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Re: An actual technical post/question, just for a change of pace....

"An undithered digital system exhibits increasing distortion of a simple sine wave as the signal level drops, with a spectrum that appears to have similar levels of all harmonics."

I don't know what you mean by "system." A *recording* is what is dithered or non-dithered. Playback of the signal does not use any additional dither. The digital filter takes the dithered signal, and converts it to an output signal that is truer to the pre-digitized signal that it would with a non-dithered signal. But then again, a dithered signal will likely sound *worse* on a non-oversampling filter-less DAC.

The distortion indeed increases, but "similar levels at all harmonics" is not really the case, because no distortion contains harmonics that are remotely close to such character or consistency.

"Question: Since this is a numerically-predictable situation, what is the function that describes the distortion spectrum at a given level?"

This might be "numerically-predictable" in theory, but there are so many variables in signal, offset, wave amplitude, frequency, dither techniques, and how DACs handle dither signals, there is really no set "function" for this.

"Are all harmonics present in equal quantities?"

No. And I cannot think of a condition in audio where the answer would ever be "yes."

"If not, what does the envelope look like?"

Once again, there is no definitive answer. For the reasons stated above.

"I was told that a dithered digital system eliminates these harmonics, essentially turning the harmomic distortion components into noise."

Only in the ideal case... Which would imply playback with a true "brickwall" digital filter.... But you would need a recording with optimized dithering and a DAC that perfectly complements the dithered recording. Almost impossible in the real world, since different DACs handle dither differently.

"Question:Is this correct? Is it true that a dithered system exhibits no artifacts that are harmonically-related to the signal?"

The distortion would be reduced, but not close to eliminated. The dither is an enhancement, not a cure-all. And dither is as much an art as it is a science. (Many analog-mastered recordings with tape hiss do not even need applied dither- The tape hiss itself applies the dither.)
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