Thank you Everest, that was very interesting. . . for one thing, according to John Stronczer in the video, , the front ends of Ref500 and Ref1000 amps appear to convert AC to DC and store temporarily the energy in a bank of capacitors. Feeding the machine stabilized DC is also the general idea behind the JRDG approach using PFC modules. . . in fact, when listening to Ref 500s in Denver, I was struck by a finesse that reminded me of JRDG 312. . . Even at the time I was wondering if Bel Canto was perhaps preconverting AC to DC in R500s.