Help me understand measuring/calculating tube plate dissipation under load

[Helmholtz]

Not sure I can follow... Last time I checked voltages were limited values in tube data sheets?!

Sure, but the tube can't limit its voltages in the amp.

[Enzo]

If I max out the limits on an old 6L6G, and then stick a 6L6GC into the socket, there will be no increase in power. Limits are about what you can do to the tube, not what the tube does for you. Plugging in a higher voltage rated tube won't raise the voltages in the circuit.

[Helmholtz]

You'll also know that a 3 dB change of SPL equals a factor of 0,816 in loudness, that's a reduction of ~20%. And loudness (being the subjective perception of sound pressure) is what we hear, not SPL and not max output power.

So you think that a 20% loudness reduction justifies the risk and trouble of abusing 6V6s?
(What about using lower efficiency speakers?)

[Helmholtz]

But you and me know what Fender did to those poor 6V6s in some amps waybackwhen...Still we love some of them for their tone, right?

Yes, but these smaller amps had considerably more power supply sag.

[tubby]

So you think that a 20% loudness reduction justifies the risk and trouble of abusing 6V6s?
(What about using lower efficiency speakers?)

If that gets me the sound I'm looking for, the short answer is: Yes!
A lower efficiency speaker is a valid option of course. Although I'll get 5 pairs of 6V6s for the price of a nice alnico speaker.
Nevertheless I'd be glad to hear what people are using in their Tweed Bassmans as favourite speakers with lower sensitivity (< 99 dB).

[Helmholtz]

Nevertheless I'd be glad to hear what people are using in their Tweed Bassmans as favourite speakers with lower sensitivity (< 99 dB).

I like the Jensen P10Rs (94.2dB) in my '59 BM RI.

Did you think about a (PostPI)MV?

[tubby]

Yes, but these smaller amps had considerably more power supply sag.

Absolutely correct. An exception seems to be the Deluxe Reverb II which also uses a SS rectifier, much more filtering and about 400V on those 6V6s. Never seen or heard one, they might sound crap or be all gone up in smoke
And just for fun, there is the infamous Jim Kelley FACS with 485V on plates and screens of 4x 6V6s. Apparently rather unreliable. I wonder why?

[Helmholtz]

An exception seems to be the Deluxe Reverb II which also uses a SS rectifier, much more filtering and about 400V on those 6V6s.

Don't forget the smaller, more saggy PT.

[tubby]

I like the Jensen P10Rs (94.2dB) in my '59 BM RI.

Thanks, I'll check that out!

Did you think about a (PostPI)MV?

Yes, like mentioned in the first post, I implemented a PPIMV (Frondelli-type) in this build. I tend to leave it wide open, since I want the sound of driven powertubes.