I checked, and the manual refers to the biasing in terms of odd and even harmonics. I have a feeling that reflects the way that Cliff thinks about these things because I think piling on harmonics is a way of creating wave shapes that look clipped. There's a chance that is how he programming this stuff with the DSP hardware (that's just a wild guess), so that might be how he explains it. But most people would find the explanation slightly obscure.
I'm not sure about the pedal but I can tell you that in Class A/B the even harmonics are cancelling out. And in A they're there.
As in if you run a 100 Hz sine wave you get well a peak at 100 Hz, as I'm certain you know. Add odd and even harmonics you get the whole series, 1,2,3,4,5,6,7,8,9,10 etc...as in 100,200,300,400Hz etc...in A/B it drops 2,4,6,8,10, etc...
Then there's the how much of any of them which is the finger print of any piece of gear.
Funnily enough this is single notes of instruments that are to very harmonically complex.
You add the 5th regardless of as harmonic or second note and you get in addition to the expected...say the note G and D, a bit sharped for simpler math...100 and 150 Hz together and you would expect to get say on a tube screamer 100, 150, 300, 450, 900, etc... but it also gets you an undertone with those over tones...obviously 50 Hz, and then the row looks like 100, 150, 200, 250, 300, 240, 400, 450, 500 Hz etc...which stems from inter modulation distortion which is the difference of the tones. As in 100 and 150 Hz having the 50 Hz as the frequency where tgatblives and repeats.
Add in the guitars inherent tuning issues and most deigns overtones not being in phase and it gets messy quick especially seeing that the next strong harmonic after the 5th the Class A/B reproduces is the 3rd...thsat's why the higher the gain the more unstable chords that have a bunch of alterations or extensions get funky.
When you look at asymmetric clipping and you get the even harmonics added in at less level than the odd ones. BUT when you have a complex input since the frequency where the even harmonic is has already been occupied by the odd predecessor from the other fundamentals of the input. All that happens is the amplitude of them go up, kinda like the same as cranking the tone up.
