How close to the real thing?

Atmasphere, I noticed that the output impedance of one of your amps is about 4 ohms, and I assume that impedance is not perfectly linear across all ten octaves. So, isn't that high output impedance going to affect the audible frequency response of the amp-speaker combination, and in ways that vary with every different loudspeaker's impedance curve?

Tim,

Triode.......

Frank ,

I hope Kirkus have you figured out, this way at least one of us can follow along ... :) :)

Waryn,

Ever Heard of the practice of medicine .. yes they are still in the dark there 2 my friend...

Regards,

Kirkus, thank you: your statements, "it takes just ONE instance of having experienced reproduced sound as being real" and "been dumbfounded by amazing experiences from really crappy stuff, and also underwhelmed by my experiences with some really beautiful machinery", is precisely where I'm coming from. My particular angle, "obsession", etc, for many years has been to work out, and am now repeating myself, what the HELL IS going on!! I have been attempting this essentially by the process of elimination, and for me the answer is (drum roll ...) the glib statement, Everything Matters! I've found unless one becomes totally anal (sorry!) about the whole kit and kaboodle, or you fluke it to some degree, then it won't happen, it won't be "real"!

To whip out yet another analogy -- love those things :-) -- take a typical commercial passenger aircraft. To me, the audio industry is full of people who say, for example, it's all about the engines, you've gotta have turbines using this very special metal, and the fuel lines going to them have to be made out a really esoteric plastic, don't worry about the wings or landing gear, any old stuff will do. Another says, no, no, no, it's all about the cockpit, unless you get this set up perfectly it's hopeless, what's used in the rest of the airframe is pretty irrelevant ...

Would you fly in a plane designed or maintained by these people? No, I don't think so ... and for me that's what it's all about in hifi too, to get the experience of a system sounding "real" each and every time you listen to it, you have to fussy about EVERYTHING ...

Frank

Hi Kirkus, that one is easy! Its the same issue of when you hear a really good digital recording, one that is really convincing. What would it sound like it had been done analog?

The whole experience here comes down to one of expectation and intent. If you *know* that the system is underpar (maybe its only a table radio) *then* you don't have much expectation of it. But if its a real high end system- it had better bring home the bacon, because it has some high expectation attached.

I heard a system across the hall from me at THE Show about 10 years ago, maybe a little more. It was Joni Mitchell, singing with a full orchestra. It had been recorded by Sony, digitally, in 6 channels. The system was entirely solid state. The format was a digital reel to reel, 1/2" wide. I really did not hear the system, it was only the experience of the music.

So what would it have been like if it was 2" analog with my amps on each speaker? Hey, maybe it would have been better. We'll never know. I can say this though- if that system/recording does the job for you, if somehow it manages to sound *real* than that is worth paying attention to.

I have never said that feedback should be eschewed- all I have done is point out what it does. Now if you are reading between the lines, you will also see that I have also been pointing to how things can be dealt with. I'll give you a couple of examples. FWIW, these are all on the cutting edge of the art.

1) since feedback is bad, build tube or transistor amps without,
2) since the evil of feedback has a particular cause (propagation delay), build circuits that gets around this problem. Then you can have all the feedback you want.

There are people who are doing both, or at least are approaching both. Nelson Pass is one, Spectron is another. I think there are some class D amps out there that do some timing things to get around this issue too. And of course there are all the zero feedback tube amps out there...

Weseixas...
KT88's? UT or Triode?

How close are we to the real thing?

Since I listen exclusively to classical, I find this subject fascinating.

The truth is: we are very far. Why? - Because audio and acoustics are still treated as an art, not a science. I think that audio is now in the same stages as medicine was in the Middle Ages: we know the basics (anatomy), but the remedies are still experimental. A trepanation is made to extract madness; blood letting is supposed to be the cure for many illnesses. Our amps, cables or speakers are tweaked in the same empirical way.

Sound engineers and other people along the music production line DO NOT scientifically aim at achieving an exact reproduction of the acoustic sound; instead, they mainly make sure that the recording sounds nice, and they all use different microphones, monitors, consoles, room sizes, etc.

On the listener's end, we all use different amps, speakers, and our rooms all have different acoustics.

If there was a real willingness to achieve the sound of the real thing, the whole process would have strict standards: microphones, amplifiers, consoles, cables, loudspeakers, rooms, etc. would have ideal specifications. Listeners who can afford would be able to reproduce these specifications at home - if necessary going as far as building a room to the exact specifications.

The Middle Ages ended 600 years ago. Let's hope we won't have to wait that long for audio to be close to the real thing. All what it takes, is one producer setting up a recording standard that can be replicated at home.

Better yet , how many KT88's would one need for 500 watts necessary for the real thing ?

.......

