Locating the Source of Hum

Just today I started getting hum through the speakers. Amp is MF A308 cr, plugged directly into wall, preamp/CD into PS audio Ultimate Outlet. Is hum usually caused by poor AC in home, or is it generally a problem with equipment? Thunderstorms were in area and wonder if that could also cause issues. I'm planning on getting a dedicated 20 amp outlet for system, does this usually solve problems with hum? Few days ago wife turned on blow dryer and I noticed hum from amp as well. thx
I had hun after a storm last year, in a day it went away but I have no idea why it caused hum or how it was resolved.
I do know tube amps can hum occassionally from crapy incoming power.Once in awhile my Thors will hum and found out that Massachusetts isn't the best power source state for sure..For me its just an occasional annoyance...