Auxiliary Input For A Car Stereo

auxiliary in

Matt Gilbert was tired of using his noisy cassette adapter with his iPod so he added an auxiliary input to his factory radio. Normally this type of thing isn’t possible with factory stereos, but Matt’s 2001 Corolla has the factory CD player as a separate component from the head unit. He starts a CD playing and then uses a toggle switch to swap the sound coming from the iPod with the sound from the CD unit. This would also work with a factory CD changer, but you can’t just plug straight into the head unit because it needs to receive the “everything’s okay” signals from a CD player in order to turn on the input. You might be able to do this with “premium” factory stereos since they usually have a separate amp. All this hack needs now is a clever dock; I bet you won’t even miss that clock.

[thanks Matt]

52 thoughts on “Auxiliary Input For A Car Stereo

  1. My friend did something like this for my 98 Audi with crappy Panasonic head unit. He got a bunch of stuff from radio shack and then stuffed this little black box into the nether regions of my car’s dashboard. I too have a little switch that I need to toggle to switch between the radio/CD player and the iPod. Hums a tiny bit but not enough to notice when you have the music on.

  2. You can acctually buy an adapter that plugs into most cd changer ports that allowes rca connections instead of the cd changer. But what is the fun in that without hacking anything.

  3. Great project, but I question your choice of hardware for a switch.
    Hit that sucker with a black sharpie or something and it will blend in with your interior a wee bit better. (if you care about that kind of thing. I haven’t seen the rest of the car!)

  4. This is actually pretty easy to do with any stereo that has an input for a cd changer, without the need for any toggle switches. I added one for my Chevy S-10 stock head unit with an adaptor from PIE ( They have adaptors for nearly any unit, factory or aftermarket.

  5. Very cool hack, But before i go chopping up my car i think theres a much easier way. My freind purchased A Fm radio broadcaster thing from best buy for not much at all. If you are just wanting to play your ipod through your car speakers, you can go down spend a few bucks (not much all) and there ya go. It’s as simple as setting your radio station to a certain radio station and the connecting your ipod to it. Pretty easy and cheap plus your not chopping up your car. Still really cool.

  6. the only problem with FM transmitters is they get wicked lots of interference from surrounding radio stations. This might not be important if you live in podunk nebraska, but for people who live in big cities like Seattle or LA, Houston or New York New York, there is going to be way too much crowding on the FM band. the best option, but usually the most difficult to implement, is a direct line in

  7. This would be great, but as the article says, make sure you have a separate head unit or amp, because if you try to splice directly to just speakers, you aren’t gonna get much sound.

  8. Now this is the reason we come to hackaday… I like this hack. I knew it could be done, but I didn’t think it was this simple.

    In response to matt Russell’s comment: you can probably get rid of the hum by attaching a wire to your car’s frame as a ground. This fixes 99% of humming problems (provided you don’t hum along with the music).

  9. thanks all!

    you may have convinced me to add a jack to this thing, but i’ll put that off until after my cross-country roadtrip that was the main reason i wanted to get this done now.

    As far as prettying up the toggle switch… i don’t care. maybe I will when I’m trying to sell my car, if I don’t just remove the thing entirely.

  10. I purchased an fm transmitter and wired it under my dash right next to my radio taping it to the antenna cable which makes it overpower any local channels, and i don’t have to cut up my radio i just added an extra power line from my fuse box which also powers some other stuff under my dash. the only problem i have is my cellphone is so strong it gives interference to the speakers but that is on any station or when i use my cd player.

  11. I use an FM modulator/power adaptor for my XM Radio and it SUX! I’m ready to remove the CD for a tape player! I’d like to wire something into my aftermarket stereo like this…

  12. would it be possible to just use an Ipod and a regular Amp. Unless i’m forgetting something it would be easy to just throw out the radio all together and use Ipod jacked into the amp which feeds the speakers. then you have a big hole in your console just begging for other goodies to be put in there that the makers didn’t think of. or not. just a thought.

  13. I just did something similar, but got a CD player in the vehicle so I didnt need an AUX in anymore. I had a factory ford tape deck with a bad tape part. I opened it up and removed the tape unit, two harnesses – one with red white and black(or gray i don’t remember) for speakers and one with like 6 white wires and 1 red. So i hooked up the speaker wires and taking a guess started jumping the white wires. Found the right two and wired in a switch. Worked like shit, but I didn’t take time to put some resistors in line, it had too much gain on the input and sounded like shit. Then I got a new CD player and just said screw it. But it worked.

  14. this is a great hack…i have a aftermarket cd player and there are 2 aux input plugs but the thing is there is no toggle switch so i kinda through hooking my ipod up out the window. but this sounds ground. can i get any of these parts like at a local radio shack or do i have to go online to get them?

