new GAN amplifier

All digital audio is built around the sampling theorem, not the other way round.  There are places in the signal chain where high sampling rates make sense. The final reproduction stage is not one of them. Why, and how it can be harmful is well explained here:
https://people.xiph.org/~xiphmont/demo/neil-young.html

All digital audio is built around the sampling theorem, not the other way round

I wasn't singling out digital audio, but it's worth mentioning the use of oversampling to remove the necessity for analog brick wall filters in AD-DA conversions. Class D amplifiers don't require brick wall filters but they do still add multi-pole low pass filters to an already band filtered signal path for playback of a wide range of recorded music that's already passed through a diverse range of low pass filtering even before it leaves the mixing desk for digital recording and mastering.  

For the record (no pun intended), my highest fidelity recordings are all high res 24/192 digital. To my ears they're the closest thing to real live music. 

purify look good but keep in mind those IMD measurements conducted at relatively low power and with a LPF in line.

Not just low power Arty, but "very low" power, as the testing equipment used, the Audio Precision in line external Class-D switching noise filter has a LP slope of 52db per octave, and any more than a few watts through it would burn it out a flash.
Would be very nice if you could listen to normal power music through this AP filter, as then everyone would love Class-D (even me), virtually no switching noise or phase shift in the audio band, no heat, light weight, low power and cheap, what could be better

Cheers George

I see you are parroting what someone told you about using the AP to measure a Class D amp. Funny I have tested Class D at 100’s of watts on our AP. Can’t imagine how I did that ....

I’m talking about the Audio Precision’s auxiliary AUX-Filter which goes between the Class-D and the AP Analyser, it’s a 52db per octave passive low-pass filter and can only take low power, it eliminates the Class-D’s switching noise for testing purposes only can’t be used for real music levels, even Stereophile state they can only put low power wave forms through it with it in use.

I said it years ago if you have a look in their comments, when Stereophile first started using this AP AUX switching noise filter, I complained they weren’t showing us anymore what is representative of what comes out of the speaker terminal of Class-D with this AP filter in between the Class-D’s output and the AP Distortion Analyser, especially the screen shots of the 10khz square waves.