But the implication of Rob's design thought is that 44.1 is good enough, as the DAC gets nearer to the ideal, the sampling rate becomes less important. This is, as I understand it, why 44.1 sounds closer to the higher sampling rates/upsampled files as the taps are increased. Ultimately, as Rob has said, an infinite tap length filter reconstitutes the original sample perfectly. As an infinite tap length also, I think, implies an infinite sampling delay, the perfect DAC is only mathematical. But we don't need perfect, just a DAC that surpasses our ear/brain sensitivity.
I also have a BLU and an Indigo with the HDSD upgrade. I find it quite difficult to tell the difference between a single optical connection at 88.2 vs AES dual data. I run dual data mode with AES simply because I made my own connectors from certified AES cable and I use the Indigo optical input for my DAB tuner. I can't tell the difference between my AES cable and expensive (£2k) cables although A/B'ing is more difficult.
I think clicks and pops and interference via coax are nonsense, if the cable is as specified and terminated correctly there won't be any clicks and pops unless something else is fundamentally wrong. Again, I had expensive coax cable and could hear no difference between my AES cables and coax in dual data mode - I sold the coax. All of this is with the QBD76 or Indigo, with the DAC64 I found dual data to clearly be a better solution and thought that the coax sounded better - marginally and subjectively.
One caveat, I have done a simple electrical installation (around £200) that made a significant difference to the sound of my hifi, no clicks or pops at all. Before this I could hear cable differences including mains cables - but not now
Finally, the BLU upsamples to a single AES/coax/TOSlink connection too albeit at 88.2.
H.
