Yeah, thanks, I finally noticed that the fuses were labeled and so figured it out. I still find the hum switch odd though because the amp is dead silent (a good thing) no matter which way the switch is. The reason I turned it on is because neither my cd player or tuner have a third prong so I assumed having the set 120 chassis grounded would be a good thing. I'll have to try calling them tomorrow about that and because I have a couple of other questions about the unit I'd like answered as well. Having said that, the amp sounds beautiful, actually shockingly so, and with the silver face plate its quite attractive.