I have a MkI DIP that I've used for several years. I've found its effectiveness ultimately hinges on both transport quality and the DAC's receiver section in particular. It brought significant improvements to a older CD player's toslink signal when feeding an older receiver chip. However, with either a quality low jitter transport or a newer Crystal receiver chip (the CS8414 for example), the results were marginal. I would imagine that for the best low jitter transports and DACs, the DIP may actually degrade performance. I suspect the DIP reclocks via its PLL no better than a certain design limited level of jitter (I can't imagine it would ever be better than 250 ps, considering the age of its design). 250 ps was considered a very good jitter specification five years ago - if that's better than your transport and DAC's native jitter levels, you've gained; if not, you've taken a step backwards. I believe the latest Crystal receivers have intrinsic jitter around 150-200 ps. The DIP doesn't compare to the new technology jitter busters, IMHO (the 2 ps output D2D-1 that I now use comes to mind). But at its price and in the right system, the DIP is still a good value.