I recently had a power cut in my area this Monday just gone, power was restored quickly, in about 5 seconds. However now whenever I go to plug in and turn on any of my amplifiers in my studio or anywhere in my house for that matter they are all making a humming/buzzing noise without the guitars plugged in. What's even stranger is that I had both my electric and bass amp plugged into the mains (on at the mains but the amps were off) however my acoustic guitar amp wasn't plugged into anything and is still making the same noise. This wasn't a problem before the power cut, I'm assuming this has something to do with there being too much voltage going around the house but that's just a wild guess. My studio in question was a contracted build so the electrics were fitted by professionals, also worth mentioning the power cut wasn't just localized to my house. Everything else in the studio (equipment wise) is working fine, I was actually working on the studio computer when the power went out and I writing this question from it. My KRK Rokit 6's (studio monitors) are fine and are not buzzing, my external sound card, a Focusrite Saffire Pro 40 is fine. This issue only seems to be affecting guitar amplifiers.
The amplifiers in question are:
Peavey Vypyr 15w modeling amplifier
Wuhan Eleca Eleconics AB-30 30w bass amplifier
Fishman Loudbox Mini acoustic guitar amplifier
Thanks for reading and I look forward to hearing your responses to this problem if you have any solutions. :)
*Also if you have any other questions feel free to ask them!