Multitone vs wideband sinad

[EngineerNate]

Does the multitone test plot show everything "audible" in the range shown?

Take the 3A Audio A7 results for example. Comparing the 5khz curve to the multitone result at 5/10/15khz there is a significant gap in THD+N. Is all of that harmonic distortion > 20khz? I would have expected higher 2nd and 3rd harmonics for the frequencies in the 1-8khz range to make the two graphs match more at the same output level. I am curious what parts of the signal are/aren't captured in each of these to improve my understanding.

 

[DonH56]

You must remember that the distortion plots do not include all the noise and intermodulation distortion you can see in the multitone plot, and also that the results of the distortion plots are essentially the sum (RSS'd, actually) of all the harmonic distortion terms (plus whatever noise falls in the harmonic bins) for each frequency. The multitone plot also cuts off at 20 kHz, so you do not see harmonic distortion spurs from anything above 10 kHz. Finally, the power level of each individual tone in the multitone plot is much smaller than a single sine wave, since you must allow for large peaks when the series of tones occasionally "lines up" to produce higher signal levels. The average signal level of each (individual) tone in a 5 W aggregate (average power) multitone signal is much less than the level of a single-frequency tone producing the same (5 W average) power. They are not really comparable.

HTH - Don

 

[EngineerNate]

You must remember that the distortion plots do not include all the noise and intermodulation distortion you can see in the multitone plot, and also that the results of the distortion plots are essentially the sum (RSS'd, actually) of all the harmonic distortion terms (plus whatever noise falls in the harmonic bins) for each frequency. The multitone plot also cuts off at 20 kHz, so you do not see harmonic distortion spurs from anything above 10 kHz. Finally, the power level of each individual tone in the multitone plot is much smaller than a single sine wave, since you must allow for large peaks when the series of tones occasionally "lines up" to produce higher signal levels. The average signal level of each (individual) tone in a 5 W aggregate (average power) multitone signal is much less than the level of a single-frequency tone producing the same (5 W average) power. They are not really comparable.

HTH - Don

Ah! The difference between 5w at 5khz sine vs 5w distributed over multiple tones wasn't immediately obvious to me. Thank you!