Don’t shoot the messenger, but if you need to get access to the underlying system, you’ll have to choose something else, because Harry decided to make Ropieee a true appliance experience only - no tinkering allowed any longer…
It all worked the first time I tried it! The only problem is that there is a delay at each step, If the amp is powered off and I press the play button in Roon, it takes about 3 seconds for the amp to become fully powered, and the first few seconds of the initial track may get cut off. A remedy I found (not ideal) is that after pressing play, I wait to hear the relay click in the power strip and then I immediately press pause. I wait a couple of seconds for the amp to be fully powered, slide the play position back to zero and hit play again.
Ok, I see. Using a service running directly on the RPi to monitor the audio system would have been super easy. The methods described above are either limited to Roon (I also use Spotify or AirPlay), and the Toslink method seems a bit complicated and expensive to me.
I might just use a self-contained setup using an Arduino Nano to sense the audio signal and control a solid-state relay for the mains power of the power amp.