I have been having some bizarre signal drops during performances. It's as if someone has cut my volume from 7 to 2. It seems to be related to how hard I push the amp. You might think this is by design, but it has been getting worse and worse over the course of the last year. I've swapped to tubes out twice. I removed the head from a touring case that, I might add, was designed for this model. Any suggestions would be great. I'm trying to avoid what will likely be a long and expensive Ampeg repair.