Interesting that was after my time... I need to soak it in beer.
The JDB signature is JD Bennet, a pretty well know Crest big amp designer who went to work at Peavey years before Peavey purchased Crest. I knew him and worked (argued) with him a few times last century (mainly about cost analysis) on new amp designs.
The OTA in the input stage looks like the traditional Peavey DDT (clip limiting) circuit... So it detects when the amp output is not correct and reduces the input signal level. That circuit may be working as intended and triggering because the amp output is not tracking.
IR is major switching FET manufacturer so logical they would make a driver and other glue circuitry to drive the big dog switching devices. Those high-voltage high-current parts were not available back last century when Peavey was trying to make cost effective class D amps. Looks like they nailed (after I left
). Since a handful of companies have come out with similar high power/low cost amps I suspect the secret sauce is new generation modern devices and/or some associated IR driver technology (guess).