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Old 24th October 2011, 09:58 PM   #1
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Default The 6934A Triode Tube

Please check out this 6394A Triode Tube's | tube data If you'll go to page 4, in the second paragraph it states "A 30 second cathode time is recommended before the plate voltage is applied." What I'd like to know from those who are more knowledgeable than I am. Does that mean just when the 6394A tube is being used as a passing tube as described in that same paragraph or does that statement apply to the 6394A tube at all times and in all circumstances? The reason I'm asking is I think this would make a very interesting preamp tube. Might also make for an interesting SET tube as well...

TIA for any and all replies...


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Old 24th October 2011, 10:02 PM   #2
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You want to do that for any use at all. I don't know that particular tube, but generally when you see that on a datasheet, it means that the plate has some scavenging metals which need to be hot before current flows in order to prevent poisoning. This is especially common for tubes with graphite plates.

edit: Pulled up the datasheet and confirmed. This tube looks very similar to 6336. Not terrific for linearity, but would work well in a push-pull circuit.
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Old 24th October 2011, 10:30 PM   #3
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The 6394 is the 26 volt filament version of a 6336A. Otherwise it's the same. I have a couple of dozen.
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Old 24th October 2011, 10:42 PM   #4
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This might be a great build:

Un ampli chargecathodique de 30 W (G.Marec)

30 watts cathode output ...
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Old 24th October 2011, 10:54 PM   #5
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Hi,

That's one of those high altitude aviation regulator tube. Forget about it, it's too rare to be of any use.
Similar to its smaller brother the 6082.

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Old 24th October 2011, 11:06 PM   #6
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Quote:
Originally Posted by fdegrove View Post
Hi,

That's one of those high altitude aviation regulator tube. Forget about it, it's too rare to be of any use.
Similar to its smaller brother the 6082.

Cheers,
Unless of course you happen to have a bunch of them..

Otherwise as Frank says they are relatively rare..
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Old 24th October 2011, 11:06 PM   #7
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Quote:
Originally Posted by fdegrove View Post
Hi,

That's one of those high altitude aviation regulator tube. Forget about it, it's too rare to be of any use.
Similar to its smaller brother the 6082.

Cheers,
Forget about it?
If I had "a couple dozens" of these like Hollowstate I would not mind use them for an amplifier.
I have heard excellent amplifiers with this kind of tubes (6AS7, 6336, 6C33C) especially when used cathode output.
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Old 25th October 2011, 12:06 AM   #8
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Hi,

Any half decent amp (power and Zout-wise) amp will take up about four of those already.
With a OPT you could do with a pair per channel but then matching pairs are going to come from your small stash.
From experience I can tell you that matching anything like a 6080 and up in power is going to take more than just a few dozen of those bottles...

All in all not that great an idea not even to mention the mere ecological footprint of these babies....

Ciao,
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Old 25th October 2011, 12:22 AM   #9
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I had very similar problems with the 6C33, I had to purchase dozens to get just 6 well matched ones per channel. That OTL amplifier was ill-fated for a lot of other reasons including my need to design a needlessly complex amp which as designed was never going to work, and then I discovered low power SE..
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Old 25th October 2011, 12:36 AM   #10
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Hi,

The difference between chasing mere numbers and musical bliss, I reckon?

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