Matt Gilbert

Car Stereo iPod Input Hack

Tutorial · May 14, 2007 by Matt Gilbert

I was tired of using a cassette adapter with my iPod, because it added lots of noise. If I tried to turn the iPod up loud to drown out the noise, the levels would get messed up somehow, and the treble would sound painfully loud. After looking around online for auxiliary input things you can install in your car, I found that they all ranged from $80 to $200, plus installation. While this may be nothing to some people, I thought that an aux input can't possibly be that big of a deal. So I poked around with my stereo and figured out how to do it while buying only a toggle switch that I got for 50 cents, and using some wires and stuff that I already had lying around.

I got sort of lucky, because my 2001 Corolla was a little easier to hack than I imagine some cars will be. I'm just using the factory system here, with no aux inputs built into the head unit and no amp or anything like that. The difference is, mine has a CD player unit that's seperate from the head unit. This means that there is audio being passed from the CD player to the head unit, and those wires can be clipped and redirected to other uses. I imagine any car that has a seperate CD player, CD changer, or whatever will be hackable in the same way I did. If not, then I guess you'll have to figure out some other way of doing it.

So the way I have it set up, I tell the stereo to play from a CD, and it does, but I switch out the audio with the audio coming from my iPod or other aux input.

Clicking on the small images will take you to larger ones, some of which have descriptions.

Opening the Console


 
  Here's the console. The upper part, with the AC vents, clock, hazard button, and main stereo unit, is the part I needed to remove. That little blank part that's the same size as the hazard light button doesn't do anything, so that's where the toggle switch will go.


 
  There are little slits on the bottom of this part of the console where you can poke in a screwdriver and pry it out.


 
  Like so.

 
  Do this on both sides, and you should be able to pull it out the rest of the way by hand.


 
  Like so.

 
  There are two connectors going to the hazard light and to the clock.


 
  Disconnect them so you can get the console part out of the way.

Finding the Audio Connections


 
  The back of the stereo head unit looks like this. The 2 harnesses to the right go to the speakers and other stuff in the car, and the harness on the left goes to the CD player. This is the one that we are concerned with.


 
  I didn't know any of the color codes for my car, so I had to poke around to see which connections were listening for audio. To do this, I had to start the stereo with everything connected in the back, and start playing from a CD. Once it started, I unplugged the harness connecting the CD Player to the head unit, and connected an audio cable from my iPod to each of these connectors until I heard something coming out of my car speakers. I did this one at a time so i knew which was right and which was left through trial and error. It will sound like crap if you only have the positive connected but not the negative, or the other way around, but don't worry because it will sound good once everything is connected.


 
  It turned out that the two green wires were the left channel, and the two grey wires were the right channel. A wise man who lives in a fairy castle once told me that it doesn't matter if the positive and negative channels are flipped, as long as the right and left channels are flipped in the same way.

Finding a Spot for the Toggle Switch


 
  Before clipping and soldering all these wires together, I planned out where the toggle switch was going to go. This unused hole in the console was perfect. This is how to remove the plastic piece stopping it up.


 
  I just pried this part out with a screwdriver. I manage to break a tiny part of it while doing this, but nothing that make anything stop working, and nothing visible.


 
  I'll save this piece for later in case I sell my car to someone who doesn't want the aux input.

Wiring the Toggle Switch


 
  I took this headphone cable I had left over from some other project, and wired this in to the toggle switch.


 
  Here's the toggle switch I found. Clicking on this image will show a diagram explaining how I wired it up a little better, but basically, the center part connects to the head unit, one side connects to the ipod, and the other side connects to the CD player. I got lucky when I found this toggle switch, since it's actually four toggle switches in one, so I can use it to switch the positives and negatives of both left and right channels all at once.


 
  This was the hardest part because I had to solder this stuff together in the console of my car. This is because I couldn't get the CD player removed from the console, so I had to work on it there. I clipped the green and grey wires leading from the CD player to the head unit, and connected to CD player to the toggle switch, and the toggle switch back to the CD player, doing my best to keep all the left/right, positive/negitive stuff straight. I used this audio cable that is 2-conductor and shielded mainly becau se I had some lying around. I don't know if the shielding is neccesary, but it can't hurt. It also helped me keep the wires well organized by pairing up the positives and negatives of each channel.

Done-ness!


 
  I got lucky because the toggle switch I had fit perfectly snug in that hole in the console. I just have a headphone wire dangling out, which is fine by me, but I know some people would prefer a headphone jack so they could remove the cable when they wanted to.

