Bela thanks but I've tried similar steps. Raspify was the successor to Volumio. So those fixes have already been implemented in Volumio. If you read the guide you'll see that previously he was limiting the mpd output to 16bit to get around the problems with async USB dacs. All those problems do indeed sound familiar to the problems I'm having, the difference being that I only have a problem with picore. As I said, Volumio and arch have no problems.