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Old 7th February 2015, 12:23 PM   #1
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Default LTSpice Error Log THD values

I just noticed the LTSpice error log states two different THD values. Summing the squared normalized components and taking the square root in Excel gives 0,00000143047276833332% so the first value seems to be the correct one.

Now what is the second value in ()?

Interestingly the amplifier's measured performance is much much worse and closer to the value in brackets. I'm confused now


Harmonic Frequency Fourier Normalized Phase Normalized
Number [Hz] Component Component [degree] Phase [deg]
1 1.000e+03 9.669e+00 1.000e+00 -0.06 0.00
2 2.000e+03 1.203e-07 1.244e-08 -76.56 -76.50
3 3.000e+03 6.289e-08 6.505e-09 107.36 107.42
4 4.000e+03 1.560e-08 1.613e-09 -79.82 -79.76
5 5.000e+03 1.203e-08 1.244e-09 13.66 13.72
6 6.000e+03 1.280e-08 1.324e-09 150.68 150.74
7 7.000e+03 4.926e-09 5.095e-10 -170.64 -170.58
8 8.000e+03 5.076e-09 5.250e-10 3.96 4.02
9 9.000e+03 9.867e-09 1.020e-09 -3.43 -3.37
10 1.000e+04 1.942e-09 2.009e-10 133.98 134.04
Total Harmonic Distortion: 0.000001%(0.000207%)
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Old 9th February 2015, 07:21 PM   #2
Mooly is online now Mooly  United Kingdom
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This is the official answer,

What's LTspice doing there?
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Old 12th February 2015, 08:07 PM   #3
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Thanks for the answer. Including the 200th (!) harmonic makes the two figures equal. God knows what the second figure could be useful for.
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Old 12th February 2015, 08:21 PM   #4
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You're welcome
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