So the way this works is you tell the stereo to play a CD, and it does, but you switch the signal that it's getting from the CD player to the iPod, or other aux input. Your stereo keeps spinning the CD, and it keeps showing the track number and time of the CD, and you can switch the audio back and forth from CD to aux at any time.

It sounds really good as far as I can tell. There's definitely no noise like when I was using the cassette adapter, and the levels don't get all messed up when I play the iPod loudly. (This is something that was happening a lot to me with the cassette adapter, but I know this doesn't happen for everybody.)

  1. Awesome. I definitely would have drilled a little hole in the toggle switch plate for a 1/8” jack, but, man, that’s cool.

    timsamoff · Jun 7, 11:59 AM · #

  2. right on, thanks.

    this hack got featured on hackaday.com, and got some pretty good comments from peopleon there. check it out here:
    http://www.hackaday.com/entry/1234000897045842/#comments

    Matt Gilbert · Jun 7, 03:17 PM · #

  3. Any idea if this will work in a corolla with the same radio but no cd player?

    M · Jun 10, 03:59 AM · #

  4. Wow – this looks just like the hack that I did a while ago with my Mazda – Here’s the link to a page that I made.
    http://www.geocities.com/blhobbs.rm/Mazda_stereo.html

    brian · Jun 10, 11:55 AM · #

  5. to brian: right on! i wish i had found your page before. i thought that this must have been done several times before, (so much so that i hesitated to submit it to hackaday) but i couldn’t find anything about it online, so i went ahead and did.

    to m: no idea. this thing i figured out probably won’t, but who knows, maybe you have an input for a cd changer option you didn’t take, or something like that. you just gotta get back there and see i guess.

    Matt Gilbert · Jun 11, 02:35 AM · #

  6. I just finished a similar hack myself, simply put, I cracked open the stereo itself (a low end aftermarket Pioneer) found the am/fm signal leads to the output stage with an o’scope, lifted them and injected the ipod signal. The results were fantastic compared to the FM modulator I was using previously. Next step is to put in a switch to toggle between radio and aux in. Hopefully I’ll post the results in a few days.

    -mlaargh (logged in as “Thurston” via BugMeNot)

    Thurston · Jun 13, 10:04 PM · #

  7. If they haven’t already, audio manufactureres should take notice and start including an aux. input for ipods.

    Keith · Jun 14, 07:02 AM · #

  8. This page was also mentioned on winxpnews (whatever that is). It was linked in the issue on Tue, Jun 14, 2005 (Vol. 5, 24 – Issue 180).

    Matt Gilbert · Jun 17, 02:07 PM · #

  9. Most excellent. We’re blogging a pointer to you on Songzilla Blog.

    Thanks for sharing this…

    EP · Jun 17, 02:27 PM · #

  10. Matt, you should be careful with impredance matching between your iPod’s output and the auxiliary/CD input of the stereo. You can overcharge and burn the output amplifier circuits of your iPod or the input of the stereo. I wish I had specs for the stereo input (or CD output) to point you to he right impedance transformer.
    Another thing that might work well is to use a headphone female connector with a switch inside (like the headphone connectors in any tv or boombox). Using such connector you can switch from CD to iPod by just inserting the headphone jack..no other switches.
    Nice initiative anyway!

    TJoker · Jun 17, 07:04 PM · #

  11. i’m looking into tjoker’s concerns with impedence. i’ve used this rig a lot already with no problems, so i doubt it’s a problem, but i should be thorough. if anyone can tell me how you check audio impedences, plz contact me.

    also, another blog has linked this page: gizmodo’s link

    Matt Gilbert · Jun 20, 12:53 AM · #

  12. btw, if you’re looking for the right toggle switch, search/ask for ones with “4PDT” in the name.

    Matt Gilbert · Jun 20, 01:12 AM · #

  13. I saw a similar hack somewhere else but the interesting twist was that the person just spliced the audio into the cd input line without using a toggle switch. he then used a “silent” cd. basically a home made audio cd with a completely silent track. So whenever he wanted to listen to the ipod he selected the silent cd on his changer and he was done.

    Sanjay · Jun 20, 05:11 AM · #

  14. Nicely done.

    FYI the + and – DO matter. The speakers will run backwards which will make the sound less than optimal.

