My 'installation' expert told me he had former experience with Empeg car players and tried everything, but didn't succeed.

Your installation expert's previous experience was probably with a Mark 1. The Mark 2 doesn't have the same ground loop problems and shouldn't have the same symptoms. It should be as quiet as any other car stereo. If you are getting noise problems with a Mark 2, then you would probably get the same noise problems with any other stereo (i.e., it's something else in the installation that's causing the issue.)

Did you try the noise-reduction PDF documents at Install Doctor, here and here?

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Tony Fabris