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In Reply to: RE: Some Other Voltage Issues posted by FlaCharlie on July 31, 2016 at 11:47:11
It's actually more significant than you think because you have to consider that you are getting much more peak transient power,especially under dynamic conditions..You don't want to be pumping 430vdc into an EL84 because you will shorten the life of the tube and then you won't even make the rated power of an EL84 after a few months.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Edits: 08/02/16Follow Ups:
Michael Samra, I disagree with what you said,"..You don't want to be pumping 430vdc into an EL84 because you will shorten the life of the tube and then you won't even make the rated power of an EL84 after a few months."
As long as the plate and screen dissipation are withing the rated spec, the tube will last just as long with the possible exception of an arc over due to the lower, 300v plate voltage rating.
I'm confused. You warn against "pumping 430v into an EL84", yet earlier both you and others agreed that plate dissipation is more important than plate voltage in determining how hard a tube is being run and, I would assume by extension, its expected lifespan. Both 7189 and 6BQ5 have dissipation ratings of 12 watts.
I don't doubt that 7189s "take abuse better", as Doug put it. My earlier response was: I don't doubt the 7189 responds better to "torture". Would you characterize running a tube rated for 12 watts plate dissipation at only 10 watts as "torture"?
I can see how the 7189 would be the clear choice if the dissipation is pushed to the 12 watt limit or over, but at more reasonable levels does it really matter?
Say both tubes are being operated at the same points - running at 430v on the plates but only 10 watts plate dissipation, is there any compelling reason to use a 7189?
Fla Charlie, you said, "Say both tubes are being operated at the same points - running at 430v on the plates but only 10 watts plate dissipation, is there any compelling reason to use a 7189?"
Yes, because the 7189 has a higher plate voltage rating (400v) so it would be less susceptible to arc over.
Would you characterize running a tube rated for 12 watts plate dissipation at only 10 watts as "torture"?No I would not and don't misunderstand,you can run EL84s in your S-5000 but keep in mind that we are running the full 425vdc across the tube being we are using fixed bias with a small value cathode resistor.
When you rebuild your Sherwood,did you put a 35uf film cap off the GZ34? That makes all the difference in the world for stability,deep bass,and increased power bandwidth.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Edits: 08/04/16
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