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Old 12th June 2013, 10:42 AM   #9351
SY is offline SY  United States
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Second Law.

No R&R. No error bars. It's nonsense.
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Old 12th June 2013, 11:03 AM   #9352
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Firstly, we're interested whether an effect takes place which is measurable, and whether it's consistent, repeatable. In that paper they claim that it is, and I see no reason to doubt that. Then, one can argue what is the cause of that, and especially whether totally conventional and reasonably priced methods can achieve the same results.

Our big headache in this is nailing the 'problem' occurring, actually being able to point to a clear 'reading' that some abberation of the signal is taking place. If statistical or other relatively complex analysis has to be done to confidently point the finger, so be it - the point is to be able to corner the mongrel ...
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Old 12th June 2013, 11:05 AM   #9353
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Quote:
Originally Posted by bcarso View Post
Yes, it's a time-honored technique. As with most bootstrapping the bandwidths achieved are usually a bit disappointing.

One of the possible features I'm exploring for some new phono preamps is determining the net capacitance of the interconnects and providing the ability to reduce it if desired, in addition to the conventional choice of loading capacitances and termination resistances.
Anything on bootstrapping is pure gold to me be they for or against . I never witnessed walking on water so can not give an opinion . Bootstrapping I have seen and love it .
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Old 12th June 2013, 11:29 AM   #9354
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Originally Posted by fas42 View Post
In that paper they claim that it is, and I see no reason to doubt that.
This is the hazard of not having any real experience in setting up and running proper experiments.
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Old 12th June 2013, 11:40 AM   #9355
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A question . I have built a very simple mostly pentode amplifier which is pleasing against my friends 300 B design . Where I might have an advantage over some is that I tried to define the problems before even starting . To my advantage I have a big bucket of valves to try . Some are close to death and others above spec . I was given serious warnings by others I can not expect the performance of an amplifier like this to be repeatable . Well whatever it is I got wrong that is not true .

I have no loop nor plate to plate feedback . I have no transistor current source or sinks . The design is modest in it's aims . The speakers suitable to use with it .

Here is the question . No valve measures very differently to the next . Before anyone says I have lousy equipment I do have access to an Audio Precision test set . Results I get and from AP are not too different if a valve design . The question is why do various EL 34's sound different ? To sum it up it is like this . It is like you wake up having slept 5 years . Everything is subtly different . Same newsreader looking older . Cars are a littler different . It is the same , yet it is different . I stress all are full spec devices here . Bias is fine if asking .

I feel as my amplifier is so simple it should have no mysteries . The differences are real . Almost like Invasion of the Body Snatchers real . One guess is how back EMF is handled ? I slightly discount impedance differences as this seems not to have a strong correlation . If a journalist it would be 5 or 3 stars differences .

One thing my amp does do is help OK recordings sound a bit more detailed . I value that , it was my belief it would . I don't like euphoniuc additions . I accept a little .
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Old 12th June 2013, 11:50 AM   #9356
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Quote:
Originally Posted by fas42
In that paper they claim that it is, and I see no reason to doubt that.
I have no reason to doubt that they sincerely believe that. Given the flaws in their method, I have every reason to doubt it. Essentially, they are measuring the time domain response of two sets of filters (CD out, sound card in) yet without synchronising clocks. They are doing the inverse of Stuart's digital insertion test: they are inserting an analogue channel into a digital path and then measuring the result. The large differences they initially see expose the flaws in their method. Careful alignment eliminates most of these; much of what is left is just noise.
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Old 12th June 2013, 11:56 AM   #9357
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Originally Posted by nigel pearson
The question is why do various EL 34's sound different ?
The exact mix of distortion harmonics and IM depends on bias point and signal level, which in turn depend on details of valve response. With no feedback it would be surprising if there were not small differences in sound when you swap valves. That is partly why feedback was invented: to make circuit behaviour more independent of device details.

Back EMF and impedance are just two different ways of talking about the same thing. People who don't realise this, or hope others don't realise this, can bamboozle with 'science'.
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Old 12th June 2013, 12:03 PM   #9358
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Quote:
Originally Posted by SY View Post
This is the hazard of not having any real experience in setting up and running proper experiments.
As indicated in the document, it is a briefing paper, a commentary on work done to date, a progress report - a quote at the end sets the perspective:

Quote:
As audiophiles we all intuitively know one fundamental thing - basic published
measurements (whether they come from manufacturers or magazines) whilst they might,
for instance, guide us when it comes to matching the electrical characteristics of an amp
and speakers, bear little or no relation to the musical quality of the resulting listening
experience. We've all heard systems where the bits of kit measure with 0.01% distortion
yet the system sounds bad; and weʼve all heard other systems, with higher levels of
measured distortion, say 0.1%, which deliver extremely enjoyable musical results. How
can this be unless our existing measurement techniques are missing something absolutely
fundamental?

The work done by Acuity does NOT provide all of the answers. It does NOT
provide any one critical answer. What it does provide is a wholly new perspective that
significantly extends the usefulness of what we already know. This is an addition to
existing measurement techniques, which gives us a new viewpoint both when it comes to
system performance and how we can interpret and understand the results of what we
already know.
What I'm taking from it is that at least they've had the courage to try and gain some greater understanding of a 'bigger picture'. Whether they're doing more, to get decent meat on the bones, is another question, and there's every possibility it's bogged down into an "it's all too hard!" stalemate - to be just used, as is, for marketing propaganda ...
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Last edited by fas42; 12th June 2013 at 12:07 PM.
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Old 12th June 2013, 12:26 PM   #9359
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Originally Posted by DF96 View Post
The exact mix of distortion harmonics and IM depends on bias point and signal level, which in turn depend on details of valve response. With no feedback it would be surprising if there were not small differences in sound when you swap valves. That is partly why feedback was invented: to make circuit behaviour more independent of device details.

Back EMF and impedance are just two different ways of talking about the same thing. People who don't realise this, or hope others don't realise this, can bamboozle with 'science'.

I feel I took that into account . I would say it still surprises me . I am so pleased the amplifier is almost as predictable as a loop feedback amp on measurements .

One guy advocates putting a 1N4007 diode from UL tap to G2 of the EL 34 to overcome back EMF problems . I was warned off as a friend says it then becomes a voltage doubler . Mine is an SE amp at 450 V . I suspect it would be OK . It must happen in PP versions even without the diode ? What a minefield .

The opposite is true if motorcars . In a darkened street these days I have no idea of the make . Wasn't true in the past . So sickening to have a copycat world . The wind tunnel said NO is I suspect the reason . The little Fiat 500 is easy to spot so it is not required by science to be identical . The 500 measures well . Fiat and Ferrari , great .
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Old 12th June 2013, 12:27 PM   #9360
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Quote:
Originally Posted by DF96 View Post
I have no reason to doubt that they sincerely believe that. Given the flaws in their method, I have every reason to doubt it. Essentially, they are measuring the time domain response of two sets of filters (CD out, sound card in) yet without synchronising clocks. They are doing the inverse of Stuart's digital insertion test: they are inserting an analogue channel into a digital path and then measuring the result. The large differences they initially see expose the flaws in their method. Careful alignment eliminates most of these; much of what is left is just noise.
To me the implication in the paper is that the differences are reversible - that is, after alignment to minimise differences they make a change to the environment, by changing a cord say - and the results alter. To have reasonable confidence in their results they would need to reverse that change and repeat the experiment, which should cause the first set of results to be replicated. Even though not precisely stated as having happened the tone of the article implies those sort of procedures would have been followed.
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