I've searched the forums and have found similar posts but they all kind of danced around my question and if I've missed the answer to my question I apologize . But here's my situ, just bought this amp used from my local GC a couple of weeks ago it was in almost knew condition with all of the documentation including hang tags. Gigged with it twice, the first time I did not use the effects loop and had no issues but last night I decided to use the effects loop for the solo boost feature and I got the dreaded cutting in and out problem that I've read about on here and it is intermittent. When I put a patch cable in the jacks and engage the loop I don't seem to have the problem. So bad tube or do my jacks just need cleaning? By the way this amp freakin' rocks otherwise. I was iffy on it at first because of the brittle highs I got when I set the eq with my eyes but when I set it with my ears and let go of my instinct to have everything at 12 o'clock ...wow it's an amazingly toneful amp.