    Sounds crazy but its true…

    My Name is Coupe · Jun 20, 09:31 AM · #

  15. If your sound is good I wouldn’t worry much about an impedance mismatch. Such a mismatch will sound terrible. It’s likely both your stereo head unit and the iPod use standard ‘line level.’ Similar hacks have been done by builders of the mp3 player from pjrc.com

    weitrhino · Jun 20, 09:44 AM · #

  16. Unfortunately my 2003 Corolla doesn’t have the same unit. It’s an all-in-one CD/Cassette player. Right now I use a cassette adapter which doesn’t sound very good. Does anyone have a hack for the 2003 model?

    Mike · Jun 20, 11:42 AM · #

  17. Now Correct me if i am wrong. I think you could hook up any cd radio to support an aux port using a swithc in the following manner. if you take the 4 speaker output off of the radio and take that into a switch…then you can use the swithc to have it go from;

    aux or radio to speakers…

    you might still need to have the radio turned on for the amplifiers on factory speakers (if you have them) to be turned on.

    AcidSun · Jun 21, 07:54 AM · #

  18. for those of you looking for similar hacks that work on systems with different setups (no seperate changer, etc.), hackaday had a follow-up post with links to my method and several other methods that popped up after i posted mine. the blog entry is here.

    Matt Gilbert · Jun 22, 09:36 AM · #

  19. this hack has also been linked by engadget, although the article is exactly the same as the one on hackaday, with the same comments and everything. weird.

    Matt Gilbert · Jul 5, 08:21 AM · #

  20. hi matt. just one question: does it mean that yo need to play a CD at your CD changer and then switch to the ipod? (in effect, two units will be running, you CD changer and the ipod). Please clarify. Thanks.

    Vince · Jul 25, 08:51 PM · #

  21. to vince:

    quoted from the how-to:

    “So the way I have it set up, I tell the stereo to play from a CD, and it does, but I switch out the audio with the audio coming from my iPod or other aux input.”

    and later:

    “So the way this works is you tell the stereo to play a CD, and it does, but you switch the signal that it’s getting from the CD player to the iPod, or other aux input. Your stereo keeps spinning the CD, and it keeps showing the track number and time of the CD, and you can switch the audio back and forth from CD to aux at any time.”

    Matt Gilbert · Jul 27, 08:18 PM · #

  22. uh…yeah, you should read up on matching the impedance. Unless the impedance of 4 of your stock speakers are equal to 2 speakers on the headphones, you will overdrive your ipod amp circuit. not the best way to add an aux imput. If you want to do it the right way, buy a cheap 4 channel amp or two 2-channel amp.

    Flavaj78 · Aug 17, 02:51 PM · #

  23. has anyone done this without having the cd changer? my car stereo has the inputs for it but i do not have an actual cd changer. connecting the wires as shown is not enough. there must be some other connection to trun it on or something :)

    Ailyn · Sep 30, 03:37 PM · #

  24. to Flavaj78:

    The audio isn’t goign from the ipod to the four speakers. That would definitely be an impedance mismatch. The audio is going from the ipod to the head unit, which amplifies it and sends it off to the speakers.

    Matt Gilbert · Oct 30, 02:37 PM · #

  25. Thanks for the great write up. Do you happen to have the entire pinout (what signal each cable is suppossed to carry?

    If you look at this link, the connector in question is the one at the bottom right hand corner…

    http://www.philsteels.co.uk/flying/rav4/images/radcon.gifz

    macness · Dec 15, 12:54 AM · #

  26. Thanks a lot, Matt for the excellent pictures. I went ahead and removed the trim of the 3-indash-cd changer & the cd unit too. This way I was able to put the switch below the cd changer. I had a rear defogger switch in the top right side where Matt put the switch.

    Instead of a 4PDT switch I used a stero jack (from radio shack) that has a inbuilt mechanism for switching :-)

    Note: If I don’t start the car the audio system’s power fluctuates. It took me a while to figure out that my Corolla was having problems with battery.

    soch16 · Jan 23, 12:53 PM · #

  27. Matt, thanks so much for your great photos and info.

    I too have a 2001 Corolla with the same stereo setup. The only difference is that my wire colors were different for some reason. In my car,

    pink = right +
    green = right -
    yellow = left +
    white = left -

    Also, for electronic beginners like myself, it is helpful to know that on an RCA wire, the outside part is + and the inner part is -.

    The sound is GREAT! Thanks again.

    dako81 · Feb 10, 11:28 AM · #

Commenting is closed for this article.

Previous Article:
Next Article: