I was hoping to have a setup wereby I could use the Volumio GUI to activate one of the RPI’s GPIO’s to switch a relay that would be used to turn the rest of the audiosystem on. Does anyone know if such a thing has been done?
Yes I did but I couldn’t find anything that met the requirements and I dont have the skills to do it myself.
I have no idea how I managed to load this image into this thread 
Ah, I misunderstood what you were asking. There’re a few links here, and I wouldn’t be surprised if there are more if you do a little searching.
Believe me I have done the searching!
I’m sure people have done this here … it’s just getting them to volunteer their experiences As a starter have you tried PMing likely plugin authors? It sounds as though it should be a fairly simple thing to achieve. Perhaps also look outside Volumio for people controlling a relay from gpio in Raspbian, and then apply that to your specific needs.
Have a look at the amp switch plugin to see if you could use that.****