Check 1bit-DA converter, and the influence the clock rate has on precision. Actually some (most) class-D have no quantization at all. They don't work like e.g. 10bit parallel R-2R D/A-converters but like switched mode PSU, with either continually modulated pulsewidth at a fixed frequency, or fixed pulswidth at continually modulated frequency. Either way the modulation is done via analog means, like delta-sigma comparators. See http://www.beis.de/Elektronik/DeltaS...eltaSigma.html figure 1. (a class-D amp is a delta-sigma converter with analog output and usually even analog input)
Class B has most problems with the power dissipation in output driver transistors at I/2, when both current and voltage across a transistor C-E are at 50% of maximum. IOW when for a 4Ohm speaker the transistor has also "4Ohm" between collector and emitter, and both the speaker and the amp dissipate same amount of power. Class-D efficiency is theoretically 100% since either voltage or current is zero, dependng on switch (transistor) open or closed. Thus class-D in embedded.

full ACK for nonsense of ear protection.