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Steve[_15_] Steve[_15_] is offline
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Default Do all amplifiers sound the same?

Some time ago the now defunct stereo review had an interesting article
on blind a/b tests between different amplifiers - I saw a reprint
here;

http://bruce.coppola.name/audio/Amp_Sound.pdf

After a hiatus of many years I am now putting together a system and
every one I talk to tells me there is a difference between amplifier
sounds. I am sceptical and in a recent audition could not tell a Creek
EVO from a NAD 325 BEE (through EPOS M12.2 speakers with a Creek cd
source).

Has any more work been done on this subject, esp. blind a/b tests?

Steve
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Randy Yates Randy Yates is offline
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Default Do all amplifiers sound the same?

Steve writes:

Some time ago the now defunct stereo review had an interesting article
on blind a/b tests between different amplifiers - I saw a reprint
here;

http://bruce.coppola.name/audio/Amp_Sound.pdf

After a hiatus of many years I am now putting together a system and
every one I talk to tells me there is a difference between amplifier
sounds. I am sceptical and in a recent audition could not tell a Creek
EVO from a NAD 325 BEE (through EPOS M12.2 speakers with a Creek cd
source).

Has any more work been done on this subject, esp. blind a/b tests?


I can't answer your question, but in my opinion, output impedance is one
of the most important distinguishing features. The lower the amp's
output impedance is over frequency, the better, although this (as
anything) can be taken to extremes. Unfortunately, I don't believe
many manufacturers publish their output impedance, especially over
frequency.
--
% Randy Yates % "She's sweet on Wagner-I think she'd die for Beethoven.
%% Fuquay-Varina, NC % She love the way Puccini lays down a tune, and
%%% 919-577-9882 % Verdi's always creepin' from her room."
%%%% % "Rockaria", *A New World Record*, ELO
http://www.digitalsignallabs.com
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BEAR BEAR is offline
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Default Do all amplifiers sound the same?

Steve wrote:
Some time ago the now defunct stereo review had an interesting article
on blind a/b tests between different amplifiers - I saw a reprint
here;

http://bruce.coppola.name/audio/Amp_Sound.pdf

After a hiatus of many years I am now putting together a system and
every one I talk to tells me there is a difference between amplifier
sounds. I am sceptical and in a recent audition could not tell a Creek
EVO from a NAD 325 BEE (through EPOS M12.2 speakers with a Creek cd
source).

Has any more work been done on this subject, esp. blind a/b tests?

Steve


Amplifiers do not all sound the same.
Some may.
Some do not.
They certainly do not measure the same.

The THD or IM specs do *not* tell the story.

Those who are still doubters, may review Dr. Earl Geddes research on
this subject. It provides the necessary scientific and engineering
basis for the above assertion.

There are a few other 'confounding" factors to account for when
an individual is trying to decide these things:
- there may be masking effects from other parts of the system
(for example a perfectly blameless amp could not be discriminated
from one that was not blameless, if there was sufficient "objectionable"
harmonic signature produced by another element in the system).
- the listener may or may not have physical deficits that prevent
such a discrimination.
- the listener may never have heard a system without many of the
typical "objectionable" artifacts (no basis for comparison).
- there may be other factors, including subsonic sound and ultrasonic
sounds in the environment, excessive reverberation, etc. that
interfere.

As far as "A/B" or "ABX" tests, they are usually valid for the specific test
condition, as made. Suitability of those tests for generalized
application, if they lack controls for at minimum the above factors, and
some others (such as basic THD, IM, polar response, room reverberence,
noise floor, etc...) makes the ones that I have seen published
so far - that is a preponderance of those I am aware of - not meaningful.

Others will disagree, I am sure.

The key to assembling a system that one enjoys listening to depends on
one's thresholds for certain types of "irritants" (and avoiding them),
a bit of luck, serendipity, and in some cases knowledge of matters
technical and acoustic. Money, per se, does not play the major role
in this respect, since there is lots of excellent used gear, and the
possibility of DIY... :_)

_-_-bear
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Greg Wormald Greg Wormald is offline
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Default Do all amplifiers sound the same?

In article ,
Steve wrote:

Some time ago the now defunct stereo review had an interesting article
on blind a/b tests between different amplifiers - I saw a reprint
here;

http://bruce.coppola.name/audio/Amp_Sound.pdf

After a hiatus of many years I am now putting together a system and
every one I talk to tells me there is a difference between amplifier
sounds. I am sceptical and in a recent audition could not tell a Creek
EVO from a NAD 325 BEE (through EPOS M12.2 speakers with a Creek cd
source).

Has any more work been done on this subject, esp. blind a/b tests?

Steve


Steve,

This is two of the topics most likely to generate a lot of heat--amps
sounding different and blind a-b tests.

Before it gets too wild let me put my two cents (Australian) in.

Of course different amplifiers sound different. Since they are made
differently, with different components, and they measure differently,
how could it be otherwise? Whether the differences are significant is a
matter of personal decision. You make your decision and plonk down your
money.

Some will argue that well-made amps that measure the same will sound the
same. This is necessarily true--it is a tautology--assuming that we
measure everything that can be heard.

Blind a-b testing is the gold standard of testing for difference. It
does however have to be done well and usually isn't. Some of the subtle
differences in music reproduction are very difficult to pick, and often
require extensive experience or training to distinguish. As well, some
differences show up after long trials (days, weeks, or months!) and
testing of this longitude are as rare as hen's teeth.

Our auditory memory is very short, and often very inaccurate, and that
is an argument NOT for short duration tests, but for using something
that is longer lasting and more reliable, namely the emotional response
to the music.

I know from my own experience swapping interconnect cables that while I
couldn't pick which cable was in my system at any one listening session,
over months I came to prefer one set--based on my desire to put on
another record and listen more, or turn the music off and do something
else. These preferences were a surprise to me and I performed enough
swaps to make certain.

If you can, audition each amplifier on your list for long enough to know
whether you enjoy the way it produces music. After all, you will be
using it to produce music, not listen to sound.

Greg
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jwvm jwvm is offline
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Default Do all amplifiers sound the same?

On Dec 24, 11:32 am, Steve wrote:
Some time ago the now defunct stereo review had an interesting article
on blind a/b tests between different amplifiers - I saw a reprint
here;

http://bruce.coppola.name/audio/Amp_Sound.pdf

After a hiatus of many years I am now putting together a system and
every one I talk to tells me there is a difference between amplifier
sounds. I am sceptical and in a recent audition could not tell a Creek
EVO from a NAD 325 BEE (through EPOS M12.2 speakers with a Creek cd
source).

Has any more work been done on this subject, esp. blind a/b tests?

Steve


The reprint is a nice summary of the eternal battle between magic and
engineering. Inexpensive but well-engineered amplifiers have
performance specifications that are very similar to (or perhaps even
better than) than very expensive audiophile amplifiers and under
double blind testing will be essentially indistinguishable. The really
weak link in sound reproduction is with respect to loudspeakers. Money
is best spent on good speakers rather than exotic amplifiers.

Similar disputes also continue with D/A converters, cables,
preamplifiers, etc. in which measurements indicate little or no
improvement with high-priced hardware.


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Steven Sullivan Steven Sullivan is offline
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Default Do all amplifiers sound the same?

Steve wrote:
Some time ago the now defunct stereo review had an interesting article
on blind a/b tests between different amplifiers - I saw a reprint
here;


http://bruce.coppola.name/audio/Amp_Sound.pdf


After a hiatus of many years I am now putting together a system and
every one I talk to tells me there is a difference between amplifier
sounds.


Maybe you should talk to more people.

I am sceptical and in a recent audition could not tell a Creek
EVO from a NAD 325 BEE (through EPOS M12.2 speakers with a Creek cd
source).


If levels are matched on all channels, and the system isn't being driven to
distortion, your result is not unusual.

