I’m no sure that harmonic distorsion is a harmonic experience
the term is loaded with positive values .
When you get a THD it’s always overtones that bunch up higher in frequency? I’m not sure that will sound good on all music ? Especially when you stack this components up , add this to the tube DAC recently tested and even the distortion from the DAC will have distortion
I’m not sure about this 2nd harmonic sounds warm thing . It looks like a one size fits all solution it can’t really work properly ? For all music in all situations.
The safe bet re THD is as low as possible, do no harm to the signal. Then it won’t matter if it’s even or odd harmonies in a falling magnitude etc etc as they are not audible anyway . This would actually work for most people as at least the sound is as it is fro the source . If sounds meh write angry letters to the producers and then use tone controls or eq