I set about to solve problem back in December 2019. Not truly a problem, just an annoyance. In my office I have a music player (RPi 3 + Hifi Berry Pro XLR) that feeds a pair of Behringer powered subwoofers and M-Audio BX5 powered monitors. We have several similar arrangements, creating five separate music zones across the property.
I’ve had this arrangement for years. I’m pretty happy with it, with one exception. The audio gear does not have signal-sensing power on/off. What I wanted was a way to turn the gear on/off automatically based upon the status of the media player. How hard could that be?