Outlier, shpouldn't be burn in or PC's on amps, etc. - that's too noticeable for that. Etthan contacted me and said he was having hum problems too, so you may want to talk with him about what he's doing. Its usually grounding issues or phono cord issues, ie not shielded enough. You may want to look into things there (good phono stages are invariably quite sensitive, some more than others).
Hum is a perennial hobgobblin in phono stages and every analog enthusiasist sighs relief when he/she doesn't have any - and sometimes you just don't know where its coming from! You just have to slog away, talk to other people like you're doing, and keep at it. However, if it is the phono stage itself then the manufacturer needs to address that. Finding another analog system to plug it in that is already stable is always a good idea, although not dispositive.
Keep us updated please.
Hum is a perennial hobgobblin in phono stages and every analog enthusiasist sighs relief when he/she doesn't have any - and sometimes you just don't know where its coming from! You just have to slog away, talk to other people like you're doing, and keep at it. However, if it is the phono stage itself then the manufacturer needs to address that. Finding another analog system to plug it in that is already stable is always a good idea, although not dispositive.
Keep us updated please.