I have a microphone receiver and a raspberry pi. I'm trying to power them using one DC jack. The receiver uses 12v and the PI uses 5v. The PI is outputting music which goes into an IN port on the receiver and the receiver is supplying the microphone audio. The receiver then has an out AUX port which will send both the microphone and music to my amp/speakers.
I'm using a step down converter to convert the 12v to 5v and then power the PI. Then a ground loop isolator to remove the noise however I am still getting a large buzzing sound. When I power the PI and receiver on their own power source all of the noise goes away.