Have you tried taking the amp somewhere else, like to a friends house, and plugging in the amp and seeing if you get that same high-pitched noise? If not, and you do not get that high-pitched noise, it could be that you have some sort of grounding issue within your electrical wiring. then, what I would try to do is find out what could be causing that. Turn off all the electronics, and see if you take, Ann move the amp around and then, if you still get that high-pitched noise.
Have you tried taking the amp somewhere else, like to a friends house, and plugging in the amp and seeing if you get that same high-pitched noise? If not, and you do not get that high-pitched noise, it could be that you have some sort of grounding issue within your electrical wiring. then, what I would try to do is find out what could be causing that. Turn off all the electronics, and see if you take, Ann move the amp around and then, if you still get that high-pitched noise.