... I'm quite willing to accept that there are genetic, developmentally and training gifted people who do hear things I never will - when they show up for and pass well designed, well executed, controlled listening tests with positive results
none that I would accept - not without controls, blinding - the 1st rule of sighted listening is that you will convince yourself you hear differences - simply the way human brains are wired
To me this says you're claiming all the listening reports of differences are the result of placebo. That claim itself, if its to be within science needs to be falsifiable. How are you going to test the claim?
you are indeed making a strawman argument. look at what I quoted from him, then look at what you yourself quoted, you're the one making it a "all" the listening reports are result of placebo. he didn't say that. he said that he didn't put his faith in uncontrolled tests, not that they were all false. that's a pretty clear difference to me.
please argue about what he said, not about what you feel like he meant deep down secretly.
now about DACs, most measure amazing, and most other parts of the audio chain have lower measurement fidelity. so if you believe you own a transparent amp or a transparent headphone/pair of speakers, then it kind of implies that most DACs are also transparent as they measure better for most specs. it's not a proof, just a rational comparison.if you don't feel like any amp or headphone are ever transparent, then maybe it's worth looking into DAC audible differences too.
-if the source makes a difference, then it's a problem with the source, so I wouldn't put it on the DAC sounding different. and because of how DAC and amps are linked(impedance bridging) the analog section of a DAC shouldn't have much trouble delivering a very clean signal.
-then if the amp itself behaves differently, it might be because of the voltage output of the DAC being different or stuff like that, but then on a good amp you would expect to find a gain setting to adapt optimally to the DAC's voltage, if that isn't on the amp, then isn't the amp the one to blame for sound difference?
once that is put out of the way, we still need to make sure whatever we test is volume matched. else the test itself is a waste of time as we can't trust the results. you may of may not believe how important volume matching is, but I feel there is a consensus on the subject, we do perceive louder music as better music(until it's just annoyingly loud music). I think starting 0.2db variation will make a difference. when you read about DACs, they go from 2V to slightly above 3V, and portable stuff can go as low as 0.4V on my sony. if we just take a DAC with 2V and one with 3V, that's more than 3db louder on the 3V one. so denying the need to volume match and testing without doing it precisely, that is enough to make a test worthless.
so, if only because all DAC won't have the same impedance and same voltage output, that would make it a necessity to control the test at least for loudness. and that makes me agree entirely with all of jcx's first post. it doesn't mean that some DAC will not happen to have the same maximum output and impedance and whatever, and that the guy doing an uncontrolled test can't be right about his impressions. but it does mean that we shouldn't trust his results unless he makes sure there was no need to volume match. and then sighted evaluation is another problem, so yeah, uncontrolled tests, that's not something I will ever trust.