Audio, hi-fi and car audio - how good are class D amplifiers?

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how good are class D amplifiers?

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

snip

and surprisingly (to me) there doesn't seem to have been many
rigorous tests to underpin the 'little if any difference' thesis.

You would need to clarify what you mean as I am unsure of the point
you are making.

I'll try.

1. It is maintained that most amplifiers sound the same;
2. I haven't see many tests that support (1)

That does not seem to me to be the same point as you made above. :-)

Nor it is clear to me who "maintains" this as it isn't something I've
said. :-) I've seen various people say variations on "well designed
and appropriately used" amps give indistinguishable results. But that
isn't statement (1). So are you asking for evidence for a claim no-one
has made?

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.

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.

You would then have to devise a performable test/experiment and do
so on a basis that deals with why you feel all the tests thus far
have somehow been 'unrepresentitive' of "most" amplifiers. This means
giving a plausible and testable reason for why the previous tests
all 'selected' amps such that none of them were in the same alleged
catagory as "most" according to your claim.

You would then have to *perform* the tests and collect the evidence.
There would have to be a statistically significant number of tests
and you'd have to be able to establish the level of significance.

Then a decision could be based on that *evidence*.

If the above isn't done, then your idea is a speculation which the
current evidence seems not to support. This puts it into the "teapot
orbiting the sun" class. i.e. a fanciful speculation which can't be
tested and which the evidence we have shows no sign of supporting.

It is easy to make up speculations that remain untested or are
essentially intestable. However this means we can invent an infinite
number of them which may all conflict. Given this, it seems to me
to be a waste of time to take them seriously *unless and until*
someone does the above process to find evidence from a test whose
outcome had the ability to either conflict or support the idea.

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.
Interestingly, this includes cases where I and others were quite surprised
that those involved *couldn't* distinguish as there were quite large,
easily measureable, differences. Indeed, in more than one case the
amps compared were deliberately chosen with the aim of being able to find
clear differences. Some of the participants chose them for this reason,
but then failed when tested to tell one from another.

This means that we have in audio a history of people who are confident
they can 'hear differences', but when tested fail to show they can hear
what they believe. In this context it seems reasonable to be wary of
claims - although it is quite clear that some differences are indeed
audible, and hence are not contentious. So, for example, tests generally
proceed on the basis of level matching as it is generally accepted that
a change of level can be audible if reasonably large.

Given this, I'd be interested in *evidence* to the effect that it isn't the
case that 'most' amps *don't* sound indistinguishable in an appropriate
comparison - excepting for reasons which are uncontenious and already
understood/accepted. Alas, arguments, discussing the meanings of words,
opinions, speculations, etc, aren't evidence

Of course, if your point is that 'most' exhibit problems in use like
obvious distortions, changes in response, etc, then I can see why you would
be concerned. There may well be 'many' amplifiers that produce audibly
different results - indeed there are various ways to cause audible
changes if we wish. However note the qualifications I have made about
what was being compared, and how.

However in the absence of evidence I can't see much point in what you are
now saying.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

how good are class D amplifiers?

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

Is that simply a 'concept'? I would have regarded it as a description
of something which arises in physical reality. 'Concept' seems to me
to be a term which sounds more like it was an abstract idea.

Yes, that's right - 'distortion' is a concept, and not a thing.

You point being that anything we observe in reality and then have a word
for is a 'concept'?

Does that approach serve any purpose when we are trying to deal with
reality? It seems to me to be no more than playing with words and doing
this as a replacement for dealing with reality. In effect, a displacement
acitivity.

and not a single or pejorative (in the context of valves discussions
say) fact.

Pejorative would be 'in the ear of the belistener' I guess. :-)

Quite! If (and I say 'if'; I don't know) distortion is the cause of what
I consider to be the 'accurate' sound I get from a valve amplifier and
LPs then it's beneficial.

That is OK for you as an individial if you are making up your own meaning
of 'accurate', etc. The problems arise as soon as you try to communicate
with the rest of us since you are using the Lewis Carroll version. :-)

Afraid you have to make decide which you prefer. Playing with words and
confusing the issues, or dealing with reality and being able to communicate
with others.

The reality, though, is that if the output has a nonlinear relation to
the input then it is a 'fact' that the result is being distorted
according to the relevant definitions. This can be measured, and may
be audible, depending on circumstances.

