Any of my existing amps work on Quad ESL-57's

Look for McIntosh MC30s.Magical with RCA 1614s and 8 ohm output tap for 15 watts.I have heard dozens or more amps with 57s.

The Quads are unusual in that they require a surprising amount of power to sound their best but that tweeter panel can be damaged quite easily. The solution: Get the protective 'clamp' circuit installed on the tweeters and then you can use any amp you want without fear of damage to the 57s.

I used a Rogue Atlas Magnum on my 57s and it was a superb match. The Atlas was a significant improvement on the ST70 and the UA-1 (rebuilt by Mapleshade). I have not heard the Cary model you mention but it might be interesting to try.

I tried a 300B SET amp with my Quads (KR Enterprise 18 BSI) and did not like the result very much. The midrange was very nice but the top end and bass were significantly rolled off. Dynamics also suffered considerably.

A powerful solid state amplifier like the Classe would be very interesting and it would not suprise me if you found this to be the best of the lot. But get that clamp board installed to protect those tweeters first.

Terry

I was introduced to Quad 57s in the 90s and listened to quite a few other enthusiasts setups.
The best set up I heard was with either the Quads tube amps or Luxman equivalent to the quads. I had the Quads on the 15 ohm tap. This is a matched system. It was very immediate and detailed. All the other Tube amps created smaller dynamic swings and put you more in the back row of the concert hall. I preferred to be nearer the front row. This was to my taste but is not ever ones cup of tea.
Too little power from a tube amp will just sound poor when over taxed. It should not damage the panels.
A tale of caution about too much power.
My wife left the quads on for a week when I went on a business trip, burning out the Quads tubes. I used an Audiolab transistor amp (60 watts per channel) while I waited for new tubes. My wife turned the Audiolab amp up and telephoned me at work to say that the 57s sounded distorted - She blow up the treble panels on Both. So if you use a more powerful amp then be very careful that you turn them down when they distort (you should already have the 57s snubber circuit mode installed if they are latter Quads 57s - this is a diode and a resistor network that kick in when the panels see too much voltage and protects the panels hence you hear the distortion and turn them down. If you do not turn them down in a reasonable time then the diode will burn out leaving the panels unprotected to voltage spikes.
hope this helps
Russell b

Terry is right on the money - Snubber circuit is the clamp module.

Russell and Terry - thanks for you good input. I've read that the Rogue is a good match, so I'll wait until one shows up. The speakers do have the snubbers installed on them. In fact, the previous owner did push them too hard and stressed the diodes on one snubber, causing distortion in that speaker. He got a replacement snubber from WP and all was restored to normal.

It sounds like as long as I'm careful, I will be fine with what I have. The Cary may be an excellent fit too.

Best, Peter