If you get a chance to hang out with John, it's a lot of fun. I would encourage it. We first met at a conference in Germany and had a blast.OK, looked again, and skimmed the Tube CAD Journal article. I had not heard of TCJ, but had heard of John Broskie, though forgot he lived just a couple of hours (more like three now, traffic) north of me. Don't know him at all, just by reputation. Wish TCJ had been around back when I was actually trying to design tube circuits. Mostly preamps, though; aside from some conventional designs, my only unconventional (direct-coupled, OTL) tube amp worked fairly well -- until it failed spectacularly.
My excuse is that I've been peering at some feed-forward stuff just for fun, using dynamic current dumping to enhance the output slew rate, but all I can say is "brain fart" when looking again at the schematic. Duh. Keeps me humble, hopefully. I would've expected them to just split the input signal off to the top device instead of mirroring it around (sort-of) and needing the N-FET, and also imagine the toroidal transformer hits the latest audiophile buzz-words better than a typical EI gapped transformer with the B+ routed through it conventionally'ish. This thing looks like it was invented mostly to give the appearance (but not the fact) of a single-ended tube design, with a patent thrown in for good measure because most of us probably wouldn't do it that way (for good reason). Must be large degeneration Rs to keep the thing marginally stable without bias drifting all over...
But, it's pretty...
Edit: TCJ's front page had a link to "DVC" that I had to click to see what that meant... My first subwoofer was a servo design using a dual voice coil woofer from an Infinity IRS, using the second coil for feedback. The actual speaker used an asymmetric crossover, Arny's design I think, pretty much as John described. Sharp cookies, them guys!
Yes, the more you look at the circuit, the more it seems to be a commercial exercise. Seeing "Western Electric" as a brand now reminds me much of seeing a classic rock act, there are no original members, and the only person who ever actually played in the band was their fourth or fifth bassist, but someone owns the group's name.