Has any more work been done on this subject, esp. blind a/b tests?


http://www.provide.net/~djcarlst/abx_pwr.htm

see also

E . Brad Meyer
Stereo Review 1991
Are your speakers turning your amplifier into a tone control?
http://www.soundandvisionmag.com/fea...interface.html

___
-S
"As human beings, we understand the world through simile, analogy,
metaphor, narrative and, sometimes, claymation." - B. Mason
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Steven Sullivan Steven Sullivan is offline
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Default Do all amplifiers sound the same?

Greg Wormald wrote:

Of course different amplifiers sound different. Since they are made
differently, with different components, and they measure differently,
how could it be otherwise? Whether the differences are significant is a
matter of personal decision. You make your decision and plonk down your
money.


THe logical fallacy here is that 'measuring different', or using
'different components' must lead to audible difference. It doesn't.

Some will argue that well-made amps that measure the same will sound the
same. This is necessarily true--it is a tautology--assuming that we
measure everything that can be heard.


Blind a-b testing is the gold standard of testing for difference. It
does however have to be done well and usually isn't. Some of the subtle
differences in music reproduction are very difficult to pick, and often
require extensive experience or training to distinguish. As well, some
differences show up after long trials (days, weeks, or months!) and
testing of this longitude are as rare as hen's teeth.


So, where are the careful blind test results done by 'amps sound
different' believers? WHo is doing the assuming here?

Let us take the case of John Atkinson, editor of Stereophile. By his own
account , his Damascene conversion to 'subjectivistm' came after he chose
the 'lesser' of two amps, after he failed to hear a difference between
them in a DBT. After a few weeks of living with it he was dissatisfied,
and upon swapping in the other amp, found it sounded much better. His
conclusion was the blind testing misled him, while living with the gear
-- a 'long trial -- revealed the truth. But he didn't bother to do what
wold be obvious to a scientist -- re-take the blind test *after* the
'acclimation period'. Surely the effect of long expsire doesn't 'go away'
under blind conditions, right?

Btw, Tom Noisaine has done 'long term' trials, and the results were
negative when levels were matched and amps were driven below their limits.

Our auditory memory is very short, and often very inaccurate, and that
is an argument NOT for short duration tests, but for using something
that is longer lasting and more reliable, namely the emotional response
to the music.


You have managed to actually reverse the implication of short aural
memory. It points to using short sound samples during a trial, to gain
best dscrimination of difference.

However, if acclimation is thought to be necessary for best
discrimination, I ask again -- where are the blind test results from
people who make such claims?

I know from my own experience swapping interconnect cables that while I
couldn't pick which cable was in my system at any one listening session,
over months I came to prefer one set--based on my desire to put on
another record and listen more, or turn the music off and do something
else. These preferences were a surprise to me and I performed enough
swaps to make certain.


And then you did a blind test, after you were sure you could hear the
diference...right?

THe fact is, your typical audiophile or high-end magainze reviewer is SURE
they hear a difference, often without any long-term trial. So, are they
folling themselves, or likely to be right?

If you can, audition each amplifier on your list for long enough to know
whether you enjoy the way it produces music. After all, you will be
using it to produce music, not listen to sound.


And again, it's as easy to 'fool' yourself -- perhpas easier, given
possible emotional investment -- after a long trial, as short one, *if*
the comparison is sighted.

___
-S
"As human beings, we understand the world through simile, analogy,
metaphor, narrative and, sometimes, claymation." - B. Mason
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Steven Sullivan Steven Sullivan is offline
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Default Do all amplifiers sound the same?

bear wrote:
Steve wrote:
Some time ago the now defunct stereo review had an interesting article
on blind a/b tests between different amplifiers - I saw a reprint
here;

http://bruce.coppola.name/audio/Amp_Sound.pdf

After a hiatus of many years I am now putting together a system and
every one I talk to tells me there is a difference between amplifier
sounds. I am sceptical and in a recent audition could not tell a Creek
EVO from a NAD 325 BEE (through EPOS M12.2 speakers with a Creek cd
source).

Has any more work been done on this subject, esp. blind a/b tests?

Steve


Amplifiers do not all sound the same.
Some may.
Some do not.
They certainly do not measure the same.


The THD or IM specs do *not* tell the story.


Those who are still doubters, may review Dr. Earl Geddes research on
this subject. It provides the necessary scientific and engineering
basis for the above assertion.


Hopefully it provides the blind test results to demonstrate audible
difference.

There are a few other 'confounding" factors to account for when
an individual is trying to decide these things:
- there may be masking effects from other parts of the system
(for example a perfectly blameless amp could not be discriminated
from one that was not blameless, if there was sufficient "objectionable"
harmonic signature produced by another element in the system).
- the listener may or may not have physical deficits that prevent
such a discrimination.
- the listener may never have heard a system without many of the
typical "objectionable" artifacts (no basis for comparison).
- there may be other factors, including subsonic sound and ultrasonic
sounds in the environment, excessive reverberation, etc. that
interfere.


or, the two amps really do not sound different, when used within their
limits.

As far as "A/B" or "ABX" tests, they are usually valid for the specific test
condition, as made. Suitability of those tests for generalized
application, if they lack controls for at minimum the above factors, and
some others (such as basic THD, IM, polar response, room reverberence,
noise floor, etc...) makes the ones that I have seen published
so far - that is a preponderance of those I am aware of - not meaningful.


Double Blind tests have been and continue to be used by Harman for
generalized application in loudspeaker development.

And amplifier (and cable, btw -- mentioned because you sell 'high end'
cable that you claim sounds better than plain cable) difference tests have
been done where the listener who claimd to hear difference between *his*
gear and others, was tested with his gear, against other gear. And failed
the test.

Others will disagree, I am sure.


The key to assembling a system that one enjoys listening to depends on
one's thresholds for certain types of "irritants" (and avoiding them),
a bit of luck, serendipity, and in some cases knowledge of matters
technical and acoustic. Money, per se, does not play the major role
in this respect, since there is lots of excellent used gear, and the
possibility of DIY... :_)


Have you ever ABX'd differences in amps, and if so, under what conditions,
and what scores did yuou obtain?

___
-S
"As human beings, we understand the world through simile, analogy,
metaphor, narrative and, sometimes, claymation." - B. Mason
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Steven Sullivan Steven Sullivan is offline
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Default Do all amplifiers sound the same?

From Earl Geddes' online book chapters, concerning objective measures and
blind tests

http://www.gedlee.com/downloads/Chapter4.pdf

"If one accepts the fact that subjective evaluations are less reliable
than we would like, then it should be obvious how objective measurements
would play a crucial role in audio. Whatever one might say about
measurements, for the most part they are stable and yield the same results
over and over. something that subjective assessments have trouble doing. I
used to believe that objective measurements alone were all that one
needed, and I still believe that objective measurements can tell us most
of what we need to know about a system or component. I believe that I
could predict the judgement of a panel of blind listeners with an accuracy
of about 90-95% correct from objective data alone. I know one company that
claims a 99.9% accuracy in correlation between objective data and panel
judgements. Objective data should always be the place where one starts
when looking for system components. That is, if one knows how to interpret
the measurements that are available or the data that they are shown. I
find that most people shy away from objective data simply because they
don.t really understand it.

As far as believing that objective data is all that we need, at the
moment, that probably isn.t the case. There are things that we are
learning day-to-day that have a strong bearing on the correlation between
measurements and subjective preference. But that.s also not to say that we
can.t ever get to the point where objective data alone is sufficient. In
fact this point may be closer than you think. What I do find ridiculous is
the position of many that because measurements don.t tell us the complete
story that they are of no use at all, that listening alone is the only way
to truth - that 'Measurements can.t tell us what we hear'.. I personally
love that one."

In other words, Geddes finds the mainstream 'audiophile' view of
evaluation, where 'sighted listening trumps all' , to be *ridiculous*.

Me too.

___
-S
"As human beings, we understand the world through simile, analogy,
metaphor, narrative and, sometimes, claymation." - B. Mason
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Sonnova Sonnova is offline
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Default Do all amplifiers sound the same?

