I have also heard there have been some issues with the Perpetual Technologies P1A, and I don't know if it is an ongoing problem or if PT has fixed the problems. In any event, I posted the link purely for informational purposes and not to endorse any particular product--just to be clear. Although PT's implementation of the technology may leave something to be desired(although a friend of mine was quite happy with his P1A and there have been some very favorable reviews of the product as well), the general overview still provides useful insights into the basic components of the upsampling process(i.e. not specific to Perpetual Technologies), which is what I thought would be interesting given the many questions and misconceptions on upsampling that seem to repeatedly appear here.
Tim
Tim