In article , Nick Gorham
wrote:
Eiron wrote:
I was looking at 'Audio Electronics' by the late John Linsley Hood
this morning while waiting for the newspaper to arrive, and was
amused by this:

" Experiments in the late 1940s suggested that the level of audibility
for second and third harmonics was of the order of 0.6% and 0.25%
respectively, and this led to the setting of a target value, within
the audio spectrum, of 0.1% THD, as desirable for high quality audio
equipment. However, recent work aimed at discovering the ability of an
average listener to detect the presence og low order (i.e. second or
third) harmonic distortions has drawn the uncomfortable conclusion
that listeners, taken from a cross section of the public, may rate a
signal to which 0.5% second harmonic distortion has been added as
'more musical' than, and therefore preferable to, the original
undistorted input. This discovery tends to cast doubt on the value of
some subjective testing of equipment."

So the SET set is right. single-ended valve amps are officially 'more
musical'.


The interesting thing there, is the statement that because it seems some
may prefer 2nd harmonics, this means that it "casts doubt on subjective
testing", not that it casts doubt on the validity of the measurement of
distortion :-)

I am not sure that is the correct interpretation of the wording. However I
haven't checked the context.

When the above says "may rate a signal" the implication seems to me that
this varies according to either the individual and/or the specific material
being played. Note the word "may", not "will".

The point then would be that it "casts doubt" on subjective testing because
the subjective opinions expressed may not be useful to the reader of said
opinions, for reasons not made clear in the report of the subjective
testing report.

FWIW This has always seemed to me to be a critical weakness of many
'subjective reviews'. Even if they reliably describe the opinions of the
reviewer, it is not clear if the reader would agree with them. Any
differences in circumstances or personal details might make the subjective
comments worthless to the reader. and they might have no way to judge...

Unless, of course, they do their own assessement. But if the 'test report'
is so unreliable as to mean we have to always do this, then the review in
practice has zero useful content for readers. What point is there in a
'subjective report' from someone else if we find that it is just as
likely to mislead us as not, so we end up having to decide for
ourselves, regardless of such reviews.

The above tends to be made worse when said reviews don't employ any
sensible experimental protocol. Then, the conclusions in the report
of the review might actually not even be valid for the reviewer,
either, as they may simply be misleading themselves.

The view that some people may prefer the results when some form of
nonlinarity (or other systematic alteration) is imposed isn't exactly a
revelation, though. People have been commenting on this for decades so far
as I can recall.

Above said, I have reservations about some of the tests which have led
to 'conclusions' like the above. For example: How did they ensure the
speakers they used provided levels of nonlinearity way below the levels
they were trying to assess? It is all to easy when people run such 'tests'
to focus on one area and forget others that may be affecting (or even
swamping) what they are doing.

In other words, the people who prefer the distortion are wrong, and they
should be ignored. And it clearly indicates that his goal was the
production of an amplifier that measured well, not one that people liked
to listen to.

As above, it would depend on how you interpret his wording. :-)

Slainte,

Jim

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