"My conclusion is that it is just one of many design and execution factors that affect results depending on how well it is executed."

That seems sensible to me. It's hard to believe that anyone would employ negative feedback in their design if there wasn't, at least in the designer's mind, some net benefit to doing so. Maybe not directly, but perhaps because it allows the employment of something else in the design that more than compensates.

Hi Mapman,
I was speaking to an old friend of mine who built equipment 35 years to 25 years ago and hasn't built since. He was just telling me that he just might start building again considering the improvements in parts ie, speed, linearity, etc. I'm sure that you have heard some terrific old amps. After talking with him, I believe that even the old engineers could come up with some terrific products today. I believe a good engineer is a good engineer, we just must wade through so much mediocrity to find them. Good Listening, Tim

Well, the whole negative feedback issue has been beaten to death pretty thoroughly already in other threads.

My conclusion is that it is just one of many design and execution factors that affect results depending on how well it is executed.

Having heard a lot of gear over the years, my ears tell me that good engineers working for companies making good products have a much better handle on all such things that matter these days than they did 30 years ago.

I think the most interesting aspect to the original poster's question is the fact that it forms the logical basis to objectively improve our art - that is, "Does it sound real?" is actually a falsifiable question. The answer is definitely highly dependent on an unfathomably large number of personal differences in perceptional acuity . . . but one can always ask oneself this question and come up with a relevant answer. So the main thing we *should* be striving for in the technical studies of audio (i.e. measurement and controlled listening tests) is repeatability.

For reading on some of the logical basis of falsifiability, I'd recommend starting with the work of Karl Popper, or at least his Wikipedia page:
http://en.wikipedia.org/wiki/Karl_Popper
http://en.wikipedia.org/wiki/Falsifiability

Under the logic of falsifiability, it takes just ONE instance of having experienced reproduced sound as being real . . . to validate the conditional plausibility of all the technical and methodological basis for its reproduction. Not that the reverse isn't true as well, but if "reproduction" as an abstract is the goal, then at least for me its occurrences are much more noteworthy than its absences.

Here's the problem I have with setting up camp in any of audio's little belief-systems (i.e. tubes/transistors, cones/panels, feedback/no-feedback, analog/digital, etc.). If I'm truly honest with myself, I have at times been dumbfounded by amazing experiences from really crappy stuff, and also underwhelmed by my experiences with some really beautiful machinery.

And since audio is really a trivial pursuit (no lives at stake, no big "origins of the universe" questions), I view the the craft of audio thusly (my quote):

To examine a wide variety of data from both measurement equipment and listening experiences, and establish correlations that logically fit as much of the data as possible . . . then assume causality based on well-established principles of physical science.

This is why I think audio is so interesting in general -- we get to explore a truly genuine frontier, consisting of abstract and profound questions of the limits of human perception in sound and music. We also get to explore many aspects of human psychology in the listening process, and sociology in the marketplace and hobbyist communities. And really, the assemblages metal, wood, plastic, paper, and whatnot that we fashion to this pursuit are not really so profound . . . after all, it's all going to be in a landfill in a couple hundered years at the very most.

Atmasphere, here's the main reason why I'm so routinely perplexed by your dogged determination to proselytize the whole anti-feedback thing . . . What do you do when you have an amazing experience listening to music through a system, and THEN learn that it's a solid-state amplifier using a pile of global NFB? Because it's happened for me often enough that I can't imagine it hasn't happened at least a few times to anybody that's made a career in audio.

Agree and not just about Irv's response to Atmasphere , but for everyone in general no need to make it personal when in disagreement.

That aside It must be said Ralph did peg SS a bit in his response before pulling out the encyclopedia and totally forgot to mention Tube fog and distortion ..... :) :) :)

12-17-10, Irvrobinson: Your explanation above is such nonsense that I can't help but reply.... And then concluding that all of this mumbo-jumbo you're discussing indeed describes why solid-state amps sound harsh and lack low-level detail is just so much malarkey. Solid-state amps have neither of these characteristics you claim they do just for promoting your tube products.

Irv, I would suggest that it would not be too difficult to find more appropriate targets for this kind of insulting language than someone who has devoted a career to studying these matters, and who for many years has designed and manufactured some of the world's finest and most respected amplifiers.

Disclaimer: I have no affiliation with Atmasphere or his products, not even as a user.

Regards,
-- Al

Irvrobinson, in a nutshell, frequency response variation is not why tubes sound different! I've heard that idea expressed before, but its hard to find real world examples so I have to chalk it up to mythology. This is easily proven by using a speaker with a flat impedance curve.

The fact of the matter is that the ear interprets non-clipping harmonic distortion as tonality. With tubes, quite often we see a great deal of lower ordered harmonics, which the ear hears as warmth or 'bloom', IOW because the lower orders are seen by the ear as musical, humans are more tolerant of their presence although such will mask detail.