  15. I have done something almost identical to this with three different car radios, and won around $300 for it in a high school techprep-CIS (dont ask me why it won the ComputerInfoSystems category). the point is, i kinda think its time lazy ass people like ourselves started doing this for people for like, $50, and F-ing companies that charge like $600 for it in the A.

  16. I’ve been wanting to hook my ipod up to my car stereo for a while but I’ve just never been able to find the information on how to go about it with my setup. Having all your music playing in your car through one little device would definitely be nice.

  17. Attaching a seperate ground to the chassis from an imput source will probably make a ground loop, as opposed to fixing it. Ground your input to the case of your head unit.

  18. ct: should i have a ground wire somewhere in mine? I noticed that there was a black wire coming from the CD player to the head unit that was grouped together with the other audio wires (left and right, positive and negative). My aux input is just a headphone wire, so there are only these 4 audio wires and no extra ground wire (that i noticed), so i didn’t even know how i would go about adding a ground wire. is it necessary?

  19. I have a mp3 CD player and trying to build my own fm transmitter [ I have lots of vacation to take :-( ] anyone know a website or something that i can refer and build it. By Anyone has hacked a 2003 camry.

  20. I have a mp3 CD player and trying to build my own fm transmitter [ I have lots of vacation to take :-( ] anyone know a website or something that i can refer and build it. By Anyone has hacked a 2003 camry.

  21. There’s a project for doing something like this to a Volkswagen car radio’s CD Changer interface. It’s called a “vwcdpic.”

    The VWCDPIC sends CD Changer data, so you don’t need the factory CD Changer hooked up. Since it has the full protocol to work with, it can remote control a lot of different MP3 players. Ex: iPod, Archos Jukebox, PJRC, WinAmp, etc.

  22. What is better though?
    Connecting the iPod through an existing head unit (or new head unit w/aux input) OR scrapping the head unit altogether and connnecting the iPod to an amplifier, which is connected to your speakers (though, can this work without a head unit??). All I want is nice sound direct from my iPod, that won’t get screwed up when I upgrade speakers.

  23. my radio has a possibility of cd changer but i don’t know what are the pin out and i really don’t know what to do to cheat the cd changer. the radio simply says that is no cd changer connected. though i konow where the speakers are, but they don’t really work because i don’t know what’s the pin out to cheat the radio. Can anybody help me…my radio is a grundig Alana. please help me i want to connect my mp3 player there.

  24. If you can live without radio stations (I sure can), try unplugging your car antenna and attaching an “in-car” antenna – just a short piece of hookup wire will do. This should cut out some of those annoying DJs and leave room for your fm transmitter.

    Of course, the direct-in method always gives better sound quality. You won’t get the compression/expansion that happens when feeding your signal over the Fm band.

    If you’re going to switch a line signal in, you can always go direct to the volume pot (if it has a volume pot) or into the capacitor at the input to the audio amp.

  25. Seth. That’s what I’ve been looking for in this thread. You said that I could maybe tap in just before the amp? What it’d like to do is tap directly into headunit so it’d intercept the signal coming from the cd or radio. I was looking at a schematic that another dude posted earlier in here (just for referrence)
    Right after the volume system, I see a cap “C20” and resistor “R19”. Is that where you’d go in? I assume all head units are pretty similar once you’re at the amp’s inputs. I’d like to look for the equiv. of this crap inside my head unit, tap into it, and run a minijack for an ipod or portable something.

    The only problem I can see is the headunit’s switching systems being confused. Maybe I can just make a blank CD with 1 long quiet track with no sound. That would make trick it into lighting up the amp and tone controls.. There’d just be a hickup everytime the disk finished and started again(once an hour or so).

    WHat do you think about the spot for tapping in on that schematic?

    Thanks bud.

  26. I did something like this for my 03 Matrix. I found the how to on the genvibe website. the only difference in mine from this one is I used a 3.5 phone jack from Radio Shack for my input that way I dont need a toggle switch. I mounted the jack inside my center console and when I want to use my ipod I just plug it in and it switches the input from the head unit cd player to my ipod. I can controll the volume from the head unit.I chose this way because I wanted the car to look stock and have a “clean” appearance.

  27. Hey i’m trying to do a similar thing, but without the actual stereo. Does anyone have any hacks for going from the cars cables (harness if necessary) to only the auxilary input (RCa which then goes into headphone). I recently had my stereo stolen and i’m sick of it, i only want the auxilary and a simple black panel where the stereo used to be. if anyone can help me out with this twisted approach to car audio, any advice would be appreciated. thanks.

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