- Written by Ross Jones
- Published on 07 April 2008
On the Bench
At 1 kHz and 2 volts at the pre-out, THD+N was 0.007%. Clipping (1% THD+N) was reached at 5.65 volts output.
At 1 kHz and 5 volts at the speaker output (two channels driven into 8 ohms), distortion was about the same, but the noise floor was quite a bit higher.
Now, we present a new type of analysis. We asked SpectraPlus toÂ develop a script that will let us calculate the ratio of odd-ordered harmonic distortion to even-ordered distortion. This takes the absolute number (THD+N in percent) one step further and tells us how much of it is odd-ordered (very irritating to the ears) and how much is even-ordered (pleasant to the ears).
So, here is the analysis of the graph shown above for 1 kHz at the pre-out. It shows the amplitude, in dB, of all the harmonics through the 11th, and down at the bottom, the relative amounts of the odd vs. the even-ordered. In this case, the odd-ordered harmonics are 16.64 dB higher in amount than the even-ordered harmonics. Since these are the first analyses that we have performed, we can't say much about the result for now. But, as we test more receivers, SSPs, preamplfiers, and power amplifiers, there will be much more to talk about.
And, here is the harmonic analysis for the speaker output, 1 kHz, 5 volts. In this case, the odd-ordered harmonics are 13.62 dB higher. Keep in mind that one also has to take into account any absoluteÂ distortion value differences, but in this case, THD+N was about the same for the pre-out and the speaker output. So, what this particular comparison says is that the speaker output has a better ratio, as a lower value means less odd-ordered harmonics in relation to the even-ordered harmonics.
At 10 kHz and 2 volts, pre-out, THD+N was, again, about 0.007%.
But at the speaker output, it had risen to 0.01%.