Ok, I get it. Thanks.

Wow! That means at the levels I listen to music (about 85 to 90dB), I experience about 1.5% THD max (room acoustics excluded)...and that's over a very narrow range of frequencies. Over the majority of the range, THD is about 0.5%. That's incredibly impressive actually. It would be even more impressive if it's all second harmonics .

I'd be curious to know how THD varies at lower SPLs.