Short?

Can you put that AC on another circuit ?    Sounds like noise on the AC line caused by the compressor kicking in

found these, didn’t read them, hope it helps.

https://carvinaudio.com/blogs/audio-education/proper-power-up-sequence-explained#:~:text=So%2C%20proper%20power%20up%20sequence,power%20amps%20to%20the%20speakers.

https://www.sweetwater.com/insync/power-power-off-sequence/

https://www.sinbosenaudio.com/info/the-correct-sequence-of-turning-on-and-off-audio-equipment-i00156i1.html

In a long ago setup I had the same issue. Some equipment can and other equipment does not send a signal to the speakers. Went on for years, didn’t damage anything (luckily?)

Some power protection devices have timed delays for activation of individual outlets dedicated for specific equipment to eliminate that problem. Also, timed sequential turn off.

Amazon Power Sequencer

https://www.amazon.com/Monoprice-Power-Conditioner-Sequencer-Outlets/dp/B01MYNCACV/ref=sr_1_5?keywords=power+sequencer&qid=1691324281&sr=8-5

I forgot to mention that I also have a Niagara 1200 power conditioner.  Not sure if its also supposed to act like a surge protector but it doesn't help prevent the problem either.

This doesn't sound like a grounding issue, unless you have very high amounts of static (low humidity).

Sounds much more like a failing cap and it needs to be serviced.

erik, I'm not sure what that means - cap.  Capacitor?  And where, the house, the outlet, or the amp?