this is for troubleshooting purposes only...

not using the car power - use a separate, independent power, like a stand alone 12 V battery, or a 12V AC-to-DC converter. the point is, to power the unit using the power source that is not connected to the alternator and see if the whine is still there... then, it means that the whine is induced in audio cables... if the whine is gone, then you power lines need to be "cleaned" up...