Using an iPod Car Adapter Without a Head Unit

listening to ipod without head unit
Short of headphones, or an external amp, a head unit is required to listen to in iPod in your car. Sam Edwards / Caiaimage / Getty

Question: Can I use an iPod car adapter without a head unit?

My head unit is broken, and I don’t want to replace it. So far we've been stuck with headphones. What kind of iPod car adapter do I need to just bypass my head unit altogether?

Answer:

Unfortunately, there’s no easy way to bypass your head unit, connect your iPod (or any MP3 player, for that matter) directly to your speakers, and have it work the way that you probably want it to.

While it is technically possible, there isn’t an iPod car adapter on the market that will get the job done. That means you would have to cobble something together yourself, at which point might be better off just buying a cheap head unit with an auxiliary input. For a little more, you'll get even better sound if you find a new head unit you can afford that includes a USB port or any kind of direct iPod control.

When a Head Unit Isn't Just a Head Unit

The problem with using an iPod without a head unit, and the reason there isn’t an adapter designed to do it, is that iPods aren’t designed to drive speakers. At first glance, it seems like there shouldn't be a difference. You can plug headphones or earbuds in and it works just fine, and you can plug your iPod into your car or home stereo without a problem, so what’s the big deal?

The crux of the issue is that it takes a lot more power to drive speakers than it does to drive headphones or earbuds, and your iPod just isn’t up to the task.

When you plug an iPod into a head unit, one of two things happens. Either the head unit passes the audio signal through an internal amplifier before sending it to the speakers, or it transmits the unamplified signal to an external power amp. If you have a stock car audio system, then it’s a safe bet that you’re dealing with the former.

In some cases, it's even more complicated than that. For instance, if you connect your iPod via a USB or proprietary cable, it may send digital information to your head unit instead of an audio signal. That allows the head unit's built-in DAC to convert the digital file into an analog signal, and then either amplify it internally or forward the signal to an external amp.

See more about Car audio basics

So What About iPod Car Adapters?

There are a lot of different iPod car adapters out there, but they all do the same basic thing: pass an audio signal to a head unit so that it can be amplified and sent to the speakers. Whether you use a cassette adapter, a dock connector to 3.5mm plug, or even a specialized direct iPod control cable, that’s all that’s really at work.

If you want an “iPod car adapter” that will bypass your head unit and actually work, then you need to have an amplifier somewhere in the equation. The easiest way to accomplish this is to just install a power amp that has RCA inputs. You can then use a 3.5mm TRS to RCA cable, which should work. You may also need a line driver depending on your particular setup.

Depending on whether you already have an amp with RCA inputs in your car, and if you can get away without using a line driver, then this is actually a low-cost option that’s definitely worth trying.

Otherwise, you’ll probably have better have better luck (and spend less money) picking up a cheap head unit that has an auxiliary input.

Also see: Head unit buyer's guide