Are solid-state products necessarily technically superior to tube gear? I offer up the LAMM gear -- see all the measurements that Bascom King did on Vlad's gear -- and I will put that up against any solid-state gear out there. And then of course, what measurements are meaningful and relate to the sound of electronics. I'd profer that there's far less of a corrolation between the sound of electronics and their measurements than for speakers-that is maybe with the exception of phono stages where quietness with a low output MC cartridge enters into the picture.
I have never heard nor researched LAMM gear, but my answer is
no, SS gear is not necessarily technically superior to tube gear. Most SS equipment will measure better, however, on almost every parameter. (N.B. I am generalizing horribly here, so please keep that in mind. Also, I am certainly no expert on this stuff, and a lot of my experience is pretty old now.) It takes a very good tube amplifier to approach the specs of an average SS amp. Tube preamps are much closer, often losing a smidgen on noise but matching or exceeding most everything else. The added gain required for MC does not always translate to lower noise for SS; there are plenty of "hissy" SS preamps out there. Or at least there were last time I auditioned them, years ago. And, in the phono stages, tubes generally offer much more headroom than SS pres. One issue they had (have?) is that Miller effect often increased the load capacitance on the cartridge relative to a SS design, and a lot of preamps did not take that into account, rolling off the high end. A lot depends upon the design(er), of course. At low or modest levels, tube and solid state components can sound (and measure) very much the same.
The transformer output tends to make tube amps "soften" the sound of many speakers. I'd have to really dig for papers on the subject, and given the state of the black hole in the basement I am sure others could find articles on-line much faster. The bottom line for me is that tube amps by and large simply do not provide accurate drive to most speakers. The resulting sound is an attraction, not a drawback, for many folk, myself included. What sounds better is not always, and perhaps not even usually, what people want to hear (or what sells).
I have posted before on the distortion characteristics of tubes vs. bipolar transistors. I'll simply repeat that intrinsically tubes have
lower distortion than transistors at the same general operating conditions. SS amps achieve lower distortion through a combination of balanced circuits (almost invariably internally, even if the external connections are single-ended) and feedback that is generally higher than that in tube amplifiers. Again, generalizations. The argument has been made that lower feedback provides better sound; there is no reason that is inherently true -- there are many factors at play, and the LF or mid-range feedback factor typically quoted is just one of a myriad of variables.
In my experience, tube gear that strived for SS accuracy was panned as being "unmusical" and/or "too much like solid-state". Which, of course, it was (the latter), since that was the design goal. I built a very nice (and excellent-measuring) differential tube preamp with cathode followers to buffer the outputs in a little tube op-amp sort of circuit. It measured and sounded more accurate than my SP3a1. In the end, I sold the homebrew for a princely (to me) sum, and kept the ARC. As I said, I liked its color, and it was very accurate indeed if not quite so much as the homebrew.
That was also in the madness of ultra-wide bandwidth and ultra-low distortion. I am glad people seemed to finally realize that 1 MHz or more bandwidth and 0.0001% THD does not matter in the real world of RFI and speakers with 1% to 10% or more distortion. At least, some have... I am sure we all have friends that buy on specs and not their ears. I use the specs, and more so features, to narrow my choices, then listen.
The oft-cited "tubes clip nicer" is false, of course, at least in the limit. Clipped is clipped and generates wideband distortion. What makes the statement true is that tube amps tend to soft-saturate the transformer core and output stages, resulting in higher even-order distortion before hard clipping, and the limited output bandwidth tends to roll off some of the higher harmonics. If you want to delve into math, SS tends to clip right into square waves, while tube amps tend to create cosine-like pulses before hard clipping, then the output transformer rolls off the higher harmonics after hard clipping. Limited slew rate can be a blessing to the ears.
Didn't McIntosh produce SS amps using autoformers? I really did not like those amps, but I suppose they sold well. I felt their reasons had more to do with keeping the winders busy and (much more likely) protecting the speakers from unreliable transistors than sonic benefit, but that's pure conjecture.
There's much more, but there are folk much more competent than I to debate the issue, and it often falls into the realm of "faith" anyway. I loved my tubes, and perhaps shall again, but for now economics and various other factors dictate a SS system for me. I will say I am considering keeping and upgrading the SP3, especially if I decided to set up my TT again.
I glitched on the correlation comment, sorry. Are you saying that speaker measurements are more meaningful than ones for electronics, or the other way around? Taking meaningful measurements, interpreting those measurements, and correlating them to what we hear, that's where science meets art and ears, IMO.
All the best - Don
