Stereo/DVD: Weird AUX noise?

[YorkshireDave]

Perhaps my experience may help.

When swapping out my aftermarket system for a spare in order to sell my V70 I found I had a very similar noise when it was powered up. As someone who's installed systems in my myriad of cars over 40 years it wasn't a sound I recognised at all.

When I installed the aftermarket into the V70 I cut all the plugs off and soldered using heat shrink sleeving - it was cheaper

The root cause turned out to be that one of the signals from the head end to the amp had come adrift within the heat shrink. When soldered back together it was once again perfect and noise free. So, perhaps check all connections to the amp. If you can, pull one at a time and see if it makes a difference.

Good luck.