Help with Low Level hum in phono

I've noticed a low level hum in my phono section of late. IT is low level, mostly noticeable only when the stylus is raised off the record, not during playing, at higher volumes.

Strange thing is the hum level does not change either with or without the ground wire connected to the ground on the preamp, which is something I am not familiar with. I would expect more audible hum with the ground wire disconnected.

Any ideas or suggestions welcome.

Thank you in advance.