do you agree/disagree with his arguments? I find them compelling, I am no design expert, however, his findings are scientific and repeatable for all to see.
at times I find him TOO objective, I listen to music to enjoy it, and his arguments about all music going via 100s of 5534 chips hold no sway, as he says thus the sound of other opamps don't matter simply bcos your signal has passed via these, its like saying bcos of that, you can't hear the effect of altering valves.
he also questions resevoir capacitance, I am as yet undecided as to size and effect
it has been known for decades, the effect that a tube characteristic has on distortion, ie asymetrical giving 2nd harmonic distortion and symetrical giving odd, ie cancelling even, however, I feel he deserves nigh on a nobel prize for his work in deconstructing each stage and showing the type of distortion each produces. he also argues cogently that distortin should be reduced ad infinitum as long as the price is negligible, bear in mind moving coil speakers distort perhaps 5% or more this swamps even 0.1% distortion so one could argue like he does that one can't hear that for the speaker non linearity.
but full marks to doug for his landmark work.
I have only one real problem with it, it makes amplifiers boring, as in if we followed it, we would all end up with the same amplifier.
finally, would you like anything to be added to the books? ie areas you think are not covered sufficiently? or you would like to see more of?
at times I find him TOO objective, I listen to music to enjoy it, and his arguments about all music going via 100s of 5534 chips hold no sway, as he says thus the sound of other opamps don't matter simply bcos your signal has passed via these, its like saying bcos of that, you can't hear the effect of altering valves.
he also questions resevoir capacitance, I am as yet undecided as to size and effect
it has been known for decades, the effect that a tube characteristic has on distortion, ie asymetrical giving 2nd harmonic distortion and symetrical giving odd, ie cancelling even, however, I feel he deserves nigh on a nobel prize for his work in deconstructing each stage and showing the type of distortion each produces. he also argues cogently that distortin should be reduced ad infinitum as long as the price is negligible, bear in mind moving coil speakers distort perhaps 5% or more this swamps even 0.1% distortion so one could argue like he does that one can't hear that for the speaker non linearity.
but full marks to doug for his landmark work.
I have only one real problem with it, it makes amplifiers boring, as in if we followed it, we would all end up with the same amplifier.
finally, would you like anything to be added to the books? ie areas you think are not covered sufficiently? or you would like to see more of?
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I think his book makes a valuable contribution. He covers points which sometimes get ignored. However, like all authors, he has assumptions/beliefs/prejudices so it depends to some extent on whether you share these. If you do, then you will follow his advice. If you have the opposite ones, you will probably want to ignore him.
I would love to have a perfectly boring amplifier, which adds nothing and takes away nothing. Too many people seem to confuse amplifiers with effects boxes. For me at present that means a reasonably neutral valve amplifier (no "tube sound"!).
Self was not writing for beginners, and the information he gives is not all common although some of it may be.
I would love to have a perfectly boring amplifier, which adds nothing and takes away nothing. Too many people seem to confuse amplifiers with effects boxes. For me at present that means a reasonably neutral valve amplifier (no "tube sound"!).
Self was not writing for beginners, and the information he gives is not all common although some of it may be.
Doug has done a lot of really good work and measurements over the years, but he and I have not always had the same point of view. I am less comfortable stating that amplifiers will sound the same if they both measure well under traditional laboratory conditions. I am not one to throw out measurements, as many of you know, but I do believe that much more needs to be done in the way of measurements and in terms of how amplifiers behave in the real world, as I discuss in several chapters in my book (CordellAudio.com - Home). I believe that one reason amplifiers sound differently is that they misbehave differently.
There have been times when Doug has poo-poo'd some things that I thought needed to be taken more seriously. For example, he was late to the party with DC servos and the benefits of output Triples. I also disagree fairly strongly on the merits of CFP output stages (I don't like them). And of course then there are MOSFETs, on which we totally disagree.
But this is all what makes amplifier design so interesting. We have different design philosophies and interpret measurements differently sometimes. There is plenty of room for different opinions and approaches in the amplifier design business. Doug has done a very good job of uncovering and de-mystifying a lot of amplifier design issues over the years, and for this he deserves a lot of credit.
