Continuing observations regarding my GT 12AX7-M tubes

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After using the GT 12AX7-M "Mullard copy" tubes in my ARC SP6-A preamp since December of last year (6 months with about 800 to 1000 hrs of use) I have enjoyed the sound. The GT tubes sound fantastic.
Their lifespan leaves a bit to be desired however.
I have had 3 out of the six fail now. No warning, no microphonics, just one dead section. The three tubes that have failed all test "dead" on one section (no shorts or gas) and "good" (new actually, per my refrence test results from when I tested them before putting them in my unit) on the other section. Two of the dead sections are #1 and one is section #2.
They sound just fine until they conk out with no warning.
So IME, the Groove Tube 12AX7-M is an 800 hr tube in my ARC preamp. Every other new production tube that I have used in this unit or my SP3 has lasted 3000 hrs minimum before showing degredation in the test results on my Hickok 6000 tester.
Has anyone else had a sudden failure of the GT 12AX7-M?
--
Al G
Travelin' light; It's the only way to fly - J.J. Cale

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Kimber Kable

Topic - Continuing observations regarding my GT 12AX7-M tubes - anumber1 14:54:24 06/26/06 (1)

Re: Continuing observations regarding my GT 12AX7-M tubes - SirAnthony 19:37:14 06/26/06 (0)

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