My Neopak has been a great and trustworthy little workhorse for quite a while now. I came home from a gig Sunday, set up (Monday), and noticed a LOT more distortion. I backed down the preamp gain - I'm now getting the same amount of grind at about half the gain (well before the preamp light comes on, whereas before I was set to have my highest transients flash the light). If I go even a click or two higher than where I am now, a big attack will cause a nasty "farty" distortion, almost a pop. I swapped out the tube to a new Sovtek - same issue at pretty much the same settings. If I dial the preamp way back, I can crank the power amp quite loud without any distortion artifacts (e.g., much louder overall volume, no bad distortion) so it's not a speaker issue - I can be loud and clean, just not with the preamp dialed up anywhere close to where it was before. Any thoughts? I've got a gig Thursday, and though I've got a workaround (keep the preamp gain down) and a backup, I'd like to be able to fix this if I can.