Cheers,
Bob
As long as you write down the titles of the books you are standing on when writing your audio review.
I haven't read Self's, Cordell's or anyone else's power amplifier books (I recall from browsing Amazon there are other authors out there), but years ago I was fascinated by his webpage "Distortion In Power Amplifiers" which (as I remember) described what Self saw as the eight most significant sources of distortion in bipolar audio power amplifiers.
I may eventually get these books, but despite being an electronics design engineer with an interest in audio, I don't know if I'll ever design or build my own power amplifier(s). It's not that it's not an interesting project, but I have too many other interesting projects I want to do, and I might actually contribute something worthwhile to the field elsewhere (like here) whereas I doubt I could with power amplifiers.
I don' think anyone disagrees with that, I feel there's still good reason to reduce distortion as much as practical. Speakers and solid-state amplifiers generate different types of distortion (they tend to generate more high-order harmonics, speakers tend to generate mostly lower harmonics, as well as more stuff I mention below), and one type doesn't completely mask the other type. They each generate a different "spectrum" of distortion. This is a fact that is easily forgotten with the ubiquitous use of THD as the only and all-encompassing distortion figure. I recall mentioning this in a long op-amp thread here.
Even with tube amplifiers, the distortion is for the most part caused by the tube's nonlinear transfer function (though audio transformers give a yet different kind of distortion), whereas much distortions in speakers are caused by all sorts of resonances and diffractions, things one might think of as "ringing, delay and echo effects," things not generated by amplifiers. Again, the distortions are different and don't fully overlap, and the ear can usually hear the presence of one type of distortion even through another type, regardless of the "THD" figures of each type.
When I go to the doctor for a diagnosis, I don't want to hear about 'room for different opinions', I want to hear 'this is what you've got and you won't hear much disagreement about it'. This is the kind of service doctors would prefer to offer, and there is a constant striving in medicine, as in all but very few professions, to eliminate disagreement, which is basically an indication of an incomplete understanding. It is an approach which is, to all intents and purposes, a sine qua non for a discipline to qualify as a science.
I don't find it at all encouraging that you seem to revel in the situation prevailing in audio engineering.
Perhaps you think it's entertaining or potentially profitable for you to have a little niche where there's a load of disagreement among 'experts', but I can assure you there are many of us out here who look forward to the day when the arguments about audio engineering have been thoroughly beaten to death as they have been in other disciplines.
Doug may have been 'late to the party' in some instances, but as they say, 'better late than never'. A certain caution is appropriate in an engineering professional anyway. His attitude certainly seems to me to look forward to the day when there will be little or no room for differing opinions in an entirely seemly way.
w
That argument assumes that there is only 'one right way', which is too much like religion to me. What I'm seeing in reality is multiple valid approaches to electronic design, given the available knowledge and technology. This may result in many good designs, with a few outstanding designs, depending on the depth of one's finances.
I doubt there will ever be a 'perfect' and 'ultimate' amplifier design, and that future engineering will be exercises in gilding the lily. There are too many variables and requirements, which makes necessary practical compromises. That's just the reality of the matter. Some of us find that fun.
I doubt there will ever be a 'perfect' and 'ultimate' amplifier design, and that future engineering will be exercises in gilding the lily. There are too many variables and requirements, which makes necessary practical compromises. That's just the reality of the matter. Some of us find that fun.
I don't know exactly what is being discussed here, but I will say something that many probably don't realize...
I found that it is easy for everyone, even for every designers, to realize that some other designers may have better electronics knowledge, experience and skill. But I found many have difficulty to realize that others may have better hearing. This difficulty in realizing one's limitation affect many things. Just because you cannot hear something, it doesn't mean that others also cannot.
Many designers don't have good hearing, but if they are wise and realize their limitation, they may find a better way to design a more market-acceptable designs.
BTW, many builders have built many high end amps but still they may not have "good" ear, so I don't follow their paths (anymore). So you see, if you want to build every "best amps", you need to follow other builders' paths, but of course you cannot follow just everyone that says this and that amp is the very best, you need to know his background (amps that he has built AND IMPORTANTLY his hearing "skill"). That's why I have my own "database" of who's ear I would trust.
Often, debates on theory is caused merely because of this limitation from a designer (but he doesn't realize that he has one)!
