The Cal Alpha or Sigma II that is specified as being 24/96 capable is just that. Capable of accepting a signal UP to that point. It is NOT an upsampler contrary to popular belief.
In the Stereophile review, the Sigma II that they reviewed showed the unit passing 17 bits of information even though it was a 24/96 model. John Atkinson felt the limitation was due to a high noise floor, probably generated by the nearby internal power supply. While i'm not sure if this also applies to the Alpha, but one might assume so as the units are almost identical in size.
Don't take this the wrong way and think that there is NOT a big difference between the 16 bit Sigma's and Alpha's and the 24 bit versions, because there is. Tonal balance is quite difference between the two with the 24 bit sounding quite a bit more open on top with better extension. Using the factory tubes, the 24 bit pieces sound more "detailed" whereas the 16 bit versions sound both warmer and smoother. Depending on the rest of the system, one may work better for you than the other. The advantage to these units is that you can "fine tune" the output simply by popping in new tubes. I might add that these do respond quite favorably to doing such.
As to transports to use, there seems to be good synergy with the two CAL pieces running together. I have tried quite a few different transports with the three CAL's that i own and the Delta always comes out best. Of course, that is a matter of personal preference and system synergy, etc... My (limited) experience with using DVD players as a transport has not been nearly as good as some others have reported. As previously mentioned though, most DO NOT output a TRUE 24 bit signal. Since the CAL's aren't really passing a 24 bit signal, this is NOT that big of a deal.
If i was hunting for a "reasonable" transport, i would probably look at some of the used Wadia's and Theta's floating around. Sean
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