Radio in 1921, TV in 1946. Because of how expensive each was at first, radios really caught on in 1924 and TV's in 1951.
You won't see a very large bubble in the market with the advent of TV because of how soon it occurred after the War and the Great Depression, as well as the fact that the relatively new SEC had teeth in those days.
The bubble that occurred with the advent of radio, particularly in the late 20s, was profound. And it wasn't just radio but the new widespread availability of recorded music and the beginnings of what we call today the "Music Industry." Prior to 1925, music what mostly sold as sheet music.