The closest approach: what amplification?

SET all the way!

honestly I think most of it is speaker dependent ... people find a speaker they LOVE and then try to match an amp to those speakers. some speakers mate best with powerful solid state some with SET and still others with push-pull tubes.

so find a pair of speakers you love then match it with the "right" amp for your musical taste! and try all sorts of combos, sometimes things look like they could NEVER work on paper but in actuality sound pretty damn good. in other words, don't rule out an amp based on its topology or specs ... try it, YOU might like it.

Merry Christmas!

Jeff

Find your own religion - don't buy into someone else's beliefs. All the various amplifier topologies have their merits as well as their weak points. There is NO one easy solution, no one right answer. Listen to all kinds of systems and figure out which one connects to your idea of what a live even should sound like (if that is your criteria for what a good system should do to make you happy and engaged with the music). I agree that the interface between amp and speakers is critical, especially when considering SET amplification where potentials are more limited, or electrostatic speakers that require gobs of current to sound their best. Enjoy the ride!

Merry Christmas!

At a live event the actual sound waves will be the same for different listeners in the same place but what they HEAR will not. So there can never be an answer that fits everyone, leaving aside the critical speaker-amp interface already pointed out.

Any reproduction can only be selections from the original, plus the additions and distortions. I can tolerate loss of information and distortions better than the additions! So low hum and noise go to the top of my list. The distortions and editorializing of tubes often bother me less than the nasty noise of many solid state designs. Oddly, digital amplification seems to distort less and be quieter than much conventional amplification. That said, there seems to still be plenty of room for improvement, especially in getting the amplifier to remain unaffected by the speaker it is driving.

P.S. As I recall, some interviewer once asked Peter Walker how far he had pushed audio reproduction towards the goal of perfectly accurate reproduction. He said; about 15 per cent!
(I have not looked this up so be kind, it's Christmas)

I should have phrased my question better: I totally agree that system configuration is critical and that speakers are decisive. That said, I guess my question was the following: assuming a very well configured system, is there a type of amplification that gets you closer to the real thing?

Stanwal, you make an interesting point, but the fact that people hear different things given the same actual sound waves does not prevent us from trying to find a system that gets us as close as possible to the actual sound waves. That is what I am looking for in a system.

Samujohn, I am intrigued by your comment about class D amplifiers. I have been playing with a few of them, and never found them too satisfactory. As for your point about Peter Walker, well, I did not read that interview but I am not surprised by it: closest does not mean close :)

Merry Christmas to all and thanks for your thoughts

To try and answer your rephrased question, triode tube amplification has most often yielded the best result for me across a wide range of speakers, however, since it has also been a giant pain at the practical level, I have looked for alternatives. My Tact digital amp has its own limitations and weirdness, however, in its own, very cool and quiet way, it gets me as close to the music as the triodes, and holds out the hope of improvement. My full range electrostats require a good bit of power plus stability into a capacitive load.

Setting aside the speaker, and from a strict theoretical standpoint, an OTL design seems to make the most sense.

IMO

Stanwal,

Excellent point established with your 12/25/09 post!

Happy Holidays,

I can't speak to OTLs but in my experience, high power push-pull has the greatest potential for communicating the enthusiasm of a live event. There are many attributes coveted by audiophiles that have little bases in live music - precise imaging being one of the most obvious. On the other hand, live music presents tremendous dynamic contrasts compared with audio. Low powered amps like SETs tend not to fare too well in this department. And while powerful solid state designs are dynamic champs, there are just too many other areas in which they fall short.

Bill, what about the high output impedance?

It depends what sort of live event you are trying to reproduce.

I think it is possible to convincingly reproduce small scale acoustic music which has been well recorded.In this regard I find SETs or OTL are most rewarding.

Forget orchestral music or rock concerts however.At best you get a scale model of the real thing.
For orchestral music Bose 901s are probably the most convincing, seemingly regardless of amplification.Nothing else I have heard gives a realistic sense of soundstage width and venue acoustic.I hate to say it but Bose is right about this.Some sonic deception is required.

For me, it's zero-feedback, fully-balanced solid state matched with time
and phase aligned speakers. YMMV.

Unsound asked Bill about high output impedance... obviously I'm not Bill, but I'll take a shot.