On Tue, 25 Dec 2007 08:39:58 -0800, Randy Yates wrote
(in article ):

Steve writes:

Some time ago the now defunct stereo review had an interesting article
on blind a/b tests between different amplifiers - I saw a reprint
here;

http://bruce.coppola.name/audio/Amp_Sound.pdf

After a hiatus of many years I am now putting together a system and
every one I talk to tells me there is a difference between amplifier
sounds. I am sceptical and in a recent audition could not tell a Creek
EVO from a NAD 325 BEE (through EPOS M12.2 speakers with a Creek cd
source).

Has any more work been done on this subject, esp. blind a/b tests?


I can't answer your question, but in my opinion, output impedance is one
of the most important distinguishing features. The lower the amp's
output impedance is over frequency, the better, although this (as
anything) can be taken to extremes. Unfortunately, I don't believe
many manufacturers publish their output impedance, especially over
frequency.


Output impedance is one of many criteria. Mostly, it affects damping factor
for the loudspeakers. The way I understand it is If a dynamic speaker is
looking down it's cable into the output stage of an amplifier and sees, what
is in essence, a dead short, the cone will stop instantly when the signal
stops, because of the back EMF being generated by the shorted voice coil in
the speaker's magnetic field (try this experiment: Get a raw driver and flex
the cone by hand at the dust cap. Then connect the terminals of the speaker
together with a jumper and flex the cone again. Notice how much more
difficult the cone is to move this time. That's the phenomenon behind
regenerative dampening) But even this is an oversimplification. In reality,
most speaker voice coils are looking into an inductor in the crossover and
the resistance of the speaker cable before it sees the output stage, so its
anybody's guess how much a low output impedance actually affects the overall
result.

Frankly, I think that the sound of an amplifier is more a result of the
complex load presented by the speaker system that it's driving than the
speaker's sound is influenced by the amplifier.


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Sonnova Sonnova is offline
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Default Do all amplifiers sound the same?

On Tue, 25 Dec 2007 08:44:45 -0800, bear wrote
(in article ) :

Steve wrote:
Some time ago the now defunct stereo review had an interesting article
on blind a/b tests between different amplifiers - I saw a reprint
here;

http://bruce.coppola.name/audio/Amp_Sound.pdf

After a hiatus of many years I am now putting together a system and
every one I talk to tells me there is a difference between amplifier
sounds. I am sceptical and in a recent audition could not tell a Creek
EVO from a NAD 325 BEE (through EPOS M12.2 speakers with a Creek cd
source).

Has any more work been done on this subject, esp. blind a/b tests?

Steve


Amplifiers do not all sound the same.
Some may.
Some do not.
They certainly do not measure the same.


That is true.

The THD or IM specs do *not* tell the story.


That is correct. Up to a certain point, both seem to be relatively
unimportant. Research has shown that humans aren't very sensitive to the
harmonic and IM distortion produced by amplifying devices. Back in the
"golden era" of tube hi-fi, manufacturers would outdo themselves trying to
get the most zeros between the decimal point and the numbers. This made them
bias their tubes far into the linear portion of the tube's transfer curve.
This lowered distortion all right, but it made the tubes run very hot and
self-destruct with alarming rapidity. After it was found in double-blind
tests that levels up to over 1% in amplifiers were undetectable by humans,
manufacturers started backing off on output bias. over the last thirty years
or so, we have seen the life of output tubes increase dramatically from a
mere few hours to many thousands of hours over a number of years. Of course,
the tradeoff is that harmonic and IM levels have gone from 0.001% to 0.1% or
even higher. Nobody notices.
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Sonnova Sonnova is offline
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On Tue, 25 Dec 2007 08:47:44 -0800, Greg Wormald wrote
(in article ) :

In article ,
Steve wrote:

Some time ago the now defunct stereo review had an interesting article
on blind a/b tests between different amplifiers - I saw a reprint
here;

http://bruce.coppola.name/audio/Amp_Sound.pdf

After a hiatus of many years I am now putting together a system and
every one I talk to tells me there is a difference between amplifier
sounds. I am sceptical and in a recent audition could not tell a Creek
EVO from a NAD 325 BEE (through EPOS M12.2 speakers with a Creek cd
source).

Has any more work been done on this subject, esp. blind a/b tests?

Steve


Steve,

This is two of the topics most likely to generate a lot of heat--amps
sounding different and blind a-b tests.

Before it gets too wild let me put my two cents (Australian) in.

Of course different amplifiers sound different. Since they are made
differently, with different components, and they measure differently,
how could it be otherwise? Whether the differences are significant is a
matter of personal decision. You make your decision and plonk down your
money.

Some will argue that well-made amps that measure the same will sound the
same. This is necessarily true--it is a tautology--assuming that we
measure everything that can be heard.


Isn't that the "rub" as Shakespeare would say?

Blind a-b testing is the gold standard of testing for difference. It
does however have to be done well and usually isn't. Some of the subtle
differences in music reproduction are very difficult to pick, and often
require extensive experience or training to distinguish. As well, some
differences show up after long trials (days, weeks, or months!) and
testing of this longitude are as rare as hen's teeth.

Our auditory memory is very short, and often very inaccurate, and that
is an argument NOT for short duration tests, but for using something
that is longer lasting and more reliable, namely the emotional response
to the music.


Exactly. People talk about "calibrating their ears" by listening to as much
live music as possible. Human auditory memory is so short, that it has been
found that just a couple of hours after a concert, the listener has already
reverted to his personal "taste" in sound, I.E. what type of bass he likes,
how much presence in the midrange, what kind of highs ring his bell, etc. It
has also been suggested that the female of the species has a far better
auditory memory than the male....
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Sonnova Sonnova is offline
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On Tue, 25 Dec 2007 08:48:47 -0800, jwvm wrote
(in article ) :

On Dec 24, 11:32 am, Steve wrote:
Some time ago the now defunct stereo review had an interesting article
on blind a/b tests between different amplifiers - I saw a reprint
here;

http://bruce.coppola.name/audio/Amp_Sound.pdf

After a hiatus of many years I am now putting together a system and
every one I talk to tells me there is a difference between amplifier
sounds. I am sceptical and in a recent audition could not tell a Creek
EVO from a NAD 325 BEE (through EPOS M12.2 speakers with a Creek cd
source).

Has any more work been done on this subject, esp. blind a/b tests?

Steve


The reprint is a nice summary of the eternal battle between magic and
engineering. Inexpensive but well-engineered amplifiers have
performance specifications that are very similar to (or perhaps even
better than) than very expensive audiophile amplifiers and under
double blind testing will be essentially indistinguishable. The really
weak link in sound reproduction is with respect to loudspeakers. Money
is best spent on good speakers rather than exotic amplifiers.


Agreed. Many component manufacturers are, I believe, aware that there is
little difference above a certain engineering level and seek to distinguish
their brand (and justify its price) by using every "expensive" looking
cosmetics. Thick, brushed aluminum front panels, chromed transformer
end-bells, fancy receptacles and jacks, etc.

Similar disputes also continue with D/A converters, cables,
preamplifiers, etc. in which measurements indicate little or no
improvement with high-priced hardware.


Now it's not true that everything sound alike and an outboard D/A converter
might very well sound better than the D/A that comes in a stand-alone CD
player because the D/A in the player is fraught with design compromises that
the outboard D/A may not be.

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Arny Krueger Arny Krueger is offline
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Default Do all amplifiers sound the same?

"Greg Wormald" wrote in message
om

Of course different amplifiers sound different. Since
they are made differently, with different components, and
they measure differently, how could it be otherwise?


Two amplifiers can be different, but sound the same, if their deficiencies
are smaller than that which can be reliably heard. This happens all the
time.

Whether the differences are significant is a matter of
personal decision.


Not if the differences are too small to be audible. You have no choice -
they have no audible signficance to you.

Some will argue that well-made amps that measure the same
will sound the same.


The myth here is that two amps could measure the same. Even each channel of
a stereo amplifier will measure differently, given sufficiently accurate
measuring gear.

This is necessarily true--it is a
tautology--assuming that we measure everything that can
be heard.


Reality is that we can readily measure things that we have not a chance of
hearing. There have been no reliably observable exceptions for decades.

Blind a-b testing is the gold standard of testing for
difference. It does however have to be done well and
usually isn't.


