Loved original look of blaupunkt radio for my w114, and came across this (see attached).

Installed it and works nice (ran line through ashtray). However, when I crank volume really high I get feedback (wining noise); and when engine is running, it has a low murmur which seems tied to how much I accelerate (ie, when I punch accelerator low humming sound occurs)?

Maybe I need new voltage regulator (maybe new speaker)?

Anyone ever installed one of these?

Attached Thumbnails

 

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Current:
1971 Mercedes Benz 250 (Euro Spec)
1972 Mercedes Benz 250 (US Spec)
Past:
1972 Mercedes Benz 280