If the amplifier has a very high output impedance (very low damping factor), to a certain extent the loudspeaker's impedance curve will "modulate" the amplifier's wattage output; that is, the amp will put out more wattage where the impedance curve is high and less where the impedance curve is low. This is the opposite of the behavior of an amplifier with a low output impedance, where the wattage goes up when the impedance goes down and vice versa.

Putting on my speaker designer hat, in my opinion the answer is to design speakers with as smooth an impedance curve as is practical. They will thus have virtually the same tonal balance with either type of amplifier, and one consequence is that such a speaker will allow a more apples-to-apples comparison of various amps. In practice it's usually not possible to avoid some impedance peaking in the bass region, and it might not even be desirable to do so; the increased wattage output of a high output impedance amp in the bass region can be leveraged to extend the bass deeper than it otherwise would have gone.

Having built such speakers for several years, and having had the opportunity to hear them on a fair number of amplifiers, in my opinion high quality OTL and high quality SET amps in general do sound the best. For most of the past few years my personal amps have been OTLs.

If the speakers were designed for contstant-voltage amps (most are) and have significant impedance peaks or dips above the bass region (most do), then I would still look for an amp with little or no global negative feedback.

All that being said, let me give an analogy from the world of amateur speaker building (my thing for twenty-something years). Many's the amateur speaker builder who sets out with high hopes intent on combining the best woofer with the best midrange and the best tweeter in the best enclosure using the best crossover. Almost never does the result live up to the promise of all these bests. The reason is, our enthusiastic amateur designer friend isn't taking a wholistic systems approach, based on the best outcome, and working backwards from there to assemble those components that will give this best outcome. Turning now to the question of what is the "best" amplifier, I would say look at the amplifier+speakers+room as a single system and go from there.

Duke
dealer/manufacturer

I would like to go back to Stanwal's point, which is an interesting one. Stanwal says that there are actual sound waves, but each of us HEARS different things. In my opinion, the personal experience of what we hear should be irrelevant to the discussion of what makes for a good audio system. The closer I get to capturing actual sound waves, the closer I get to the real experience. Then each of us can focus on different things in the listening experience. In other words, take Mahler fifth symphony. Out of the whole symphony there might be two minutes in which the deep vibrations of low frequencies are dominant. I know some people who love the symphony precisely for these two minutes. That's what they want to hear. Does it mean that for these people a good audio system is one that exacerbates low frequencies? I don't think so.

When I go to the symphony I am acutely aware that where I sit in the hall dramatically affects the experience. Under the balcony the bass is emphasized. Seats far away homogenize the sound. Up close the orchestra really does "image" with the violins on the left etc. At all points, however, the dynamics and the texture of the sound make all reproduced sound seem...well..simplified, flat and lacking in a host of important qualities. I think all of us agree on that. As Peter Walker said, like listening through a window. And a smudged window at that. So, what to do? For years I was in the "straight wire with gain" camp. Often that led to highly detailed sound that nonetheless still managed to get on my nerves! I have slowly migrated to the "are we having fun yet" group. A truly accurate map of the earth would have to be...well....the earth. So since we are of necessity in the simplifying and simulation business, I strive to recreate not the most mathematically complete model, but rather use a bit of trickery to recreate a bit of the emotional experience that draws me to music in the first place.

I hope the OP will forgive for going a bit off topic.
Duke, with re: to "...the answer is to design speakers with as smooth an impedance curve as is practical." Would that be easier to do by lowering the impedance or by increasing the impedance?

Samujohn, I misinterpreted your original post. Excellent points...thanks for clarifying.

Unsound, an across-the-board raising of the impedance curve (a la Speltz autoformer) will usually make a speaker more high-output-impedance-amp friendly, if needed. Redesigning the crossover to smooth out the impedance curve is seldom practical, but in some cases the addition of an external filter to tame an impedance peak (often present in the crossover region) can be beneficial. I would estimate that taking the impedance curve into account in the crossover design phase can more than double the workload, as the designer is trying to simultaneously optimize both impedance and frequency response, and often that which helps one hinders the other.

I like Samujohn's comment:

"I strive to recreate not the most mathematically complete model, but rather use a bit of trickery to recreate a bit of the emotional experience that draws me to music in the first place."

In my opinion the goal is to recreate the perception of the original (or fabricated) event, and focusing on perception is different from focusing on recreating the waveforms. For example, very low percentages of high, odd-order distortion are both audible and objectionable, while very high percentages of second harmonic distortion are inaudible or barely audible, and are not objectionable. I've seen data that indicates 30% second harmonic distortion is statistially inaudible, but it looks bad on paper if the yardstick we're measuring with is THD. A perception-based yardstick has been proposed, but has not found acceptance unfortunately.

