Heya,
I just wanted to share my experience with internal and external grounding on Technics 1200 series TT's.
About 6 months ago I returned to vinyl after a very long time away. I picked up a very nice restored MK II and last week a 1210 M5G. Both for analytical type listening not DJing. In both cases these tables had their external tonearm grounds eliminated and were wired for internal grounding.
Using Beyer T1 and T90 phones with a WOO WA2 and recently my newly built Crack, ground loop hum was easily detected. Pretty subtle but still obvious.
To solve it I simply returned the tables to external grounding (re-installed the ground wires) and the hum from the tonearms completely disappeared.
I am positive this has been discussed to death but just wanted to make an observation here. I am super impressed with the Crack and now the tables just pair greatly with it at the lowest noise floor possible.
What I most regret is my long absence from analog. It spanks the pants off nearly all things digital for me except for a couple of really well done SACD masterings.
Enjoy friends!