I have smaller brother... Sister..? The 550ax2 and a class as well. No hum I've noticed but I'm in a city with good supply and 230v here (which may be a reason)
As for heat mine gets warm to touch but I can still hold hand to case after hours. A bonus in fact for cold Scotland
As for heat mine gets warm to touch but I can still hold hand to case after hours. A bonus in fact for cold Scotland