P Floding;172034 Wrote: > I see how you are thinking. > However, you can't extrapolate anything down in level when it comes to > crossover distortion. It's a discontinuity in the transfer curve which > is of equal size regardless of the signal level. It doesn't scale with > the signal. Put a low enough signal in there and it will be 100% > distortion. (Well, depending on exactly how the discontinuity looks.) > > I hope that made it clearer?
Actually you're wrong - that's precisely the case in which my extrapoloation is correct. Suppose the measured amplifier signal is A = A0 + N, where A0 is the ideal (non-distorted) signal, and N is some componenent which doesn't scale with A0. What's plotted is the log of the ratio of the distortion component to the ideal: log((A-A0)/A0) = log(N/A0) = log(N) - log(A0). So the distortion is linear in log(A0), which is indeed what the graph shows, and is exactly what I assumed above. Now that I think about it, you stated before that this was evidence of crossover distortion - actually, it's simply evidence that there's a component to the THD+N which is independent of the power. That is always the case - even with the amp switched off you'll measure some voltage across the outputs due to random noise. On the other hand the FT shows most of the noise is from harmonics, so I suppose that indicates it's related to the signal. -- opaqueice ------------------------------------------------------------------------ opaqueice's Profile: http://forums.slimdevices.com/member.php?userid=4234 View this thread: http://forums.slimdevices.com/showthread.php?t=31843 _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/lists/listinfo/audiophiles
