Thanks Gerner.
For others ... I maybe add this :
Gerner here is THE example to whom I possibly 1,000 times have said : go get your nos-DAC and try it. Gerner wouldn't because the past had shown him that his os-DAC (a rather special one) presented more "music" and all.
But this was the past, and the past did not include XXHighEnd.
So true Peter
To put my problem with the OS-DAC in this conteXXt... let me eleborate.
I can verify any bit of what Peter just wrote. #3 ->Vista ->Fireface -> NOS-DAC is superior to the same track on #1 Vista to OS-DAC.
My problem was of another kind than just the digital route. My problem were an analog one.
My TD+ NOS of first beta-version has a impedance ratio to my amp input impedance of: DAC-output 2.7 kOhm to a tubeamp input of 10 kOhm. The DAC is as per its DAC to trafo amplification, not able to output more than 0.7 V P-P!
Throw in a TVC as a Django i.e.. This doesn't work! The TVC act like a low pass filter and it cannot do the job just using the +6db tap. That even worsen the lack of treble.
My OS-DAC on the contrary has a very very low output impedance 2 Ohm!!!! 2 V RMS output!!!
So this is why it works without cutting the treble and being able to saturate the tube amp through the TVC.
Hence the NOS-DAC didn't deliver juice for my amp and the TVC cut the treble.
NOW:
Still I'm able to detect the "bettered" #3 true bitperfect machine despite the above mentioned mess. At very low listening levels the TVC doesn't act like a treble filter and I can compare.
Now you know.
The problems are now solved and in August I throw in a new amp that has a different gain and a higer input imp.
As from then, for sure, I will run bit perfect to nos-dac. Period.
Gerner