I’m also worried about how much of the harmonics in the music is LOST by the amp?

@Georgehifi - great link, thank you. The comments below the video from Paul and others are worth reading too. 

While it's easy to measure THD, is it even theoretically possible to measure loss of harmonic information?

But in a long chain of gear, it would be amazing to know what's getting lost where. At least with the final step, comparing speakers to headphones is one option. 

If we can’t measure the musical information lost throughout the chain, the measurements we do have about what gets added in terms of distortion are a smokescreen.  If you lose 25%, but add negligible distortion, you pretty much still suck.  Right?

I mean, signal to noise ratio would seem to be the most relevant stat in common usage, right?

A very strong SNR of 120dB is almost certainly beyond audible range, but could be important for the fragile harmonics.  I’m sure there are people here who know this scientifically.

@kennyc - my point isn’t that measurements trump listening, it’s that the measurements we generally rely on, like THD, are so basic and uninformative.  While less distortion is better, wouldn’t it be great to see a measurement of harmonic richness or degradation?  Whether a speaker, dac, amp, or cable?

@tweak1 - indeed.  My new silver ICs from Darwin cables are recent proof of this!

@kennyc - hah! 

@pedrob - thanks for the advice. I've always been curious what an extra grounding system would do, for instance. And some shielding plugs has also been recommended. I like that idea too. 

@atmasphere if amps are not losing harmonic information wholesale, are the other components and cables generally more prone to losing it? Or is my worry about lost harmonics not necessary, and distortion the main culprit through the chain?