Are you referring to the "female 3 plugs-to-male 2 plug" adapter (Like cutting the ground plug off)? I would suggest using an isolation transformer before defeating the earth ground to your system. Defeating the earth ground gets rid of the 60hz noise, but can leave your system (and anything touching it) vunerable to electrocution. We run into this problem all the time in recording studios, and the dangers of the "3rd prong clip" solution outweigh the benefits. If I'm off topic, I apologize for the intrusion.
Ground Cheaters-Good or Bad?
I experience hum problems which I assosiate with grounding. I wonder if using a ground cheater defeats the purpose/advantages of aftermarket power cords. If so, does anyone know of an "audiophile grade" cheater plug?