Yesterday at rehearsal was running my SVT-II thru a 410, was sounding great as usual, when this hideous crackling sound started coming out of the cab. It wasn't just when I played, but would also happen if the drummer hit his kick hard. At the sametime, it was still amplifying the signal from my bass. I thought I blew a speaker, but took off the cover and they seemed fine, so I figured the tweeter was gone. Not wanting to stop playing I just swapped in an 810, figuring I'de deal with the 410 later. Well the loud crackling was still happening! It sounded sort of like lightening striking in a movie. Before taking this to a tech, does anyone out there have any ideas about what could be causing this? p.s. I checked all my cables, tried bypassing effect pedals going straight in, played another bass, all the external things I could think of. Thanks for any help.