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On 7 Nov 2004 19:55:49 GMT, (Robert C. Lang)
wrote:

Stewart Pinkerton wrote in message ...
On 28 Oct 2004 23:59:55 GMT, (Robert C. Lang)
wrote:

I was not going ignore my personal experience of the 3A in
my system just because Stereophile had given it a glowing review on a
single unit. This is why I, in part, reject your unrelenting reliance
(you have held it up as being an unimpeachable reference several
times) on a single measurement, done on a single hand picked unit,
performed nearly 9 years ago by Stereophile. Scarcely scientific.

I have done no such thing, I have simply pointed to its existence.
That a production sample would have a bass rolloff significantly more
than *ten times* the specified value beggars belief, even for a
'cottage industry' product. Hence, either your perception is wrong,
the unit was *seriously* broken, you somehow wired it up wrongly, or
there is something *very* peculiar about your system, mwhich other
preamps don't reveal. If you have any other explanation, I'm sure we'd
all be happy to know it.

OK, I can't really disagree with your synopsis. Actually, in its
barest form it's a summary that does reflect the possibilities. It
does not, however, comment on the *likelihood* of each possibility. I
wish to add the following comments:

"Hence, either your perception is wrong"

I am appreciative that you lowered the "red flag" from your earlier
comment that remarked, "Your imagination seems to be the most likely
culprit". I believe that of the four possibilities you have listed the
"wrong perception" possibility, given the tangible physical phenomenon
that occurred (or didn't occur) and experienced by me an one other
person, is by far, the least likely.

Obviously I was not present, but IME that remains the most likely
solution.

"or the unit was *seriously* broken"

I agree with the possibility that it was broken. I also believe that
this is the most likely possibility. In this case I'm defining
"broken" as in it didn't meet spec, in my system, for the lowest
octaves" because the unit I sounded great otherwise. It certainly, in
my opinion and according to Audible Illusions, would not meet its
published specs in my system. As you saw Audible Illusions would not
admit that it was broken whether it was or not. But they probably are
the only ones that may really know the truth.

Questions: When a magazine makes a measurement, such as the bandwidth
measurement that "Stereophile" conducted, is the test simulated? Would
such a test always reflect real world load situations? Are these tests
standardized?

If you look up the S'phile review, you'll see that they quote measured
values for input and output impedances of the device, and they also
quote the load values used when measuring FR. These values are all
reasonably to be expected in normal use. The only scenario of which
I'm aware that would have resulted in the effect you report, would be
if a capacitor of less than ten times the required value had
accidentally been fitted to *both* channels of your preamp. Even for a
'cottage industry' product, this seems unlikely. However, *if* we
accept that your report is based on the physical reality of that 23 Hz
note being significantly attenuated, there is no other sensible
explanation. Such a gross error would of course show up immediately AI
checked the unit.

"you somehow wired it up wrongly"

I raised this possibility here in this discussion and with Audible
Illusions when this all took place in February 2000. With Audible
Illusions I went over with them (the engineers) step by step on all
connections, especially as it related to the crossover. My crossover
is at a relatively high 200hz so my thinking is that if I had screwed
up those connections somehow it would be immediately noticeable. Also,
an errant hook it up wrong could have some disastrous consequences. As
it was, as I said in my Audioreview.com comments, the Audible
Illusions passed some *great* overall low bass, just not below 25hz.
(I'm going on Telarc's literature that stated the 90-second organ note
was 23hz). I believe an errant hook up is an unlikely possibility. But
I never ruled it out.

Seemed unlikely to me too, especially since you did not report
problems with any other preamp.

"or there is something *very* peculiar about your system, which other
preamps don't reveal"

Again I appreciate you modifying your previous language in which you
stated "unless there was something *seriously* wrong with your
system", replacing "wrong" with "peculiar" even though a thin line
that may sometimes be. "Peculiar" as a term related to an audio system
is something I can live with. Some audiophiles might consider it a
badge of honor. Some components that have had that label are of
stellar quality. One that comes to mind are your speakers that I have
always held in very high regard but were widely considered peculiar or
quirky because of the alarmingly (for sheepish amplifiers not up to
the workload) low impedances it presented. Interestingly around here
(hometown for Audible Illusions) we have always considered Audible
Illusions to be "quirky" or "peculiar". But it is, nonetheless, well
regarded.

Having said this, my system's components, if the manufacturer's
specifications are to be believed, are plain Jane pedestrian; real
chocolate and vanilla stuff. Although, Mr. Art Ferris of Audible
Illusions thought my system presented a "peculiar" problem for its
line stage. However, as noted other line stages, passive and active,
work fine in my system.

Quite so, which would indicate that there's nothing unusual in the
load presented to the preamp by your system. Hence, we may reasonably
discount this possibility.

--

Stewart Pinkerton | Music is Art - Audio is Engineering