TDA7850 Car engien whine, buzzing noises

[KevinDB]

Hello,

would someone confirm my mistakes on this TDA7850 schematic??
There is a ground loop isolator BA3121 on inputs and softstart mosfet to limit inrush current.
Ignition/remote ON provides a buzzing noise, as soon as engine or cabin heater/fan starts you can hear the whine amplified trough speakers….
Any tip is welcome :)
 

 

[Karl Yamashita]

The good old BA3121 is a life saver. 

FL- and FR- don’t seem to be going anywhere? If i remember correctly, you should feed the FL- and FR- to the VM1 and VM2. The BA3121 will convert the differential audio signal to single ended audio for the TDA7850 

[AScha.3]

...but little problem:

 

[Karl Yamashita]

The OP didn’t ask where to purchase the BA3121 but instead asked for help with his schematic and ground loop issue. 

[AScha.3]

afair When i had problems with noise on ground in cars, i used the cheap isolation transformers, like this:

 

or