Check with Glenn Buckley at Aesthetix. I've found an excellent replacement for the 12AX7 is a 7058 tube. NOS 7058s turn up on Ebay in quantity every once in a while at reasonable prices, but are not especially cheap when bought one or two at a time. No ideas on replacing the 6922s, and I'm not even sure what types (6922/6DJ8/etc) i'm using now in my Aesthetix and Rhea. Great components, by the way. Power them down, as Corby recommends, before changing tubes.