I watched the one on SETs and it was fun seeing some of the amps he had to show. I've seen and heard some other giant transmitting tube amps too, but, I don't have a need for that kind of power so it is more of a curiosity thing for me. I did not agree with his quick dismissal of the lower-powered triodes that are commonly used in SET amps, such as the 2a3 and 45. Yes, they are lower in output, but when used with the right speakers, they can sound quite good; for my taste and system matching, they sound better than 300bs. I don't automatically think that the 300b is the go-to tube for low powered SETs.
He also said something that was wrong about tubes that have a wire running to the top. This does not mean that the tube is a directly heated tube. A wire running to a top cap is either attached to the anode or the grid of the tube; it is not the source of current feeding the cathode/heater part of the tube and has nothing to do with whether on not the tube is a directly heated. I run 348A tubes that have indirectly heated cathodes and the cap on top is a control grid cap.