I was doing a little recording the other day and got a pretty nice little shock. I had my SM57 plugged into my soundcard with an XLR to TRS cable, and then after a while I go to adjust the input level on the front of my soundcard and touched the metal sleave on the end of the cable and it gave me a nice jolt that went from my hand almost up to my shoulder. Nothing sounded out of the ordinary, but I went ahead and unplugged everything just in case. What could have caused this, and could it have been harmfull to my soundcard?