[Bret L]

In going back and reading through some of the books I have and
recommend it's astonishing now how the audio world had pretty much
everything it needed by 1955. After that, it's just detail
improvement, or in some cases deprovement.

They didn't have cheap silicon diodes, so you needed tube rectifiers,
not only for HV but bias as well unless you wanted to use a battery.
And a relay to open if no bias voltage was there and bring in a
cathode resistor. Also, low impedance B+ supplies were tougher, but Hg
vapor or xenon tubes were available that worked well.

Are we better off today? Well, yes, in all objective measures. But it
isn't as much fun is it? And in a lot of ways we aren't that much
better off. A lot of audio equipment still sells for stupid sums.