Compare that to sighted evaluation with is never done well, because there is
no way to do it well.

Some of the subtle differences in music
reproduction are very difficult to pick, and often
require extensive experience or training to distinguish.


Interesting that people don't seem to need any extensive training or
experience to hear differences in sighted evaluations.

As well, some differences show up after long trials
(days, weeks, or months!) and testing of this longitude
are as rare as hen's teeth.


The point is that people obsess over the problems with blind tests, and the
inherently flawed results of sighted evaluations with nary a concern.

Our auditory memory is very short, and often very
inaccurate, and that is an argument NOT for short
duration tests,


?????????????????

but for using something that is longer
lasting and more reliable, namely the emotional response
to the music.


That's an unproven assertion.

I know from my own experience swapping interconnect
cables that while I couldn't pick which cable was in my
system at any one listening session, over months I came
to prefer one set--based on my desire to put on another
record and listen more, or turn the music off and do
something else. These preferences were a surprise to me
and I performed enough swaps to make certain.


Yet another unproven assertion.

If you can, audition each amplifier on your list for long
enough to know whether you enjoy the way it produces
music. After all, you will be using it to produce music,
not listen to sound.


If one is not listening to sound, what is one listening to?

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On Dec 26, 12:01 pm, Sonnova wrote:

snip
Similar disputes also continue with D/A converters, cables,
preamplifiers, etc. in which measurements indicate little or no
improvement with high-priced hardware.


Now it's not true that everything sound alike and an outboard D/A converter
might very well sound better than the D/A that comes in a stand-alone CD
player because the D/A in the player is fraught with design compromises that
the outboard D/A may not be.


Are you saying that D/A converters that provide essentially the same
measurements will still sound different and can be differentiated in
double-blind tests?


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On Dec 25, 11:47 am, Greg Wormald wrote:
Our auditory memory is very short, and often very inaccurate, and that
is an argument NOT for short duration tests, but for using something
that is longer lasting and more reliable, namely the emotional response
to the music.


Sorry, but this is complete nonsense. Before the data passes
into long-term memory, it MUST pass through short-term
memory. If you assertion is that short-term auditory memory
is defective in some way, than long-term memory cannot be
better.

And, in fact, contrary to the fantasies and wishes of any
number of audiophiles, this property of auditory memory
is supported by quite a bit of actual research.
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Sonnova writes:

On Tue, 25 Dec 2007 08:39:58 -0800, Randy Yates wrote
(in article ):

Steve writes:

Some time ago the now defunct stereo review had an interesting article
on blind a/b tests between different amplifiers - I saw a reprint
here;

http://bruce.coppola.name/audio/Amp_Sound.pdf

After a hiatus of many years I am now putting together a system and
every one I talk to tells me there is a difference between amplifier
sounds. I am sceptical and in a recent audition could not tell a Creek
EVO from a NAD 325 BEE (through EPOS M12.2 speakers with a Creek cd
source).

Has any more work been done on this subject, esp. blind a/b tests?


I can't answer your question, but in my opinion, output impedance is one
of the most important distinguishing features. The lower the amp's
output impedance is over frequency, the better, although this (as
anything) can be taken to extremes. Unfortunately, I don't believe
many manufacturers publish their output impedance, especially over
frequency.


Output impedance is one of many criteria.


That's why I said it's one of the most important distinguishing
features and not "it's the only distinguishing feature."

Mostly, it affects damping factor for the loudspeakers.


I think damping factor was an attempt at simplifying output impedance,
so this is a little circular.

The way I understand it is If a dynamic speaker is looking down it's
cable into the output stage of an amplifier and sees, what is in
essence, a dead short, the cone will stop instantly when the signal
stops, because of the back EMF being generated by the shorted voice
coil in the speaker's magnetic field


I have heard of this effect and admit I do not fully understand the
dynamics between back-EMF and output impedance. However, it seems that
such effects are secondary. What seems even more important is that the
correct output voltage is applied to the speaker. A zero output
impedance makes an amplifier an ideal voltage source, i.e., the correct
output voltage will be maintained up to the limits of the current-sourcing
ability of the amplifier.
--
% Randy Yates % "She tells me that she likes me very much,
%% Fuquay-Varina, NC % but when I try to touch, she makes it
%%% 919-577-9882 % all too clear."
%%%% % 'Yours Truly, 2095', *Time*, ELO
http://www.digitalsignallabs.com
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On Dec 26, 11:58 am, Sonnova wrote:
On Tue, 25 Dec 2007 08:44:45 -0800, bear wrote
(in article ) :



Steve wrote:
Some time ago the now defunct stereo review had an interesting article
on blind a/b tests between different amplifiers - I saw a reprint
here;


http://bruce.coppola.name/audio/Amp_Sound.pdf


After a hiatus of many years I am now putting together a system and
every one I talk to tells me there is a difference between amplifier
sounds. I am sceptical and in a recent audition could not tell a Creek
EVO from a NAD 325 BEE (through EPOS M12.2 speakers with a Creek cd
source).


Has any more work been done on this subject, esp. blind a/b tests?


Steve


Amplifiers do not all sound the same.
Some may.
Some do not.
They certainly do not measure the same.


That is true.



The THD or IM specs do *not* tell the story.


That is correct. Up to a certain point, both seem to be relatively
unimportant. Research has shown that humans aren't very sensitive to the
harmonic and IM distortion produced by amplifying devices. Back in the
"golden era" of tube hi-fi, manufacturers would outdo themselves trying to
get the most zeros between the decimal point and the numbers. This made them
bias their tubes far into the linear portion of the tube's transfer curve.
This lowered distortion all right, but it made the tubes run very hot and
self-destruct with alarming rapidity. After it was found in double-blind
tests that levels up to over 1% in amplifiers were undetectable by humans,
manufacturers started backing off on output bias. over the last thirty years
or so, we have seen the life of output tubes increase dramatically from a
mere few hours to many thousands of hours over a number of years. Of course,
the tradeoff is that harmonic and IM levels have gone from 0.001% to 0.1% or
even higher. Nobody notices.


Part of the reason could be coming from the other end: the source has
gotten much cleaner. Before it was vinyl and cassette recordings with
distortion levels magnitudes higher than with digital lossless files
we play today.

On a slightly different note, I found one way to easily distinguish a
lossy audio file from its lossless counterpart: distortion. The
Lossless file will play much louder and cleaner than the lossy file on
the same system.

CD
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Default Do all amplifiers sound the same?

Steve wrote:

Some time ago the now defunct stereo review had an interesting article
on blind a/b tests between different amplifiers - I saw a reprint
here;

http://bruce.coppola.name/audio/Amp_Sound.pdf

After a hiatus of many years I am now putting together a system and
every one I talk to tells me there is a difference between amplifier
sounds. I am sceptical and in a recent audition could not tell a Creek
EVO from a NAD 325 BEE (through EPOS M12.2 speakers with a Creek cd
source).

Has any more work been done on this subject, esp. blind a/b tests?

Steve


Some amplifiers sound different, some don't, depending on what they
are connected to. Don't get hung up about others opinions and blind
tests, there is no definitive answer. Select a few well regarded units
to audition and make up your own mind. With those speakers, the
differences between amps will be subtle compared to a speaker upgrade.

I used to own Epos ES11, worked well with Audiolab 8000A, but I can't
recommend NAIM.

--
S i g n a l @ l i n e o n e . n e t
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"Steve" wrote in message
om...
Some time ago the now defunct stereo review had an interesting article
on blind a/b tests between different amplifiers - I saw a reprint
here;

http://bruce.coppola.name/audio/Amp_Sound.pdf

After a hiatus of many years I am now putting together a system and
every one I talk to tells me there is a difference between amplifier
sounds. I am sceptical and in a recent audition could not tell a Creek
EVO from a NAD 325 BEE (through EPOS M12.2 speakers with a Creek cd
source).

Has any more work been done on this subject, esp. blind a/b tests?


What was your recent "audition"? These things have to be done carefully,
with the exact same system (I assume it was) but also well volume matched
(use a test tone and multimeter to check the voltage output from the amp.)