I found that it is easy for everyone, even for every designers, to realize that some other designers may have better electronics knowledge, experience and skill. But I found many have difficulty to realize that others may have better hearing. This difficulty in realizing one's limitation affect many things. Just because you cannot hear something, it doesn't mean that others also cannot.
Many designers don't have good hearing, but if they are wise and realize their limitation, they may find a better way to design a more market-acceptable designs.
BTW, many builders have built many high end amps but still they may not have "good" ear, so I don't follow their paths (anymore). So you see, if you want to build every "best amps", you need to follow other builders' paths, but of course you cannot follow just everyone that says this and that amp is the very best, you need to know his background (amps that he has built AND IMPORTANTLY his hearing "skill"). That's why I have my own "database" of who's ear I would trust.
Often, debates on theory is caused merely because of this limitation from a designer (but he doesn't realize that he has one)!
My old dad has spent a lifetime engineering some of the worlds largest bridges. There are several types of bridge design used around the world. There are high bridges, low bridges, hanging bridges, and even within the hanging bridges there are several types. I've allways thought that it was because there are different ways of building a bridge, but now I know it's because they simply don't know what they're doing!!!
I'll never cross a bridge again...
The problem with most audio electronics books is that the author has preconceptions and they leave out what doesn't interest them or they don't think is consequential or they don't have the time and resources to research. A book that completely covers all aspects of contemporary audio design would be an enormous tome and would represent a life time of dedicated work. Self's book is great, I have read and studied it, but where choices of design direction are presented, he usually takes one course and the others are dismissed with little treatment.
Not a very good analogy I suspect. Go to two doctors and you get three different opinions. Not radically different, but different nonetheless.
Why do people always get 'second opinions' from doctors? And yes, those opinions are allmost always different.
The same with audio. The marketplace has solid state, tube, low feedback, high feedback, no feedback, single ended, push-pull, bridged, ad infinitum. Each has a dedicated following ready to swear that their brand is The Best.
For me, one of the attractions of audio is this multitude of opinions and options and avenues for experimentation. Enjoy it!
jan didden
If you think that there should be such a big room for different opinion in audio, imo you should not play in the business.
The analogy is like food. People have different likings. Some like seafood and don't like pizza, some like pizza and don't like seafood. But it doesn't mean that you can not find/cook food that will be liked by a huge majority. There are people who have "taste" for good food as an analogy for people who have "ear" for good audio.
BTW, last week I brought someone to a place to eat ba-sho (some kind of food made from meat ball). I don't like ba-sho but he really likes it that's why I brought him to a place that I thought he would like (I didn't eat myself). Today he said that it was the best ba-sho he has ever had.
I know about different preferences in audio. I know that others do not have to prefer what I prefer. But I know that there should be less room for different opinion on good sound. And if in reality there is such a big room, I can fully understand.
Getting back to the original post (a) I think many of us are grateful for his very detailed work on specific sources of distortion but (b) I think a preoccupation with low ultra THD may not encompass all that needs to be measured. I may be wrong but when reading his articles I think I have seldom, if ever, seen a photo of a square wave into a reactive load. Both JLH and King were of the opinion that this was a worthwhile indication of listenerbility in that it was an indication of stability issues within the amp'.
Agree with Doug?
Well, Doug has now written on more subjects than Audio poweramplifiers. It would seem wise to be informed on what is out there in technical literature. Goodness knows, we might even learn something factual rather than stumble about in the mists of guesswork and imagineering.
Doug's title subjects you might read and consider cover:
Psychoacoustics
Power amplifiers
Small signal audio
Role of the E, Engineer
Website miscellania
A much bigger field and more ground for disagreement now, eh? One day we might even read his thoughts on carpet weaving or musical appreciation but for the moment, his published work sticks firmly within his well qualified and respected lines of authority.
I would ask forum guys to think about the value of a book or anything you pay for, which presents facts that are just subject to opinion. I have assurances that mathematics and the sciences are an accumulation of facts but still a work in progress at the level of current exploration. I can't find many electronics texts that don't responsibly warn us where their work is incomplete, dubious or still in progress and therefore subject to qualified opinion.
