Have you moved from tubed amplification to solid state amplification... Why?

I run Quad ESL's. They need protection from high voltage spikes. The protection circuits sound like hell (it's relative).

What to do? The obvious thing is to optimize and upgrade the Quads' circuitry, run low voltage SS amps, and remove the protection circuits. That is, engineer the system as a whole. So I read a lot and sought expert advice. Thus DIY. The results are full complementary push-pull SS amps that run on +/- 25 V rails.

The phono/pre proceeds from different requirements. Most importantly, no (as in zero) ripple voltage, hence batteries. SS is easily done this way, tubes not so much.  And Analogue Devices was still selling its legendary PNP / NPN aerospace matched dual transistors (MATxy). Hence a full complementary push-pull circuit.

Another advantage of SS is that it can remain powered up indefinitely, improving for several days after a shutdown. Dead stable, dead quiet, exquisite refinement, superb dynamics, no maintenance. And no remote possibility of frying the Quads.

It may be that there are some amps which sound better than mine, there may be preamps that sound better than mine, but I'll bet there are damn few systems that sound better than mine. And I couldn't do that with tubes.

After I replaced my power tubes a few times, several hundred dollars each time, I realized I was only listening when I had a couple hours or more to listen.  If I only had a half hour, I just wouldn’t warm up the tube rig.  Now that my amp is solid state, I don’t hesitate to turn it on and listen, even if I just have few minutes.  I listen a lot more now.  My wife was a little intimidated by the big tube rig and its mysteries.  She finds the SS simpler and more approachable, so she listens more, too.  Other factors that led to the change were the substantial heat and power consumption of the tube rig.  The SS is much more efficient, using less power at idle and in use, and it is barely warm to the touch.  Bulk and weight of the tube amp, with large heat sinks was a factor as well.  Finally, I audioned a number of SS amps and found there are very nice sounding amps being made. I really enjoyed my time with tubes, but I’m not looking back.  All my guitar amps are tubed, though, and will remain so.

Not sure what Quads are referred to, but I have always been perfectly happy with mine (first ESL57s, now 2805s) driven by first a Q303 and now a Q606-2 solid state amplifier. I have also had the privilege of being given a private comparative demonstration by Quad's Peter Walker himself, at the time when people started to argue that his earlier valve amplifier sounded better than his later solid state designs, and in particular better than the Q405 current dumper. He thought all this was absolute nonsense, and commissioned an independent research project by James Moir: http://www.keith-snook.info/wireless-world-magazine/Wireless-World-1978/Valves%20versus%20Transistor...
As I said, he gave me a private demonstration with a blind setup with his three designs, playing master tapes on a professional recorder. The comparison was level matched and blind. I thought I could just about hear slight differences, but afterwards Peter smiled: my identifications had not been better than random. All three amplifiers had simply been straight wires with gain; the only relevant difference had been that each successive generation had been more powerful than the previous one. I had learned a useful lesson.

Pairs of Quad 2905’s, Willem.