Tricks: Digital amplification is inherently capable of performing complex processing without causing additional (unintended) distortion. I can compensate for room acoustics, draw and save my own response curves, program various real time corrections for loudness contours, and more. I have no wish to be a commercial for any product, merely to illustrate that we are at the beginning of a total revolution in audio as we marry computers to amplifiers. Preamps will disappear and programmable amps will detect the input requirements (my MacIntosh does) and equalization required for the speakers. Interconnects will disappear. I can't wait!

Duke, using an auto transformer would, at least to my sensibilities, be a bit beyond typical speaker design. In my limited experience, those speaker designers that have designed their speakers to have a smooth impedance curve such as Jim Thiel, as part of what I sususpect to be an effort to have a steady amplitude response, have adjusted their crossovers in just such a manner. It appears to me that it might be easier to adjust a speaker to have a smooth impdeance curve with a lower rather than a higher impedance curve. Then again, I really have no real personal experience or technical back round to claim this with any authority.

Samujohn, I couldn't agree more! The promise is very exciting. On the other hand, I would have thought further inroads would have been already made.

Unsound, I agree that it is developing slower than it could. My amp's basic design is ten years old. I have done no marketing research, but I suspect that since all the money is in home theater, the larger HT companies are waiting until that market is saturated before they spend scarce R&D money on sound, which is after, all a mere adjunct to the Video world. Perhaps Steve Jobs will make us a SUPER IPOD!
In the mean time, we audiophiles appear to most folks as just a bunch of old nostalgic guys- like the Radio Amateur clubs- vacuum tubes and all. My only encouragement is now that my daughter is in her thirties, she is willing, on occasion, to unplug her headphones and listen to my speakers.

OTL of course!!! Sorry to say, the rest of the world doesn't know what music reproduction is all about ;)

Hate to sound like I'm getting on the OTL bandwagon, but I guess I am. I've tried all types of amplifiers, many very highly regarded Class A tube and SS, at least with my speakers (Merlin VSM - smooth, highish impedance)nothing has sarisified me more than the Atma-sphere M60 OTLs. They may not be a good match for all speakers, but with tube friendly speakers, I think the OTL approach is hard to beat for "realistic" presence. And yet, 15% might be a close estimate of the sound of live acoustic music; which doesn't make listening to music any less enjoyable, it is just a different experience than live.

Unsound, obviously I should have made it clear which part of my response was about things an owner of existing speakers could do, and which referred to something that would have to be done during the design stage.

In my opinion using an autoformer is something a speaker owner would do to make his speakers more compatible with OTL amps.

If we're just looking at the design stage, then yes it is easier to smooth the impedance curve by lowering it. But if the end goal is compatibility with OTL amps, for example, lowering the impedance curve can be counter-productive. Some of the design choices that lead to a medium to high, and smooth, impedance curve need to be made before the crossover design stage. For example, I can't expect to build a 2.5-way system using two 8-ohm 6" woofers and end up with an OTL-friendly design.

Duke, thanks.

We listen to a system not a ampifier. So how can your ? be answered? many ways to skin the audio-cat and all the amp types you mentioned can make for a great sounding system if used in the right way.

Johnk, Here is a metaphor. A racing car can race and finish in the top three only if it has an engine, four wheels, and thousands of other parts. Now, I think it makes sense to ask whether it is more likely that a gasoline vs. a diesel vs. an electric engine is more likely to get a given car to finish a race, doesn't it? These different engines require different car configurations. Still, as of today it is more likely that a gasoline engine will get you close to the top three. I guess this was the spirit of the question. System configuration is key. that said, are there types of amplification (and associated configurations) that are more likely to get us close to the real thing?

"We listen to a system not a amplifier"
Yes and we listen to different recordings, so how can we determine anything beyond that we liked a specific song, on a specific system, on a specific occasion?
I maintain that with experience and consultation with others, one can form a reasonable opinion as to what component in a system is causing what result.
I have gotten together with friends gathering a dozen amplifiers in the floor and comparing them. Then I often have borrowed the amp that gave a certain impression and taken it home for a week to evaluate. I have deliberately sought out speakers with
difficult loads like Wilson, Thiel, and Soundlabs. When I get a similar result despite all this, (as I have with Conrad Johnson solid state amps for example) I can say with reasonable confidence that the amp has a certain set of characteristics. Words may fail me, but over time I can hear the difference.

