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Hoffman Amps Forum image Author Topic: 12ax7 safe voltage  (Read 2536 times)

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Offline Boone

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12ax7 safe voltage
« on: October 23, 2013, 05:03:57 pm »
I have tweed princeton - 12AX7 V1 at : pin one 200.4V and pin 6 at 204V. Will this high of plate voltage prematurely wear out the tube? Thank you for the help

Offline HotBluePlates

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Re: 12ax7 safe voltage
« Reply #1 on: October 23, 2013, 05:21:22 pm »
Not in the least. MANY tube amps have much higher voltage on their 12AX7 plates

Offline Boone

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Re: 12ax7 safe voltage
« Reply #2 on: October 23, 2013, 05:32:29 pm »
Thanks hotplates. Another reading: the 6V6 is at 356 on pin 3 and 333V on pin 4. I am running NOS 50's Sylvania in there now. Is that safe without premature tube failure as well?

Offline HotBluePlates

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Re: 12ax7 safe voltage
« Reply #3 on: October 23, 2013, 05:33:28 pm »
Yep, just fine. And about 70v lower than some Fender amps.

Offline Boone

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Re: 12ax7 safe voltage
« Reply #4 on: October 23, 2013, 06:00:13 pm »
Thanks for the input. I appreciate it

Offline tubeswell

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Re: 12ax7 safe voltage
« Reply #5 on: October 24, 2013, 03:58:49 am »
This is a good read on triode characteristics (a 12AX7 is a 'dual triode') http://www.valvewizard.co.uk/Common_Gain_Stage.pdf

You will find some information on typical 12AX7 ratings on pages 33-35 (which should provide a fuller answer to your question)
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