Is the popping sound loud? If so, then it also could be that your power amp gets too hot after a while. Years ago I had that problem. I could solve it by removing the top plate of the amp, so it had some extra cooling.
Popping sound
There’s an intermittent popping (electronic) sound coming from my left speaker only. It occurs at intervals of maybe 20 minutes or longer. I can live with it but I think it’s odd that it only emanates from one channel.
Any ideas?