6V6: 12W or 13W plate dissipation?

[slidincharlie (Carlo P)]

Different tube data sheets give different plate dissipation ratings for 6V6 tubes.
The Tubes page in the Weber forum (http://www.webervst.com/tubes/index.html) give access to three different databases: the Franks and NJ7P archives give 12W plate dissipation for 6V6, 6V6G and 6V6GT; the Duncan archive gives 14W for the same tube types.
Who is right?
I seem to recall that 12W was the correct value for 6V6G tubes, while 14W was correct for 6V6GT tubes, but maybe I'm wrong.
I ask in order to set properly the bias in my 6V6 amps. I have Westinghiuse 6V6G's and RCA and others 6V6GT's.

[Tom Phillips]

Carlo,
Here are values from a few original tube manuals for "Maximum plate dissipation"

1946 Sylvania Tube manual lists 12 W for both 6V6 and 6V6GT
1963 RCA manual lists 14W for 6V6, 6V6GT and 6V6GTA
1976 GE manual list 14W for 6V6GT and 6V6GTA

HTH,
Tom

[slidincharlie (Carlo P)]

Thank you Tom.
Does it mean that the MPD may be different on different brands?
How do I know if my "x branded" 6V6 (for instance my coke-bottle Westinghouse 6V6) has got 12 or 14 watts MPD?

[Enzo]

And are the distortion levels the same on those different tubes? When they say a tube puts out X power, it is always under certain conditions. The tube might put out more power if you include more distortion for example.

I bet if you just assumed 13 watts, things would be OK. The difference is mnimal.

[Old Tele man]

...only the "GTA" models are rated 14W, the "A" suffix denoted the use of better heat dissipating plate materials (same as "C" on 6L6's moved them from 19/23W up to 30W).

[slidincharlie (Carlo P)]

...only the "GTA" models are rated 14W
Thank you OTM (maybe I know you from another forum...?), that's what I suspected.

[Old Tele man]

...probably, 'cause like a "bad penny" I tend to show up everywhere (wink,wink)!

[stokes]

Most tube data is very conservative for guitar amp purposes.Like Enzo said the difference is going to be very little between 12 and 14 watts,let your ears decide.I think it was Enzo who in a different post pointed out the fact that the tube manufacturers where stating the tube limitations for other uses than guitar amps,we like to push things to the limit and arent concerned about tubes lasting a lifetime.Biasing a 6v6G to 14 watts instead of the rated 12 watts isnt going to cause an immediate meltdown,it may shorten the life some,but if it gets you the tone you want,that is just the price we pay.

[slidincharlie (Carlo P)]

Ok, thanks for all the advice.
:)