Originally Posted by funkahdafi
...which doesn't automatically make it the better option. Just saying. I know for a fact that the line-out of iPhone/iPod dock connectors is very good (straight signal, no EQ, good DAC). This signal would be fed into the BMW via the Y-cable without further analog/digital conversion. So I would believe that way it has the least "signal loss" and tampering.
The other way, feeding the BMW through USB alone, would mean that compressed sound decoding would happen on the car's side, not the iPod. It would also include A/D conversion in the car. I am not sure if they use good components for that.
Not trying to argue here. Just wondering.
Why would there be any Analog -> Digital conversion via USB? The point is to send a digital signal to the car's DAC and let it decode the files (Digital -> Analog). Whether the iPod/iPhone's DAC is any good is probably debatable and perhaps subjective. I'm used to using external standalone DACs in my audio systems so I've gotten a bit sensitive to differences. I know that the 5G iPod Classic had a decent DAC, but not so much the newer ones.
Forgetting the DAC part, there's an analog path from the aux in port to the HU. On my Dad's car, if the plug moved at all in the aux port, the audio signal would be affected. That makes me think that the plug quality - or at least the reliability of it long term is suspect. I hope I'm wrong, but to me going the aux in route introduces more issues than simply sending a digital signal (including those mentioned above).
I'm not saying using the y-adapter is bad ...it's just if I was given a choice, I'd go digital. But that's just me.