Un-crapifying A Car Stereo


[Noah Farrington] has just accomplished a major milestone in his life, purchasing his first car! A glorious 2001 Ford Focus wagon. While it may be a fully loaded luxury vehicle, it is missing one thing poor [Noah] can’t live without. An aux-in port.

He had a few options for rectifying the situation. Live with it as is, hack the strange Ford media protocol out of the back, or fool the CD player into playing his input. Naturally he chose the third option.

His first challenge was removing the deck from the car. People told him he’d have to buy fancy stereo removal tools — he made do with tent pegs and coat hangers. Using the same method as described in a past aux-in hack, he identified the audio in leads on the CD player’s ribbon cable. By carefully soldering in his own aux-in plug, he’s almost ready for business! Unfortunately, the CD player also needs to think that it is on for it to properly output the audio. [Noah] chose the simple solution — record a silent CD to always leave in the deck.

Stick around after the break to see it in action.

He might not be driving a classic 1974 Pacer, but at least now he can rock out to the digitally remastered Bohemian Rhapsody off of his phone!

49 thoughts on “Un-crapifying A Car Stereo

      1. a LOT of pontiac and GM radios have a plug on the back that is for the CD changer, trivial to add a jack to those and fool it. did he look online for any of the info on hacking the Ford stock radio? A lot of the car forums cover that stuff with just a bit of research.

  1. I’m so glad my car is from before the ‘CD with no tape deck or AUX input’ era. I have a tape deck, so it was simply a matter of soldering a plug onto the L R and GND pins on the preamp line-level input coming off of the tape deck, then tricking the head unit into thinking there was a tape inserted by jumpering the tape-insert switch. No more dicking around with noisy, distorting tape adapters.

    1. Those horrible tape adapters were also fantastic to use when transmitting with a mobile ham radio. There’s not much that scares you as much as 140db (yes, I’m exaggerating) of white noise being blasted out of all 6 car speakers.

      I only had to do that once before I learned to shut the car radio off before I turned the ham radio on.

      1. Interesting. I use one of those adapters in my Jeep and haven’t had that problem. What band(s) are you on? I’ve used mine while talking on 10m thru 70cm. I wonder if you might have some sort of grounding issue.

        I did find one useful interaction between my radios though. If I am listening to 88.7FM transmitting on 29.6 (the 10m FM calling freq) silences the stereo. No doubt that’s because 88.7 is really close to the thrid harmonic of 29.6. It’s actually kind of convenient!

  2. or couldnt you just solder wires to the amplifier chip .

    however i am not sure about todays electronics they may be digital all the way to the amplifier chip so no digital to analog conversion like in older cd players.

    1. I know, I know, ya gotta do it the hard way. Anybody heard of bluetooth? 10 bucks get ya a device that plugs into the lighter outlet and retransmits a bluetooth paired signal into FM that can be tuned by your piece of crap radio. Some of those devices even have a USB port to charge your android phone. By the way the MP3 audio coming out of your phone will never match the quality of a CD. Cheers, Keep hacking

      1. FM Transmitters are limited to FM bandwidth (ie, craptastically small,) and if you live in even a moderately urban area you’ll constantly be getting interference from actual FM radio stations and have to change the frequency every time you drive 20 miles. And modern phones with 320K MP3’s are pretty much indistinguishable from a CD player if you use the same headphones/speakers; you’re thinking of 2006 when everyone was using 128K MP3’s from Limewire that’d been reencoded so many times they were barely listenable.

        1. With respect. Dont know where ya live but I know lots of people with crappy cars and radios that have no problem with FM transmitters – here in sunny So Cal. You might be thinking about those old crappy in car FM tx units.
          In my noisy ride I can hear the diff between 320kcrap and a CD. Its sad that all the artists you might respect record pristine tracks but everybody listens on MP3crapified playback, truely sad.

          1. SamKook

            At that point, it’s not the music that’s the limiting factor, it’s the device playing it… No smartphone (or media player, except for a handful of units) out there is capable of outputting CD quality audio… Playing FLAC files on a smartphone or media player is pointless and a waste of valuable storage space, as you won’t get the benefit of the increased audio quality, so you’re better off sticking with 256 or 320 kbps MP3s.

        2. There’s no denying that but those guys with their FM tx units just don’t know any better. You can get excellent sound in a car with a well designed system but when the dynamic range is compressed by an FM modulator and a crappy FM tuner there’s no way to improve it; it just sounds flat.

          In another life I built custom car audio (1984 ~ 2000) and we used to sell lots of CD players just by showing the difference between modulating a CD player into the FM tuner and using a proper CD player. There’s no question if you listen/compare both.

      2. I’ve bought two or three of those cheap BT-to-FM things and none of them have worked for me. I can make phone calls through them but sending audio is a no go (and yes, they were sold with the intention of being used for music).

      3. Please. You can get the full 320kbps on almost any device nowdays, and if you want the absolute best quality, you can download FLACs – which are lossless. CDs skip, get scratched, and are a pain in the ass to manage (and also cost money). Phone wins here every time. Especially if you have android and you can do all kinds of cool things like have a specific audio profile for your car, or even start playing the music automatically.

