Home » Audio » Thermionic Emissions » How long do EH ff 300b's last
How long do EH ff 300b's last [message #9687] Thu, 08 June 2006 12:16 Go to next message
Tre' is currently offline  Tre'
Messages: 34
Registered: May 2009
Baron
I have a set of 4 300b's that I have been running at 355volts @72ma. for 6 months now. They sound great and still test new. How long will they last.

Thnaks...Tre'

sorry, that's gg (gold grids) [message #9688 is a reply to message #9687] Thu, 08 June 2006 12:17 Go to previous messageGo to next message
Tre' is currently offline  Tre'
Messages: 34
Registered: May 2009
Baron
.

Re: sorry, that's gg (gold grids) [message #9689 is a reply to message #9688] Sat, 10 June 2006 23:48 Go to previous message
Thermionic is currently offline  Thermionic
Messages: 208
Registered: May 2009
Master
Barring catastrophic failures like filament breakage or shorts, a decent 300B should last several years. By design, type 300B is a long life tube. Even the cheaper Russian or Chinese 300Bs should outlast most indirectly heated octal power tubes by at least a factor of two, at minimum.

According to everything I've studied about DHTs, your EH 300Bs are probably just now hitting full cathode activation, where they have reached their full emissions potential. Different manufacturers dope their cathodes differently. Some apply an oxide doping formula that allows the tube to reach it's full emissions potential quickly, at the expense of some absolute lifespan. Others may formulate the cathode coating to give maximum lifespan, at the expense of reaching full potential more slowly.

Eric B. is the ultimate authority on stuff like this. He's mighty busy and isn't seen much around these parts, but perhaps he'll see this and chime in, or maybe someone else with a definitive answer.

Thermionic

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