I'm currently listening to the end of the Russian Revolutions part of the Revolutions podcast (the last one), and I'm quite happy with the quality and depth, i recommend it heartily. I had a decent understanding of the subject matter from generic history knowledge and The Great War series on YouTube ( which i also recommend!) and there was still a whole lot i learned. I do listen it on 1.1x however, the normal speed is a bit slow for me ( and slightly overflows the slot I've alloted for podcasts).