Ground loop hum

The only time I had a hum that sounded like a ground loop from my turntable was when I was using a set of interconnects that were not properly insulated for turntable use.  Morrow literature made it clear to use their phono specific interconnects for turntable use but I thought I would try my non-phono interconnects anyway and hence the hum.  I then installed "regular" insulated interconnects, and the problem vanished.

Perhaps your new preamp is more sensitive to this.

Try a different set of interconnects. 

@kavakat1 

Somehow you have ignored my post above which I believe is your problem.

I could be mistaken, but I think that your problem is that the interconnects between the turntable and phono stage and/or the interconnects between the phono stage and preamp are picking up interference.

If so, insert more insulated interconnects to test.