I am using a Lumia phone. I think the reason might be that the phone does some strange stuff with the Aux's GND when supposed to mute the sound. I will test the radio with some other source of sound and will see then.

In the meantime I've also tried to resolder the GND cable, solder it directly to the TDA7313's GND pin, then behing an elko which is connected to that pin, and even between the LOUD R and LOUD L pins (as found on one of the photos of the e30-talk tutorial) - no change...
the only thing I managed to achieve (when the Aux GND was soldered behing that elko, which is connected to the 7313's GND) was that the interference was a bit "smoother"

I already got an advice, that if this persists with other devices, I should try to add some elkos to the R and L channel...

Hi everyone.

I am new here - so hello!

I have a problem with my BMW Business RDS Aux-in modification. I have done it accordingly to this tutorial from e-30talk.com (with GND channel connected to the radio's ground).
I have tried it with my smartphone and... It sounds good, except moments, when nothing is played (i.e. between songs) - I get some terrible static interferece, sometimes hear some radio broadcast... this also happens when there is a pause in a song (or just a silent moment). any idea what is going on and how to fix it?

will be grateful for any help!