I'll add mine to the growing list of amp problems. One of my Phase Linear 400s just developed a problem. There is massive distortion in both channels. The music sounds like it's coming through a "Fuzz Box". There is no background noise, just distorted music. There was no warning or lead up to this. It just began the last time I turned on my system. I'm waiting for the shop manual to arrive before I tear it down. Any thoughts as to where to begin my search?