Hum in Sub

Curious issue w my Sub. Paradigm Monitor 10. When I use my turn table It gets a random intermittent low level hum Just in the sub. 60 hz I think. It comes and goes every few seconds. It doesn't hum when I use any other source; CD, Computer etc. Oddly enough when I listen back to my TT thru headphones its perfectly clean, so I'm quite sure it's not my Pre-amp or TT. TT is a VPI Scout. Phono Pre is a Pro-Ject Tube Box S. Integrated Amp is Peachtree Audio Nova 300. I also have another set up consisting of a pair of KEF LS50Ws. When I connect the sub and same sources the sub does exactly the same thing. Again no other source causes this random intermittent low level hum in the sub. Wondering if I should ground the TT to the Sub? I've seen a few posts talking about locating the sub further away from the TT. I might try that too. Any input would be appreciated. Aside from this minor annoyance, my system sounds great on all sources.