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Actually, no, i don't consider myself a Guru at all ...

... and i don't own a spectrum analyzer. But i do apologize for the swipe about "laughably biased/inaccurate".

i didn't want to respond to your post because i did think it was biased and inaccurate. you've listed all the advantages of PCM/DVD-A and all the disadvantages of DSD/SACD, but neglected to point out the disadvantages of the former and the advantages of the latter. Since in the past you've shown a disinclination to have an "open mind" i didn't think it was likely that i will be able to persuade you otherwise so i didn't bothered.

in reality both formats are good, and both formats have their compromises/limitations. i certainly enjoy both, and i've listened critically to both on a variety of players and setups (i've personally reviewed half a dozen players on my system). i own more than 150 SACDs and 50 DVD-As.

as an example of your bias/inaccuracy, you mention something about SACD have an "equivalent" bit depth of 20 compared to DVD-A at 24.

well, first of all, i don't think that DSD is necessarily "equivalent" to 20 bits resolution. in fact, at least one paper has quoted that you need about 384/32 to be able to represent DSD accurately for editing purposes.

but let's assume for the sake of discussion SACD actually is equivalent to 20 bits of resolution. you are still comparing apples with oranges because 24 bits is an upper theoretical limit for PCM 96/24 or 192/24 resolution. the actual resolution is likely to be less because:

(1) PCM resolution is directly proportional to signal amplitude. if you have a sine wave at maximum amplitude to that the peaks are encoded at maximum values, then yes, that sine wave is recorded at 24 bits resolution. if your sine wave was half that amplitude, you are recording at effectively 23 bits resolution (because the most significant bit is never used therefore it is "wasted"). very low level signals are effectively being recorded using only a few bits of resolution. In most well recorded music, the average peaks of the signal is far below the maximum, so the effective resolution is less than 24 bits. Low level signals are probably being captured at less than 10 bits resolution.

DSD on the other hand has an interesting property in that resolution is not linearly proportional to signal amplitude. yes, it is still somewhat dependent on signal strength, but DSD is probably better at capturing low level detail.

to take an extreme example - a zero signal is recorded as a stream of zeros in PCM - effectively with only 1 bit resolution. a zero signal is recorded as a string of alternating 1s and 0s - no bits are "wasted".

(2) PCM hard clips when signal exceeds the maximum level. therefore when recording PCM, it is absolutely important to preserve some "headroom" to avoid the possibility of clipping. good engineers will leave around 2-4 bits of headroom when recording. that's one of the reasons why early CD recordings didn't sound too good - they were effectively being recorded at only 12-14 bits resolution instead of 16. Modern 24-bit recordings are likely to only be effectively recorded at 20-22 bits. In fact, the original reason why studio equipment is at 20 or 24 bits when the delivery format is only 16 bits is to allow engineers to have that headroom without sacrificing the quality of the final product (CD).

DSD on the other hand is more tolerant of clipping. it behaves more like analog tape in this respect.

(3) As we know, current technology makes it very hard to realise more than about 20 bits of resolution in A/D and D/A converters. even if it were possible to build accurate converters, most analog circuitry has a noise floor that will prevent full 24 bits being passed through. so the 24 bits are "marketing" bits - they are not really realisable practically.

Once you take those into account, PCM does not seem to have an inherent advantage in resolution. i would say hi-rez PCM and DSD have "similar but different" resolution - DSD with an advantage in low level accuracy and impulse response, PCM with a higher theoretical dynamic range and better editability.

i could make similar points to just about every statement you've made in your post so hopefully you'll see why i chose not to initially respond otherwise i would still be typing!


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