Can 6AK6's take high voltages? - diyAudio
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Old 9th June 2008, 05:42 PM   #1
PRNDL is offline PRNDL  United States
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Default can 6AK6's take high volages?

I'm having problems with my 6AK6 low-watt tube guitar amp.

It has two 6AK6's in push-pull with about 280 on the cathode and slightly less on the screens. The 6AK6 max ratings are 300 on the cathode and 250 on the screen.

It was connected in triode, but I changed it to pentode after reading that it shortens tube life. The tubes had several months in triode, which may have burnt them out.

I have several questions.

Are currently available 6AK6's able to handle 280 volts on the cathode and screen?

Should I get GE JAN military grade 6AK6's, or will those from be fine (no manufacturer is specified, but its a very reputable supplier)?
The old ones were Motorola.

Is 280 on the screens a big problem?
Lowering it may not be so easy.

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Old 9th June 2008, 07:05 PM   #2
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180v, both anode and screen.

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Old 9th June 2008, 07:28 PM   #3
PRNDL is offline PRNDL  United States
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I based the design on an old Epiphone schematic that shows 240 volts.
The transformers were from a Dynavox amp, which used 6AQ5s.

The Epiphone schematic listed several tubes that could be used:
6AQ5, 6AK6, 6BA6, 6AU6, 6AG5, 6AN5, 9001, 6CB6
6AK6 had the lowest watts.

6AQ5 is the obvious choice, but has 250 max and is 12 watts. I have two, but they also scratch when playing guitar (that's the problem I'm having, which I believe is due to bad 6AK6s).

These two look like good candidates:
6BA6 has 330 max screen and grid.
6AN5 has 300 max screen and grid.

What do you think of the 6BA6?
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Old 10th June 2008, 04:35 PM   #4
PRNDL is offline PRNDL  United States
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The 6AN5 is a beam power tube with 6AK6 listed as a substitute.
(6BA6 might work, but isn't a power tube)

Would the 6AN5 work with 280 volts?
Does it also have 180 max volts?

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Old 10th June 2008, 05:22 PM   #5
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Either one will work at 300V IF you keep the plate (and especially screen...) dissipation down. First step is to add some series screen resistors - maybe 2K-4.7K on each screen. 6AK6 actually has the higher dissipation rating...
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Old 20th January 2009, 10:06 AM   #6
chimpy is offline chimpy  United States
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Which model epiphone amp lists those other tube choices, PRNDL?

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