History: bought a JCM 800 amp that was blowing fuses when I got it. Replaced power tubes. Great for 2 gigs. THen started blowing again after running hard for a gig. Took to tech who found no problem and replaced with different power tubes. (I have had a little reliability issue with the Groove tubes I was putting in). First gig with new tubes last night and amp was running good..but then I got a crackling noise when I adjusted volume pot on guitar. I thought the pot on my guitar was bad as that is exactly what it sounded like. Crackling and just noise when I turend the pot. Grabbed other guitar...same thing. This kept up for about a set. Last set problem went away. I'm wondering if there is still something wrong with the amp or if this could have been a weird grounding issue.