My first thought was, what makes you think that the circuit breaker is faulty? Sounds to me as though it's doing exactly what it's supposed to do.
My next thought was, no way that's an 11 amp breaker. Putting in too large a breaker will allow the amp to draw too much current, potentially burning things up. From what I can find online, 4.5 amps looks right.
It sounds to me as though this problem is beyond your ability. Something in the amp is drawing too much current and popping your circuit breaker. No way to know for sure what that is without a closer look. If you're lucky, it's just a power supply cap, and is easily replaceable. Could be any number of other things, though.