KeithEmo
Member of the Trade: Emotiva
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If you want to know whether there is a point to DSD, or rather want to disprove supremacy of DSD, you don't really have to compare it to anything at all.
All you need to do is to show whether the current system of digital capture and playback is transparent, which maverickronin's set-up lets you do. Whether the source is a DSD output, tape, vinyl, or directly from a pair of mic pre-amps in a concert venue, if you can't differentiate it from the PCM AD/DA loop, then that's that. You can't improve on transparency. One kind of homeopathic remedy doesn't work any better than another kind of homeopathic remedy.
I agree - if you can't differentiate the "original" from the version that's been through "the PCM loop" then you have indeed proven that PCM is "effectively perfect" at reproducing whatever your original source is. However, you seem to be missing a huge piece of the equation, which is that DSD is not "a reference source"; it's simply another way of doing capture and playback - like PCM. All that test will prove is whether PCM is capable of perfectly reproducing a particular source - which, in that case, is simply a DSD copy of a real source.
So, yes, if you can't tell the difference between a signal played directly from a DSD source, and one that has then been recorded and played back using PCM, then you have indeed demonstrated that PCM is "perfect enough" to make a perfect copy of a DSD source... or you could say that you've proven that PCM is "at least as good as DSD"... but that is precisely all you've proven.
(My point here is that, even if you find out that you CAN hear the difference between the "DSD original" and the "PCM copy", you still have NOT proven that DSD is better; you've simply proven that PCM isn't perfect. And, for the record, I promise you that you WILL be able to measure the difference between a PCM copy and a DSD original, AND between a DSD copy and a PCM original; AND between either a PCM or DSD copy and an analog original; the only question in my mind is whether that differences will be audible.)
The problem is that there are a whole bunch of other things we sort of need to know....
What if DSD significantly alters the original in a bad way?
If that's the case, then all we're testing is whether PCM causes enough additional damage to be noticeable.
What if DSD and PCM both alter the signal a little bit - equally? (Which is what I would expect based on the science.)
If that's the case, then both are equally good as recording formats, but neither is better, and one should avoid converting between them (and so suffering the flaws of both).
If you want to prove "the supremacy of DSD", then you need to prove that it reproduces something better than PCM.
Which means that you need to quantify the reproduction quality of BOTH - and then compare them.
Another thing you're ignoring is that there is a "downside" to DSD; it is a nuisance to record and edit, and PCM is already the de-facto standard.
So, if it turns out that both are "equally perfect", then, in terms of justification "DSD loses on points".
In order to justify its existence as a REPLACEMENT for PCM, DSD has to demonstrate that it is actually BETTER in some way.