[BaronKyle]

Why do tubes tend to create even order harmonics, but solid state can make a lot of the odd order variety?

[Guy 13]

Yes, I would also like to know. 

Guy 13

[Freo-1]

Check out this thread:  (Read Warren's write up #5)

https://www.physicsforums.com/threads/vacuum-tube-amps-vs-solid-state.133967/

[daves]

There are single ended tube amps, and push-pull tube amps.
Single ended normally do not use any feedback, so the output tube is providing the full amplitude wave. Most prominent divergent harmonics are even ordered, and if I remember, the second harmonic will have up to about 35% of the energy of the fundamental, and the fourth harmonic will have up to about 2% of the energy of the fundamental. This pretty much corresponds to the same harmonic structure acoustic instruments display, and rounds out the fundamental note as in nature.

In push-pull feedback the two output devices operate in antiphase (i.e. 180° apart). The two antiphase outputs are connected to the load in a way that causes the signal outputs to be added, but distortion components due to non-linearity in the output devices to be subtracted from each other; if the non-linearity of both output devices is similar, distortion is much reduced. Symmetrical push–pull circuits must cancel even order harmonics, like f2, f4, f6 and therefore promote odd order harmonics, like (f1), f3, f5 when driven into the nonlinear range.

Virtually all SS devices besides Class A amps run either local, global, or some combination of these two feedbacks, so the odd order harmonics survive and prosper.

Because the odd order harmonics are both non linear and do not represent natural harmonics, our ears have a logrithmic ability to discern them. Even a non-musician can pick out when a piano key in a scale exercise is out of tune.

[michaelhigh]

There are single ended tube amps, and push-pull tube amps.
Single ended normally do not use any feedback, so the output tube is providing the full amplitude wave. Most prominent divergent harmonics are even ordered, and if I remember, the second harmonic will have up to about 35% of the energy of the fundamental, and the fourth harmonic will have up to about 2% of the energy of the fundamental. This pretty much corresponds to the same harmonic structure acoustic instruments display, and rounds out the fundamental note as in nature.

In push-pull feedback the two output devices operate in antiphase (i.e. 180° apart). The two antiphase outputs are connected to the load in a way that causes the signal outputs to be added, but distortion components due to non-linearity in the output devices to be subtracted from each other; if the non-linearity of both output devices is similar, distortion is much reduced. Symmetrical push–pull circuits must cancel even order harmonics, like f2, f4, f6 and therefore promote odd order harmonics, like (f1), f3, f5 when driven into the nonlinear range.

Virtually all SS devices besides Class A amps run either local, global, or some combination of these two feedbacks, so the odd order harmonics survive and prosper.

Because the odd order harmonics are both non linear and do not represent natural harmonics, our ears have a logrithmic ability to discern them. Even a non-musician can pick out when a piano key in a scale exercise is out of tune.

This is why daves is my friend.

Humble and smart. Knowledgeable when called upon, and a silly fool most the other time. 

[Guy 13]

There are single ended tube amps, and push-pull tube amps.
Single ended normally do not use any feedback, so the output tube is providing the full amplitude wave. Most prominent divergent harmonics are even ordered, and if I remember, the second harmonic will have up to about 35% of the energy of the fundamental, and the fourth harmonic will have up to about 2% of the energy of the fundamental. This pretty much corresponds to the same harmonic structure acoustic instruments display, and rounds out the fundamental note as in nature.

In push-pull feedback the two output devices operate in antiphase (i.e. 180° apart). The two antiphase outputs are connected to the load in a way that causes the signal outputs to be added, but distortion components due to non-linearity in the output devices to be subtracted from each other; if the non-linearity of both output devices is similar, distortion is much reduced. Symmetrical push–pull circuits must cancel even order harmonics, like f2, f4, f6 and therefore promote odd order harmonics, like (f1), f3, f5 when driven into the nonlinear range.

Virtually all SS devices besides Class A amps run either local, global, or some combination of these two feedbacks, so the odd order harmonics survive and prosper.

Because the odd order harmonics are both non linear and do not represent natural harmonics, our ears have a logrithmic ability to discern them. Even a non-musician can pick out when a piano key in a scale exercise is out of tune.

Hi Daves,
that a super good explanation. 
Thanks.

Guy 13