Recently installed a Chinese made 10" touchscreen, used the Schosche SLC4 (https://www.scosche.com/car-stereo-output-converter)adapter and two pac SNi-1 RCA noise filters (https://catalog.pac-audio.com/catalog/audio-interfacing/sni-1). Thoroughly grounded the head unit caseing/housing to the dash metal structure with a separate ground wire.

I have a very annoying alternator whine (increases volume and frequency with engine speed) in the rear door tweeters only. Anyone ever run in to this and have a fix?