I finally came up with a good test strategy to measure max output power for these single ended triodes, so now I can go back and more accurately test the get*set*go and Darling Clementine, too. Previously, I thought I would select 5%THD for the measurements, but this didn't reflect max output swing into the power triode or pseudo-triode. Instead of a fancy test setup monitoring the voltage swing and cathode bias, I am just increasing the input signal until the cathode bias peaks and then starts to decline. This can be done quickly with one DMM and a hand on the signal generator adjust. I adjust upward in 10mV increments and then do fine adjustments of 1mV to get the exact peak. Note that the preponderance of the distortion is second harmonic. Noise was extremely low, too.
-3dB bandwidth is around 15Hz to 31kHz. Not bad for a simple 6SL7 driver and budget Edcor iron. I used a Russian 6L6GA that I pulled randomly from the tube vault - I think Ed Brown sent me these a few years ago. Note that '11' is a junk number. The distortion data here was garbage due to my automatic data collection method.
Tests at 1W (adjusted for a 2.828V output at 1kHz):
http://www.diytube.com/clementine/russ6l6_383mv.pdf
Tests for max output power (adjusted at 1kHz as described above):
http://www.diytube.com/clementine/russ6l6_695mv.pdf
Shannon