We had a gig last night and we were all sharing amps, so i brought my bass amp. The amp was working fine at the start turned the power supply on at the head and it powered the speakers fine and everything was nice. Then just as we go to do sound check the amp turns on (as usual) makes a quick pop sound (as usual) then hums quiet nicely (as usual) but when i put a lead in nothing came through no sound regardless of settings, we tried multiple leads and multiple basses but nothing. The amp sounds and looks like its functioning properly but isnt giving any sound from the basses. I already had the fuse replaced before cause the amp wasnt even turning on. But i dont know what it is. eletrical problem? I read somewhere that if the speakers are humming then there are still fine. If so then what the hell is wrong? anyone please