Re the OP:
tubes aren’t mellow.
they merely generate less odd order distortion and they don’t misplace the transients in time or don’t smear the transients in a non linear manner.
they are complimentary to how the ear works and don’t create signals that are separated improperly from the actual signal.
Transistors do all those wrong things, tubes don’t.
so the softer sound is actually less ’banging on a tin can-totally out of time and place’ kind of inconstant distortions that transistors have.
the ear hears this ’out of position’ unwanted spurious distortion(s) that transistors create ....and we tend to mistake it for detail. Until the levels of them become large enough that we finally recognize it as the ugly screech that it is....
It comes down to the native linear gain characteristic of a tube vs the native non-linear gain characteristic of a transistor.
the trick is to not look for or listen for fake distortions that are mistaken as detail, when both transistors and tubes are incapable of adding anything useful to the signal.
The most we can hope for, in any audio system, is ’least damage and least loss’.
the vast majority of audio folks don’t understand this fundamental. It’s is even poorly understood by the vast majority of audio engineers and designers. This, as it is impossible to get by and to realize the truth would make most of their business model unsuccessful, incorrect..or possibly even ...- dishonest in those who practice good self truth. They build what can be made and sold, and this is the reality we deal with.
by fiat of the logic in and the fundamental physics of each, with the transistor and the tube... the least damage and the cleanest signal is only capable of being realized, at this time, by a triode tube.
With a gun in my face and the threat of real death if I lie or mis-state, these are the the thoughts and words from my mind and mouth.
The End.
the ONLY other option outside of the triode tube, is the V-FET transistor, or Nelson Pass' SIT transistors (First Watt SIT amps)he had specially made for him by South Semi transistors before they were bought out.... or the new Japanese equivalent, which are V-FET copies. Those are made for one company in Japan.
Other than that...it is ALL lies, lies, lies - and more dammed lies.
