As I had committed, I posted the first schematic diagram of tube amplifiers. This is the WE91, an original design of Western Electric from 1930 that was used to sound the movie theaters at the time. Despite only 10W of power this was enough to sound the rooms with the use of super-efficient speakers system with horns. In 1992 an article by Joe Roberts for the Sound Practice magazine catalysed the revival of WE91A, to the delight of audiophiles.

See more at page WE91A