Archimego's Harmonic Distortion internet blind test.

[Jean-Marie]

Given that measurement tradition would have it that the performance of the measuring instrument needs to be at least an order of magnitude better than the device under test, distortion in this case, and the measuring instrument here is speaker/room/ear I would not expect low levels of distortion to be heard, personally, rather than imagined.
Very, very few speakers have mid band distortion of 0.1% or better, which is -60dB so expecting being able to consistently detect less than 1% distortion by listening goes against established norms.

If I set my volume control at a nice listening level with a -15dB signal, which is probably about the average of most non classical music (or non loudness wars at the other end of the scale) I can just hear a -75 dB signal in room.
The idea that I would actually be able to detect this barely audible level of sound added to actual music is absurd to me.

After my experience, post retirement, of careful level matched blind (I get my daughter to make the changes) comparisons at home most of my existing held beliefs about telling kit apart by listening have been debunked.
I still hear clear differences between microphones, record players and speakers though.
All the differences I thought existed between my very expensive cables and cheap adequate ones evaporated when I didn't know which I was listening to what a lot of money I have wasted.
It was before I went Devialet but comparing DACs, from the one in my Metric Halo recorder to a Linn Klimax all the differences I was sure i heard disappeared when the levels were matched and I didn't know which was being used.
I did hear differences between power amplifiers, but all were explainable by clipping, very high distortion in bass or by the frequency response alteration caused by high output impedance in transformer coupled valve amps and amps with low levels of feedback.

Nowadays if the distortion is better than 0.1% and SNR better than -80dB I expect a device will be audibly transparent to me playing music recordings through superb speakers in a domestic room.

I am much more relaxed now since I always hated evaluating kit when I could be listening to music.

^
|_______ This a thousand times!

cheers,

jean-Marie