I just put in an order with Ceriatone - I plan to build a Plexi50 (1967 specs). I asked Nik to give me the JTM50 chassis, however, so I could put a tube rectifier in and make it switchable. I also plan on putting a second bias pot on the same switch so I can bias for the tube-rectifier separately from the diode rectifier. The main problem with switching from diodes to tube recto, of course, is that B+ will drop significantly when I switch to the tube from the diodes. A few questions: 1. Is it possible for the setting bias pot to make up for this loss? Or does the bias pot only control the voltage on the power tubes, meaning all the other tubes will still be receiving less voltage than they should be? 2. Is it worth getting a transformer that has both a 625v tap for the diode rectifier, and a 690v tap for the tube rectifier? This one seems to have that capability: http://www.classictone.net/40-18054.html If I did this, would I still hook up the diode/rectifier switch after the rectifier, between the rectifier and the filter caps, like in this diagram? Or would it be better to move the switch to be before the rectifier, to stop the actual flow of current from the tap to each rectifier? Would running both rectifiers from different taps simultaneously (but switching after the rectifier) be a waste of energy? Or would it bad for any other particular reason?