Also, you'll want to use material that you're very familiar with.
Ultimately the overall resolving power of the entire system (the system
includes the room acoustics) will determine if you can tell a difference (as
well as if there is any discernible difference between the amps, of course.)

Sometime of course you can tell a slight difference, but is one really
better than the other, or just slightly different? Is the difference worth
paying for?

I was able to tell the difference between an Adcom 545 and 555 (voltage
matched of course) every time. Both were operating well below max capacity.
That was enough to convince me there are differences between amps (I don't
even think the company intended there to be any difference here.)



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Default Do all amplifiers sound the same?

"Arny Krueger" wrote in message
...

Some will argue that well-made amps that measure the same
will sound the same.


The myth here is that two amps could measure the same. Even each channel
of
a stereo amplifier will measure differently, given sufficiently accurate
measuring gear.


I don't believe the measuring tests are really that accurate. If you doubt
this, consider: voice recognition is extremely difficult for even the most
sophsticated equipment, yet trivially easy for even children. The same is
true for image recognition. Measurements might be good enough for the cell
phone generation, but that ain't sayin' much.

Theoretically, if it can't be measured it can't be heard. But just because
it can be measured doesn't mean it is being measured.

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Default Do all amplifiers sound the same?

wrote in message
...
On Dec 25, 11:47 am, Greg Wormald wrote:
Our auditory memory is very short, and often very inaccurate, and that
is an argument NOT for short duration tests, but for using something
that is longer lasting and more reliable, namely the emotional response
to the music.


Sorry, but this is complete nonsense. Before the data passes
into long-term memory, it MUST pass through short-term
memory. If you assertion is that short-term auditory memory
is defective in some way, than long-term memory cannot be
better.


Well, short term memory is defective in some way. These things are very
simple and have been known forever. For example, drive to work and when you
get there you can't remember anything about your trip.

The point is not that long term memory is "better", the point is that we
take a lot of things for granted when saying that a short term test (of
anything really) is going to be reliable. Lots of people get buyer's
remorse, or after a time start appreciating new aspects of a product.

Another simple example: look at a picture but just don't see what's there.
Then one day you realize it's a picture of Jesus. It could take a minute it
could take a year. But once you see it, you can't not see it.

This isn't rocket science, or voodoo, or snake oil marketing. These are
well known phenomenon.

Having said that, when an advertiser claims "dramatic, obvious, jaw
dropping,
my-non-audiophile-wife-could-tell-immediately-from-across-the-street
differences, and you are straining to hear any difference at all, be it long
or short term, then something is obviously not as claimed.

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Default Do all amplifiers sound the same?

"Steven Sullivan" wrote in message
...
. I
used to believe that objective measurements alone were all that one
needed, and I still believe that objective measurements can tell us most
of what we need to know about a system or component.


Well, try looking objectively at a chess board at the beginning of a game
and determine who will win - black or white. Objective computers
measurements can't figure out that one either.

There is a lot in this world that isn't known or understood, trust me.

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Default Do all amplifiers sound the same?

On Dec 26, 11:57 am, Sonnova wrote:
Output impedance is one of many criteria. Mostly,
it affects damping factor for the loudspeakers.


Mostly, it does not at all.

The way I understand it is If a dynamic speaker is
looking down it's cable into the output stage of an
amplifier and sees, what is in essence, a dead
short, the cone will stop instantly when the signal
stops, because of the back EMF being generated
by the shorted voice coil in the speaker's magnetic
field (try this experiment: Get a raw driver and flex
the cone by hand at the dust cap. Then connect the
terminals of the speaker together with a jumper and
flex the cone again. Notice how much more difficult
the cone is to move this time.


Unless you're moving the cone VERY fast, you're not
going to see any difference.

Now, try the experiment REALISTICALLY: Try doing
it and trying to sense the difference between a 0.4 ohm
resistor across the terminals vs a 0.1 ohm resistor
across the terminals.

That's the phenomenon behind regenerative
dampening)


There is no "regenerative damping." It's just damping.

But even this is an oversimplification.


Yes, it is an oversimplification to the point of being
wrong.

In reality, most speaker voice coils are looking into
an inductor in the crossover and the resistance of
the speaker cable before it sees the output stage,


And, in oversimplifying, you neglected the fact that
the single LARGEST resistance is ALWAYS there,
and that's the DC resistance of the voice coil. The
inductor might add a fraction of an ohm, same with
the leads, but the DC resistance of a typical niminal
8 ohm driver is in the realm of 6-7.5 ohms, and
THAT resistance completely dominates all others,
including the amplifier's output resistance, and it
is the voice coil resistance that essentially determines
the damping of the system.

so its anybody's guess how much a low output
impedance actually affects the overall result.


Actually, it's not guesswork at all. The series resistance
the voice coil dominates, and unless the other series
resistances are pathologically large and the so-called
damping factor is larger than 10-20, the amplifier's
output resistance will have NO appreciable effect on
the damping of the system.

Frankly, I think that the sound of an amplifier is more
a result of the complex load presented by the speaker
system that it's driving than the speaker's sound is
influenced by the amplifier.


That may be the case, but, again, it's something that
can be determined. If we have an amplifier whose
damping factor is "low" by contemporary standards,
say, 20 at 8 ohms, and we connect it to a speaker
whose impedance varies from 6 to 30 ohms. The
result is that the voltage at the speaker terminals
varies by 0.44 db between the minimum and maximum
impedance.

Now, get yourself an amplifier with an alledged damping
factor of, oh. 200. The resulting error is now on the order
of 0.05 dB. Do you think that you can hear the difference
resulting from a smooth change in broadband frequency
response of about 0.4 dB in a room with dynamically
changing music?
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On Thu, 27 Dec 2007 08:47:53 -0800, codifus wrote
(in article ):

On Dec 26, 11:58 am, Sonnova wrote:
On Tue, 25 Dec 2007 08:44:45 -0800, bear wrote
(in article ) :



Steve wrote:
Some time ago the now defunct stereo review had an interesting article
on blind a/b tests between different amplifiers - I saw a reprint
here;


http://bruce.coppola.name/audio/Amp_Sound.pdf


After a hiatus of many years I am now putting together a system and
every one I talk to tells me there is a difference between amplifier
sounds. I am sceptical and in a recent audition could not tell a Creek
EVO from a NAD 325 BEE (through EPOS M12.2 speakers with a Creek cd
source).


Has any more work been done on this subject, esp. blind a/b tests?


Steve


Amplifiers do not all sound the same.
Some may.
Some do not.
They certainly do not measure the same.


That is true.



The THD or IM specs do *not* tell the story.


That is correct. Up to a certain point, both seem to be relatively
unimportant. Research has shown that humans aren't very sensitive to the
harmonic and IM distortion produced by amplifying devices. Back in the
"golden era" of tube hi-fi, manufacturers would outdo themselves trying to
get the most zeros between the decimal point and the numbers. This made them
bias their tubes far into the linear portion of the tube's transfer curve.
This lowered distortion all right, but it made the tubes run very hot and
self-destruct with alarming rapidity. After it was found in double-blind
tests that levels up to over 1% in amplifiers were undetectable by humans,
manufacturers started backing off on output bias. over the last thirty years
or so, we have seen the life of output tubes increase dramatically from a
mere few hours to many thousands of hours over a number of years. Of course,
the tradeoff is that harmonic and IM levels have gone from 0.001% to 0.1% or
even higher. Nobody notices.


Part of the reason could be coming from the other end: the source has
gotten much cleaner. Before it was vinyl and cassette recordings with
distortion levels magnitudes higher than with digital lossless files
we play today.


That could be true, but "source" distortions tend to sound very different
from amplifier distortion. For instance, I would never mistake an over
modulated audio tape for amplifier distortion. They do not sound the same.

On a slightly different note, I found one way to easily distinguish a
lossy audio file from its lossless counterpart: distortion. The
Lossless file will play much louder and cleaner than the lossy file on
the same system.


