I just bought this Tripp Lite. My system has developed a new hum, so I was hoping the old Monster unit I had was being stupid and needed to be replaced, but the hum persists. The hum isn't constant, though, and I can't figure out what's causing it so far. Anyway, the Tripp Lite is doing what it needs to. I do want to get one of those UPS units that Chris linked to a while ago, though, when I move my system to the basement. Just because.