@ClaraListensprechen@universeodon.com @Ralph058 @SrRochardBunson @sergio_101 @LGsMom Yep. I remember all those brands, Ken-Rad, Tung-Sol, GE, RCA, Sylvania, Mullard.

In the mid-70s I had a repair business in Los Angeles / Hollywood. I and my partner, Ken Sime, were the primary Hammond Organ and Leslie speaker factory repair guys. We also did Gulbransen organs. Some of the organs I worked on dated from the 1930s, including a couple of Hammond Model A's from 1935, the first ones. Speaker cabinets used dynamic speakers, not permanent magnets. Tubes were obviously 1930s vintage components.

Since this conversation is wandering all over the place, into early electronics, early radio, etc., there's an article I wrote on my ham radio blog that might be of interest. The middle section of the article is a brief background history of radio, thermionic emission, the first tubes, Armstrong's inventions, etc.

https://kw2p.shuttersparks.net/the-radiola-20-a-restoration/