Rega hum

By grounded internally, do you mean via the interconnect and/or power cord? If so, try a cheater plug and also check the RCAs to make sure they are not loose or otherwise not making a good connection = ground. If neither of those work, I would try an external ground to a screw or post on your pre.

line the bottom of tt with aluminum foil

Do you have a lamp or other non-audio electrical device turned on nearby? My P25 only hum when I turn on the nearby lamp (not on the same circuit) to change records.

Just a thought.

All RCAs were tight - no lamp on nearby but I do have a ceiling light that is on a dimmer switch. Light was not on though during play. By internal ground I mean that is the way the Regas are designed. There is an internal ground wire within the tonearm and I believed grounded to one of the RCAs. I was told by the Rega US distrubutor that there will be some hum until the coils in the cartridge are put to use (when stylus sets down on LP). Maybe I am being too anal about my vinyl rig. He also suggested unplugging TT PSU from power conditioner and plugging directly into the wall. I don't like that idea.

How would I externally ground a rega table?

Any other ideas? I have plugged the TT PSU into the wall outlet - no change, still hums. I am looking for dead silence when phono is selected on my pre (Rotel RC-1090) and no LP playing. This is when I notice the hum the most. I am at my wits end. Am I asking too much for silence through the phono stage? I am using a MM cartridge.