Shadorne,
You are on the right track. The reason you cant see it with a THD analyzer is because it is way too subtle to show up. If somehow you alter the gain/velocity by a factor of 2:1 double the velocity! Then your 1khz signal will shift up to 2khz. A full octave away! That is represented by the spike you see on a spectrum analyzer at the 2khz mark. The length of time it spends at this accelerated velocity will determine the size of the spike.
Now imagine a much smaller shift in velocity like 1:1.005
This will cause a 1khz tone to shift up to 1005 hz At this level it is a mere twinkle in the eye of harmonic distortion but is distortion nonetheless. In fact the worse case example (2:1 above) actually had to pass through 1005 hz to get to 2 khz. This is because it is analog and continuous and therefore cannot be in 2 places at once. (Translation) Energy measured at 2khz is missing from the fundamental frequency (1khz) for the length of time it has been shifted. The same is true for the shifted 1005 hz energy.
Roger
You are on the right track. The reason you cant see it with a THD analyzer is because it is way too subtle to show up. If somehow you alter the gain/velocity by a factor of 2:1 double the velocity! Then your 1khz signal will shift up to 2khz. A full octave away! That is represented by the spike you see on a spectrum analyzer at the 2khz mark. The length of time it spends at this accelerated velocity will determine the size of the spike.
Now imagine a much smaller shift in velocity like 1:1.005
This will cause a 1khz tone to shift up to 1005 hz At this level it is a mere twinkle in the eye of harmonic distortion but is distortion nonetheless. In fact the worse case example (2:1 above) actually had to pass through 1005 hz to get to 2 khz. This is because it is analog and continuous and therefore cannot be in 2 places at once. (Translation) Energy measured at 2khz is missing from the fundamental frequency (1khz) for the length of time it has been shifted. The same is true for the shifted 1005 hz energy.
Roger