What's going on with this Standel phase inverter?

[oldmacman]

Attached are a couple of gut shots from a Standel 20J12 that was listed on eBay. I'm trying to figure out what's going on with the phase inverter. The tube is supposed to be a 7025, but I can't figure out the topology. There's a single plate load resistor from B+, and it looks like the first half of the triode gets its B+ from the second half, sort of like a cascode. But the rest of it looks more like a cathodyne / split-load PI. Any ideas?

[Tony Bones]

Can you draw a schematic of the PI? it would be easier for you with the amp than me with just a couple of photos.

[oldmacman]

To clarify, I don't have the amp, and I'm working from photos.

I found another photo of this from the last time the amp came up for sale, and I was able to work out how the PI is configured. I've attached the schematic and an LTSpice sim of it working. Has anyone ever seen another amp using this PI topology?

[martin manning]

Interesting; never seen that one before. It seems to be a cathodyne with a gain stage in front, but overall it will have more gain due to counteracting of the NFB in the cathodyne. As it is it's not vey well balanced, but that could be fixed by adjusting the lower 220k downward, and taking it to ground instead of the top of the lower triode's cathode.