MikeC wrote:OK, it's true that I have had occasion to hear significant differences between "good amps", but in retrospect, I can't be certain what external factors were involved. It was, as you admit, never as big as the difference between source components or speakers. And while I might have had a preference for one or another, this does not confirm superiority, merely my preference under those conditions. But with regard to active xover speakers, I stand by assertion that amp difference are trivial -- again, assuming a certain minimal level of fidelity.
I have vastly more experience to draw on in single amp per channel passive x-over contexts but I was fairly confident I was hearing differences in bi-amp set-ups using a good analogue x-over (probably most commonly, but not exclusively, the Bryston). I have never, to my knowledge, heard a system with digital x-overs. The problem in these contexts is that you've introduced yet another variable and it becomes very difficult to sort out what is going on, e.g. are you not hearing a difference because there is no difference or because the x-over is introducing a masking or homogenizing effect?
My hierarchy of differences:
Speakers (and rooms): I believe most people can almost always clearly hear the differences although they may not be able to articulate them very well.
Vinyl reproduction chains (turntable cartridge, tonearm and you could probably include phono stages too): Usually clear differences between chains but differences between individual parts of the chains are difficult to pin down because of the difficulties in setting up controlled comparisons. I believe with a fairly high confidence level that the sonic differences among cartridges are significant. I also believe that there are fairly audible differences among tonearms and among turntables but my personal confidence interval is lower. Phono stages are easier to compare and again I'd say that there are significant differences.
Digital sources: I have heard some comparisons between comparable (price and period) CD players where I thought the differences were dramatic but not in all cases, subtle to almost non-existent in some comparisons. The differences between early '80s "good" CD players and late '90s early/2000s "good" CD players are massive IME. DACs (above the dross level) IME the differences usually tend to be subtle but not non-existant. Of course if you go from say a $100 DAC to a $5k (or even a $1.5k) DAC the differences can be quite noticeable.
Amps and linestage preamps: Again, dramatic, or at least very audible, differences in some cases and subtle to non-existent in others.
If there are a takeaways from this IME (I'm not touting these as universal truths) they are:
1 Execution usually trumps theory
2 There is almost always an exception out there to try the rule
I'm a subjectivist who believes in science. There are quite a number of people out there purporting to represent the objectivisit or "scientific" perspective whose grasp of statistics and how science actually works seems tenuous to me at best.
None of this is directed at you Mike and I don't think we really disagree all that much.