Not sure what I have to add here, but I will bloviate anyway. I started in this hobby about the time solid state started becoming good--1978. I have had precisely 2 jaw dropping listening experiences since then. When the Rowland Model 7 was new, I spent an evening in Jeff Rowland’s house listening to his system. That was not one of them. The speakers were Sound Lab A-1s. Recently I toured the PS Audio factory and heard the Infinity IRS V with PS Audio’s top of the line gear. That was also not one of them. Both of my experiences occurred in stores. The first was the Audio Research SP-6 and D-79b playing through Acoustat 2+2s. The second, and most impressive, was Mark Levinson ML-2s with the ML-1 preamp through Magnapan Tympany IV panels. I was looking at the preamp when the music started, and my head snapped around and I uttered one word--"damn!" I remember it to this day.
Fast forward nearly 40 years, and I am now enamored with the sound of single ended triodes. I saw a speaker by Fikus Electric in Poland that is full range and will run on single ended power, but they do not export it out of the E.U. I decided to copy it using vintage Altec drivers which I already owned. The result, much to my surprise, was so good that it made my primary system, Sound Lab A-2s powered by a Musical Fidelity NuVista 300 and Nuvista preamp, unlistenable. I had been using this system for the past 18 years. So I started looking for a way to make my old speakers sound as good as the new, as I knew they could. Since the ML-2 was the most impressive amp I had ever heard, I started researching it. I had always thought that the output of that amp, 25 watts into 8 ohms, was insufficient to power the Sound Labs. But it turns out it is very high current and was designed for electrostatics, specifically the Quad 57. I found a pair, reasonably priced and recapped, and bought them.
They are everything I remembered from that one moment circa 1980, and my Sound Labs are once again my preferred speaker. In addition to my three S.E.T. amps, using the 45 output tube, I have a single ended transistor amp, a kit designed by Nelson Pass. This experiment has caused me to draw the following conclusions: First, single ended class A amplification is by far the most appealing for listening, despite, or maybe because of their high distortion. The transistor amp is as pleasant as the tubed amps. These amps will not power electrostatic speakers. Second, push-pull class A is nearly as good. I have calculated that my ML-2s draw about 1 penny per hour of electricity, I can live with their inefficiency. Third, any amp with crossover distortion cannot, to my ears, equal class A. This means class AB. As for class D, I have never been impressed, but this opinion might change if and when I ever hear a high end class D amp.
To get back to the subject of this thread, since I choose to listen to 40 year old SS amps, and tubed amps that could have been built 70 years ago, no, I see no real advancement in electronics design, at least when it comes to audio amplifier design. This statement is obviously not true for electronic design as a whole; micro-miniaturization has brought us computers, cellphones, and class D amplifiers, among thousands of other conveniences. But is a modern resistor or capacitor really better sounding than what they used 50 years ago? Are modern amplifier circuits significantly different from the classic ones? To a basic amplifier circuit, all you can add is complexity, and that, in my opinion, is not necessarily a good thing.
