I extracted this from Archimago's Musings - However, there is one situation where upsampling makes sense... The same reason Benchmark chose to use ASRC (Asynchronous Sample Rate Conversion) for the DAC1 and DAC2 - jitter reduction. Although by no means high, the sidebands are more pronounced using coaxial and TosLink interfaces. The sideband peaks around the primary signal clearly were reduced with 24/192 upsampling using the TosLink input. As usual, whether anyone can actually hear this difference in properly controlled testing is another matter!
And this - For years we've been worried about the "dreaded jitter". However, we know that these days, with asynchronous interfaces like USB and ethernet, there's nothing to be concerned of. Sure, we can see jitter anomalies with old S/PDIF, but I doubt anyone should purposely not use the interface for fear of audible issues assuming otherwise decent gear.
I use SPDIF/Coax digital cabling only.
Also, I loved the sound of DAT tapes after leaving behind R2R (Tandberg 900 and Technics 1500).