Well I've tried a number of different Class-D amplifiers in my home; Digital Amplifier Company, Class D Audio, and now some B&O ICE module based amps, and all have put audible hum through my speakers. My Audio Alchemy OM150 amps have some transformer hum, but that hum does not come through the speakers. I find it odd that all the Class-D amps I've tried hum, but my Class-A/B amp does not. Is this something that is problematic with the AC I have coming from my wall, and is it something inherent in the design of Class-D that lets it manifest itself, while my Class-A/B amp filters it?