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I have been experimenting with Hi Resolution files and have not been blown away. I have done ABC comparisons of the same music with Hi Resolution files, Redbook and SACD and do not see a huge difference in the experience. Frankly, Amarra Mini makes a bigger difference than Hi Resolution files. I don't believe it is worth either the cost or the hassle to download Hi Resolution files.
So I did a little research to find out why:
http://people.xiph.org/~xiphmont/demo/neil-young.html
I would be interested in the opinions of the audio engineers in our group.
I don't claim to be the authority on this topic, but I second the motion. Firstly, I find that it is really difficult to do A-B comparisons because often times the audio is sourced from different masters. For instance, a minute difference in volume can be perceived as a better source. Often, different formats are mastered by different engineers in different studios with different equipment. It's simply unfair to make any such comparison unless all such variables are eliminated.
I've run some experiments on my own taking a hi-res source with large dynamic range and converting it to redbook with and without dithering. The only variable here is the quality of signal processing software (which in my view well exceeds the dynamic range of 24 bit or DSD sampling hardware, because most of them operate at a rediculously high resolutions available in the computer, such as 32 floating point. But that's another topic). To me the difference is very settle, and mostly manifests itself as slight flattening of the soundstage in 16 bits. With dithering, the difference is often imperceptible. If the dynamic range of the music is shallow in the first place, as in recordings that are already heavily compressed, there is likely to be no perceptible difference at all.
I've also done similar experiments comparing the sampling rates and reached the conclusion that while I can occasionally tell a minute difference between 44K and 48K, I have trouble resolving any improvements beyond 48K. The 44K can sound slightly grainy and dry in comparison on strings, hi-hats and guitars.
Additionally, if you look at the spectrum of ,say, 192K master you will notice that there is typically no useful signal energy in the upper band (e.g. >40KHz ) -- just noise. I presume same argument applies to SACD. I have yet to notice a recording that has anything really useful up there (nevermind the question of whether you could actually hear anything in that range). It doesn't matter to me if there is a miniscule harmonic signal burried in there somewhere. Noise is noise. So when you pay premium for, say, 192K vs 96K download consider that you are likely paying the premium for noise.
A fair A-B comparisons may also be somewhat swayed by DAC's response varying with sampling rate. In principle, frequency response should scale proportionally, but DAC designers may choose an implementation that doesn't simply switch the sampling rate. For instance oversample the data to some higher rate and at that point you'd be also be including the quality of the oversampling and reconstruction filters for at various sampling rates.
Lastly, and most disturbingly, some of the "hi-res" downloads are still being heavily brickwalled for loudness, just like majority of redbook that are optimized for loudness. The audible distortion on these is often appauling. I have seen a number of hi-res masters also follow the same trend. I've even seen that on SACD in at least one case. As you end up paying premium for these downloads you expect to receive what you pay for. Unfortunately, not the case and there is no way to tell about quality of master up front to see if it's worth the extra $$$.
Again these are my ears. Your milage may vary.
People argue if the difference can be heard between 16/44 and 24/96, it is also discussed that the difference between nicely compressed file and flac is very difficult to hear.
