Home Tube DIY Asylum

Do It Yourself (DIY) paradise for tube and SET project builders.

To tell the truth, I'm sorry I asked...

Eli, I looked into these more after getting home from work. I missed the dual grid connections earlier, and like you say, that means they're designed for UHF grounded grid service. They want to oscillate, and they need the shortest possible connections from the grid pins to RF ground. And the 5842 you mentioned - four grid connections and transconductance of 25,000-30,000 umhos! Holy Moly! Sorry, this is just too much to deal with. Any piece of audio gear built with these tubes needs to be vetted with a microwave spectrum analyzer. Even then, the circuit might age into instability in a year. That's exactly the kind of thing I don't want to deal with in hi-fi equipment that should be routinely and unconditionally stable. Now I know why the 6AF4 is so cheap.

Anyway, I've gone back to published tube curves in search of other types for use as choke-loaded CFs. I'll post more in the thread below. Thanks for your comments on these little triodes.

Buy Chinese. Bury freedom.

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