When were the best tube amps made?

@alexberger Thank you for your list. Matching the amp to the speaker is critical, similar to a cartridge to an arm. However, there are many choices of amps for most speakers. I also have an upgraded Dynaco ST70 in my living room system. It is not ultralinear any longer but voltage regulated using different taps on the transformer as well as the standard upgrades to power cap (huge), ss rectifier (kept the tube for slow turn on) RCA plugs and speaker terminals, etc), . It has superb bass and is extremely musical sounding lacking only the resolution of the EAR 890 I use in the main system. Those 35 watts work great on a Legacy Signature III with 6-10" woofers. It’s a little underpowered for my Focus with 6-12" woofers and much lower bass impedance.

The science is settled. 

Really great thread with lots of thoughtful responses. Thanks!

To me, the answer becomes obvious when you substitute “motorcycles” or “cars” for tube amps.  Clearly the best are being made today. But it doesn’t mean that all cars today are “better” than all cars made in 1960. It would also be logical to suggest the best amps from 1960 (and all amps were tube then) will outperform many of the tube amps made today.  This is especially apparent when based on subjective levels of performance or aesthetics. 
 

I’m interested also in the comparison to the recording side. Are all recordings made today better than all recordings made in 1960?  No, but the best recordings are being made today.

Transformers are the key element for both SET and push pull.  Even for OTL the power transformer is relevant.  Likely the best commercial winders were in Japan in the late '90s, companies like HIrata Tango and Tamura.

@rogerh113 Excellent power transformers can be made by a good number of companies here in the US.

If you take an OTL and run the ZERO autoformer on it, you wind up (if you see what I did there) with the possibility of an amplifier with much greater bandwidth than any conventional tube amp. This is because the ZERO has such low turns ratio and extremely low distributed capacitance that its bandwidth is very wide- about 2Hz to 1 MHz- wider than any tube amp made. Usually the bandwidth limitation is in the output transformer.