Forgive me if I missed some of the posts in the last 26 pages but...
DACs show a wide range on the SINEAD (THD) measurement spectrum - so is one in the blue range really undetectably different (properly done listening test; dbl-blind, levels matched, etc.) from one at the lowest end (red?) - is that right?
You clearly seem to be an SBAF fan.
As has been said a million times before SINAD is NOT the sole indicator of sound quality in DACs, which is what the fearless leader of SBAF wants you to believe 'ASR' thinks.
SINAD is an
indication of noise and distortion levels at 1kHz only at FSD or slightly below. This says
something about electrical performance. Here comes the tricky part. You have to understand that there is a voltage coming out of a DAC. It can be made audible with transducers and measured with equipment that can 'sample' the same voltages but with much lower noise, much higher accuracy and a much wider bandwidth than ADC's in a studio. No magic alas nor missing signals that cannot be measured (voltage amplitude and time are the only aspects).
Then there is a second and most variable part which is the transducer/hearing part which isn't anywhere near the accuracy of test equipment even if that consists of a $100 soundcard.
At SBAF the fearless leader also realizes that distortion below 80dB is inaudible yet at the same time is fine with distortion reaching -30dB.
He also claims everything that is ASR approved is pure evil and sounds bad.
The problem here is that at ASR there is a realization that a SINAD may well be 90dB yet distortion at other frequencies or levels may be higher than the SINAD. Does this make SINAD a worthless measurement ? No.. it is ONE measurement among many others that all tell part of the story.
So this means that you may well need a SINAD above 90dB to be fairly sure there is no alteration of the to be reproduced signal and noise levels are low enough not to be audible using 'normal efficiency' transducers. You may need more if you
also want to use sensitive transducers on the same system. This means that one may need a higher SINAD when it is noise dominated or mains hum dominated at 'normal' listening levels.
There you can see the 'value' of that single number that is ridiculed at other sites. But it is just a number which is easily ranked just like certain gear and its performance is 'ranked' by some folks at other sites with nonsensical aspects they personally perceive and put in diagrams which seems fully acceptable.
On ASR there are folks that like the least amount of distortion added as they realize their transducers are magnitudes higher. Most of them look for gear that is known (not claimed or said) to have proper performance that meets minimum requirements for this which can be seen from several measurements combined.
Yes, there is no correlation to preference of people. Most people
prefer added distortion but prefer to call it house sound, musicality, magic, reality and what not as long as it doesn't jive with measurements (because of lack of understanding). Its preference.
EVERYONE has preference / taste and it may differ or be similar to that of others. Human nature is to seek out similar 'minded' folks and crap on the rest that does not follow suit or thinks otherwise (a form of audio-racism).
It's perfectly fine to love a certain brand, sound signature or certain types of (linear and/or non-linear) distortion and care or not care about measurements. One can believe whatever one wants and cuddle with like minded people.
It's also perfectly fine to 'believe' that measurements say something and can set the mind at easy.
In both cases this can set the mind to enjoy reproduced recordings better. Nothing wrong with that.
Some like jewelry others may enjoy pushing the limits of optimal performance with lowest investment and spend money on other things (like the next best SINAD device ?).
But to finally answer the question... SINAD value is NOT the only sound determining factor. It is one off the aspects that should be taken into account along with other aspects. NEVER should it be (nor does Amir suggest or think this) the ONLY decision factor. It's an indicator.
Some gear with a high SINAD can sound different from a low SINAD device where the lower SINAD device is actually closer to the original signal.
So... one really cannot tell whether the higher numbers actually are the better electrical performers at all.
My personal opinion, when using normal efficiency gear and listening to music at comfortable levels, is that a SINAD above 80 is probably fine (when other aspects are also O.K.) and can not be told apart in
properly conducted level matched blind tests from also well performing (other aspects) gear with higher SINAD.
But... when using high efficiency transducers and sometimes playing at concert levels a higher SINAD may well be essential.