My son bought a used Mark Bass Little Mark Tube 800 amp from Guitar Center. A year later its on the fritz. We cracked it open and the little tube is soldiered onto the circuit, no way to replace. The amp crackles bad when the signal is boosted, like my son does when playing his bass through a pedal board. I took the amp back to Guitar Center and they don't have a clue what to do with it. I've googled Mark Bass and its an Italian company, there doesn't seem to be any official way to get this amp repaired. I'm disappointed here that the amp went bad so soon, and Guitar Center won't support it, and I don't know how to get it fixed. Suggestions appreciated.... Edit, found this page - http://www.vstservice.com/t-markbass.aspx List of places that do non warranty work on MB stuff. Oh well, I guess I'm shipping the amp to Dallas. Wish me luck. Anyone else had issues with their Mark Bass amps?