I don't think so, as the limit to that would be the output transformer, but the Dynaco easily makes 20K. As usual there was a lot of folderal about this. I would bet the real reason was actually sourcing the tubes.
New-looking 7199 are all over e-bay- I would bet the sellers of these mods just don't want to pay the price but I saw several listings at $18.99/pair. I would hope the sellers have a large supply of the 12AT7 because tube failures would be an ugly situation.
To be honest, I think that almost any tube can be sourced pretty easily- I have only bought more than a few one time, the rest were all specifically for an amplifier at the time, not for reserve. Even then, I probably have 150 various tubes and I donated close to 50 to an electronics service association. Estate/rummage sales are a great way to find them.
I'm pretty sure the sellers of these mods are betting that the customers have more hope than brains.
