Unobtanium audio output tubes - The NEC 50CA10 Triode vacuum tube.
Luxman had a thing for "special" vacuum tubes back on the 1970s. The 6RA8 triode (also used in the Sansui BA-202) and the big, robust 50CA10 used exclusively by Luxman. Both were one-off units made by NEC (Nippon Electric Company) in Japan and no modern or vintage equivalent exists. They are no longer in production since the late 1970s. The 50CA10 was (is) also a triode tube capable of a max of 30 watts. Fairly robust and really excellent as an output tube. Shuguang Tube Factory in China made a copy for a time, but they were of questionable reliability and not much is known about them. They are no longer in production from Shuguang. Any 50CA10 is most likely available in Japan, used or NOS, for pretty steep prices. Amps that used them were the excellent SQ-38F, FD, FD MkII and some of the MQ series. They are long-lasting and sound excellent...as long as they are in a well-restored and balanced amp.
I have a fairly sizeable stock of these tubes. :)