Whether someone likes or dislikes (or can even tell the difference)
the results is up to them. Of course, I'd like them to be able to make
an 'informed' choice - hence my previous comments. But that isn't
compulsory... ;-

Yes. I think it may follow that you're led my measurement and I'm led by
the sound I hear.

....or it may not. :-)

False and inappropriate dichotomy. :-)

Actually I've been trying to point out that I am not 'led' by either in
isolation. I try to be guided or informed by both, and try to be so in
a way that is appropriate for the relevant situations or issue.

That's fine in the main, of course - it's your world and it suits you
(and probably many others). I'm not so happy, though, with lumping
enthusiastic commentary and enquiring minds in with 'wilful
ignorance', which I'm afraid is how I read the essence of what you
seem to be saying.

Why are you assuing that enthusiam and enquiry mean wilifil ignorance?
I'd have said the exact opposite. I'm afraid that you are reading into
what I wrote something that I neither said not meant.

You skip from 'nonlinear' audio to 'informed choice' to 'unfounded
claims' to 'wilful ignorance'. I do the first three, but don't consider
myself wilfully ignorant. Delusional but happy maybe :-)

The 'wilful ignorance' arises when people don't want to know about any
measurements or to understand the relevant physics, etc. The 'ignorance'
part comes from them not knowing the measured results or having any
understanding of them. The 'wilful' comes from this being a result of
their deliberate choice, not from not knowing measurements can be
made and their meanings understood. Of course, that's fine if it
keeps one 'happy' but it may mean that any comments they made beyond that
are worthless for anyone else, and may simply mislead or confuse.

It is perfectly reasonable for someone to decide to remain ignorant
about some topic. There are many topics in which each of us have
no interest. However this means our views on such topics may be
worthless.

The bit where I would go along (in part at least) with your obviously
strong and informed opinions on this arise around the 'unfounded
claim', and the extent to which the adherent rams it down somebody
else's throat. But then I don't think an unfounded claim is incorrect,
or ignorant - wilful or otherwise.

in physical science and engineering 'unfounded' does not simply mean
there is no evidence or plausible argument consistent with what
has been established. Ideas for which there is no evidence one way
or another, and which can't be assessed for consistency are 'untested'
and/or 'unassessed' not 'unfounded'. Such ideas remain speculations
and may be void of value *until* tested, etc.

An 'unfounded' claim is one which clashes with established physics
(i.e. clashes with the evidence which it describes) or is simply
confounded by directly relevant experimental evidence. If you wish to
continue to accept such ideas, you are free to do so, but so far as
science is concerned it then becomes an 'article of faith' on your
part, nothing to do with science.

An 'enquiring mind' would seek to *understand* what they experience -
and also seek to check if their impressions or ideas have any
reliability or are errors. Enthusiam is one of the things that can
drive this.

OK, no doubt. 'Understanding' is, again, conceptual.

Again you seem fonder of playing with words than with dealing with the
reality. :-)

The point of 'understanding' is that it allows you to deal correctly with
reality. i.e. you can then design, analyse, predict, etc, and find that
things do behave as intended in cases that were not identical with your
original evidence. The 'understanding' is evidence based and tested by
proving successful in such ways - or is discarded/altered as appropriate.

Is it 'conceptual' that when you build a bridge it does not collapse the
next day? If you think so, then your meaning of the word differs from mine.
I would also be reluctant to employ you to build bridges, or walk on/under
any you designed. :-)

And here I think it's important to define your paradigm. I work in an
applied social science department,

That may be the reason for your approach and the source of some of the
inappropriate nature of some of your arguments/definitions on this group...
:-)

I'm afraid that 'social science' is not a 'science' in the same sense as
physics or engineering, and may well use terms or arguments in a
quite different way. Thus your background may simply be causing you
problems with understanding what I and other have been explaining.

FWIW The main reason I've spent decades studying, building, testing,
etc, audio amplifiers and other kit is that I am largely driven by my
enthusiasm for the results - being able to enjoy the music. My point,
therefore, was that measurements, etc, are very valuable (if you
understand them), and allow you to make more progress.

And modesty no doubt forbids the qualification: 'measurement is not all'
:-)

No idea why you wrote that.

Being able to make measurements and analyse designs, etc, does not
prevent you from also listening to the results. There is no inherent
dichotomy here.

