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RE: harmonics added

Posted by dave slagle on September 20, 2021 at 15:45:40:
I am specifically looking for a citing in support of the following statement:
The 2nd and 3rd are relatively innocuous so the ear can tolerate a lot of it.
this seems to suggest they are on equal footing and 1% 2nd is equivalent to 1% third. My experience has been that even order distortions are "friendlier" than odd and as the order increases the level of distortion needs to go down substantially to avoid objectionable sonics.
In respect to Nelson's 2d generator, I am having a hard time understanding what he actually means by the phase of the H2. As near as I can tell he is operating under the belief that there will already be some H2 in the signal and by adding additional H2 from an external source the phase relationships of the two are important.
I dove into spice and built a simple 300B stage that has 1.3% distortion with this spectra.

I then attenuated the signal to make it a unity gain stage and fed it to the grid of a second 300B operating in the same manner. I could then reverse the phase of the two "H2 generators" to illustrate what I believe to be the two conditions (H2+ and H2-) that nelson is referring to and came up with these two spectra.

if we then compare these harmonic profiles to nelsons genral tonal description things become much more (or less??) clear
from listening tests we learn that there is a tendency to
interpret negative phase 2nd as giving a deeper soundstage and improved localization than
otherwise. Positive phase seems to put the instruments and vocals closer and a little more
in-your-face with enhanced detail.
It does seem to me that this is not a 100% direct correlation to exactly what nelson is discussing but I cannot envision how the phase of any given distortion spectra is relevant until it is combined with another spectra so you can get sum and difference effects. The biggest 2nd order generator in a system is typically the air speaker driver interface so none of this exists in a vacuum.

dave