    1. It probably does the same thing mine does. It mutes the audio for 3 to 4 seconds once an hour (or every 74 minutes for a full CD) with the disc is on repeat. I seldom notice the short interruption, but if it concerned me I could restart the disc (and reset the timer) between songs by hitting prev/next.

  3. I’m planning on doing something similar, only using a nc trrs jack to enable control of the mp3 player/phone using the built-in radio controls and allowing it to disconnect the cd audio and jump the cd detect. Will post once I’ve got it working.

  4. This reminds me of a modification my younger brother and I made to his ’84 Corolla’s tape deck. He wanted to be able to play CDs on it, so we added a 3.5mm jack by stabbing the face plate with a hot soldering iron until it complied and glueing a jack behind it. The jack was spliced onto the tape head. We hooked up a PC CD-ROM drive to the battery and connected its headphone jack to the tape player’s new aux in.

  5. He’s lucky when he tried to yank the deck with the keys he made from coat hangers that he didn’t bend the clips out instead of in. Those cars, especially the Focus were notorious for bending the clips on one side the wrong way which permanently locks it in, even with the $30 “Ford Keys”.

  6. Anyone else notice the other signals around that ribbon connector? MOSI, MISO and SCK sounds a lot like SPI, I can see a CDMUTE pad, and also ones labeled RESET, BRST, CSCD and CDSRQ. I do wonder if any of those control if the amplifier is on/off (ie if it thinks a CD is playing) that would then allow you to get rid of the CD-of-silence altogether.

  7. Good work, always good to see basic hacks like this. I did this some years back on my VW Gamma head unit. Pretty much the same hack and I had to leave a CD in there to trick the head unit, the one thing I did though was to put a switch in that would allow me to choose between “Aux” and the CD that was playing, no need to have a blank audio cd! :)

  8. Empty CD trick is nice hack. But I guess a little more poking with pins would result in finding something like CD_ON pin which is high when CD is present, and low when it’s not. Or opposite. Just guess that seems logical to me.

  9. I did a similar hack to my deck in my RSX. But instead I broke the traces between the radio and the amplifier. Put in a switching jack, so when my aux is plugged in and on radio aux is used. Unplug it and the radio is back again.

    1. depending on the cd and how it was printed, that’s a good way to scratch the heck out of the laser… if you’re going to do that, use a completely blank cd-r disc, with nothing printed on top. anywhere the ink stands proud of the disc risks a collision with the laser.

      1. I don’t think this will happen, as the disk is spun when inserted, then the laser gives up focusing on the inked side withing seconds, and disk stops spinning. The interesting thing is that the “CD” is still active on the input selector and the amp isn’t muted, although it must say “No CD” on the display.

  10. Why not just break down and spend the money? If you have your heart set on saving as much money as possible and are on a budget there are ways of saving yourself all sorts of your hard earned money. Back in the 1980’s some incredible head units were being sold as well as some classic amps that some people are still running today. Technology was pretty darn good back then and now it’s even better! If one is willing to do the leg work and their not in a hurry to have that custom sound system installed tomorrow there’s so many different ways of saving yourself some serious cash. These days when someone’s down on their luck usually one of the first things to go is their high end car audio system. The same usually applies to couples that are expecting a newborn baby or just had one. They need the money and badly so the first toy that goes is again the car audio system. The first thing you’ll need to do is get an idea of just what kind of system you want to build and the amount of money you’re willing to spend. Once you’ve done this then go stop by the car audio stores in your area and inquire if they have or know of anyone that’s looking to sell used equipment. Most audio shops usually have some equipment laying around collecting dust. Next start checking the car audio classifieds. I have personally found that this is usually one of the best places to find some deals. There’s no reason to be afraid of used equipment but, know what it is you’re looking at first and do your homework then decide just how much work you’re willing to do yourself, design the system that’s right for your needs and to your wallet, track down and find the necessary products and spend your money wisely and lastly, the install.

  11. DId the same thing here to a sony deck, then realized the radio module nicely labels its outputs. Undid the CD mod and added a switch to switch between radio and aux. No need for a blank CD, then, and I retained the option to leave a MP3 CD in for when I’m too lazy to break out the phone.

  12. blank CD is a bit “janky” but a good hacekr gets the job done lol. on my past two cars (92 taurus and 02 corolla) i just found the amplifier Left, Right and Ground and just soldered in a cable that way. i dont have any volume bass treble balance or whatever but i dont mind (aux device always has volume control). just plug in a 3.5mm device and the radio automatically cuts out and goes to the aux input.

  13. The photo shows that the CD deck also has AM/FM radio. I would have thought that intercepting the audio from the radio section with a switched stereo headphone jack would solve the problem without the need to run the CD deck constantly. With the jack plugged in the amplifier gets the external audio from an MP3 player or smartphone. With the jack removed, the normal AM/FM radio flows right through.

  14. FM Transmitters are limited to FM bandwidth (ie, craptastically small,) and if you live in even a moderately urban area you’ll constantly be getting interference from actual FM radio stations and have to change the frequency every time you drive 20 miles. And modern phones with 320K MP3’s are pretty much indistinguishable from a CD player if you use the same headphones/speakers; you’re thinking of 2006 when everyone was using 128K MP3’s from Limewire that’d been reencoded so many times they were barely listenable.

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