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Why are digital streaming equipment manufacturers refusing to answer me?

I have performed double blind tests with the most highly regarded brands of streamers and some hifi switches. None have made any difference to my system on files saved locally. I have asked the following question to the makers of such systems and almost all have responded with marketing nonsense. 
My system uses fiber optic cables. These go all the way to the dac (MSB). Thus no emi or rfi is arriving at the dac. On top of this, MSB allows me to check if I receive bit perfection files or not. I do. 
So I claim that: if your dac receives a bit perfect signal and it is connected via fiber optic, anything prior to the conversion to fiber optic (streamers, switches, their power supplies, cables etc) make absolutely no difference. Your signal can’t be improved by any of these expensive pieces of equipment. 
If anyone can help explain why this is incorrect I would greatly appreciate it. Dac makers mostly agree, makers of streamers have told me scientific things such as “our other customers can hear the difference” (after extensive double blind testing has resulted to no difference being perceived) and my favorite “bit perfect doesn’t exist, when you hear our equipment tou forget about electronics and love the music”!
mihalis
audio2design
1,351 posts
 
If you were a PhD with said qualifications, you would know the X has nothing to do with identification, it is to test reliability. If you can't match A or B to X, then you can't tell the two apart and you hence have no preference as you don't as actually prefer either.


Given the light discussion around ab(x) testing, as a scientist with phd training in human data collection and cognitive functioning, I object to the (x) part of the judgment task.

Identification should not be the goal. We listen to equipment to decide which we prefer... which is better. That should be the decision when doing (blind) ab testing.

cal3713's avatar
cal3713
1,421 posts
 
Please tell me how matching is different than identification.

And please see above for a discussion of why the brain is better at determining preference than identification.

https://scholar.google.com/citations?user=NQGcNPQAAAAJ&hl=en
audio2design
1,351 posts
 
Again, you obviously don’t understand ABX testing which is NOT about absolute identification, i.e. picking out the 98 Bordeaux from the 96 and the 99, it’s about having 3 bottles, two 98, and one 96 and being able to tell the two 98 are the same. If you can’t tell a 96 and 98 apart then you don’t actually prefer one over the other. ABx increases the statistical reliability of an AB test. ABx testing IS a preference test essentially as it requires no absolute identification.
cal3713's avatar
cal3713
1,421 posts
 
It's about saying a = x. That is an identification judgment. You don't have to believe me, but the brain is worse at that than at determining preference. 

They have studies with patients who have zero long term memory. Every day they fail an X test by failing to identify people with whom they've interacted with repeatedly.

Nonetheless, they form adaptive preferences for these individuals based on whether those past interactions have been positive or negative.  That is because the area of the brain responsible for preference is different (and more basic & important) than the area responsive for identification.
cal3713's avatar
cal3713
1,421 posts
 
And just to highlight. With those memory patients, the preference test is highly reliable (defined in testing science as a consistent, repeatable judgment). Their performance on the identification test is completely unreliability (i.e., no different than chance). You do not need to be able to say x = a to make a reliable preference judgment.  I suspect if you instructed people to base their identification judgments in an abx solely on preference they'd do significantly better.
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