A masterpiece A-brick

That is a very high power density for how small that amp is at 50mm x 30mm. It is bigger than the photo in the PDF makes it look - by far that is the biggest inductor on the smallest amp. Looks like a self oscillation type circuit similar to IRS2092 except with feedback after the inductor. I wonder what honey sell for?

From CES booth - you can see once integrated into a motherboard with requisite filtering, dual rail supply, logic etc, the size is not any smaller than an equivalent 400w stereo LJM IRS2092.

That's not that small if you look at what a +/-44v rail class AB can look like (built by member borys):





A-Bricks or Audio-Bricks are now Ice-Bricks.
After a couple of years of "please enquire" they are now listed as available from profusionplc.com
ENGINE-400 Amplifier
AUX-PLANT DC-DC converter to generate the various voltages required and
MOTHERBOARD-1 If you don't want to design your own peripheral circuitry.
And you still need to provide a DC supply.