[JaZZ]

Translation from a (German) fundamental article in «stereoplay»


«With new analyzing methods stereoplay cottons on more and more to the complex amplifier sound on the basis of measurements.

stereoplay, as the «inventor» of the distortion theory, knows about the importance of the distorting behavior since quite a while. It's not the amount of distortion that counts, but the spectral distribution of the harmonics. So the state-of-the-art spectral analyzers of the eighties showed an evenly decreasing spectrum with the most euphonic sounding amps. But only the DSP power of the System Two Cascade from Audio Precision enables the display of every single harmonic's course (if desired, even up to 15th order) over the whole power range without any Sisyphean labor.

In the varicolored band of curves (see graph 1: sample amp with display of up to 9th harmonic on real and complex 4-ohm load) suddenly things are getting clear which have been hidden up to now: With increasing power the single overtones increase with different rates, depending on the load impedance, or even decrease. This explains why some of the amps which looked good according to traditional punctual measuring methods didn't sound that good. Then when the single harmonics decrease with increasing order, but at the same time increase with increasing power, the result is euphony.

... This method also shows in an impressive manner the importance of a certain warm-up phase for good sound (see graph 2). Due to the display of the distortion amplitude depending on the power (from few milliwatts up to the measuring limit – to be seen in graph 1 by means of the steep increase of distortion on the right border) instead of the distortion factor, the harmonics contrast more with the amp's noise floor, recognizable by its fidgety course parallel to the baseline. The transformation into a three-dimensional chart (see graphs below) makes the distortion behavior of the amp particularly descriptive.»

 

[JaZZ]

I think this is a really good basis for the explanation of «amplifier sound». It's always been a mystery how amps which measure that similar, if not identical, can sound that different. Obviously it's the distortion and in particular its spectrum which make the main difference. I think it's not too presumptuous to conclude that a «good» sounding amp is one with a «harmonic» harmonic-distortion spectrum, not one with a low distortion. In audiophile circles it's broadly known that negative feedback used to reduce distortion has a negative impact on the sound. So is this quasi-theorem also to be challenged? Maybe it's just the missing distortion which makes the sound «worse», less appealing, whereas a «healthy» and well-defined dose of distortion brings the right euphony audio enthusiasts expect from amplifier sound? I really don't know. Anyway, this idea is not too absurd by all means.

Since headphone amps are very easy to change and to compare to each other, they are auspicious objects for the analysis of the «amplifier sound». To throw my experience with direct-path experiments into the discussion: amplifiers have indeed very multifaceted ways to alter the source sound. I'd like to make clear (once again) that my tests have taken care of all the concerned factors (such as impedance matching and low-impedance-load current-supply issues of the source devices) to make sure that the direct path sound indeed represents the original source sound, at least in a very high measure.

I'm not an electronics expert, and my knowledge of amplifier technology is just marginal. But you really don't need such knowledge to hear how subjectively «better», warmer, smoother, more colorful, more coherent, more spacey and more convenient amps consistently sound compared to the unamped original signal directly fed to the headphones. This even compensates for the loss of dynamics, transparency, resolution and focus the additional amplification stage causes. Of course you can't renounce amps. Speakers need power. Even output stages of CD players consist of amps. But is it really indispensable to amplify those signals further? You may say: yes, of course – the more so if it brings a better sound. I agree so far. Even to me the subjective impression is more important than the knowledge of the theoretical superiority of the direct path. But my actual concern is to challenge the common «consumer» attitude to expect wonders from expensive amplifiers. If they were really great in the original sense of «high fidelity», they would sound exactly like the direct path. I'm sure a lot of people wouldn't rate such amps as the best ones, the less so would they buy them for lots of money. I'm sure it's possible to simulate the distortion behavior of the most highly rated amps in the digital domain (there are such features in some wave editors, e.g. to simulate tube amps), and this would cost much less. This is not meant as polemic, BTW (at least not in first place...

)

JaZZ

 

[Rotareneg]

That's news? I thought everyone knew that amps that sound "musical" have a certain harmonic distortion of the sound, that's the entire point for having tube amps anymore.

 

[Budgie]

This seems like a reasonable idea to me. The proof , I would think, will be when an amplifier is designed with this method of testing being the primary design criteria- or a body of evidence is generated, relating distortion, as measured with this criteria, against subjective reputations of an exsisting amplifier's sound quality.
I think there are a great many manufacturers who will have a vested interest in resisting any method that could reliably indicate the sound of a product, before it is purchased. Such a method could greatly alter the audio market.

