Hi Peter,
I was not around in the valve days, and have never actually built any valve equipment. It's just that the development of amplifier design is well documented, the principles have not changed, only needed to be modified to the new technologies as they came along with their own particular new parameters.

Without a knowledge of the history, you may fall into the trap of making the same mistakes that others may have solved long ago. A few more politicians could do with studying history!