I've noticed that most of the tube amps I've seen, when the amp is removed from the cabinet, have 2 transformers. From reading a bit, I believe these to be the Power Transformer and the Output Transformer. I'm guessing the Output transformer is to "match up" with the impedence of the speaker cabinet. Is the power transformer used to step up the voltage to the large voltages that the tubes require? Could someone provide an "Idiots Guide" to the transformers in a tube amp ?