But, perhaps partly as a result of this magazine's positive coverage of the dCS upsampler, a veritable slew of products has appeared offering that "96kHz" magic bullet. Like the Bel Canto DAC 1 reviewed by Robert Deutsch in this issue (p.143), or the
MSB LinkDAC III chosen by
Stereophile's scribes as our "
Budget Component of 2000" (p.69), many of these products use
Crystal's new CS8420 sample-rate converter chip to produce a high-sample-rate datastream from CD data. Others, such as the dCS 972, use a digital filter with several choices of topology and noise-shaping behavior.
Now I
am sure.
It is important to remember three things about all of these products:
1) other than making active the lowest 8 bits of a 24-bit word, no new audio information is created by any of these products;
2) as susceptibility to word-clock jitter increases with sampling frequency, it is always possible that upsampling audio data can make things worse, not better; and
3) no matter how good these upsampling products can sound—and the dCS, Bel Canto, and MSB products indeed sound excellent—there is no conceptual difference between them and traditional CD playback systems.
I am now convinced that the sonic differences we have heard and reported on are due to the different choices in digital filters made by the designers of these products with respect to the number of taps, passband ripple, and stopband rejection (footnote 2), and to changes in the jitter performance.