I have a 95 lexus es 300 with a new sony head unit. Problem is with the switch on(Not running or accesory position, just on) the stereo is fine no noise or anything. As soon as i turn it to accessory , You can hear a low hum. And when the car is on there is the old alternator whine. I had purchased a 20 amp noise filter for the power to the head unit and that had no effect. I have run a direct ground line to the unit itself and still the noise remains. I even have 2 ground loop isolators for the rca inputs, so all signals leaving the unit are filtered. no good. Have checked rca's for cuts , no power wires/speaker wires together. ANY help would be mucho appreciated!
Where are the amps grounded to and what amplifiers are they? If they are screwed down to metal, unscrew them and temporarily place on a board or piece of cardboard. Do a search for noise or ground loops to learn more.
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Top Secret, I can tell you but then my wife will kill me.
The amp for the front is mounted under the seat directly bolted to the body, where the passenger seat is. I have removed the amp from the setup(completely ungrounded w/no power), and still have the same noise with the head unit only. But no noise with the car switched on, just with the acc and running. I also have added new battery terminals today,gold connects. I have read that installing a second main ground to the body from battery can fix this(?). Not sure though.