When were the best tube amps made?

and an honorable mention to the OTL crowd: Futterman, Graaf, Ralph Carsten and Dave Berning

D-150  1975.  I have heard that the 1995 Ref 600 III was as good.

Did I fit your "timeline?"

Any amp that can't even reproduce a simple sine wave doesn't count. If the negative half of a sine wave doesn't go down as far as the positive half goes up the amp is non linear and may be musical but it's not fidelity. If it does that to a sine wave think how poorly it will do on much more complex music wave forms. By the way this means every single ended amp and it's not curable since it's inherent in single ended topology.

2022. Audio Research, Conrad Johnson, VAC… unless you have different sound preferences from me.

@jasonbourne52  they all sound the same the cheaper the better. Snake oil!