Hi All, Well today has been a waste of time! Driving along one day and the rear amplified speakers started squealing, the higher I revved the higher the pitch... At this point I just thought the standard amp was knackered. Ripped out the standard unit today, brought a decent 4 channel amp - wired all up and the engine noise is still there! Tried it with the front speakers also, exactly the same noise. The ground for the amp is the ground behind the standard sub, also tried it on the sub but same thing happened.. Anyone have any ideas? Started this at 11 and just finished / gave up. Thanks in advance!