Seems correct. I did some back-of-the-envelope calculations for a TZ20 output stage operating at 300V with a 100k + 20k feedback network, indicating quiescent point at around -20V and a +-80V voltage swing.
I have two pairs of speakers in my hobby room, one smaller pair that prefers amps with a medium to high damping factor and a pair of big BR/horn hybrids that sounds better with low DF amps. This opens up for some cretive amp building, including amps with adjustable NFB to tune the output impedance to match both pairs or speakers.
I've been on a little thorium shopping spree lately with the ambition to build an amp with adjustable filament and HT supplies and multi-tapped OPTs to employ a wide range of different high mu triodes as output tubes. Now I'm leaning more towards splitting this project into two different amps, one smaller for T20/TZ20 tubes and a bigger one for the fatter bottles.
Philosphically. the smaller one could be allowed to be a bit of an FX box with moderate amounts of feedback while the larger amp probably would benefit from more feedback to flatten out the differences between the larger selection of output tubes.
