Yes, I fixed a ground loop hum by doing exactly what jmcgrogan2 recommended. First make sure it's not your power plugs. If it's not, the cable may be it. I ran a separate ground cable to one of my cable splitters and that seemed to reduce the hum a lot. I've also had to run separate grounds to my tonearm and preamp in the past. I have a Rega TT which has a bad hum unless I have a dedicated ground run from the cartridge that I can ground. It's a very frustrating thing sometime. Start by making sure that all your plugs get power from only one outlet and go from there.
Turntable hum
I have a Pro-Ject 2 Experience turntable with a Pro-Ject Phono Box SE and a Sumiko Blue Point 2 cartridge, the phono box out is going to a Sherbourn PT 7030 preamp then to an Emotiva UPA 700 power amp. I have a pretty significant hum when I turn the turntable on the turn table is setup next to a plasma TV. I kill the power to the plasma but this doesn't help. Anyone have any ideas on what could be causing this hum?