What kind of squealing noise is it? Is it when the engine is running? Is it just straight powered on and nothing else on? Is it the head unit signal? A little more info here would help us to help you out better
What I've seen happen in the past is the torriod (spelling) coil vibrates and causes that squealing noise. Find a silicon that has a high tolerance to heat and rub it onto the coil. It will dampen the vibration and hopefully stop the squealing.