, or Clarion), most of these units either come with a pair of RCA inputs, or have a simple (but proprietary) dongle for their system that enables the AUX in. (Sometimes you simply have to go through the menus on the head unit and enable it.)

Now, if your CD changer is built into the head unit, you're a bit out of luck because there's no audio wire running to the CD changer in the trunk to splice into.

But there's yet another way to get audio in, which applies to both factory and aftermarket head units. Many of these systems are labeled "XM ready," "Sirius ready," or "satellite ready." This, of course, describes yet another handful of fairly nonstandard interfaces, but the fortunate thing is, if you've upgraded to satellite radio, you may be able to piggyback onto the analog audio wires that bring the satellite radio to the head unit. In fact, if you have an aftermarket satellite-ready radio, you can use the XM Direct interface (from Terk, about $50) and you'll get a happy pair of RCA jacks, and it will work even if you don't buy an XM receiver--the head unit will simply say "no signal" but the audio will come through.

Figure 5. XM Direct units from Pioneer

So, the easiest ways to get audio directly into your head unit are:

• Splice into the CD changer audio input, for factory head units

• Upgrade to an aftermarket head unit with AUX input

• Splice into the audio input on any satellite-ready head unit