Hello, Jim, very interesting - yes, this is the stuff.

A) with different THD spectra for a sinewave we may mean the distortion has
different audible effects )snip)

B) perceived or assumed difference in sound may not be due solely
or primarily to behaviours shown by
a different in the spectra.(snip)

Statement (A) seems to me reasonable as a generalised comment. However (B)
tries to work the argument in the reverse direction

Yes - this seems very reasonable.

1) The distortion measurements do not tell us anything about how the
distortion pattern might vary with the input
sinewave power or frequency. (snip)

Would you be happy introducing the idea of probability here, or induction
rather than deduction? Though not a mathematical proof, a 'risk assessment' may
say that 'it would be more likely that the distortion pattern would
substantially follow that indicated in other conditions'?

2) Real musical waveforms tend not to be pure sinewaves. ~we can't really work
out if the results of distorting more musical signals would be as he assumes.

Idem

3) The actual waveforms may have significantly different features. and
their properties may vary in complex or semi-random ways. e.g. the
violin waveform (snip)

This, on the other hand, seems to show that you would be uncomfortable with
estimating on the basis of probability

4) He does not give any real reasons for accepting that 'MC distortions' are
different to 'MM distortions' (snip)

This may be a different issue, as in your b) clause above.

(2) and (3) mean that the effects of distorting a real musical waveform may
not be as he assumes

does this rule out estimations of probability?

his claims may be a part of the situation, but perhaps may not be the most
significant part.

If his claim about harmonic spectra are 'reasonable per se', could it be said
that while his efforts at proof are not conclusive, neither is there a 'counter
argument' (harmonic spectra have no effect on sound) that is any further on the
road towards proof?

Nor does he provide much evidence to establish that you or I would agree with
his comments on the 'sound' of all the items.

I think you'd say 'if this is taking us into subjective listening tests, don't
go there'?

There may well be later articles that deal with this in a more careful manner,
though.

I'm not sure how much of an academic theorist he is - he certainly designs
circuits. I don't know whether his circuits follow his theory or vica versa
(not that this is a very useful distinction, maybe) Andy



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=== Andy Evans ===
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