The amp I just got secondhand off my friend (actually third hand because he got it from his friend...) has a bit of a problem in the grounding dept. One of the first things I noticed was that the plug didn't have a ground on it. It did, but it was torn off/broken. Is this a problem? I have it plugged into a power strip if that makes any difference. If it is a problem, how urgent is it? Should I even play it, or could that cause damage?