In the case of transistor amplifier audible distortions we are indeed talking about -70, -80 db phenomena. General Electric proved how sensitive humans are to odd orders back in the mid 60s- its not like this is rocket science, but OTOH if you don't know about this quality of human hearing there may be nothing I can say.

So I think quoting research references just clouds your argument.

So when making a point of fact, one should never point to basic long-standing research?? Don't confuse the situation with facts??

However, it is readily proven, and here is how it is done. Take any amplifier and speaker, you will also need a VU meter and a sine/square wave generator. This is very simple test equipment. Set the sine wave to 1KHz 0VU into the speaker.

Now cover the meter and turn the signal all the way down. Set to square wave (odd ordered harmonics). Turn up the volume until you perceive the same sound pressure. Uncover the meter. You will find that it is reading between 20 and 30 db less.

The human ear is very sensitive to odd orders because it uses them to tell how loud sounds are. To claim that we cannot hear something that is 70 db down is beside the point- we are not talking about something that is being masked. I think you must be thinking that these harmonic distortions are somehow going to always be buried and they are not. This is one of the most basic rules of human hearing.

Now negative feedback is well-known to inject odd ordered harmonics into the output of the amplifier although at low level. Its easy to hear too- but best done on an amplifier that is functional operating open-loop (transistor amplifiers that meet that requirement are rare but they do exist). Norman Crowhurst pointed out in the mid-50s that the addition of negative feedback injects harmonics up to the 81st into the output of the amplifier- this stuff is not imagined by any stretch. Take a look at Nelson Pass' article on distortion:

Audio, Distortion and Feedback at
http://www.passdiy.com/projects.htm

if you have trouble believing that I do my homework. Nelson Pass is one of the leading designers alive today.

Chaos Theory says that an amplifier that has loop feedback is an example of a chaotic system that exhibits several stable states. Interestingly and not by coincidence, the formulae you see to express feedback in an amplifier are *identical* to the classic formulae for basic chaotic systems.

Now Chaos uses the term 'bifurcation' to refer to distortion and what it says confirms what Norman Crowhurst pointed out decades earlier, that the addition of feedback will destabilize the amplifier and inject low level harmonic and inharmonic noise (the inharmonic noise is the result of intermodulations at the feedback node).

The way this happens is that the amplifier has a time period, called propagation delay, which is a finite time in which it takes the input signal to propagate to the output. It is nowhere near the speed of light! In fact it is so slow that at high frequencies by the time the feedback gets back to the input of the amp to do its work, the input signal will be seen to have changed. For this reason the negative feedback is always lagging behind and so is unable to correct the signal it was supposed to. As frequency goes up, the phenomena becomes more pronounced.

With steady-state signals the damage is not too severe, but with a constantly-changing waveform (music) the resulting distortion is much higher than -70 db.

Now most transistor amplifiers are push-pull and so they have even-ordered harmonic cancellation at the output. If the amplifier is balanced throughout (and many of them are) then this even ordered cancellation will occur throughout the amplifier (we do this in our amplifiers for the same reason). So really, the main distortion components of a transistor amplifier are going to be almost entirely odd orders!

Now you may think I am a big tube proponent, but if that is the case you may not have read some of my earlier comments. It is *easier* to make tubes sound more like music because it is easier to build tube amps that work without feedback. But go back and look at what I said about transistor amps without feedback.

Atmasphere says:

"OK- you obviously understand how low the distortion levels are we are talking about. I think I did express that 100th of a percent is audible- seems like that needs more emphasis. Since we humans use the odd orders (5th, 7th and 9th) in order to determine how loud a sound is, obviously while the ear is not sensitive to *some* things, this is one thing that the ear is *very* sensitive to. BTW all of this has been known since the 60s and Norman Crowhurst was writing about this subject in the 1950s.

So this is indeed a way that explains why transistor amps can sound harsh while having otherwise flat frequency response. Note also that with many transistor amplifiers, as power output decreases there is a dip in distortion and then it rises again as power output continues to decrease. This is one of the reasons that low level detail is challenging for transistor designs."

First of all, pardon my ignorance for not knowing that you are a producer of tube amplifiers. That just occurred to me last night while reading some of your responses, and I do realize that arguing tube versus solid-state with you is probably not productive.

But your explanation above is such nonsense that I can't help but reply. I'll buy that humans are very sensitive to certain kinds of harmonic distortion, but I'll reiterate that the distortions you are discussing in high-quality solid-state amps are very likely well under -70db, probably more like -80db, and that's below the noise level of the large majority of recordings. Certainly that is under anything reproducible from vinyl.

