Some people claim that class D will suffer from intermodulation products caused by the 450 kHz (or so) switching-frequency. Basically I am open to this argument, but why don't I see these intermodulation products then in the 32-tone test? What is it I don't understand?
The usual concern about high-frequency intermodulation effects is because the tweeters (in the speaker systems) generate IMD when presented with such high signals, modulating "electromechanically" to create distortion that falls into the audible frequency range. An electrical test at the output of the amp will not show that.
About 10mA(rms) 400kHz flows from my NC252MP to my speaker in a "room listening" configuration. With all the cable and speaker inductance.