When were the best tube amps made?

1987

the best tube amps are being made now.

modern power tubes are in some important ways “better”, i.e. kt-120, Kt-150 and Kt-170 have greater plate dissipation.  So amps using those tubes can be designed which exceed past efforts, in a more compact form factor.

modern biasing controls have advanced, yielding better sound see, e.g., VAC.

even transformers have advanced; amps can be designed are quieter toroids with wider bandwidth.  Capacitors and other parts are improved. 

I loved my Mesa Baron, but 12 power tubes was too much to deal with.  Keeping an old tube amp going is like having an old sports car - more ongoing maintenance is required than a modern design.  To send it back to the factory cost over $500, round trip. 

the build quality of my Rogers integrated is Nasa-satellite level, way better than anything from ”back in the day”

Today, also with recent output and input tubes coming into focus past 3 years. 

If value is a concern, Quicksilver, Aric audio, Don Sachs, others + with a few small upgrades can be a great value with some patience and letting go of some of the vintage stuff. Clean simple designs, easy to repair, less-is-more circuit designs.   

Absolutely right now. Just heard a pair of VAC Master 300 monoblocks. Holy cow. These have me thinking that AMP is the most important component of the audio chain. Including room.

In terms of engineering brilliance and sheer transparency, timbre and attack Nobu Shishido’s Wavac designs are unequalled in my mind