I was reading the post by Nelson Pass about the BA3 amplifier and the whole post was THE most wonderfully written explanation of the circuit I have ever read in my entire life. Very easy to understand when so many articles you read from electronic engineers are very poorly written from a layman's perspective. I did have a question about the THD diagram as I still do not understand how to read the plot. Nelson Pass states that you can clearly see the distortion is of 3rd harmonic????
http://www.diyaudio.com/forums/images/articles/archive/fig10.jpghttp://www.diyaudio.com/forums/images/articles/archive/fig10.jpg
http://www.diyaudio.com/forums/images/articles/archive/fig10.jpghttp://www.diyaudio.com/forums/images/articles/archive/fig10.jpgThe upper sine waveform is that of the input signal. The lower waveform is that of the output with the input waveform subtracted, which would be the resultant distortion to the signal. The resultant waveform is sine-like and its frequency is three times that of the input so it is predominantly third harmonic. If the frequency was two times the input waveform frequency, it would be second harmonic, and so on.
Between the two positive peaks (one period) of the output waveform,
there are 4 (negative) peaks (three periods) of the distortion waveform.
So, third harmonic. This is easy to see here because the distortion is
mostly third harmonic.
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