Differential amp.Do they pass 2nd harmonics or reject them?

[chd_diy]

I've been reading this forum for a while, and have gained a lot of knowledge from the experiences of others who have posted here.
Thank you for sharing your expertise.
Now, on to my question.
I've read a lot about SE tube circuits, and have gathered that they tend to sound better because they don't cancel 2nd harmonics, thereby giving a much fuller and richer tone at the output.
My question is 3 part.
Is a differential amplifier circuit considered a SE or PP?
Do they pass (favor) 2nd order harmonics?
Do they cancel 2nd harmonics?
I'm aware that they reject power supply noise because it does not present a voltage difference at the output, but I'm not sure about 2nd order. Logic sugests that 2nd order passes unobstructed, but I'd like to get confirmation on that thought before building anything.
Thank you for your help.

[Eli Duttman]

A differential amplifer produces 2 out of phase signals that represent the difference of the signals applied to its I/Ps, period. Therefore, non-common mode 2nd order distortion products present in the I/P signal get amplified.

Remember, common mode rejection ratio (CMRR) is a figure of merit for diff. gain blocks.

[Andrew Eckhardt]

Differential amplifiers pretty reliably cancel econd harmonic distortion. It's just two single-ended circuits sharing a common cathode, emitter, or source.

[mashaffer]

A couple of points. The magic of SE probably has more to do with not generating as much of the higher order harmonics (generally speaking) rather than the lack of any cancelation.

Also any distortion products generated before a particular stage of amplification will be passed regardless of stage design. PP amps pass (i.e. transmit) any existing 2nd order distortion it is just that they tend to cancel (to the degree that they are balanced) the 2nd order distortion produced by the two devices in that stage.

[chd_diy]

If I understand the conept correctly, a PP stage (or differential stage) will pass 2nd order harmonics from previous stages, but it will not tend to add 2nd harmonics (in that stage) because the balanced nature of the PP stage will cancel out any additional distortion generated within that stage.
In other words, There is no 2nd harmonics added by PP stages, but they will pass them unobstructed.
Thank's for the info.
Chris.

[SY]

You've got it.

[bear]

Well sort of... the term "no" is not technically correct. It's a question of degree...