A few highbrow channels keep making their way to my 'watch later' list due to their solid scholarship and entertainment value.

Timeline - World History Documentaries has a broad range of subjects chosen in part from user suggestions. Length is 30 minutes to 2 hours based on how much they feel like telling you. Chernobyl, Victorian medical practices, Mayan temples, and debunking a conspiracy of Hitler making it to South America are covered.

Biographics - it is only biographies, but there are lots of them. I like biographies as good light listening. It is a good intro to a field of history where my own knowledge is limited. Bonus points for the narrator being an English guy who sounds like Dr. Baltar from Battlestar Galactica (which I reference here because the show is technically based in our distant past, no violations of the 20 year rule from me today! :P )

Various channels from Indy Neidell - WW2 is his focus. He narrates dressed in a WW2 shirt,vest, and tie, at a WW2 desk, with a WW2 phone, and other WW2 paraphernalia. Some of his pieces are on the short side, as little as 10 minutes. Still, when the focus is narrow, like the British Women's Land Army, 10 good, carefully researched and articulate minutes is sufficient.