Yes, power and whatever else is around makes a difference. Power in Australia is generally very good too. In my studio, I get almost no hum (assuming I'm not near an amp or other power supply). My original studio in Sydney was noisier. I used to regularly use a Rocktron HUSH unit when recording guitars particularly, to minimise hum and RF noise. I picked up a second unit while building the current studio and have rarely needed either one. There is one place I play, where I can't use a stock Super 4 equipped Musician, as the hum is so bad. Nobody can work out where it's coming from either.