Frederick21 - all manufacturers will claim this. If you compare a stock Squeezebox to a stock Sonos for instance, you will be shocked at the difference in jitter. The SB is much lower, and it still has audible jitter. The Sonos has the worst jitter of any of the computer servers on the market that I have measured. I believe it's primarily because they went overboard in adding filtering to insure that they would pass FCC spurious emissions testing.
As for jitter reduction in DAC's: They all reduce it to some extent, but never to inaudible levels, even ASRC (async sample-rate converters). Even the jitter in a CDP is quite high due to the lousy clocks that they use.
Face-it, the only way that you will ever get rid of it is to use an expensive reclocker or a DAC with a really good internal clock, like maybe a Spoiler, Zanden or Esoteric. DIP is not even remotely close, but it upsamples. It does reduce jitter though.
Steve N.