Most tube amps are the equivalent of a graphic equalizer - hence a no no for me.If the amp employs about 20 db of loop feedback, it is capable of acting as a true voltage source, whether it can double power into half the impedance or not. IOW, it can be within 0.5db if there are no limitations in the bandwidth of the output transformer. The trick is not to look at things at full power, but to observe what is going on at 1/10th full power, where most of the amplifier power is likely spent. At those power levels you will see any voltage source acting like any other voltage source, doubling power when it needs to or cutting it in half when it needs to.
Most of the time the coloration that people really complain about in a tube amp is the 2nd harmonic, which adds richness. Solid state amps usually lack this on account of being fully differential. Its possible to build a tube amp fully balanced and differential as well, and if so built they too will lack even ordered harmonics as they are canceled throughout the circuit, not just in the load.
However there is a price that solid state exacts of its owners- they too have coloration, only in this case it is higher ordered harmonics. They are certainly at a low level, but the human ear/brain system uses higher ordered harmonics to sense sound pressure (likely because pure sine waves are non-existent in nature and so are not part of our evolution) ; as a result humans are very sensitive to higher ordered harmonics and can hear them easily. The audiophile terms for this are 'bright', 'harsh' and similar turns. This explains why two amps can have similar bandwidth within 0.5db yet one might sound bright and the other not. IOW we respond to distortion by perceiving it as a tonal coloration.
This simple fact is why tubes are still around decades on after being declared obsolete. If you can eliminate the oppressive nature of the top end in a system, then the system might get more listening time.
IOW the real reason behind the tube/transistor ad nausem is all about distortion.
Check your reference… you must have meant someone else yet did not include their handle to indicate your words were directed to them..@blindjim , my remarks were quoting George from the other thread by the same name in the amps section.
R