That is very true. A friend recently gave me an 340k MP3 of the end title cut
for the movie soundtrack "The Mummy Returns". When I got it home, I was
disappointed at how distorted it sounded. I then borrowed the CD from him and
did my own "rip" using Apple Lossless. The end result was as clean as the CD.
I still maintain that compression artifacts are clearly audible and very
nasty sounding, but others keep telling me that it's my imagination. These
same people also tell me that all amplifiers sound the same and that redbook
CD is perfect and indistinguishable from SACD or 96 KHz/24-bit DVD-A. One
thing is sure, though. Either I'm deluding myself or they can't hear and I'm
betting on the latter. :-


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On Thu, 27 Dec 2007 08:34:49 -0800, jwvm wrote
(in article ):

On Dec 26, 12:01 pm, Sonnova wrote:

snip
Similar disputes also continue with D/A converters, cables,
preamplifiers, etc. in which measurements indicate little or no
improvement with high-priced hardware.


Now it's not true that everything sound alike and an outboard D/A converter
might very well sound better than the D/A that comes in a stand-alone CD
player because the D/A in the player is fraught with design compromises that
the outboard D/A may not be.


Are you saying that D/A converters that provide essentially the same
measurements will still sound different and can be differentiated in
double-blind tests?


I don't see anything in my quoted post above about the D/A converters in
question measuring the same, but my stand-alone converter definitely sounds
better than the one in my pro Otari DAT recorder or the one in my TASCAM
CDR-7000P CD burner/player.
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Andrew Barss Andrew Barss is offline
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Default Do all amplifiers sound the same?

jeffc wrote:
: "Arny Krueger" wrote in message
: ...
:
: Some will argue that well-made amps that measure the same
: will sound the same.
:
: The myth here is that two amps could measure the same. Even each channel
: of
: a stereo amplifier will measure differently, given sufficiently accurate
: measuring gear.

: I don't believe the measuring tests are really that accurate. If you doubt
: this, consider: voice recognition is extremely difficult for even the most
: sophsticated equipment, yet trivially easy for even children.

Very bad analogy.

Voice recognition requires hearing the same person speaking
on two occasions, and matching them -- i.e. it's Uncle Jimmy
on the phone, the same guy that called on Thanksgiving. The equipment
he's calling on (if you're hearing a phone call -- the other factors
obtain if he's right in front of you), how much mucous he has
in his vocal tract, how loud he's speaking, and a lot of other factors make his voice
objectively different on each speaking occasion. These differences
can be measured. The problem of this sort of recognition
is thus: taking two *acoustically different* signals and somehow
extracting the components that are unique identifiers of the
source system.

In audio equipmnt land, this would be like doing the following: taking
an amplifier, and on two different occasions hooking it up to
very different components (speakers, wires, rooms), fiddling with the volume,
and maybe changing the voltage running through it, maybe
corroding some of the connectors, turn one speaker so it's facing the wall, and put th
other one in the kitchen, and so on, and still being able to identify the
specific amp out of all the amps you've ever heard.

A more correct parallel in voice recognition to the equipment issue
in this thread would be: take two copies of one recording of Uncle Jimmy's voice,
measure them, and make sure they're identical on all measures. Then label one file
JIMMY1, the other JIMMY2. Play them. Do they sound different to
you? And can you tell them apart when you're not looking at the file name on the computer
screen?

-- Andy Barss
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Default Do all amplifiers sound the same?

Steve wrote:

Some time ago the now defunct stereo review had an interesting article
on blind a/b tests between different amplifiers - I saw a reprint
here;

http://bruce.coppola.name/audio/Amp_Sound.pdf


interesting ref, although 3.76MB is a bit much

fwiw, the tubes vs solid state "squabble"
went well beyond the '60's and in fact
likely continues to this day

in my own not too distant past, tubes still
sounded better; bleeding problem is their
lack of practicality, not to mention that
they now cost so much more than in the 60's


After a hiatus of many years I am now putting together a system and
every one I talk to tells me there is a difference between amplifier
sounds. I am sceptical and in a recent audition could not tell a Creek
EVO from a NAD 325 BEE (through EPOS M12.2 speakers with a Creek cd
source).

Has any more work been done on this subject, esp. blind a/b tests?


believe nothing that you read

trust your ears

i can add that imho solid state has
come a very very long way forward
in the last 20/25 years.

bill
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Steven Sullivan Steven Sullivan is offline
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Default Do all amplifiers sound the same?

jeffc wrote:
"Steven Sullivan" wrote in message
...
. I
used to believe that objective measurements alone were all that one
needed, and I still believe that objective measurements can tell us most
of what we need to know about a system or component.


Well, try looking objectively at a chess board at the beginning of a game
and determine who will win - black or white. Objective computers
measurements can't figure out that one either.


That's an absurd argument. We're not talking about predicting the future.

There is a lot in this world that isn't known or understood, trust me.


Why should I trust you?

There are lots of things that are known. One of them is that
our senses are easily fooled. That's why blind tests are valuable.

___
-S
"As human beings, we understand the world through simile, analogy,
metaphor, narrative and, sometimes, claymation." - B. Mason
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Sonnova wrote:
On Thu, 27 Dec 2007 08:47:53 -0800, codifus wrote
On a slightly different note, I found one way to easily distinguish a
lossy audio file from its lossless counterpart: distortion. The
Lossless file will play much louder and cleaner than the lossy file on
the same system.


That is very true.


It's very not true.

A friend recently gave me an 340k MP3 of the end title cut
for the movie soundtrack "The Mummy Returns". When I got it home, I was
disappointed at how distorted it sounded. I then borrowed the CD from him and
did my own "rip" using Apple Lossless. The end result was as clean as the CD.


Then there was something wrong with your friend's mp3.

I still maintain that compression artifacts are clearly audible and very
nasty sounding, but others keep telling me that it's my imagination.


You've never presented good evidence to the contrary. As in, performance
on an ABX test, with a good mp3 vs. source.

___
-S
"As human beings, we understand the world through simile, analogy,
metaphor, narrative and, sometimes, claymation." - B. Mason
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Default Do all amplifiers sound the same?

On Dec 29, 11:40 am, Randy Yates wrote:
writes:
Actually, it's not guesswork at all. The series resistance
the voice coil dominates, and unless the other series
resistances are pathologically large and the so-called
damping factor is larger than 10-20, the amplifier's
output resistance will have NO appreciable effect on
the damping of the system.


You're speaking in static, DC terms. What about dynamically? For
example, when the voice-coil is traveling and the back-emf is opposing
the amplifier's output voltage? Yes, there is still the DC resistance of
the coil in series, but the amplifier is working harder than under DC
conditions.


Think Mr. Thevenin.

That resistance is ALWAYS there, under ALL conditions.

There is absolutely NOTHING special about the
"back-EMF" that makes the situation in any way
unique. A mechanically resonant system with electrical
coupling behaves electrically exactly the same way
a straightforward parallel RLC resonant tank circuit
with a series resistance behaves.

The onl;y time the "back-EMF" exactly opposes
the amplfier's voltage is when the two are exactly
in phase, and that occurs at the fundamental
mechanical resonant frequency. At that point, the
electrical impedance is at its highest and dominated
by the series combination of the DC resistance and
the reflected mechanical and (to a very small degree)
acoustical losses.

And by "DC resistance" of the voice coil, I do not
mean that it's only valid at DC, rather that this
resistance, for the purpose of discussion, has no
appreciable frequency dependence. In other words
measure its value at DC and at, say, 100 Hz and you
will find no significant difference.
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On Fri, 28 Dec 2007 08:59:42 -0800, wrote
(in article ):

On Dec 26, 11:57 am, Sonnova wrote:
Output impedance is one of many criteria. Mostly,
it affects damping factor for the loudspeakers.


Mostly, it does not at all.

The way I understand it is If a dynamic speaker is
looking down it's cable into the output stage of an
amplifier and sees, what is in essence, a dead
short, the cone will stop instantly when the signal
stops, because of the back EMF being generated
by the shorted voice coil in the speaker's magnetic
field (try this experiment: Get a raw driver and flex
the cone by hand at the dust cap. Then connect the
terminals of the speaker together with a jumper and
flex the cone again. Notice how much more difficult
the cone is to move this time.


