It almost seems perverse, 0.4 amps of mains current draw (at 240V) and 25
watts of 400Hz sine into 4R dummy load and a thermometer laid over the tabs
of the 4x TO220 output device, rises only 8 deg C over ambient.
And that with amp laying on bench so no convection over the external
heatsink vanes, no wonder no fan needed.

Previous D class I've played with were Stagepas , not possible to monitor
their operation without making up umbilicals to operate PA out of the little
box. And as separate clock maybe "RF" problems doing that