I have a GROM BT3 mounted in a 2006 Mini Cooper and I experience a high frequency noise when I select the GROM for audio playback during bleutooth playback, 3.5mm aux and phone call.
The frequency I hear is 10.3kHz and 13.9kHz.
This noise wasn't present when the original Ipod adapter was installed in the Mini.
I tried to solve this with a ferriet bead wrapped around the power cable thinking it could be a ground loop. But this didn't solves the problem.
I tried an other GROM BT3 with the same result, the noise stayed.
What could be the problem of this high frequency noise?