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DIY "Custom" "Head Unit"?

27 June 2020
Boise, ID
Hi Prime,

Would love if someone smarter/better with electrics than me would take a look at the below and let me know whether you think I'm crazy, or if it sounds like a good and cheap fix. If this works and doesn't burn my car down, I'd be happy to do a write-up on it for others in similar situations.


  • Failed head unit (assumed based on symptoms).
    • Distorted audio, gets somewhat better after driving with static-y radio/music for a bit. Still gets power/turns on/etc. and can change channels or sources.
    • Amps already rebuilt by BrianK Circa 2006, no reason to think these are the cause of audio problems.
    • The board in the head unit itself has some visible acid staining, causing me to assume leaky capacitors/typical signs of HU failure.

  • Am cheap, recognize Willman's mod is objectively superior, but I really only want bluetooth with the ability to control volume and turn on/off, and I don't need or would even be able to use the Apple Carplay/Android Auto/Siri/the rest of the cool stuff that would bring.

  • From what I understand, the GROM unit many others have used to add BT won't help here, since it still relies on the head unit being in working order to pass the BT signal to the amps/speakers (though please correct me if this isn't the case).


  • Solder power wire for the unit to the red/ignition wire from the SoS harness; goal is to only have power sent to the BT control when key is in ACC or IGN position, not the yellow/orange/+12v constant ("duh," but I'm bad at this, please bear with me :smile:).

  • Splice the ground wire from the unit into ground on the harness and attach to ground or attach both ground wires to ground on car ("duh," but I'm bad at this, please bear with me :smile:).

  • Split BT unit's RCA-out to left and right to match the four receiving units on the harness via two RCA splitters as described in the above DIY guide.

  • Once wired up, remove "guts" of stock head unit and mount the new contraption in the now-empty box, maintaining clean console look and retaining ability to go back to stock.

I *think* this makes sense as long as I can figure out a mounting point for the control unit after the wiring is done, but would greatly appreciate input from someone with more expertise on whether or not I'll short something and flambe my console/entire car. I don't think this setup would run the risk of causing electrical problems, but that's based on the assumption that there isn't much/any risk of swapping out the old recipient of the 12v power line (the stock, dying head unit) with a new recipient (the BT receiver and control dongle), since I'm replacing rather than adding.

Thanks in advance!
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a few things to look at:

There is an alpine m-bus to aux adapter. Whatever output from the phone can be sent to the bose amps without too much issue. Your phone would be the "head unit".

You don't need to gut a head unit. Just use a double din box, with a radio face from I_M_Legend, and a Retrosound poking through the knob holes.

Thanks for the info drew.

I already have the parts in the mail to try and create the above-described meme-machine, but good to know there's an adaptor for the m-bus in case it fails.
My phone is my head unit that bluetooths to a marine "dongle" I bought that inputs to my amp (I have Science of Speed aftermarket setup). Added a small, black volume control in the change tray in center console, and boom, music from my phone. head unit is still in place, lights up, all that jazz, but my phone runs everything.

let me know if you want more specifics on how I did it...
I imagine Swiftscott's setup is a more elaborate version of mine, but the same idea--

Current Setup.jpg


I wanted an OEM look, but with modern hardware, so I wound up gutting the (nonfunctional) radio and using the "box" to mount mine--everything behind the faceplate you see in this pic is actually empty, just housing a SoS headunit and the necessary RCA y-cables https://www.scienceofspeed.com/inde...eed-proformance-harness-adapters-for-nsx.html (item ipp-758).

I cut off the plastic from the back "screw" of the receiver unit and wrapped the now-exposed circuit board with a huge shrinkwrap piece and then epoxy'd two L-brackets together and one end of the now S/Z-bracket to the back-plastic of the receiver head (running parallel to the circuit board/"screw" part of the receiver) and used a bolt + nut to attach one end to the factory volume hole. Not the most elegant setup as you can see, but it does what I wanted: push button, receive bluetooth (and a nice volume knob and forward/backward buttons too). Only thing I regret is that I didn't account for the geometry of reattaching the center console, so I wound up making a cut to get everything to fit as seen in the pic. It doesn't bother me, since if this ever breaks, I'll just cut the rest to get a double-DIN setup, but there's no going back. I'd recommend it actually, if you can find a smaller/rounder receiver unit, since it does keep a low profile and looks pretty inconspicuous.
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Wow that looks cool. I bet you could hide that in a gutted OEM stereo easy. With the LED color adjustment you could make it look super close to OEM. This makes me want to rework my system setup back to an OEM+ look.