Of course.

If there is a problem it is in the area I referred to.

Which remains a tad fuzzy.

To you. :-)

if you really want to make more sense of this it would probably be best if
you did spent some time studying physical science and engineering.
And in learning the scientific method, and the related topics of
experimental design in physical sciences, etc. As it is, your background
may be causing you some confusion.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

how good are class D amplifiers?

"Arny Krueger" wrote in message
...
"Keith G" wrote in message

"Arny Krueger" wrote in message
. ..
"Keith G" wrote in message

"Arny Krueger" wrote in message
. ..
"Rob" wrote in message

Yes, I agree. DBT is not a trivial thing though, and
surprisingly (to me) there doesn't seem to have been
many rigorous tests to underpin the 'little if any
difference' thesis.

What would constitute many?

I've done DBTs of several dozen hi fi power amps, and
found near-total support for the "little if any
difference" thesis.

Sure, of course - and it would be stunning if it weren't
for the fact that, in a domestic environment, most
people couldn't tell the difference between two pieces
of kit after a couple of goes back and forth - even if
*they* were making the switches fully sighted!!

Yet another irrelevant statement from a member of the
"great unwashed". The relevance problem here is that the
evaluations I'm talking about have been vastly more
extensive than "a couple of goes back and forth".

The relevance problem here is yours, squire - how many
people here have actually *witnessed* a DBT,

Thousands and thousands of audiophiles.

let alone conducted one?

Thousands and thousands of audiophiles, courtesty of www.pcabx.com and
numerous sites like it.

Aha! Thought so.....

:-)

how good are class D amplifiers?

"Arny Krueger" wrote in message
. ..
"Dave Plowman (News)" wrote in
message
In article ,
Keith G wrote:

"Arny Krueger" wrote in message
. ..
"Rob" wrote in message

[snip]

I've done DBTs of several dozen hi fi power amps,

I actually doubt that....

Why?

Personal bias.

Nope, call it *real world* experience....

how good are class D amplifiers?

"Arny Krueger" wrote in message
. ..
"Keith G" wrote in message

"Arny Krueger" wrote in message
. ..
"Rob" wrote in message

Yes, I agree. DBT is not a trivial thing though, and
surprisingly (to me) there doesn't seem to have been
many rigorous tests to underpin the 'little if any
difference' thesis.

What would constitute many?

I've done DBTs of several dozen hi fi power amps,

I actually doubt that....

Your track record for being wrong at just about every turn is
unmolested, Keith.

Sadly, all too often these days, but not in the case of knowing when
'several' usually means *two* and 'several dozen' probably means either
less than 5 or no *real* ones at all...

how good are class D amplifiers?

"Keith G" wrote in message

"Arny Krueger" wrote in message
. ..
"Keith G" wrote in message

"Arny Krueger" wrote in message
. ..
"Rob" wrote in message

Yes, I agree. DBT is not a trivial thing though, and
surprisingly (to me) there doesn't seem to have been
many rigorous tests to underpin the 'little if any
difference' thesis.

What would constitute many?

I've done DBTs of several dozen hi fi power amps,

I actually doubt that....

Your track record for being wrong at just about every
turn is unmolested, Keith.

Sadly, all too often these days, but not in the case of
knowing when 'several' usually means *two* and 'several
dozen' probably means either less than 5 or no *real*
ones at all...

That would be your problem, Keith. I currently own or have ready access to
about a dozen power amps. Just one audio system of mine has 3 power amps.

Then there are the ones I borrow. For just one amplifier auditioning
session, a friend who is a well-known magazine reviewer brought over about
another half dozen power amps that he had laying around.

Then there are the ones that belong to other people in our Hi Fi club, only
a fraction of which are listed on the web.

how good are class D amplifiers?

"Arny Krueger" wrote in message
...
"Keith G" wrote in message

"Arny Krueger" wrote in message
. ..
"Keith G" wrote in message

"Arny Krueger" wrote in message
. ..
"Rob" wrote in message

Yes, I agree. DBT is not a trivial thing though, and
surprisingly (to me) there doesn't seem to have been
many rigorous tests to underpin the 'little if any
difference' thesis.

What would constitute many?

I've done DBTs of several dozen hi fi power amps,

I actually doubt that....

Your track record for being wrong at just about every
turn is unmolested, Keith.