 

[JaZZ]

Quote:

Originally posted by Rotareneg That's news? I thought everyone knew that amps that sound "musical" have a certain harmonic distortion of the sound, that's the entire point for having tube amps anymore.

Well, it's not completely new, but it's commonly only been applied to tube amps so far. And it's not even clear if the increased low-order harmonics with tubes are the whole story; there are possibly some higher-order harmonics with transistors that harm the sound more (but that's another theory). As it looks like now, harmonics - and thus a euphonic modification of the source sound - are even necessary to make a «good» sounding amp, and this - most notably - also with solid-state.

 

[Calanctus]

JaZZ, I'm very interested but I'm having a little trouble understanding the translation and the graphs. Can you tell me if the following statements accurately summarize the main point of the stereoplay article:
"Amplifiers with distortion that is proportionate among the different harmonics (1, 2, 3, etc) sound better than amplifiers with distortion that is uneven (some harmonics more pronounced than others)."

Right? Wrong? Partial? Help me out here.

 

[JaZZ]

Calanctus... Quote:

"Amplifiers with distortion that is proportionate among the different harmonics (1, 2, 3, etc) sound better than amplifiers with distortion that is uneven (some harmonics more pronounced than others)."

...yes, that's what 's meant.

And don't forget: an even dynamic behavior of the single harmonics!

 

[Dusty Chalk]

I thought it was the even order harmonics that were the good ones (to a point), and the odd order harmonics that were the "less pleasant" ones.

That said, I doubt it's the only criteria, but it would definitely be one of the ones to add to the list, I think (phase accuracy, frequency response, etc.).

 

[jphone]

Maybe this kind of measurements are a breakthrough for Stereoplay. Audio engineers used spectrum analyzers like the HP-3585A with an HP-IB interface to a computer to analyze data further without "Sisyphean labor".
Also you state that you are not an electronics expert but you are ready to accept Stereoplay's distortion theory (they are the "inventors" right? ).
And a lot of totally unsupported theories follow that down the thread....hey let's make our own science as we go.

Addition:
http://www.aloha-audio.com/library/FindingCG.html

I don't agree totally with this either but it takes the "invention" out of Stereoplay.

 

[JaZZ]

Quote:

Originally posted by jphone Maybe this kind of measurements are a breakthrough for Stereoplay. Audio engineers used spectrum analyzers like the HP-3585A with an HP-IB interface to a computer to analyze data further without "Sisyphean labor".

If it's the Siyphean labor or something else that has kept audio engineers from such a systematic analysis so far - it doesn't really matter. To me it even doesn't matter if stereoplay is kind of pioneer or not... it doesn't change the weight of their results.

Quote:

Also you state that you are not an electronics expert but you are ready to accept Stereoplay's distortion theory (they are the "inventors" right?).

Yes, I'm ready indeed. I wonder what it is that prevents you to be open for it. Are you an electronics expert? So what's wrong with the theory? That would be more interesting than an ideologcally colored denial. I don't think there's any point which can be classified as a clear error. What alternative explanation do you have to offer in terms of the sonic differences with amplifiers? I also wonder what metrological criteria you think are the ones which provide a neutral sound (apart from an even frequency response...). Or a «good» sound, respectively.

Quote:

And a lot of totally unsupported theories follow that down the thread....hey let's make our own science as we go.

This statement of yours has zero information content - except (again) for a biased attitude. Where's the ennemy? Please explain what's wrong with what!

I have no shares of stereoplay, so I don't care a pap for it if they're the inventors of anything or adorn themselves with borrowed plumes. But their theory looks very credible, and BTW it's rather conform with the article you brought into play.

 

[jphone]

Ok, I'll be .....sort

Streoplay's systematic analysis is not new.
The graphs and the info that you posted are incomplete (at least) to support any theory (pretty colored charts do not constitute proof).

I am open to all theories as long as there is a true scientific method used to prove or disprove them. And yes, I'm an electrical engineer that happens to enjoy music (live and reproduced). And no, I am not going to write a diatribe about amplification, distortion etc. There is a lot of literature out there that can help you educate yourself.

The content of my post is "reader beware". Oversimplification is the enemy ("Amplification for Dummies" ?). And my amazement that somebody that states "I'm not an electronics expert, and my knowledge of amplifier technology is just marginal" will assert that this is a credible theory or not.

