Well you are right, it is subjective given that humans are the measurement tool. I still think its a worthwhile endeavor though. Given the value of my current investment in digital audio, I’d be happy to buy a fancy switch if I can hear any improvement at all.
That said, There doesn’t appear to be any significant interest on the forum for the results of the experiment, so I’ll probably just give it a go privately rather then fan the flames.
Didn’t say I wasn’t interested to hear the outcome 
I’d love to hear your thoughts on this. I think people are interested, even if the results are only put down to your perception.
Same with Lyngdorf amps…
Do tell we want to know, it’s a worthwhile exercise for sure.
I’ll let you know what I find 
Is this a listening test? Well, it may be interesting but probably not very conclusive. I’m not in a position to validate anything really.
Get your hands on a digital pcm recorder and feed the output of th DAC into it if you can. Record the output using both switches ensuring that you don’t touch the recording level in-between sessions. Then copy the recording to a pc. Use Audacity to line up the two recordings invert just one using the invert effect. This will allow a difference comparison. If they are identical then they will cancel each other out and you will hear zilch. This will give you a scientific slant on it and it can’t lie or have bias.
My (repeated) observation is that it improves SQ. Existing science and engineering isn’t a body as such, proving or disproving. People insist it can’t make any difference but it does. Easy.
and may be of limited value
Nope. I live on the coast. No problem accepting it’s round 
People insist that it can’t make any objective difference, which is a different matter and doesn’t conflict with what you personally hear (whether or not you hear a difference).
Why so! Because it might help prove if there is a difference sonically?
That difference signal experiment will not work well. At this resolution level, D/A and A/D conversion are not deterministic. Difference signals will be inevitable.
Your earlier experiment was similarly fundamentally flawed, even more so because of room acoustics and microphone uncertainty.
AJ
Using a line out of the DAC is undeterministic? Can you suggest something else that can be done at home easily that doesn’t require test equipment if you think this is so flawed? But then that would also be susceptible to the same flaws if you go by your rulebook. I have done this a few times to test different scenarios capturing the analogue output to a digital recorder via LINE OUT not via a mic and it’s worked perfectly fine and It shows a difference when there is and none when there isnt.
Aren’t your observations that switches make a noticeable difference based on listening tests?
Lots of things make a difference, but it doesn’t mean that the SQ improves, just that your response/experience is tainted by that thing - expectation bias, smoking weed, drinking beer, being tired, being joyful, and so on. The ‘thing’, whatever that might be, mediates experience - it’s naive to grant it causal power.
Exactly why I proposed this experiment. Given that I’d be able to instantaneously toggle between two signal paths that are identical except for the audiophile switch, I’d be able to remove the effects of these distractions.
My plan is to have someone else do the switching so that it is as close to blind as practical without having @wizardofoz poke me in the eyes 
I think it’s a great idea. If you can control all the variables, other than the presence or absence of the switch, it should produce some decent evidence. That said, I’d bet my life savings that whatever you come up with won’t stop the debate 
I’m sure it won’t.