These swaps in a shop with many pieces can be very misleading. Most of this excellent amplifiers will need a reasonable warmup before they are showing their most interesting and distinct positive and unique characteristics. Such comparative auditions mostly show the bass characteristics, general tonal balance and headroom. And I have never seen a shop with a measuring device to calibrate sound levels.
At home or in long listening sessions we have time to establish the ideal level for the recording - curiously, even without watching levels, listening levels converge for each recording.
It should be remembered that if they were using Transparent Audio, cable types need to be changed between amplifiers.
But if you ignore the biases of the writer - not too difficult - Zero distortion supplies great information and good read.
Both points easily addressed.
On swapping
1. Actually, good dealers many a times have amps warmed up overnight.
2. What I look for is exactly what you said - bass characteristics, if one of them has a bad tone, what is their style of soundstage with that speaker , etc
3. Your caveats don't take into account the fact that I will do comparisons in different systems, so while one session can be misleading, if you hear the same characteristics of the amp across compare sessions, they would be usually correct. Given that all I am looking for is a final shortlist, once you have a shortlist this way, the thing is to finally try them on your speaker.
4. Example of above and non-bias: When I went to Joel, bias said that Luxman would lose out to Ypsilon aelius, which then was my theoretical dream amp - listening told me that Luxman was better on all aspects. Heard Ypsilon in 2 other sessions, and compared Luxman to Mephisto and Viola Symphony. While the Mephisto was better, Luxman characteristics always repeated and were superb for the money. I am assuming Vitus and a few others will be better too, they are much more expensive. Here Luxman is presented as a high value for money product, and not necessarily as the best despite the price. The write-up will also provide links to others who have drawn similar conclusions and what their comparisons were.
5. Zero D is actually having 2 more join in - while one will focus on classical music and LP reviews, the other will be doing in-house demos. So sometimes I will travel over to his place and give a visitor's review to what he is going to have inhouse - that will give you guys two perspectives. As you know, if he and I disagree, then you guys don't have much to go on, but if both of us agree, I think you guys will have more confidence that bias is in check.
Bias
1. To ignore my biases, you should know what the biases are. What if my bias was A, and experience changed the preference to B? Do you know my bias was A, or do you consider my conclusion B as the bias?
2. Did you know that Martin Logan was my favorite speaker, and then I changed my preference to Analysis Audio (modded), then to many horns, and for two years, I did not like Apogees, and told Justin (User 211) they were shite? So can you identify the bias? Not to mention I still hear Apogees I don't like, hear some that I do, and also now heard something that has again put a horn back on the list? Ok, so you might say I am biased against cones, but then why add YG and Stenheim above cones (though still prefer Aps and horns to them).
3. I haven't checked, but I am willing to bet a few people here that I text with like Audiophile Bill, Ron, etc expected to hear back when I visited Mike that "what a waste of money, another expensive cone system, blah blah blah". That was the bias, definitely. I was certain I would come back with a polite write-up that between the lines read waste of money, but Apogees are much better. They would have been surprised to have instead received the texts they did.
4. If you read Marty's system review, and what I have written in About Me (yet to publish), my travels started because I was biased against DRC - I traveled to Marty's to see how could DRC possibly be good. And the travel taught me that heck, just get your ass off the plane and eliminate/confirm the bias.
5. I soon learned that biases were being explained away as experience, where in reality most people were not even actually listening to the components in question. In fact, if you go around and listen to some alternatives, you will change your bias too - I don't think many here will be stubborn in changing if they listen to something, before they vest their emotional and financial interests in it. Just check how many who have challenged me on restored Apogees have actually heard one - they have heard Maggies, Apogees 20 years ago, "because planars cannot do bass Apogees cannot too", etc. My travels expose me to drastically different schools of thought - helps nip biases in the bud before they are developed and passed away as experience.
6. We again come to the same point on bias as with the word opinions - are biases being formed with or without auditions. My contention is that most people on this forum are deciding, and purchasing, without proper compares. It might appear that the two of us have different tastes, but in reality, one might have actually the heard the various components in question and one might not have. In which case, preference of the guy who has heard cannot be dismissed as bias relative to guy who hasn't done the compares yet defends a preference.
7. In the vintage vs modern hifi section, many are choosing modern without having heard the vintage in question - despite reading that Steve, Marty, and I preferred alternatives to Techdas, and Steve actually owns one, and he, DDk, and I, actually like Techdas. Yet people who haven't done those compares, do not understand how a 100k modern TT cannot be the best and continue to be so biased.
8. You will be surprised how much in sync Gian60, his friend and I were in Italy. Very different gear, very different backgrounds and music tastes. It is just a question of going through the same experiences rather than writing on a forum because I own A, and have never heard B, A still has to be the best because it is modern/costlier/of XYZ design/measures better, and I heard a product similar to B 20 years ago in a hifi show so it cannot contend.
9. Don't forget I was anti-SS and pro tubes only, so please explain the bias. Ron actually accused me (in good humor) of not sticking to a philosophy
10. I was of the school of thought that analog and digital don't make a difference, so please explain the bias. Am I now biased to analog, or was digital my bias? I was also vested emotionally and financially in the Lampi so to stay with that bias would have been a good thing.