If anything in this article is unclear or confusing, please let me know in the comments and I’ll do my best to clarify.
Disclaimer: by following the instructions below, you may end up destroying your stereo, car, MP3 player, interpersonal relationships, and everything else you hold dear. I am not responsible for any of this. That being said, it worked fine for me.
This method will work on any Alpine stereos with an 8-pin M-BUS connector in the back. (The stereo I performed this on was an Alpine CDM-9821.) The connector itself should look something like this:
After some searching around, I located the functions of each pin on this connector at pinouts.ru. The pins on interest are the bottom three:
This corresponds perfectly with the contacts on a 3.5mm headphone plug:
So all that’s left to do is make an adapter between the two. I ordered these parts from Digi-Key: CP-1080-ND, AE9918-ND, and CP1-3513-ND.
Gather up some solder, a soldering iron, and wire. Make the following connections:
- “Audio Ground” pin from the M-BUS connector goes to the pin closest to the hole on the 3.5mm audio jack
- “Right Audio Input” goes to the pin farthest from the hole
- “Left Audio Input” goes to the only remaining pin.
You should end up with an adapter cable like this:
Plug the M-BUS connector into the back of your stereo and mount the audio jack somewhere on the dash.
Now turn on your car. If all went well, nothing will start on fire. Hold the “Setup” button on the stereo and enable aux input in the menu. Now hit the “Source” button until you get to AUX. At this point, you should be able to plug in an MP3 player and have the audio routed to your car’s speakers.
Hey David,
I have a CDA 9855, It is pretty old school now but still a good deck. I want to hook up an AUX cable however alpine have changed the aux cable they sell and now the grove in the side wont line up, although from memory the pin to pin hole arrangement was the same. I considered buying the cable pulling the metal grove and pugging it in and hoping the pins are the same but I never tried.
I want to know is there any way i can stuff my unit by trial and error? and is there any way i can test the holes to figure it out.
I’ll check to night the diagram at “pinouts.ru” is the same but i think it is slightly different.
Any help would be great.
Jack
Hi Jack,
When I was looking for information about the subject, I recall that Alpine had two standards for the cables: AI-NET and M-BUS. I looked up the manual for your CDA 9855, and it appears to be Ai-NET (manual: [link]). I suspect that you probably have a M-BUS cable, and that’s why it’s not fitting.
There’s a pinout for Ai-NET at this link. The pins of interest to you are 4, 5, and 6.
David
I have the same plug in my old Mercedes branded Alpine radio. But I don’t have a “Setup” menu. I believe there is a remote trigger signal that needs to be sent to the radio to switch it into the CD Player mode.
Do you know which line needs to be triggered? I found a reference to it here http://www.rockbox.org/mail/archive/rockbox-archive-2003-11/0476.shtml but none of the links work. Do I need to add 12v to the bus pin?
The M-BUS protocol does not require a trigger signal (thought it can accept one—details at http://web.archive.org/web/20050509160913/http://joerg.hohensohn.bei.t-online.de/mbus/). Provided the radio is set to the correct mode (aux), it just amplifies whatever is sent into left/right signal pins. As for setting it to the correct mode, check your radio’s manual. If you don’t have the original, look up the model number online and I’m sure you’ll be able to find it.