Ggavetti,
But it's not a race.
The question is what's "best" (or may as well be, since the OP asks "close as possible to the reproduction of a live event")
Fastest you can quantify and measure, and all will agree on the measurement.
Best, or close as possible to the reproduction of a live event, is a different matter altogether.
As many different answers as people with answers.

Sebrof, The race metaphor was used just to make the point that it makes sense to think about types of amplifiers despite the fact presence of strong systemic effects.

Regarding your point about measurability, it's no doubt more difficult to measure "the real thing" than it is to measure speed. That said, I do believe there is a reality out there that is objective, which defines the real thing. If both you and I sit on seat 15, row 11 of the same auditorium to listen to Mahler's 5th, both you and I get exposed to the same sound waves. That's the real thing in my opinion. Yes, the real thing might differ depending of where you sit (front mezzanine is different from a side box) which complicates matters quite a bit. But we can at least start to reason about electronics that get you close to a particular manifestation of the real thing (for instance, sitting in a good, central position at a good auditorium).

" I do believe there is a reality out there that is objective, which defines the real thing"
Ah, to wax philosophic! Well yes and no, perhaps, we'll see. Sound waves are "real" in the material sense, but hearing is not. My teenager will be exposed to the same sound waves as I, but will he "hear" the same thing? How about a person from rural China? (A Chinese "opera", for that matter, is quite an experience). So much of what we hear is made up of learning, plus how our hearing actually works (a remarkable process in itself).
To go out on a limb, recognition is the key factor. We "hear" in the meaningful sense, when we recognize.
As a thought experiment I submit that if one were exposed to "perfect" sound wave patterns in a sufficiently unexpected context, that recognition would be so impeded that it would not take place at all. Our body might respond, but the brain would not "hear". On the other hand, if some one says: da, da, da daaa! the connection to Beethoven's Fifth may involuntarily pop into one's head.
(I hope you guys are having a beer while reading this.)
cheers

"Sound waves are "real" in the material sense, but hearing is not. My teenager will be exposed to the same sound waves as I, but will he "hear" the same thing? How about a person from rural China?"

Interesting, but I would argue that a machine that gets as close as possible to reproducing the "real" sound waves is what "the closest approach" is all about. Then I am less concerned about whether you and I perceive the same sound wave differently. That's unavoidable: my recognition of the real thing is different from yours, but the real thing exists independently of you and me. So, I guess the name of the game is reproducing actual sound waves. Don't yo think?

Back to amplifiers: There is general agreement about analog amplifiers. Solid state has the least distortion; the output resembles the input better than tubes. Are the tube folks all crazy? Do they like the sound of distortion? No they are not, but yes they do. Tubes compress the sound and they add harmonic distortion.
It is generally realized that our recordings are highly compressed of necessity. We simply cannot fit the sound waves of live music into our microphones, recording equipment, or our homes, so the recording engineers try to compensate to make the music sound more "natural". Among other topics, this gets us to the masking effect. Fairly slight changes in equalization can result in instruments or voices moving forward or back in the soundstage or even falling into a "hole". Engineers try to "correct" this. At 15% information recreation, recording is simply in the illusion business. Lots of folks like the illusion presented by the added distortion of tubes better than the more literal presentation of solid state. I suggest that the added harmonic distortion masks a good bit of the confusion of multi miking and of the room acoustics, but this is just a thought.

If you are going to make progress with audio, the first thing you have to do it look at the way the human ear perceives sound- IOW understand the rules of human hearing.

Unfortunately while the bench specs we are so used to were being developed, research was going on at the same time that proved that much of the bench specs were/are meaningless, but the audio industry chose to ignore this research.

Its a common phenomena to ignore things that appear to be small errors, but if you study chaos theory you find that you do this at your own risk! It turns out that the way the human ear perceives volume is not by the actual sound pressure of the sound in question, but instead by the trace amounts of certain odd-ordered harmonics, the 5th, 7th and 9th to be exact.

Any enhancement of these harmonics is instantly heard, even if only hundredths or thousandths of a percent!!

Global negative feedback, which is found in most amplifiers, **enhances** these very harmonics while otherwise reducing distortion. As a result, it can be safely said that added loop feedback to an amplifier will violate one of the fundamental rules of human hearing.

