If you’ve owned a tube amp for pretty much any amount of time, you’ve been there: Your amp starts making noise—probably at the worst possible moment, whether onstage, in the studio, at rehearsal, or when you just really want to play—and you don’t know what to do. Maybe you keep it cool, but maybe you panic: Is my amp broken for good? Is this going to cost me hundreds of dollars? Fortunately, there are a few basic things you can check before you call your amp tech in a frenzy.