I may have been confused by the website language--maybe you can sort it out? It reads like this:
“The Genus Integrated…is a small stereo SET amplifier driving a bigger stereo SET amplifier in one chassis.
The input driver stage is a small 0.7W SE amplifier built around the Siemens E280 F super triode and is loaded with a […transformer]. This single tube stage offers maximum linearity and bandwidth for maximum transparency.
The small SE amplifier uses our proprietary AC link coupling technology. This technology uses the secondary winding of the first SE amplifier to modulate the biasing circuits of the bigger 813 tube output stage.
The two 813 directly heated triode tubes use [triple passively treated filament PSUs].”
But really, over the last few years I've never seen this tube discussed on Audiogon, so I wonder why.
This tube is simply a high gm pentode (much like a 6922).
From the genus white paper it is being used triode connected to drive a larger output tube. Nothing special going on here. Lets get used to the practice of a myriad of tubes showing up to make things fun and interesting. Gotcha !!!
It is a bit wimpy to drive an 813 but best of luck to get you attention and $$..