Short?

OP:

While it can be an external source, I’m worried with amps, especially tube amps, that capacitors in the circuits can start to leak and cause these popping issues. Best to have it taken care of early.

Tube gear uses coupling caps to keep high voltages (300V DC or higher) from going downstream which expects +- 2V of AC. Sadly some of these caps lose their effectiveness and start to short. These popping sounds can be the result.

Often this happens as caps charge up, that is, when you turn the unit on, and then the effects cease, but not always. 

PS - Motors in the home, like AC or house fans, vacuum cleaners will absolutely produce noise which makes it through the filters to produce _faint_ popping sounds.  

@mojo771 There is a bad capacitor in your air conditioning unit. It bypasses the power switch (in this case the thermostat). Because its failed, when the thermostat turns the AC on or off, a voltage spike that is supposed to be snubbed by that capacitor is what causes the pop in your speakers.

Its not a fault of the electronics.

Ralph's the man, man! 🤩

+2 for Ralph. Have your unit serviced, they can clean it and check the voltages and wash the coil. That runs about $100, retail on a capacitor is $150-200 installed. Or change it yourself if you can safely. Do it now before you incur further damage to the air unit. I live in a hot area and have 2 large units. I blew a cap on one, and two weeks later on the other. Both days it was *110. One of the caps was only 2 years old. I’ve also encountered fluttering lights when a high current draw kicks on. This was a grounding issue. Depending on the age of your house you can also have tired breakers. I had a breaker for my pool get weak and it was sizzling on the bus bar. I replaced the breaker and had to move it to an unused position as the buss bar was pitted. I’m ok now , but I’m waiting on a new service panel as I have solar coming right after that. So get your air  unit checked and proceed from there. Best of luck , Mike B.