This was suggested by Anders Mikkelsen.

To the left iis a link to the PDF file for the Vacuum Tube Manual, RCA 1962: Electron Tube Design PDF, it’s out of print but has tone of information about Vacuum Tubes and Design you may find useful. 

This is a huge PDF with almost 1000pages, so it may take a while to download.

I haven’t dove  into it intently just yet, but I hope to peak at it once,  I’m in the editing phase for the podcast.