Works nicely but I did have to connect the shield of the cable to the empeg casing otherwise I got a really bad hum.

How did you do this? Please be as specific as possible..
Connected the ends of the cable / the plugs? Or dismantled the cable and somehow grounded the showing copper?
Where did you attach the grounding? Just anywhere in the case or did you use a nice warm preinitialized spot?
You had mk2, right?