I've got the standard wall-warts plugged into a Furman conditioner. Dirty power can cause problems, so that's a good point and very valid. I'd think that if it was simply dirty power, again, hiss wouldn't be the only problem. In most of the places I've played where power quality was a problem, I had a lot of hum and buzzes, static and miscellaneous crackling, much more than additional hiss, but that, too.