at soundcheck of my last gig (christmas eve) there was a farting noise coming from the speaker (trace 4 X 10) cab, which I thought was a torn speaker cone (couldn't tell which of the 4 though), got through the gig, but today trying the amp at home there's a loud humming noise regardless of the gain and master volume control settings, and the actual bass signal is quiet. the cab seems fine though- my old laney amp head works okay through it. also line out and DI out from the head into my 4track are fine- suggests that there's something wrong with the output stage- no visible problems with the board components. connections all seem secure. the 4 power Mosfets bear the no. E9902BY , and there's another transistor with a heatsink that i can't see any no. on as it is. the amp and cab are 5yrs old now, and use of distortion pedals has probably taken its toll. anyone had repairing experience with this amp, or similar? thanks.