Solid State Amps for Quad ESL 57?

The transistor amps will not give you what you want , in my opinion. I have been a confirmed user of transistors since I built a Heathkit in 1963 and was a Quad dealer for 15 years. Transistors are undoubtedly faster on cone speakers , because of higher dampening factor among other considerations. But these factors do not apply to the Quad, which is already faster than any cone. When I was a dealer I drove my 63s with Krell, Musical Fidelity and Stax class A solid state amps but could not detect a difference in speed or bass between them and good tubes. A friend drives his 57s, which I sold him in 1975, with a rebuilt Heath tube amp , it sounds as good as anything I have ever heard drive them. Foster Blair rebuilds them, they are available through Mapleshade. This is one case where having a transformer in the line helps the sound. After all, they were designed with a lower powered tube amp in mind. If I wasn't happy with the sound of the 57s driven by a good tube I would look at another speaker, they are what they are and the amp will not change them that much.

The Quads will only take a limited amount of power and can be damaged by over driving. I never had any trouble as I was careful with the volume but one of my customers bought 63s and a Musical Fidelity 270 [100 Watts?] and had to have them repaired 3 times because he constantly over drove them. A big amp is fine used with care.

I just noticed one that should do a good job if you want to use solid state, the Audiophile Boutique is closing out the Van den Hul Array 1 for under $1700 US, about 40% of original cost. They are very overbuilt for their output and should be able to drive Quads, I would check with them to make sure. If you are not familiar with Van den Huls work look him up, he knows what he is doing. My first post was not intended to say you could not use transistors on Quads, obviously I did. I just did not experience a greatly increased bass. I use transistors for the same reason Mr. T uses tubes, better vocals and top end. Many like the euphonic coloration tubes add, I prefer accuracy. On the power question, a transistor amp SHOULD double its power when you halve the impedance. Those that do are called voltage source amps, the ones that level off or decline are current source amps. The voltage amps require much bigger supplies and heat sinks etc. and are usually much more expensive. The output of a speaker is governed by the efficiency of the speaker as well as the output of the amp. The efficiency is given in terms of what its output in dbs are for one watt input. Doubling the amps power output will raise the output of the speaker 3db. So a speaker of 89db efficiency will require 1/8 the power of an 80db speaker if my math is on. [ 1 watt times 2 =2 watts, times 2 =4 watts, times 2=8 watts. ] You can see how very efficient speakers require little power.