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G6Tanuki · 26th Oct 2022, 2:23 pm

I don't know just how much of a vacuum is needed in a practical valve, but the big silica envelope transmitter valves used in times past were sometimes continually pumped rather than being sealed and gettered.

A modern turbomolecular pump can go down to 1*10^^-8 Pascal, but it isn't cheap to buy or easy to operate.

26th Oct 2022, 2:23 pm	#8
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 14,005	Re: Homemade amplifier with homemade valves I don't know just how much of a vacuum is needed in a practical valve, but the big silica envelope transmitter valves used in times past were sometimes continually pumped rather than being sealed and gettered. A modern turbomolecular pump can go down to 1*10^^-8 Pascal, but it isn't cheap to buy or easy to operate. __________________ I'm the Operator of my Pocket Calculator. -Kraftwerk.