I’ve been annoyed with the static ground loop noise on my Audi A8L after installing the TV tuner with auxiliary and bluetooth streaming. The bluetooth when plugged in to the charger, the ground loop noise is unbearable, the same with the auxiliary cable connected to my iPhone when the lightning charger is ON. I did all type of power filters and none work until I found on the internet the simple audio transformer isolator for the audio auxiliary cable. They cost less than $8 thanks to all the competitions. The box actually isolates the source ground and signals from the output using transformers, band pass filter the audio frequencies. All we need is to put it in series between the input of the stereo and the output of the source like iPhones, Bluetooth audio dongle. The static noise is totally eliminated. Another way to eliminate the audio ground loop noise is to use the USB portable chargers, just make sure you don’t plug the USB charger to charge the portable charger while using it.