Reference

Widely unrecognized, is that class-D amplifiers, depending on voltage-challenged switching-MOSFETs, are so compromised for voltage swing, that almost all rely on bridging to deliver power levels into 8 ohms that analog amplifiers managed 40 years ago. Technological retrogression sits in plain sight.

Meantime, bad digital can make the most unnatural harmonics of all. The fifth-and-a-half has been observed. There are also sub-harmonics: Fit only for horror movies. Worse, modern test instruments hide such inconvenient data, as sub-educated modern "designers" decide that only integer harmonics or products exist.—Ben Duncan