[Z K]

Interesting discussion!

I used a Fiio BTR DAC for Bluetooth to Aux in before. There's a few finicky things you need to do like set it up to turn on with USB power and turn off when USB powers off. This is in the settings when you connect your phone to the App but you need to manually set it - it is not on by default. The sound quality is good with headphones with the Fiio, but in a car, it needs Line Level output. These DACs are designed to drive headphones so are amplified. When connected to a car, it will work but it will not sound good. Usually the highs get cut off and the bass get blown out because the car is expecting line level output but is getting a high power signal designed to drive headphones. Turning the volume up and down, messing with the EQ settings does not help.

Things like the "Bovee" ones provide line level output but their bluetooth connection and built in DAC is terrible.

So my solution was the "TUNAI Firefly LDAC Bluetooth" adapter for aux in. It has Bluetooth 5.0 and a high bit rate Sony LDAC that provides Line Level Aux Output. It is not designed to drive headphones. It also is designed for car use so it will turn on and off with USB power. This solved my issues and the audio is as good as the original BMW Y cable that used to work with iPhone 30 pin connector. I sold my Fiio BTR and am happy with the cheaper and better TUNAI LDAC.

So if you are just after audio quality and not a screen replacement and Carplay retrofit, then this is a simple plug and play solution. It really makes me wonder why no one else makes quality DACs for car use with line level output. If a Bluetooth DAC says it works with headphones, run away - you don't want that in a car.