I installed new Infinity Reference ex6532 in my truck. The Headunit is Blaupunkt 940. When turning on the engine, the headunit shows Blaupunkt logo then after a second making a 2 second buzz on right speaker then the same on left speaker. It ONLY happens 3 seconds after the engine is turned on. If I only turn on the headunit with engine off, it can work for hours without an issue - but it wasn't like that with the factory speakers. Where should I start to get rid of it?