I have beat and banged on this thing several times, but not tried the reverb tank yet. I will try that next time I hook it up. None of the controls seem to have any effect on the squeal at all. Well, the volume does, it gets louder, as to be expected, lol. Before it gets warmed up good, this thing has that awesome clean sound that I have been hunting for a long time. Every aspect seems to be working perfectly, except for that annoying squeal. When I strike a note, the squeal can be heard thru it so it's not a typical "no signal" squeal.