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

Montaldo, you might want to look at this post:

http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1420484322&openflup&51&4#51

and this link:

http://www.atma-sphere.com/Resources/Paradigms_in_Amplifier_Design.php

Unless you have a very small room, you will not have enough power with a 300b-based SET. They only have 7 watts. You need more like 50-60 as a minimum to really make the speakers sing in the average sized American room (17' by 20' or so).

Quads go lower than 50Hz, unless you are cutting them off with an electronic crossover. Actually they can make quite convincing bass!

Correction the assemblage is single ended and 8 watts. Looking at so many amps I got them confused.

I don't think you can go wrong with CJ and Quads. It's more a question of whether you like the older CJ sound that you're getting with the MV-60 or the newer, more neutral and detailed CJ sound. I ran my 63's with several different amps including Music Reference RM-10's both in stereo and then mono blocks, and CJ Premier 12's. CJ combined with the Quads was always a step above everything else. Also, don't necessarily agree that you need at least 50-60 watts with the 63's. My Rm-10's in stereo at about 25 watts did just fine in a 16'x 24' room at all but very loud volumes with all types of music but some Classical.

No single-end tube amp will work well with the 63's because: sensitivity is low and the impedance curve varies from high to low (30 ohms to 2 ohms). All single-end amps have rather high output impedances (2 to 8 ohms). They will NOT have a flat frequency response into a speaker without a flat impedance (Ohm's Law!).

+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.