Finally using my RPM for vinyl which has been mostly used as a 1-in (mic and mic-pre) 2-out interface for a video editing system.

I have a Music Hall mmf-2.1 hooked up, with the ground connected, to the RPM 3/4 input which is set to "Phono +6db"

It's all connected to a PCIe card in a Mavericks OS X MacPro tower. The RPM is powered by the RME power supply (complete with the LED on the connector, why doesn't anyone else do that?) and all AC goes through the same UPS either directly or via a power bar to separate battery/surge protection from just surge protection.

Phono signal goes into RPM and line out to a passive attenuator and powered monitors. Ideally I would eventually digitize into the computer to get digital versions of some rare and older vinyl and my old DJ records. But first I have to get this problem sorted out.

The problem I've been having is a very low signal level barely peaking at -6 in the HDSP mixer and compared to signal coming out of the computer as well as a noticeable low-pitch hum. I can hear the hum increase as the tonearm goes from the resting cradle to above the platter so it makes me think there's a ground problem with the turntable.
Before I take the turntable in for service is there anything I am missing? Should a turntable and signal path like that need another phono preamp before powered monitors?
It's been a while since I worked with two 1200 decks/mixer/PA and that was in an all analog environment.
What should the proper set up/signal chain be?

Thanks