Sorry to disagree, but I disagree. I'll just start with the title: tube amps are either transparent, or they're effects boxes that can't be turned off. If the former, then the claim of "better sound" is, uhhh, hollow. If the latter is what someone wants, that's outside of high fidelity. I suspect that if the distortion is gross enough to be audible, or if the frequency response changes with high source impedance were significant, most listeners would not prefer it if tested ears-only.
Not a comprehensive critique, but some high points:
Tube amplifiers have much more distortion than solid-state amplifiers, but most of it is second-order, which is quite musical.
Errr, no. A well balanced push pull circuit will show very low second and higher even harmonics. A less well balanced one will still have second harmonic below any reasonably audible threshold. This is true regardless of whether the active device is a tube, a FET, or even a bipolar transistor. So this is dependent on topology, not device.
Not only is tube amplifier distortion harmonious, it increases as things get louder - exactly as they do in a musical performance.
Besides being a non sequitur, this is true of virtually any amplifier in existence.
The misleading graphs that follow speak for themselves, followed by the argument that you should listen to music with squashed dynamics.
No one needs or uses 300 WPC ...
Didn't Bernie Sanders say that?
The next section on capacitors is ludicrous to anyone who has ever understood the voltage divider equation. I think my measurements (
here,
here,
here, and
here) did a reasonable job of debunking these myths- and all they did was confirm what any competent engineer knows about "capacitors in the signal path."
The next section on feedback repeats a litany of common misconceptions. A few minutes reading a much better and just as accessible
analysis of feedback from Bruno Putzeys will give you an accurate understanding instead of this mishmash of audio legend.
His next argument is higher output impedance? Sure, often true, but I point you toward some of Nelson Pass's solid state designs as well as the current source amps being touted in some circles. Either way, if that's the absolutely non-adjustable EQ curve you want for your speakers, you can buy a tube amp or you can buy a small power resistor to put in series (the Carver Challenge trick). Or do the EQ upstream, a much better solution for sound. And of course, this again has nothing to do with tubes per se, any desired output impedance can be designed into an amp using any choice of device types.
The offset claim is one of those "true-but" since the offset of any engineered solid state amp is near zero anyway, and of course, this is an argument for output transformers, not tubes. You can design a nice, albeit heavy and expensive solid state amp with OPTs if that (and speaker protection) are your worry. Nothing to do with tubes per se.
Microphonics are very real, and here's where I agree there can be audible difference peculiar to some tubes in some circuits. And "better" then becomes "effects box I can't turn off or adjust" once again.
If you match everything, they will sound the same, but in real life, things are never matched.
And then walks it all back, punctuated by a homily.