These hefty (30W PD) power triodes from Mitsubishi look like some "contenders" for aSET or PP amp:
http://frank.pocnet.net/sheets/084/5/50C-A10.pdf
These have been mentioned in passing before, now we have some usable data for them.
The basics:
Filament: 6.3V @ 1.5A ; 50V@ 0.175A
PD: 30W Max
IP Max : 200 mA
VB+ max: 450VDC
Class A amplifier:
VP: 250V
VG = -22V
IP: 80 mA
gm: 14 mA/V
RP: 620 ohms
mu: 8
Plate load: 1500 ohms
PO: 6W @ 7.5% THD
Duodecar base:
Filament: 1 + 12
Cathode: 10
Grid: 5 & 9
Plate: 3 & 7
/ed B