I own a Crate GT1200H half stack amp. I had my iPod connected to it with some cable that allows me to listen to my iPod on the amp. So one day I played it super loud. Ever since then, whenever I turn my amp on, the sound becomes really faint or it just wont produce a sound. Anyone know what the problem may be? Any help is appreciated. If it's something like tubes, or if it's even repairable, what may the cost be to repair?