Amp for Quad ESL 57

The Quad II Classic (re-issue) or the original Quad II are much better amps than the Quad II Forty. I have the first and with NOS EF 86s (Amperex or Mullard) and a NOS rectifier (a Mullard GZ34 or even better a GZ32) they are very impressive.

I've tried a number of different amplifiers and find that vintage English tubes is what they prefer. I'm currently using a Radford STA-15 that sounds wonderful.

Leak Stereo 20 works as well but you will need to pot down the input.

Find a Berning EA-230.

I wonder whether the new Quad II-Forty might a better choice. Any idea?

I don't particularly like most of the new Macs... BUT my idea is, it is most unlikely. Keep the Mac. The Mac's weak point is the phono, then the pre section (BUT, you do get tone controls and a mono switch -- both work quite well). The power amp section is good, with OPT which seem to favour linearity from mid-bass up to reasonably high. The Quad is... well, "pleasant". You;re fine as is.

the quads do not need power. find a low wattage amp, under 25 watts that you like.