Many thanks for getting back to me MajorFubar and spiny norman and sorry that I haven't responded sooner. I haven't tried just running iTunes on its own into the Devialet as I have quite a few files that iTunes won't play. I really need a program like Audirvana to fix many of the issues that faces iTunes. Perhaps I need to look at jriver if Audirvana won't work with the Devialet. To answer some of your questions spiny norman. I am only using the Mac mini as a hi-fi component for music replay so I will be able to disable anything and everything that may cause trouble or slow it down. I did read that you need to find the best USB port by checking the system profile to see if any other devices are using the same port. I would have liked to use Devialet Air, but the wi-fi in my area is very congested and constantly changing. You are most certainly not teaching me to suck eggs and your advice is invaluable.
By the way, i did get the Mac mini to play initially for about three hours last week before I decided to post on this forum. The sound was not entirely right though being very bright and lacking any low frequency extension. It then reverted back to the Mac mini internal speaker! Luckily I have a cd transport that I've been using which sounds superb so I haven't been deprived of music!