Unless you're moving the cone VERY fast, you're not
going to see any difference.

Now, try the experiment REALISTICALLY: Try doing
it and trying to sense the difference between a 0.4 ohm
resistor across the terminals vs a 0.1 ohm resistor
across the terminals.


Well, of course. That's what I was saying about "real world results" But
while one cannot tell the difference between an output impedance of 0.1 and
0.4 ohms. one can certainly tell the difference (in the bass) between an amp
with an output impedance of less than an ohm and one with an impedance of
output transformer!

That's the phenomenon behind regenerative
dampening)


There is no "regenerative damping." It's just damping.


The damping occurs because of the regenerative back EMF.

But even this is an oversimplification.


Yes, it is an oversimplification to the point of being
wrong.


No, it's not wrong. It just isn't as great an effect as the classic
demonstration would have one believe.

In reality, most speaker voice coils are looking into
an inductor in the crossover and the resistance of
the speaker cable before it sees the output stage,


And, in oversimplifying, you neglected the fact that
the single LARGEST resistance is ALWAYS there,
and that's the DC resistance of the voice coil. The
inductor might add a fraction of an ohm, same with
the leads, but the DC resistance of a typical niminal
8 ohm driver is in the realm of 6-7.5 ohms, and
THAT resistance completely dominates all others,
including the amplifier's output resistance, and it
is the voice coil resistance that essentially determines
the damping of the system.


I would have thought that was a given.

so its anybody's guess how much a low output
impedance actually affects the overall result.


I agree. I was merely explaining the "shorted turn phenomenon".

Actually, it's not guesswork at all.


Not if you know all the factors, no. Then it becomes a simple matter of the
combination of the various DC resistances, and the various inductive and
capacitive reactances involved

The series resistance
the voice coil dominates, and unless the other series
resistances are pathologically large and the so-called
damping factor is larger than 10-20, the amplifier's
output resistance will have NO appreciable effect on
the damping of the system.


Modern Solid state amps can have damping factors of greater than 200.

Frankly, I think that the sound of an amplifier is more
a result of the complex load presented by the speaker
system that it's driving than the speaker's sound is
influenced by the amplifier.


That may be the case, but, again, it's something that
can be determined. If we have an amplifier whose
damping factor is "low" by contemporary standards,
say, 20 at 8 ohms, and we connect it to a speaker
whose impedance varies from 6 to 30 ohms. The
result is that the voltage at the speaker terminals
varies by 0.44 db between the minimum and maximum
impedance.

Now, get yourself an amplifier with an alledged damping
factor of, oh. 200. The resulting error is now on the order
of 0.05 dB. Do you think that you can hear the difference
resulting from a smooth change in broadband frequency
response of about 0.4 dB in a room with dynamically
changing music?


I'm not arguing about broadband frequency response, I'm talking about the
amp's ability to damp (or stop) a large, high mass magnetic bass driver
abruptly when the signal stops. This determines, to some extent, the quality
of the bass in a system.



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Default Do all amplifiers sound the same?

On Fri, 28 Dec 2007 08:45:57 -0800, jeffc wrote
(in article ):

"Arny Krueger" wrote in message
...

Some will argue that well-made amps that measure the same
will sound the same.


The myth here is that two amps could measure the same. Even each channel
of
a stereo amplifier will measure differently, given sufficiently accurate
measuring gear.


I don't believe the measuring tests are really that accurate. If you doubt
this, consider: voice recognition is extremely difficult for even the most
sophsticated equipment, yet trivially easy for even children. The same is
true for image recognition. Measurements might be good enough for the cell
phone generation, but that ain't sayin' much.

Theoretically, if it can't be measured it can't be heard. But just because
it can be measured doesn't mean it is being measured.


And since even if everything we hear could be preceisly quantified and
weighted according to the requirements of human perception, that still
doesn't mean that the ordinary audiophile would have access to the equipment
with which to make those measurements for himself. We have two instruments we
can use when choosing audio equipment and we carry them with us everywhere we
go. Use 'em!
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Default Do all amplifiers sound the same?

On Sat, 29 Dec 2007 08:40:53 -0800, willbill wrote
(in article ):

Steve wrote:

Some time ago the now defunct stereo review had an interesting article
on blind a/b tests between different amplifiers - I saw a reprint
here;

http://bruce.coppola.name/audio/Amp_Sound.pdf


interesting ref, although 3.76MB is a bit much

fwiw, the tubes vs solid state "squabble"
went well beyond the '60's and in fact
likely continues to this day


Likely? Based upon the twin facts that there are more companies building
tubed audio components today than at probably any other time since the
transistor came on the scene in the middle 1960's and that recognized tube
brands like Audio Research, VTL, VAC, etc (even Dynaco), have much higher
resale value than SS gear of similar initial costs (with some exceptions),
I'd say that this particular "squabble" was very much still with us!

in my own not too distant past, tubes still
sounded better; bleeding problem is their
lack of practicality, not to mention that
they now cost so much more than in the 60's


I have a pair of VTL 140 tube monoblocs that I'm going to be buried with
(along with my Alfa Romeo GTV-6). That's the only way I'll give 'em up is to
be dead. Also I find my tube gear to be very practical. I bought out an old
ham operator of his stash of NOS JAN WWII vinatge 807s (each amp uses six of
them) for pennies each. They're better than newly manufactured 807s. Anyway,
I think I've replaced ONE tube in the last 10 years. I'd say that's pretty
practical! Modern tube components (my VTLs were manufactured in the early
1990's), unlike their 1950's and 1960's antecedents, are not biased so
heavily, so the tubes last a really long time.

After a hiatus of many years I am now putting together a system and
every one I talk to tells me there is a difference between amplifier
sounds. I am sceptical and in a recent audition could not tell a Creek
EVO from a NAD 325 BEE (through EPOS M12.2 speakers with a Creek cd
source).

Has any more work been done on this subject, esp. blind a/b tests?


believe nothing that you read


Oh. I think you can trust a math textbook :-

trust your ears


Oh, yes. After all, they're the only "test instruments" that most of us
posses. They do require a bit of training, however.

i can add that imho solid state has
come a very very long way forward
in the last 20/25 years.


That too is true. I still prefer tubes for music though. SS amps mostly sound
too clinical for my tastes, although they are probably more accurate. In an
ideal world, where recordings were perfect, perhaps the clinically accurate
solid state amps will sound "better" than the euphonically colored tube
equipment, but I don't see that happening anytime soon. I listen to music for
pleasure and tubes give me more. There is not, nor does there need to be. any
other justification than that.

bill


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Default Do all amplifiers sound the same?

What was your recent "audition"? *These things have to be done carefully,
with the exact same system (I assume it was) but also well volume matched
(use a test tone and multimeter to check the voltage output from the amp.)

Also, you'll want to use material that you're very familiar with.
Ultimately the overall resolving power of the entire system (the system
includes the room acoustics) will determine if you can tell a difference (as
well as if there is any discernible difference between the amps, of course.)

Sometime of course you can tell a slight difference, but is one really
better than the other, or just slightly different? *Is the difference worth
paying for?

I was able to tell the difference between an Adcom 545 and 555 (voltage
matched of course) every time. *Both were operating well below max capacity.
That was enough to convince me there are differences between amps (I don't
even think the company intended there to be any difference here.)


This was at a dealers and I had no way to objectively set the volume
to equal. So I set the volume by ear changed the volume each time up
or down according to whim. Not very scientific but similar to what one
would do at home.
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Default Do all amplifiers sound the same?

wrote:
On Dec 25, 11:47 am, Greg Wormald wrote:
Our auditory memory is very short, and often very inaccurate, and that
is an argument NOT for short duration tests, but for using something
that is longer lasting and more reliable, namely the emotional response
to the music.


Sorry, but this is complete nonsense. Before the data passes
into long-term memory, it MUST pass through short-term
memory. If you assertion is that short-term auditory memory
is defective in some way, than long-term memory cannot be
better.

