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Old 10th July 2013
Lives for gear
LeeYoo's Avatar

The first thing to do if you have hum is to find out if it's pure 50/60 herz, or 100/120herz.
Clean base mains frequency hum comes from a transformer, and single and/or double the frequency with overtones comes from the electronics.
AFAIK, there is NO mains transformer INSIDE the unit that makes a mains stray field.
(Lineair) voltage regulator hum can also come from sagging mains power.
No country in your profile, but you didn't do something silly like running a 230v transformer on 110v.