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The more I deal with 6C33C the more this tube amuses me. Couple years ago when I started to use a half of 6C33C for my upper frequency channels I wired right and left my Super Milq with half of 6C33C connected to right and left side of the tubes correspondingly. The presumption was that if one of the cathodes used up (cathode poisoning etc…) then by flipping the tube to another cathode and anode side I would be able to use it longer.

I once in 6 month retest all my operational tubes and keep a log for each tube. So far I did not detect that a “used” half of the 6C33C   demonstrated any excessive wear relative to the idling half.  The used half do measure differently, sometimes 40% of transconductance was different (!) but it is not necessary in a favor of “used” or “new” side of the tube. Even more. When I take a brand new tube with identical transconductance AND gain of each half (hard to find among the 6C33C, though it is not necessary in most cases) and use it a as whole tube (two filament, two halfs of the plate and two cathodes) then after six month of operation each half still measure differently, despite of the fact that they were used identically. Tell me it is not strange? Perhaps I need to measure the cathode emission separately and the secondary grid’s emission…

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