On several occasions recently, I have
delved into the murky waters of distinctive amplifier "sound." In September, 2002, I described a
series of listening tests I observed in the Fall of 1986, and reported on in the
January, 1987 issue of Stereo Review, in which blind comparisons were performed
among a group of six audio amplifiers, ranging from a cheapo receiver costing a few
hundred bucks to a pair of megadollar mono tube models. The conclusion at that time, as
with other tests I have observed or studied, was that listeners couldn't reliably hear any
differences between the various amps.
Publishing such results always brings the
incredulous to the fore, to point out that the result can't be true. Witness the
harangue by audio journalist Mike Silverton, quoted here in my audio column in
March, 2003. Predictably, others have joined the fray. Here are a couple of reactions:
...Ian G. Masters
You said, "Six amplifiers were auditioned, ranging
from a $200 cheapo receiver to a $12,000 pair of mono tube amplifiers." What you fail
to mention, and what makes me a little suspicious, is which amp was paired with what other
amp. Did each pair of listeners get a chance to listen to all six amps? From the way this
article is worded you could have paired the $200 cheapo with a $600 amp, then a $2000 amp
with a $4000 amp, and finally, an $8000 amp against the $12,000 pair. Then I might agree
[differences] would be hard to discern.
But you can't tell me there wasn't an amazing difference
when comparing the $200 cheapo and the $12,000 pair. The only way to get a true reading is
by pairing the lowest with the best, back to back, without confusing the listener with the
middle amps. Most people may not be able to tell the difference between a $600 amp and a
$3000 amp, but I would be willing to bet that anyone could tell the difference between a
$200 amp and the $12,000 pair.
...R. Wilgus
I'd take you up on that, except I'm not a betting man.
There wasn't a lot of room in my description to go into the details of the test, but I
should point out that some 25 listeners were involved, including many who were very
experienced, and many of those who believed that distinctive amplifier sounds were a
reality. All had the opportunity to criticize (and, potentially, modify) the test
procedures -- none did. Dozens of comparisons were performed, and almost all combinations
of amplifiers were tried. For reasons of time, there was less concentration among the
mid-priced amplifiers, which most listeners expected would sound pretty much alike anyway,
and most time was spent listening to the extreme models. More comparisons were performed
between the cheapo and the mono tube jobs than any other pair -- obviously that would be
the most contentious situation -- and no, "there wasn't an amazing difference when
comparing the $200 cheapo and the $12,000 pair." There was no reliably measurable
difference at all.
...Ian G. Masters
I just read your article on amplifier sound and while I
think that the differences in the sounds of amplifiers are much exaggerated, if you listen
carefully for differences you are sure to find them.
I am a PhD chemist and so I approached this from a
different perspective than most who engage in the hobby (not those who actually design the
equipment, however). My original assumption was that similarly measuring components,
whether they are solid state or tube, would in fact sound similar and that given this
premise, power, features and warranty were more important. In fact, at one time I was an
avid reader of Stereo Review and I believe I even read the article you describe
(although now my memory fails me as to the details since I no longer have this issue).
Over the years of trying several different components and
many amps, I have now been convinced by my ears that there is a sonic difference
between amps and that it is not just a snow job by all the manufacturers and sales people.
I think the ear is very sensitive to very little things,
including usually ignored issues like phase shifts. Now I am sure that in a double-blind
session where I am hearing snippets of the same pieces over and over I cannot pick one amp
out from another. In fact, it would probably be difficult to pick out one top violinist
from another playing the same pieces in snippets using the same methodology. Memory for
this kind of thing is not so good.
I think it is because the differences are small that the
memory has such difficulty, and why living with a component over time reveals
characteristics that you can either live with or not. Determining the sound of an amp is
more like telling the difference between vintages from the same winery or detecting the
type of wood the wine was stored in. The "experts" can do this but perhaps can
be easily fooled since they haven't tasted all the tastes (and odors since this actually
plays a bigger role in the "taste" of a wine) that exist. Tasting different
types of wine is more like listening to different speakers. The differences are much more
obvious.
The situation is 1000 times (at least) worse for amps. Only
under critical conditions can one easily hear the differences, as they are generally much
smaller than with speakers. I am convinced, however, that they do exist and that the
statistics in this case don't actually tell very much with regard to whether something
sounds different or not.
Also, how an amp handles complex music is of interest. An
amp is not just amplifying one frequency at a time but multiple frequencies at varying
amplitudes. This means that many amps are much closer to clipping (or periodically going
into clipping on peaks, especially on noncompressed music) than many people would like to
believe. So the dynamic behavior of an amp is much more important than its "steady
state" RMS values. I think this is why many people find lower-powered tube amps
agreeable (higher voltage swings are generally possible along with easier clipping) and
find them more "powerful" for a given power rating. Also, the nature of the
harmonics, in addition to the level, is critical.
I would like to end by saying that even though you haven't
seen "proof" by way of statistics I think you should look at what those
statistics are really telling you. They are saying that you can't pick an amp out of a
"line up," not that the amps don't sound different. I am a scientist but I also
know the weaknesses of using the statistical argument. Also, human psychology plays a very
big role in these tests and from what I have seen it has not yet been reduced to a
science, nor is it likely to be in the near future.
It seems you have sacrificed your ears and your trust in
your senses (yes, I know that they can be fooled, which is what stereo reproduction or
surround sound is all about, right?) in the name of "science," whereas I
discovered mine in spite of it.
...Brad Morrical
An elegant argument from someone who has thought a lot
about it, and I thank you for sharing your insights. But the simple fact is that the
experiment was not designed to quantify differences or to describe them, but simply to
find out whether the listeners were able to detect any differences at all. And the
results, taking the listeners individually and as a group, and among all the combinations
of amplifiers that were tried, indicated that choices made were no better than pure
chance. They were, therefore, guesses.
I concluded my original report with "This is just the
beginning -- few scientists would place a great deal of weight on the results of a single
experiment, however extensive, and particularly not a first one. Our techniques must, and
will, be refined, and a larger body of data will be collected as more such tests are
performed in the years to come . . . But for now, for us, the evidence would seem to
suggest that . . . there are still differences between amps, but we are unlikely to hear
them." A number of further tests have been performed in the ensuing years, and they
haven't served to contradict our earlier findings.
The vehemence of audiophiles' reactions is not
really surprising, of course. In his editorial introducing my original article, Stereo
Review editor-in-chief William Livingstone said, "There is an Arab proverb that
says: The truth angers those whom it does not convince." Nothing in my experience has
validated the accuracy of that old saying so clearly as some of our listening tests of
audio equipment.
...Ian G. Masters
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