Most beneficial change .

Interesting two different camps talking about , I assume , the same results . One of tubes and no or very low feedback and the other SS with much more feedback .

I don't believe that any circuitry can opperate without a signature , whether it is added harmonics , tone differences etc. So I am thinking that , as stated , it is what one perceives as a desirable addition .

So harmonic overtones are beneficial and add to the realism of the reproduction . But 2nd and 3rd harmonics are artificially introduced by the amplifier and may or may not be beneficial . Might there be other terms used to describe 2nd & 3rd harmonics , such as warmth ?

Are there ways to determine the existance and amount of these different types of harmonics through printed specifications and/or types of circuitry , or is it a matter of user perception ?

Thank you .

Jylee, what is your evidence that tube amps "add" additional 2nd and 3rd harmonics?

I have heard that tube amps emphasize even order harmonics and that solid state amps emphasize odd order harmonics. I've not heard that either embellishes the music by creating them where they are absent from a recording. It may be true, I just have not heard it put that way and I'm curious as to the source.

Where is Ralph when you need him?

One of the few useful and credible measurements published on the web is Stereophile. Here is a random example of a tube amplifier and a solid state amplifier.

tube amp

Take a look at figure 10. It's a graph of response generated by the amp when the input signal is 50Hz pure sine wave. The vertical axis is normalized to the amplitude of fundamental signal at 50Hz. The 2nd harmonics of 100Hz is seen at -40dB of fundamental, and the 3rd harmonics of 150Hz at -60dB of fundamental.

solid state amp

The response plot of the same signal is shown for a random solid state amp in figure 7. There is almost no 2nd harmonics, and 3rd harmonics is at -90dB of the fundamental.

The relative levels of those harmonics may be low enough, but they are not present in the input signal of pure sine wave, and they are the by product. I've picked random samples, but in general tube amps tend to generate more harmonics, and solid state amps tend to generate less. There are exceptions of course.

Sorry, the link for the solid state amp measurement is here.

solid state amp

In the two test samples, it appears the tube amp adds predominantly second or even order harmonic and the solid state amp adds odd order harmonic (at a comparatively lower level (amplitude?)). It may be worth noting that the authors complained of significant hum in the tube amps tested, which could affect the output, but I'm ready to accept that both tube and solid state amps add harmonics to the source material.

The tests were performed on a 50khz pure sine wave. I am interested in seeing the results of similar test feeding the complex waves of a real instrument, say the strike of an "a" on the piano. Is that test data available comparing a tube amp to a solid state amp?