However the presence of distortion will mask detail and cause harshness (even with even-ordered harmonics) so you have to prevent it. Without loop feedback, this is a bit chanllenging, but it can be done: class A operation, Triodes, simple circuitry, fully balanced operation (cancels distortion throughout the amp) and an avoidance of things like pentodes, transistors and transformers that are known to increase distortion excessively is one technique.

Of course, such an amplifier will have a higher 'output impedance' but it turns out that the effectiveness of things like damping factor in speakers is highly qualified in any event. All speakers, if overdamped, will exhibit loss of bass (up to 8db) and transient detail, and how much damping an individual speaker needs can vary over a range from 0.1:1(!) to 20:1. However, there are no known speakers that benefit from more than about 20:1; something to keep in mind!

The point is that if a speaker cannot be driven by an amplifier that is in fact designed to obey human hearing rules, its likely that there is also no way that speaker will ever be heard to sound like real music. That should stand to reason, but I am always amazed at how many people point to bench specs- even when their own experience is that those very same specs tell them nothing about the sound of the amplifier in question! That alone should tell you that bench specs are measuring the wrong things :)

Some references: http://en.wikipedia.org/wiki/Chaos_theory

"Critical Damping: Missing Link in Speaker Operation Parts 1 & 2 http://www.pearl-hifi.com/06_Lit_Archive/07_Misc_Downloads/Misc_Downloads.html

"IOW understand the rules of human hearing" is surely an overstatement. Hearing evolved along with the brain, and our survival and social needs for eons. We are a very long way from a complete understanding how it interprets information.

Atmasphere: I must be getting tired because I misread your opening paragraph.
Please ignore my response.
cheers

Atmasphere, i am not sold on the notion that audiophiles need to be good physicists or neural scientists to make progress with audio. as far as i am concerned, i much prefer making progress with audio by educating my ears to perceive dimensions about sound reproduction that one is not aware of unless he educates his hear. so, my approach is to educate my ear and then experiment with different systems, not studying the physics of sound or the neural bases of hearing.

Ggavetti, I completely agree with you. To be clear here though, its not the audiophiles that need to understand this stuff, its the **designers**!

IOW when you see designers building equipment that follows the human perceptual rules rather than bench specs, then meaningful audio progress will result.

I think Atma-sphere's comment were meant for designers of equipment, where, if not physics, at least some knowledge electrical engineering and psychoacoustics would be more than useful.

I am sorry, atmasphere. I misinterpreted your post. Yes, I completely agree that designers ought to know about physics!

One would imagine that most audio designers know alot about electrical engineering, but you might be surprised. Always interesting to talk to folks like Ralph (Atma-sphere), Ken Stevens (CAT), or Roger Modjeski (Music Reference), that actually have technical backgrounds. One thing I have noticed from these folks (Roger Modjeski especially) is their view of the efficacy of many tweeks that some say GREATLY improves performance; they seem skeptical at best - it took me a long-time to convice Roger that I did not want his hard-wired power cord for my MR9 Special Edition:). What I also notice is a tendency to evolve a product over-time, rather than radical changes every other month, which seem to be driven by marketing considerations rather than technical ones. You look at products from Atma-sphere, CAT, Joule, Music Reference, Merlin, Vandersteen and they all seem to figure out a solid design and then evolve it, optimize it, sort it out over many years; but they all started from sound technical design and principals that were basically right the first time; they also seem to be succesful over time. I think Ralph had a pretty good idea years ago, Class A, Triode, OTL - hard to beat 20-years ago, and nothing much has changed since then - though they look better today.

Pubul57: It's hard to disagree with FVA that we are being marketed to death. I know people in trade need product to sell, but the better approach is usually the evolutionary one you suggest. I am happy to buy affordable new equipment in order to get better results, yet several of my components are old enough to vote.
An RM9 is a tough act to beat!

Other than digital, I think for the most part great amps and preamps, and possibly true of speaker technolgy as well, are fundamental designs that have around a long-time. Perhaps some minor improvement in parts (capacitors, rsistors), but basically, in my experience the great designers made great product 30 years ago, 20, years ago, and they were guided by sound engineering principles and circuit design - not hocus pocus, revolutionary breakthroughs that put all previous products to shame. Actually, Ralph probably did come out with a real breakthrough at the time with his OTL concept, but not much need to change it significantly since then. You are right about the RM9, the kind of product you would call a keeper, would not be surprised if it has the longest average length of ownership of any amp ever made.