In terms of placebo/bias effects wearing off quickly:
I don’t know the answer, but some of my experience doing blind tests seems to suggest they can wear off quickly.
For instance when I replaced one music server with another I seemed to perceive a bit of “ brittleness or brightness in the highs” with the new server. I was not expecting that and it did not make sense given house servers work, but it was nagging at me enough to have a friend come over and help me run a blind test between the old and new server. Once we did that, I couldn’t detect any difference whatsoever between them - no extra brightness or brittleness and the highs to identify.
Once I had that experience, and put my worry to rest, any sense of change to the sound with a new server essentially disappeared quickly, and I recognized my system, sounded the same as it ever did.
Another more recent instance in a bias effect, though not a blind test: when I bought an extra pre-amplifier I needed some new interconnects. I borrowed some spare interconnects just to get up and running from an audiophile and these interconnects cost something like $5000! They came trailing
“ great reviews” but I didn’t care. All I needed was a pair of connect for a while.
Eventually I gave them back and replace them with cheap $40 Audioblast interconnects from Amazon. I was not expecting to hear a difference, but I think the mere act of knowing that I changed the cables caused me to perceive “ something” a bit different in the sound with the cheap cables. I couldn’t quite put my finger on it, but there was some impression of a slight change. Amir pointed out that even he, after measuring a cable that he knows to be identical, can experience “ hearing a difference.”
But knowing that this was highly unlikely just based on electronic theory, I just moved on and sure enough, very quickly my system did not sound any different to me than it ever had. That effect vanished quite soon.
This also happened to me many years ago when I blind tested a variety of video cables from cheap to expensive (back in the analogue video cable days). Once I discovered under blind conditions I couldn’t really tell a difference, the impressions I had of any difference pretty much went on the shelf and disappeared.
On the other hand, it was interesting some of the sighted impressions that survived blind testing.
For instance, back in the late 90’s I had been using a decent Sony CD player for years in my system and I acquired a Meridian CD player. The Meridian immediately struck me as sounding different. Nothing huge, of course, but there seem to be a subtle but very distinct texture and tonality and focus that distinguished from the Sony sound.
Once again my sceptical hackles were raised, so I had an engineer family member help me to a blind shootout, random switching, level matched with a voltmeter at the speaker, terminals, etc.
And I found that subtle but distinct character very easy to identify in the Meridian player (as well against another DAC I had on hand).
Likewise, for years my Conrad Johnson tube pre-amplifier seemed to have a subtle but similarly distinct character versus other preamplifiers in my system, including against my other solid state preamplifier.
And that impression held up as well under blind test testing.
I would say there seemed to me a bit of difference between the impressions that held up under blind testing, and those that didn’t (I’ve also blind tested AC cables… no difference). The differences that vanished, under blind testing in my case tended to be more on the edge of “do I hear that or not?”
Whereas the differences that held up under blind testing seemed, even when subtle, to be quite distinct.
I don’t know that says anything though. After all people can imagine “ distinct” differences in sound.
On the other hand…
There is my 25 year experience with my tube amplifiers in which I have had a very persistent impression of specific sonic characteristics. It it’s never changed. And it has survived occasional comparisons through the years with different amplifiers in my system, including a number of solid state amplifiers.
If we take the idea that bias effects are short-lived, it could suggest the consistency and persistence of my sighted impressions with those amplifiers are accurate - they really do with my loudspeakers produce the characteristics I think I perceive.
But I doubt anybody here would draw that conclusion. Nor would I. It seems to me a sort of expectation effect could persist all those years - including expectations each time I did a shoot out with some other amplifier. So I wouldn’t rule out a long, lasting bias effect short of blind testing like I was able to do with my preamplifier.
But as I’ve said before, if it’s a bias effect, it is such a pleasant and reliable one that I’m happy to avail myself of it.
