I'm trying to connect my US Macbook pro to a power outlet in Germany. I purchased the appropriate wall outlet adapter but no power converters. As I understand, the 85W adapter that comes with the macbook pro is rated for 100-240V and 50-60Hz so this shouldn't be a problem. However, when I plug in my computer the entire case seems to vibrate when I touch my finger to it. Although it doesn't seem to be hurting the computer, I can't imagine this is a good thing. Do I need to change some setting to get the computer to accept power at different voltages and frequencies? Thanks for your help.