And, in fact, contrary to the fantasies and wishes of any
number of audiophiles, this property of auditory memory
is supported by quite a bit of actual research.


Dick,

this argument frames the issue incorrectly.
therefore the conclusions are essentially wrong or meaningless.

the issue is not so much memory.
rather it is "processing."

this can be illustrated nicely with a car radio.
most people have had the experience of "flipping" to a station
and hearing an unrecognizable song - you're somewhere in the middle
of it and in the middle of a phrase - only to find that it is
something you "know like the back of your hand."

what is going on here?

simply this: it takes time for the brain to stitch sound together into
a recognizable form, and to make sense of it.

in practice this means that when sound is presented such that the brain
can recognize it more quickly, or conversely does not have to "strip off"
artifacts, that sound is adjudged "more natural sounding".
more importantly, the easier the process of "sonic decoding" that the brain
has to do in real time, the more time per "chunk" the brain has to "decode"
more "subtle" elements, or detail.

think about it. this explains rather simply why one can hear different
things in a given recording, one that objectively (especially if digital)
contains *exactly the same data* - when only the playback chain & environemnt
is a variable!

_-_-bear
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Default Do all amplifiers sound the same?

On Dec 30, 11:55 am, Sonnova wrote:
On Fri, 28 Dec 2007 08:59:42 -0800, wrote
(in article ):



On Dec 26, 11:57 am, Sonnova wrote:
Output impedance is one of many criteria. Mostly,
it affects damping factor for the loudspeakers.


Mostly, it does not at all.


The way I understand it is If a dynamic speaker is
looking down it's cable into the output stage of an
amplifier and sees, what is in essence, a dead
short, the cone will stop instantly when the signal
stops, because of the back EMF being generated
by the shorted voice coil in the speaker's magnetic
field (try this experiment: Get a raw driver and flex
the cone by hand at the dust cap. Then connect the
terminals of the speaker together with a jumper and
flex the cone again. Notice how much more difficult
the cone is to move this time.


Unless you're moving the cone VERY fast, you're not
going to see any difference.


Now, try the experiment REALISTICALLY: Try doing
it and trying to sense the difference between a 0.4 ohm
resistor across the terminals vs a 0.1 ohm resistor
across the terminals.


Well, of course. That's what I was saying about "real world
results"


Well, here you harp about "real world results" after someone
objects to your experiment which has nothing to do with
"real world result."

But while one cannot tell the difference between an
output impedance of 0.1 and 0.4 ohms. one can
certainly tell the difference (in the bass) between an
amp with an output impedance of less than an ohm
and one with an impedance of output transformer!


And with the exception of some degenerative, patholoigcally
bad designed tube amplifiers, the typical tube amplifier with
it's output transformer exhibits effective output resistances
of an ohm or less.

That's the phenomenon behind regenerative
dampening)

There is no "regenerative damping." It's just damping.


The damping occurs because of the regenerative back EMF.


There is no "regenerative." You are either misusuing the
term or misunderstanding the concept.

But even this is an oversimplification.


Yes, it is an oversimplification to the point of being
wrong.


No, it's not wrong. It just isn't as great an effect as the classic
demonstration would have one believe.


No, your oversimplification is ORDERS OF MAGNITUDE
off the mark, enough that your suggested demonstration,
which you implicitly admit is far from "real world," simply
does not reflect the real world AT ALL.

In reality, most speaker voice coils are looking into
an inductor in the crossover and the resistance of
the speaker cable before it sees the output stage,


And, in oversimplifying, you neglected the fact that
the single LARGEST resistance is ALWAYS there,
and that's the DC resistance of the voice coil. The
inductor might add a fraction of an ohm, same with
the leads, but the DC resistance of a typical niminal
8 ohm driver is in the realm of 6-7.5 ohms, and
THAT resistance completely dominates all others,
including the amplifier's output resistance, and it
is the voice coil resistance that essentially determines
the damping of the system.


I would have thought that was a given.


No, in your discussion, it most assuredly WAS NOT a
given. If it was, you would have realized and hopefully
discussed the fact that the other resistances you cite are
simply insignificant by comparison.

so its anybody's guess how much a low output
impedance actually affects the overall result.


I agree. I was merely explaining the "shorted turn
phenomenon".


And you neglected to then point out that almost every
amplifier on the planet provides that "shorted turn,"
given that it is NOT a significant source of loop resistance.

Actually, it's not guesswork at all.


Not if you know all the factors, no. Then it becomes a
simple matter of the combination of the various DC
resistances, and the various inductive and capacitive
reactances involved


The inductive and capacitive reactances have no effect
on damping resonance.

The series resistance
the voice coil dominates, and unless the other series
resistances are pathologically large and the so-called
damping factor is larger than 10-20, the amplifier's
output resistance will have NO appreciable effect on
the damping of the system.


Modern Solid state amps can have damping factors of
greater than 200.


Try it again, a damping factor of 20 or so is sufficient
to control all resonances in a speaker. 200 will NOT
damp ten times better than 20, in fact, in most cases,
the difference is nearly unmeasurable.

Frankly, I think that the sound of an amplifier is more
a result of the complex load presented by the speaker
system that it's driving than the speaker's sound is
influenced by the amplifier.


That may be the case, but, again, it's something that
can be determined. If we have an amplifier whose
damping factor is "low" by contemporary standards,
say, 20 at 8 ohms, and we connect it to a speaker
whose impedance varies from 6 to 30 ohms. The
result is that the voltage at the speaker terminals
varies by 0.44 db between the minimum and maximum
impedance.


Now, get yourself an amplifier with an alledged damping
factor of, oh. 200. The resulting error is now on the order
of 0.05 dB. Do you think that you can hear the difference
resulting from a smooth change in broadband frequency
response of about 0.4 dB in a room with dynamically
changing music?


I'm not arguing about broadband frequency response,
I'm talking about the amp's ability to damp (or stop) a
large, high mass magnetic bass driver abruptly when
the signal stops.


And that was PRECISELY what I was talking about
earlier. Your dismissive comments that the
DC resistance "was a given," your inclusion
of inductive and capacitive reactances and your claim
that it is all"guesswork," clearly indicates
you're not grasping the true nature of "damping" in
it's formal electromechanical sense. And that very
mature is central to the operation of loudspeakers.

The damping of the entire system is determined
PRIMARILY by the DC resistance of the voice coil.
The output resistance of the amplifier has, at most
a MINOR effect.

In fact, if you look at the reciprocal of the damping
factor, THAT number gives a good indication of how
much of the electrical damping is provided by the
amplifier.

So take an amplifier with a damping factor of 10: only
1/10 of the total electrical damping of the system is
controlled by the amplifier, 90% is controlled by the
DC resistance of the speaker.

How about a damping factor of 100? Well, 1% of the
damping is provided by the amplifier, 99% is by that
DC resistance of the voice coil

In other words, the higher the damping factor, the LESS
the amplifier contributes to the damping of the speaker.
This is why the "damping factor" is such a useless
specification. It was born PURELY out of marketing.

And all this discussion ignored the fact that the
mechanical losses in the system provide more
damping than even the worst amplifier. Given that
in most high-quality electrodynamic woofers, the
mechanical losses are on the order of 1/5 to 1/2
the electrical damping due to the voice coil, it
further diminishes the contribution of the amplifier
output resistance.

Take a typical speaker with a Qt of 2 and a Qe of
0.7, and now we find that the amplifier with a damping
factor of 10 contributes only 5% or so of the total
damping.

At your leasure, try the following:

www.cartchunk.org/audiotopics

You can also google for my ame and "damping factor."

To reiterate: It is the voice coil DC resistance and
NOT the amplifier output resistance that determines
the damping of the VAST majority of amplifier and
speaker combinations "Experiments" such as trying
to see the difference between an open circuit and a
short circuit in terms of "observing" damping are
wholely unrealistic and flawed because they represent
comparisons that wuill NEVER occur in the "real world."
And all of this is quite well understood and not subject
to any guesswork at all, assuming the appropriate
compcepts and models are being used.

If not, then any guess is as bad as any other.
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