Jim Lesurf wrote:
In article , Rob
wrote:
Jim Lesurf wrote:


Is your concern simply that the evidence is based only on all the
cases tried? If so, it is open to you or anyone else to collect more
evidence. i.e. to carry out more comparison tests of appropriate kinds.


My concern (such as it is) is simply this: I maintain different modern
SS amplifiers can sound different.

It is essentially self-evident that they 'can'. Indeed, you can choose to
design two amps so that they do. However when people have done tests on
amps that were not specifically designed to do this and which were designed
to amplify, then they tend to be able to distinguishg one from another.
i.e. they are found not to 'sound different'.

But if you choose a design which is - either by deliberate choice or
incompetence - making the output sufficiently different from a scaled
version of the input then it may well 'sound different'.


I wouldn't mean to use or buy an incompetent amplifier. I take it you'd
consider anything from the big names (Sony, Cambridge, Rotel, NAD, Quad,
Behringer etc) to be competent - in the sense that if they did turn out
to be incompetent you'd be surprised.


They are particularly affected by load (speakers) in my extraordinarily
humble opinion. Others (on this NG, not you explicitly so far as I can
tell) maintain this is highly unlikely. For example, I'm pretty sure I
could hear the difference between a Cambridge audio power amp, a
semi-pro power amp, and a Quad 405 power amp.

Well you may be "pretty sure", but the problem is that many people in the
past have been "pretty sure" of similar claims - but then failed to be able
to do what they were "pretty sure" of when tested on the basis of the
sounds in a matter that excluded well known and uncontentious sources of
differences. Thus your belief is simply a statement of faith at this point,
not evidence. Given all the previous failures it isn't clear why anyone
would be wise to take your belief seriously *unless* you put it to such a
test and showed you can do what you believe. Until then...


Well, it's the result of experience. Many people claim similar
experiences. As 'evidence' of 'fact' I'd agree that it's flimsy. Faith?
Belief with reason? Yes, we agree.

I don't think there's much point going over this again. You may not
(hopefully!) remember, but this comes up every six months or so. I'm
simply trying to get across that it's a hypothesis worth testing, and
Serge has kindly offered some practical tips to test the notion. The
problem I have is that technocrats *seem* on occasion rather
condescending towards the opinions of others, without offering a
reasoned explanation for their experience.

Perhaps if I explain it this way - it's not what people think and say,
but why they think and say it, which is of most importance. Do you
*know* (or even have the vaguest idea) why people (like me) experience
these 'physical world anomalies'? I certainly don't *know*.


To do this you would have to define what you mean by "most". i.e. do
you mean more than half of all amps in use, or more than half the
designs, or more than half of those ever used, etc? e.g. can we ignore
the amps in TVs and portable radios and cheap 'music centers'? If so,
we have to define the line that rules in/out a given amp, and give a
plausible basis for doing so.


Again, Serge guided me on this. This issue has been mentioned many
times. 'Most' means virtually all modern SS amps that meet certain
criteria (1).

On such a basis the evidence supports what Serge has been saying. If you
wish to contend with that you will need relevant assessable evidence for
people to take you seriously. Given the history of this topic people will
regard claims of what you are "pretty sure" of as no more than an
unsupported belief of the kind which has in the past repeatedly been shown
to have no foundation.


Again, we've trawled through all of this. It *is* supported, albeit not
with the scientific test *you* require.



I can only point out that "most" (indeed all) the relevant tests I
know of showed no sign that those who listened could distinguish one
amp from another - given a fairly basic set of requirements like level
matching.

I find this virtually impossible to do, even (or because of?) the crude
sound meter I have. I assume the idea is to match levels between 20-20K
Hz?

You don't require a sound pressure meter if you are using the same speakers
and listening position, etc, throughout. You can then use a meter to check
the input voltages to the speakers and ensure they are about the same for
one amp as for the other. If you find differences of the order of 1dB or
more you can expect that to be audible. But if the differences are much
smaller - e.g. around 0.1dB - then that is unlikely to produce an audible
difference. Hence the aim is to make these as small as feasible, and well
below 1dB.


Yes, thanks, Serge helped me on that one as well.

Rob