Sadly, all too often these days, but not in the case of
knowing when 'several' usually means *two* and 'several
dozen' probably means either less than 5 or no *real*
ones at all...

That would be your problem, Keith. I currently own or have ready
access to about a dozen power amps. Just one audio system of mine has
3 power amps.

Then there are the ones I borrow. For just one amplifier auditioning
session, a friend who is a well-known magazine reviewer brought over
about another half dozen power amps that he had laying around.

Then there are the ones that belong to other people in our Hi Fi club,
only a fraction of which are listed on the web.

That there may be a grain of truth in your reply is at once the most
hilarious and most disturbing aspects of what you claim. But you are
talking to the wrong person anyway, because....

....because...

....because after lunch the Pixie Truck is coming here and it will be
dropping off, ooh, probably *400* power amps for me to DBT....

('Hi Fi Club' ?? - Where TF did that spring from...???)

how good are class D amplifiers?

"Keith G" wrote in message

('Hi Fi Club' ?? - Where TF did that spring from...???)

It's been around since the mid 1970s:

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

http://groups.google.com.my/group/re...a655085a0f7586

how good are class D amplifiers?

"Rob" wrote in message

Arny Krueger wrote:
"Rob" wrote in message

Yes, we've done this, and I set out a few problems I had
with your methodology and method.

I've reviewed the last 100 or so google summaries of
your posts here, and can't find any such thing. Can you
give me a range of dates or something?
6 Nov 06 - here's a snippet (I keep changing my email
'code' for reasons unknown):

Steven Sullivan wrote:
In rec.audio.tech Arny Krueger wrote:
"Jim Lesurf" wrote in message

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

What exactly is the ontological and
epistemological basis of the 'virtual reality'
methodology? I have to be absolutely clear on
these points to accept what you say.
Nice job of raising the bar to impossible heights.
I've seen this technique used many times before and
I'm not playing.

Well, it's your ball :-)

Same basic answer - questions like this were actually interesting to some
people back in the late 1970s and early 1980s. A guy named Daniel Shanefield
(AKA Daniel Sheffield) discussed them quite extensively in the BAS Speaker,
Audio Magazine, and Stereo Review.

http://www.bostonaudiosociety.org/ba...iniscences.htm

"I forgot to mention a philosophical thought that might be of interest to
some of the members: any scientific principles that are first published in
the BASS, if they are later verified by other researchers and if they prove
to be broadly useful, will live pretty much forever-or at least as long as
there is civilization. Not only do these new principles then get existences
of their own, spreading almost like living beings, but in many cases a trail
of "literature references" builds up, which brings a certain level of fame
and glory to the original publications. (You can see by my use of the word
"glory" that I take these things seriously!) However, I don't think that is
exaggerated, when it involves a big battle between truth and untruth, or if
a new methodology is made available that will help future designers innovate
better equipment for all of us.)
"One example is the equalized double-blind (d-b) listening test, which was
first suggested in my BASS article of November 1974, with results of such a
test then reported in June 1975, and with a further summary appearing in
January 1976. That seems like a long time ago, but scientists tend to keep
meticulous track of these things, partly to give credit wherever it is due
(including a legal necessity for the worldwide patent system), but also to
aid in the important task of keeping a network of tricky ideas nicely
straightened out for all to see (and maybe improve upon later).

"The trail of the now famous (or infamous) d-b test can be traced through an
article by BAS member Stanley Lip****z, who has been president of the Audio
Engineering Society (AES). Lip****z, with John Vanderkooy, wrote about the
d-b test in the Journal of the AES (July 1981). This detailed article listed
10 previous BASS articles on the subject, starting with my 1974 piece. A
lively discussion, by Lip****z and me and others, of some of the ideas
(mostly relating to the audibility of polarity) was then printed in the JAES
(June 1983). The trail was marked further when BAS member Les Leventhal
explained improvements in the understanding of d-b statistics (JAES, June
1986). And even as recently as April 1994, BAS member Dick Greiner (with
Douglas Melton) wrote further about polarity in the JAES and dutifully
referred to the 1983 discussion mentioned above, in which I had invoked some
blind-testing reports in the BASS while trying to prove a point. So, as you
can see, printed references to these BASS moldy oldies continue into the
'90s.

http://www.aes.org/e-lib/browse.cfm?elib=5549