My beloved Redhead gave me the first hint of a problem in many years of heavy abuse last weekend. Someone had bumped the Fan switch to off so it overheated at the end of the night and went into thermal shutdown.... which also kills the DI, incidentally... not good. So after it cooled back down I was able to turn it back on and hoped everything was ok. The next morning I plugged a bass into it and it works, but now with a hint of distortion added to the sound, regardless of what volume setting I use. I tried an extension speaker with the internal speakers turned off, so it's not a blown driver or tweeter. Does this sound like a partially bad preamp tube? (I'm hoping so!) The tube is over 7 years old and it's been used quite a bit during that time.