Quad ESL-63 and low-powered amps; Sun Audio, Atma

+1 I own their later incarnation, the 2805, after having owned the original ELS57 for many years. The 2805 (and 63) has a pretty low sensitivity (lower than the ELS57). Originaly I drove my 2805’s with my old 2x45 watt Quad 303 power amp, but that was not enough (we had also moved to a bigger house). So I bought a refurbished 2x140 watt Quad 606-2 (the almost identical equivalent of the more recent Quad 909, QSP and Artera amps). That was clearly better for more dynamic music. Even so, I can still hear limitations, and consultation with Quad UK’s Rob Flain suggested that in our large room the 2x260 watt monoblocks would be an improvement. This is just to give you an idea of the ballpark you should be considering. And of course, Quad’s own current dumping amplifiers like my 606-2 or its later incarnations work well with the speakers - and for a quite modest outlay. It was not for nothing that around the time of the introduction of the ELS 63 Quad came out with their 2x100 watt 405 current dumping amplifier.

No, that is a misrepresenttaion of my position. What I said earlier was that they should be judged within their design parameters. So as long as a well designed amplifier is not driven into clipping it should sound the same as another one not driven into clipping. However, elsewhere I have also argued that you need a lot of amplifier power to avoid such clipping of dynamic passages. And that is precisely what I think was happening with my poor little 303. So again, I don't doubt people hear differences, but it is important to investigate what it is that they are hearing. Beyond insufficient output power, there may also be issues with input clipping due to a gain mismatch at the input stage, or a load dependent frequency response. But those are different issues that I already discussed earlier. So my position is a bit more complex than you may have thought.
As for my experience, well I am not a novice, not at all.

Douglas, thanks for an elegant response.

How old are you?

Montaldo, I don't think we need to be omniscient for this - we will never be. Let us not forget that the job of an amplifier is an easy one: it just has to amplify an electrical signal without otherwise changing it. Fortunately absolute perfection in this is unnecessary: there are experimental data on the critical levels of imperfections: how non-flat can frequency response be before we notice, how much distortion and what kind can we have before we notice etc? And fortunately technology has progressed to such an extent that ever since the seventies of the last century it has been possible to produce amplifiers with imperfections that are below the threshold of human hearing acuity. Peter Walker's 'straight wire with gain' has been achieved, and at increasingly lower cost. There have also been subjective evaluations in the shape of blind tests to see if under controled conditions panels of experienced listeners can distinguish properly designed amplifiers from each other (I participated in one). The answer was that these panels could not distinguish them.
And yet there are continuing accounts of audiophiles who claim they can hear significant differences. How could this be? Are the differences they hear real? And do these audiophiles actually aim for neutrality or do they want a more euphonic version of the original (i.e. do we have the same objective and are we, therefore, talking about the same thing)?
When you look at measurements of audiophile amplifiers in Stereophile you can see that many do not measure particularly well, and are likely to colour the sound in one way or another. In short, they will sound differently, since they are not playing the same 'straight wire with gain' game. I presume this is intentional, and if that is what consumers want, it is up to them. I have tried to describe what makes such amplifiers different. My contention is simply that if you want a straight wire with gain, that has become an easy and fortunately also quite affordable target.
Anyway, to end this, I want to post a link to an interview with my audio hero, the late Peter Walker: http://www.meridian-audio.info/public/interview%5B4446%5D.pdf

Poor Ocham to be so abused.

You made me curious, of course, so I did a quick online test (not the equivalent of a more serious test, of course): I could easily hear 13 kHz, which is apparently pretty good for a male in his early sixties, although it reminds you of your physical decline. It does put the audiophile golden ear into perspective, of course.
When I did that blind comparative listening test with Peter Walker's setup I was some 25 years old.

Montaldo, thanks for your friendly response. My aim is what Peter Walker once called 'the closest approach to the original sound'. There are many problems with that, and the two biggest ones are the recording and mastering on the one hand, and the speakers and their in-room response on the other. The former set of problems we can do little about other than vote with our money/feet, the latter you and I have solved to the best of what I at least believe is possible, by using Quad electrostats (plus subwoofer support). In between those two ends of the reproduction chain I want to keep things neutral, and with the designer of our speakers I believe that can be achieved without too much trouble. If you believe or fear a perfect match is hard, just try the current incarnation of your speaker designer's own take at the problem of amplifier design, the Quad QSP or now the Artera. I love my more or less identical 606-2.
Of course there are all kinds of ways in which you can make an amplifier that sounds bad, and there are all kinds of ways in which you can make an amplifier that sounds very sweet but that is not neutral or accurate. And yes, you have to measure in real life situations such as a realistic speaker load. But after all that, it is still quite doable to design amplifiers in different ways, and at the end of the day have them all sound equally neutral. Here, listening tests are of course the final arbiter, but they have to be done under controlled conditions, and as I wrote, I did join one of those blind tests, run by Peter Walker himself, and the result was sobering (I had expected to be able to distinguish the different amplifiers).
By the way, if there is one suggestion I may do, it is to use a DSpeaker Antimode 8033 to tame your subwoofers. I did, and it was the best audio investment of many years, particularly with electrostats.