And my message does not revoke your right to hear differences in amplifiers because there are.

 

[JaZZ]

Quote:

Originally posted by jphone I am open to all theories as long as there is a true scientific method used to prove or disprove them.

As you may know, after some reflection, a «theory» is by nature something that's not yet proved. At least there have been true scientific methods used to elaborate it, and there's a serious background in the form of electronics professionals who happen to be audio enthusiast at the same time. I don't think they would need some technical advice from you...

On the other hand I concede that their involvement in a press medium makes it recommendable to handle their self-portayal as the inventors of the theory with care.

Quote:

...my amazement that somebody that states "I'm not an electronics expert, and my knowledge of amplifier technology is just marginal" will assert that this is a credible theory or not.

So you think you as an electronics expert are more authorized? To judge the interrelation between harmonic distortion and sound colorations I don't need to be electronics engineer (in fact to guess is all I can do). But when it comes to find the reasons for the distortion, then it's your turn.

Quote:

And my message does not revoke your right to hear differences in amplifiers because there are.

This seems to be at least the lowest common denominator...

 

[jphone]

Ok,

so your understanding is that theories are self-sustained with no need of proof. Interesting. So the Stereoplay documentation (the excerpts that you provided) are there just to support their colorful pages?
Let's assume that you are trying to analyze scientific data, and complex data at that, from astronomical observations. Would you trust an astronomer or a veterinarian (no offense) to do the analysis (given no other training)? Your perception of differences in amplifier sound cannot be attributed to coloration from distortion or anything else, it can be frequency response aberrations or otherwise. You can only guess, exactly my point. Guessing is not very scientific or accurate. That's where hard data comes in.
You are correct about the lowest common denominator. My suspicion is that our beliefs behind the reason of amplifier differences are far apart.
On the bright side we share a couple of headphone and music preferences. And I will leave it at that

 

[markl]

Isn't it possible that whatever is being measured here is not "distortion" per se, but the sum total of all the individual components in the signal path in the amp that "colors" the sound with the combined signatures of all those parts? Obviously in addition to the differences in components used, circuit design, power output and other things will affect the sound of one amp vs. another.

Also, just because we have invented 5 or 6 ways of measuring amps performance does not mean that those are the only 5 or 6 metrics that can ultimately be measured that affect sound. The tools available to us at this time for measurement may not be nearly complete enough to capture all that an amp is doing, leading two amps that measure identically to sound completely different.

In the end, to me, measurements are useful in that they can tell you if an amp has any weird anomolies, but I don't think they're capable of relating how that amp will actually sound to the user.

Mark

 

[JaZZ]

Quote:

Originally posted by jphone ...so your understanding is that theories are self-sustained with no need of proof. Interesting. So the Stereoplay documentation (the excerpts that you provided) are there just to support their colorful pages?

I really don't know what you want. A theory is a theory, not more - for the time being. It has to be proved to become broadly accepted. This is not yet the case here. You have to see what it's about: the impact of the harmonic distortion components according to some special patterns on the perception of euphony. It will be very hard to prove this, since it's a psychoacoustic phenomenon, thus subjective. It has very little to do with exact science. Well, I know the stereoplay team somewhat and trust these people quite a bit in terms of their hearings. This article is just a continuation and a metrological corroboration of some previous ones.

Quote:

Let's assume that you are trying to analyze scientific data, and complex data at that, from astronomical observations. Would you trust an astronomer or a veterinarian (no offense) to do the analysis (given no other training)? Your perception of differences in amplifier sound cannot be attributed to coloration from distortion or anything else, it can be frequency response aberrations or otherwise. You can only guess, exactly my point. Guessing is not very scientific or accurate. That's where hard data comes in.

Now you miss the point completely. The discussion was about our different «expert» statuses in terms of judging the validity of the stereoplay theory - and not about any personal listening experiences and any deductions therefrom. Your example shows that you would trust an astronomer more when it comes to judge the beauty of star nebula than any layperson...

Quote:

You are correct about the lowest common denominator. My suspicion is that our beliefs behind the reason of amplifier differences are far apart.

Well, I don't believe in anything so far, just rate this theory as quite logical and reasonable, thus credible. Whereas your own contribution to this thread was a completely «negative» one so far. It would be nice to know what theories you prefer.