Hi,
We have identified the same problem here on a french Audi forum
http://forums.audipassion.com/topic/153130-gresillement-tweeters-bo/
What we understood so far:
- It is reproducible on A3/S3
- It is not linked to the B&O system, you have that crackling noise with the standard audio system, Audi Sound System or B&O
- It is only reproducible with MMI 3G+/Advanced MMI (the one with the big screen and the 20GB hard drive), not with the cheapest one
- We get the noise when the music is played from the hard drive, the SD card, or the bluetooth. Not from an iPod or iPhone plugged on the AMI. It suggests that the pb is at the MMI DAC level, as it is ok when using the iPod DAC.
- The pb is here whatever the file format / compression method: WAV, MP3, AAC, FLAC etc.
From here I understand that:
- It is linked up with the sampling rate, this pb is only reproducible with 44.1kHz files, not 48kHz. I have converted a few files at 48kHz with iTunes and no more crackling noises. Not a real solution in my opinion, but it confirms that the pb is with the Digital to Analog converter.
- It can be fixed with a "Electronic ECU" replacement ?
Can anyone confirm that it is worth trying to have that ECU replaced to fix the pb ? I've spent so much time at my Audi dealer, trying to explain that it is not linked with my files, compression rate, SD card etc... without any satisfactory answer, I'm a bit discouraged... My solution so far was to use an iPod nano on the AMI, and not using the hard drive anymore.
Thank you for your help, sorry if my english is not so clear.