Swapping low output tubes for high output tubes?

[rabbit]

I´ve got a question about tube replacement. Is it right that, if the amp provides for the use of different tubes at all, I can only swap high output tubes for low output tubes or is it even possible the other way around?
As I understand it, all the other parts of the amp are limited to the maximum output of the normally use type of tube so higher output would cause damage to those parts of an amp but I am not sure.

Came across this question when reading about the new Fuchs line of single ended amps on their website, where Andy writes that the EL34 of the “Lucky7” can be replaced by a 6V6 which would lower the output power, but did not say so about the 6V6 model “Blackjack21” the other way around (2 EL34 instead of 2 6V6).
Thanks

[stratopastor]

it's OK with some amps... the questions are

- will the speaker handle the extra power?
- will the output transformer handle the extra power?
- is it cathode-biased? If not, the bias will need a big adjustment

I wouldn't try it. The only reason I know it works on my amp is because someone else tried it on HIS amp (same model) - did power measurements, and temperature measurements on the OT, and ran it full blast for several hours. Crazy. The designer of my amp was famous for fitting transformers which were 'too big', and that's what makes it possible to take out the 6V6s and fit 6L6s...

[rabbit]

Thanks stratopastor.

I do not intend to try it, I am happy that my amp work fine and don´t need a fried one. Just wanted to know.

[Fuchsaudio]

Yes, the Lucky-7 will take 6V6 or EL-34 (it would run 6L6, but not that swell sounding IMHO). The Blackjack cannot take anything other than the 6V6's. The filament current would be too high for the transformer to handle.