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I didn't think about the shared cathodes, so fixed bias it is. I got the UCL11 for a slightly post war Blaupunkt a few years ago. And I found on ebay the Chinese are manufacturing the sockets again, the P8A for AZ1, CL4, and the G8A for UCL11, EM12 and such, so I bought a few. I also have some that take the P8A socket; EBF2, ECH4, EF6 and a couple more.

If you were to use cathode bias for the power tetrode, then the triode grid could be biased with a positive voltage (5 to 6VDC).
In order to make its grid -2VDC in relation to the cathode.
Two of the the 60V filaments could be connected in series, and powered by the 120VAC power line.

/e B