Annoying squeel, loudness according to RPM
 

Hey guys, the last few weeks I've started to get a hum from my back amp? (Stock Bose) I do have a double din aftermarket head unit that uses the metra kit,

I'm thinking it's the Bose amp ground but don't know where that is located?

Any sudgestion?

Am I even heading in the right direction!

Thanks
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