I have a S-41G since it was new (a 1946 Christmas present) and a S-38C from a brother-in-law. Both have been recapped and both have always had a little 60 cycle hum. I think it's a product of the method they use to generate B+. They are not a hi-fi unit so just turn up the volume a little and the hum is covered. 73, Skip Magnuson W7WGM