Just a warning for anyone thinking of using Ethernet over powerline to feed data to their Runeaudio device. I've done that recently, and it's extraordinary how much noise the powerline Ethernet adapter puts on the mains. Very audible, especially on headphones through a headphone amp. I've managed to mitigate it by moving the powerline Ethernet adapter to a power socket on the other side of the room and using a long Ethernet cable, but it's pretty bad. I've used such adapters before but never in an audio critical situation.
Ethernet itself shouldn't pose a ground loop problem since the 100base-T specification required magnetic isolation and the RPi is apparently compliant, but I think the way these powerline adapters superimpose a signal over the mains seems to generate a lot of noise. I thought at first I had just built a noisy power supply in the headphone amp, but checked it on my other hifi and it was fine, and then discovered quite a few sites complaining about noise from these adapters. Sure enough, getting a huge long extension cable and plugging the RuneAudio and headphone amp into a socket physically on the other side of the house cured the problem, and by experimentation I discovered that one merely on the other side of the room seemed okay as well.
Just to contribute that I use ethernet over power plugs with no apparent problems. I have perfectly clear sound with no interruptions.
FWIW, I did considerable research before trying this and found that there were mixed opinions - some had success, others had experienced problems. My conclusion was that the problems are caused by other 'noisy' devices on the circuit - fridges (with compressor motors) were notably problematic. This appears to be the case with the original poster, who stated that better results were achieved on a different socket (circuit?). My conclusion was that if it was the powerplug itself (or the technology), the results wouldn't change on a different socket/circuit. Anyway, I took the plunge and bought the best powerplugs I could find and it worked for me. As success appears very circumstantial, there are no guarantees with this.
In case it's of interest, I use TP-Link AV500 units.