Forgot Rob's recent reply to you?
But the real interesting stuff is when you take a sinc function and try to meld it to suit the real life requirements of limited processing - or getting more sonic improvements from finite resources. Then it becomes very interesting indeed, with lots of careful listening tests, lots of evaluating and changing of parameters to create ones own windowing function.
WTA is always evolving (for 20 years) as there is no correct answer how to do this.
The theory is impossible in the real world and using just a truncated sinc doesn't work so well.
It needs massaging and tender loving care (
https://en.wikipedia.org/wiki/Window_function).
I can see why Chord didn't go down this road. The FPGA is already maxed out and tied to the hardware to a degree.
It would add more complexity to allow for updates and probably make the source code more vulnerable to copying too.
It was Ted's first DAC I believe, so may explain why there are big improvements (steep learning curve) and why they offer updates.
But if Ted can get measurements like those to sound good, he could indeed be some kind of genius.