Hacking A2DP support into an old car stereo

a2dp_tape_deck_retrofit

[Roofus] had an older car, and unfortunately his stereo’s cassette player just wasn’t doing it for him. He always wanted to simply get into his car, pull out his cell phone, and have his music ready to play without any fuss. After messing around with all sorts of different tape adapters, he got fed up and decided to rig up an A2DP (Stereo Bluetooth Audio) adapter on his own.

He pulled the head unit out and started looking around to see how he could wire an adapter in. He figured the best course of action would be to remove the tape deck, and fool the stereo into thinking that a tape had been inserted. After spending some time tracing wires and studying how his old tape adapters worked, [Roofus] had an A2DP connection wired in and was ready to rock out.

Greeted with nothing but silence, he turned to his favorite hacking site (Hackaday, naturally) for assistance. Some friendly forum-goers helped him identify a ground loop issue, and he set off to his nearest RadioShack for a pair of isolation transformers that would fix his problem.

Once he knocked out the ground loop issues, his adapter worked like a charm. He put everything back together, and aside from a tiny switch he installed to toggle between audio sources, you would never know it was there.

Comments

  1. fartface says:

    Bad design. you NEED that a2dp module on the outside so it is not inside a faraday cage. install connectors on the radio and let the dongle hang outside the radio for far better BT coverage.

    Why? so friends in the back seat can stream audio or you can have your phone with you and in your pocket while you blast tunes and wax the spinner wheels.

  2. XavierBlak says:

    Wow. I just bought a a2dp receiver with plans to do something similar. My radio has an aux in so I don’t need to worry about the tape input. What type of phone are you using with this? My phone with android os doesn’t seem to reconnect automatically. I found an app (AutoPandora) which will launch pandora automatically when it sees the phone connect to a specific bluetooth source. But I still have to connect it manually each time. Not the end of the world but it would be amazing to just get in the car and music would just start coming out of the speakers.

    • popoffka says:

      My HTC Desire auto-connects to all paired Bluetooth devices when BT is on. I also saw some players (like Winamp or PowerAMP or Zim.ly) have the “autoplay when headset connected” feature (and this A2DP is treated like a headset).

    • Roofus says:

      I have a Motorola Atrix. My old Windows Mobile powered HTC Touch Pro 2 auto connected as well. Once in a while it will hiccup, but it’s just as simple as connecting from within the menu.

  3. Slacking says:

    Nice, I have the same adapter and I have been thinking about hardwiring into my factory deck..hmm some investigation will need to take place now :)

  4. mac says:

    …. so why does your cell phone work inside your car?

  5. Zerodecoder says:

    What A2DP adapter is that? I see the blackberry logo but I can’t find any info on it.

  6. lwatcdr says:

    Makes me wonder if there is room for an MP-3 Player in there as well? You could just pop in an SD card and have it start playing like a tape player as well as having the A2DP adapter for using your cell phone.

  7. RF says:
  8. AbortRetryFail says:

    I’ve got the same A2DP adapter. You may want to wire up something so you can press the power/pairing switch without having to open up the head unit. Mine likes to error out and you have to re-pair it to get it working again.

  9. Rob says:

    If you haven’t replaced the external source switch yet, I can’t help but think that one of those toggle switches with the red flip down cover would be perfect. Just replace the word “Nitrous” with the Bluetooth rune-logo!

    And there sure is a lot of extra room in that head unit with the tape mech. gone. The obvious question is, whatcha gonna put in next?

  10. samnmax says:

    I think it would sound even nicer if you bypassed the tape preamplifier, by connecting the A2DP module to the output of the preamp chip.

    • Roofus says:

      I’m actually adding that to the list of finishing touches I’d like to do. Hope fully it won’t be hard to find info on the preamp chip. I’m assuming it’s the one just below the tape input.

  11. Partizan says:

    Nice! I wanted to do the same on my stock Toyota radio. This article is an inspiration. :)

  12. gradouble says:

    oh my, i was planning to do the same this week, after found a way to add an aux input with the LW band on a good old Alpine HU ! i bought the belkin look a like one

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