Hi Cello. Regarding the 6c45.... I have very little experience with russian tubes other than to say I am not very impressed with most of the ones I have tried whether they are output tubes, input tubes or drivers.As far as the WE 437a being a drop in replacement,sorry I can't help here,I am not so sure without comparing the tube data and curves. However,that said...not all of the russian valves are bad. The miltary version [6n23ev] equivalent of the e88cc/6922 is a very good sounding alternative to nos tubes,it is extremely quiet,very rugged and sounds nothing like the god-awful sounding current sovtek 6922. Bwhite....I am very surprised regarding your observation on the siemen cca relative to the telefunken in the phono of the cortese. I have both the Klimo merlin and the ARC sp-10 preamps that both employ the e88cc/6922 family of tubes. The klimo employs it in its line stage and the sp-10 mk2 throughout. In the sp-10's phono stage,the siemen cca trounces any other equivalent tube on the planet[telies,mullards,amperex's,valvos,or anything else out there for that matter] and it's the same conclusion in the klimo or just about any other application I have employed it in. Both of these preamps are legendary in the high-end industry and are fabulous sounding preamps by anyones standards. Yes... I really like the telefunken sound... but the cca is in another league and I would select any siemen equivalent e88cc,e188cc,7308 over the telie in any of my gear[other than telefunkens own cca version].The sound of a lot of nos tubes can be very system dependent and infact, the telie may be the one that works the best in the phono of the cortese. Most designers today are voicing their equipment with currently made tubes so tube rolling and experimentation is the only way to reach any conclusion. I must say...I am still somewhat perpexed as to the comparison though.
