What amp should I buy to power Martin Logan Esl's?

Bombaywalla, not sure what constitutes "large amounts of NF," but the ARC Ref 150 uses 14 db of it. Perhaps somewhat responsive to the issue of tubes and ESLs, ARC reports (and Atkinson confirms) that output regulation is approximately +/- .5 db off the 4 ohm tap. So ... maybe the amp may add a touch of "flavor" to the acoustic presentation, but who said life is perfect.

Can't say that I recall reading comments that the Ref 150 doesn't sing to the music, but I'm tone deaf. What do I know??

I suppose we still don't know for sure what all the techno-babble means in real life. So I echo Bombaywalla's request that folks who have matched tubes and ESLs report their real-life experiences. Kinda' an interesting topic.

Bifwynne,
In my post I did not intend to single out the ARC Ref150 (which I understand is of personal interest to you due to your ownership). I was referring to the tube amp-ESL match in general so as to not hijack the OP's thread. Thanks.

Bombaywalla -- you're right ... the Ref 150 is of personal interest to me. But not because I own it, but rather because I want to own it. ;>')

Having said that, if there is any validity to my thesis that tube amps using NF may (??) perform SS-like, and therefore may (??) be able to drive ESLs, does go to the OP's thread about ESL-amp matching.

In short -- I don't know the tech answer to whether a particular tube amp will match well a particular ESL. Perhaps the best way to answer the Q is to ask the manufacturer. Of course, a live audition, if possible, would be great.

FWIW tube amps can work extremely well with ESLs. The problem you run into sometimes (one that is common with ML ESLs) is that the impedance of the speaker has really been set up to favor transistor amps (i.e. are set to a lower impedance) more than tube amps.

So tube amps can have a tough time on ML ESLs as a result.

There is however a fairly simple solution, which is to get a set of ZEROs to go between the amp and speaker. I have seen this work quite well with our amps; I have one customer who has run that combination for over 20 years (he has one of the first sets of CLS-2s, which were notoriously hard for tube amps due to the overall low impedance).

FWIW an ESL is not by definition a low impedance speaker. Two good examples are the Quad ESL 57 and 63 which are moderate loads for smaller tube amps, as are certain Acoustats and certain AudioStatics. The more recent Sound Labs have become a lot easier to drive as well. It is the choice of the designer as to whether they are trying to make the speaker work with transistors or tubes- if transistors the impedance will be quite low (perhaps only 0.5 ohms at 20KHz!).

Best ML sound I have heard was off a Krell integrated amp about 4 years ago. I also heard a pair of Focal Profile 918s on the same system and both sounded very good. It was a very lively and decent sized Twitter listening room. Holography was off the scale with both.