Hi
I have made some ekspirement with linear power supplies for the rpi3. First I have powered it with 5v at the gpio, which gave an enormous improvement. But then I removed the "crappy" onboard regulator (for 3,3 and 1.8v) at the rpi board, and powered it direcly at pp8 and pp9. Oh my.... another enourmous improvement in sound
Are there someone who have tried something similar?