I recently picked up a 14 S4 and wanted to add Android Auto capability to the MMI system (not a fan of Android based screen replacements) and ran across the Mr12Volt adapter that seems to be well received in other cars. There isn't much discussion of it on AZ and none in this forum so I thought it was worth a post about it. Unlike most (all?) of the similar boxes sold, it has a MOST connection, so in theory sound quality should be better. Installation is pretty similar to the other boxes with the exception of disconnecting the MOST cable from the MMI and reconnecting to a harness that sends the signal to the MR12volt box and the MMI. Installation directions consist of a video that shows an older version of the box, but most of it is the same with the exception of the MOST cable and not needing to install some kind of antenna that screws onto a fitting on the older box in the video that doesn't exist on the current one. Mine came with an extra harness that said something about air conditioner on it, but it wasn't used in the video and there wasn't anywhere obvious to connect it, so I assume it is intended for other applications.
It gives you the option of a Bluetooth audio connection, Android Auto, Carplay, Video via USB (haven't tried yet), and Mirrorlink (also haven't tried since it doesn't work with Pixel phones). In theory, it allows for a wired or wireless AA/Carplay connection, but I can't figure out how to force a wired connection, which I'd prefer because the phone would run cooler and the wireless connection hiccups occasionally (not often enough to be a big issue). I contacted tech support via Whatsapp, but did not get a reply. I did get a reply on an earlier question so they're batting 50%.
One feature it does have that I don't think competing products offer is a fully parametric equalizer. It allows you to set frequency, amount of cut/boost and Q for 15 frequencies. They are grouped into groups of five (bass, mid, treble), but you can set each slider to whatever parameters you want. REW and a microphone can be used to come up the settings (filters in REW) to change frequency response to whatever house curve you prefer. Changing the settings with the scrollwheel is a little awkward, but works. A screenshot of my bass settings is attached (my car came with an aftermarket sub that played at a much higher level than the rest of the system).
Overall, I like it pretty well. One minor annoyance is that since it only wants to do a wireless AA connection and the unit powers on every time a door/trunk/hood is opened, my phone will connect to it and stop playing in my headphones if I'm listening to something. You can disconnect the mr12volt wi-fi connection on the phone to revert back to the headphones. A second issue I had that has been resolved is that people could hear me on phone calls, but I couldn't hear them while using Android Auto. The fix is to make MMI (Audi) bluetooth connection media only (no phone connection).
Update: After using it for about 6 weeks, I've quit using wireless Android Auto. It works most (70%?) of the time, but sometimes won't launch and other times, it crashes and may or may not restart with the occasional stutter along the way. The company was of no help in figuring out how to force a wired connection, but I ran into a solution on a BMW forum. There is a developer mode for Android Auto that is enabled by going to Android Auto settings, tapping version at the bottom of the screen, then tapping the Android Auto build number repeatedly until it says developer mode enabled. The developer options will pop up and a box can be unchecked to disable wireless AA. To get to the developer menu again, you have to go to AA settings, and tap the three dots at the top right of the screen. I use a Pixel phone which in theory should work well with wireless AA, but other phones might work better. It worked perfectly with a 23 BMW I rented recently, so I think it is the box rather than the phone. No experience with wireless Car Play to report.
To get the Mr12volt to restart if it disconnects or refuses to respond, holding down the center of the MMI control wheel for 8 seconds will force a reboot.
mr12volt eq screen small.jpg
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