Some guys get paid big money to efficiently produce revenue earning designs and products for wide sale and critical applications. Others, like us, tinker with designs put together with our limited understanding and resources that we hope will satisfy our needs and perhaps impress others in our community. We learn a lot doing this and a little technical input from those who do get paid really opens the doors to understanding, new ideas and opportunities.
However, I think that when you choose an author for their opinions, you place the merit of their work on the level of an autobiography or memoirs which may be entertaining but not essential reading. It may be comforting to know you agree with the most popular viewpoint of the day but far more secure to know that what you believe is adequately proven correct.
Opinions or sympathies don't change facts. If there is a point of error or opinion to consider a problem, it is what authors choose to omit rather than include. This is where peers (other EEs) get opiniated, steamed
up or prompted to write on the subject themselves. This is good, healthy and worthwhile expression from people who do know the facts and how they fit best, even if they ignore our favourite subjects like "coloured sound and its generation in audio amplifiers", for instance.
I say, read on... enjoy!
Well, Doug has now written on more subjects than Audio poweramplifiers. It would seem wise to be informed on what is out there in technical literature. Goodness knows, we might even learn something factual rather than stumble about in the mists of guesswork and imagineering.
Doug's title subjects you might read and consider cover:
Psychoacoustics
Power amplifiers
Small signal audio
Role of the E, Engineer
Website miscellania
A much bigger field and more ground for disagreement now, eh? One day we might even read his thoughts on carpet weaving or musical appreciation but for the moment, his published work sticks firmly within his well qualified and respected lines of authority.
I would ask forum guys to think about the value of a book or anything you pay for, which presents facts that are just subject to opinion. I have assurances that mathematics and the sciences are an accumulation of facts but still a work in progress at the level of current exploration. I can't find many electronics texts that don't responsibly warn us where their work is incomplete, dubious or still in progress and therefore subject to qualified opinion.
Some guys get paid big money to efficiently produce revenue earning designs and products for wide sale and critical applications. Others, like us, tinker with designs put together with our limited understanding and resources that we hope will satisfy our needs and perhaps impress others in our community. We learn a lot doing this and a little technical input from those who do get paid really opens the doors to understanding, new ideas and opportunities.
However, I think that when you choose an author for their opinions, you place the merit of their work on the level of an autobiography or memoirs which may be entertaining but not essential reading. It may be comforting to know you agree with the most popular viewpoint of the day but far more secure to know that what you believe is adequately proven correct.
Opinions or sympathies don't change facts. If there is a point of error or opinion to consider a problem, it is what authors choose to omit rather than include. This is where peers (other EEs) get opiniated, steamed
up or prompted to write on the subject themselves. This is good, healthy and worthwhile expression from people who do know the facts and how they fit best, even if they ignore our favourite subjects like "coloured sound and its generation in audio amplifiers", for instance.
I say, read on... enjoy!
I have personally found D Self's text books to be valuable as a starting point - or foundation from which new designers can build on.
There is no doubt that D Self is purely an objectivist - but I see that as more of a strength than a weakness. However, I was intrigued to see his design work on the lastest Azur amplifiers and his rather novel idea of moving the signal zero crossing point away from the actual zero point to reduce MF / HF THD. For me this exemplifies his test bench approach to amplifier design. Of course in the real world where real music signals are being amplified there is nearly always going to be far more spectral energy at the low end - which means that low or high frequencies are always riding high on low frequency signals. This situation pretty much results in the same outcome that he has achieved with his 'novel' design. This is an example of what can happen when your focus is too much on measured performance - which is confined within defined measurement parameters.
There is no doubt that D Self is purely an objectivist - but I see that as more of a strength than a weakness. However, I was intrigued to see his design work on the lastest Azur amplifiers and his rather novel idea of moving the signal zero crossing point away from the actual zero point to reduce MF / HF THD. For me this exemplifies his test bench approach to amplifier design. Of course in the real world where real music signals are being amplified there is nearly always going to be far more spectral energy at the low end - which means that low or high frequencies are always riding high on low frequency signals. This situation pretty much results in the same outcome that he has achieved with his 'novel' design. This is an example of what can happen when your focus is too much on measured performance - which is confined within defined measurement parameters.
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