Furthermore, the 9th harmonic of frequencies above 2KHz is above audibility for most people, especially accounting the -70db level of the tones we're discussing.

So I think quoting research references just clouds your argument. And then concluding that all of this mumbo-jumbo you're discussing indeed describes why solid-state amps sound harsh and lack low-level detail is just so much malarkey. Solid-state amps have neither of these characteristics you claim they do just for promoting your tube products.

Tube amps can demonstrate interactions with loudspeakers this can result in an altered system frequency response, and those alterations can highlight (or hide) details in recordings. But this isn't because of some imagined limitations of solid-state amps, or even negative feedback. I could more easily argue the differences are due to the inferior performance of some tube amps. While everything in audio can be reduced to personal preference, my preference is to try and make as many factors in the reproduction chain as neutral as possible.

Hello Atmasphere,

Are you involved in making your own recordings.....

Hi Kirkus, that was not what I recalled so I looked up the Ampex schematic... Its not the record head that has feedback- prior to that the record calibration circuit does use a feedback mechanism. The rest of the circuit has none.

I did think about the playback after posting :/

Of course LP lathes do use feedback, primarily used to control resonance. You can't get channel separation in a Westerex 3D, for example, if you don't use feedback. However there is work being done to this day to try and find a way around that. Apparently feedback is not popular with mastering engineers and for good reason: if the electronics even turn on in the wrong order at power-up, the cutting head can be destroyed.

I have a set of Western Electric mic preamps that are zero feedback. I pulled them out of a dumpster about 30 years ago and boy am I glad I did. They are really transparent, after being updated with Jensen transformers and otherwise rebuilt.

Wow, that JBL Marantz Mac setup is something else!

Hi Kirkus, I just pressed on your system and I'm so happy I did. How very cool! To saner times...

Do Ayre and Pass use zero feedback desings in their amps? I only know they sound really good.

This is incorrect. The Ampex 351 tape machine, used by both RCA and Mercury (and a host of others) has a zero-feedback recording circuit. Neumann microphones use small tube preamps which are zero feedback. I can go on but you get the point.

Sorry Atmasphere, but you're mistaken - recording, mastering, and broadcast equipment all does indeed use a variety of "feedback design techniques and circuitry, going back to almost the very start of electronic recording," as Fas42 states. Specifically, the Ampex 350 and 351 used frequency-dependent negative feedback in the cathode circuit of the record output tube, and negative feedback around the playback head amplifier for playback EQ. Additionally, the 351 had a push-pull (12AU7?) transformer-coupled line-output amp with a separate feedback winding for global NFB, very similar to a little transformer-coupled power amp.

And then there's the record cutting lathe - virtually all high-fidelity cutting heads use negative feedback from a separate winding to provide global negative feedback from the motion of the cutterhead back to the cutting amplifier.

Yes, feedback is somewhere in there. But there is correct feedback, and "bad" feedback! If feedback was inherently not good then no piece of recorded music could ever be made to sound good, since every recording device and studio is riddled with feedback design techniques and circuitry, going back to almost the very start of electronic recording.

This is incorrect. The Ampex 351 tape machine, used by both RCA and Mercury (and a host of others) has a zero-feedback recording circuit. Neumann microphones use small tube preamps which are zero feedback. I can go on but you get the point.

there is no way that well-designed solid state amplifiers "tend to have these higher odd orders all the time. This is one of the reasons they tend to sound hard or bright. Now its important to note that these harmonics do not have to be very distorted, usually 100th of a percent are audible, simply because these harmonics are so important to the human ear." Total harmonic distortion, meaning any and all spurious frequencies away from the fundamental, is normally at about -70db or better, usually better, and there's no way that such low-level distortions could possibly cause amps to sound hard and bright.

OK- you obviously understand how low the distortion levels are we are talking about. I think I did express that 100th of a percent is audible- seems like that needs more emphasis. Since we humans use the odd orders (5th, 7th and 9th) in order to determine how loud a sound is, obviously while the ear is not sensitive to *some* things, this is one thing that the ear is *very* sensitive to. BTW all of this has been known since the 60s and Norman Crowhurst was writing about this subject in the 1950s.

So this is indeed a way that explains why transistor amps can sound harsh while having otherwise flat frequency response. Note also that with many transistor amplifiers, as power output decreases there is a dip in distortion and then it rises again as power output continues to decrease. This is one of the reasons that low level detail is challenging for transistor designs.

It also points to the way to make transistors work as well as tubes, FWIW. I can point to several SS amp manufacturers that have been exploring zero feedback designs and some of them are as good as some of the best tube amps I have heard. Mind you this coming from a tube amplifier manufacturer...

Paulsax, if I don't leave my ss gear on 24/7 it takes at least an hour to sound its best. With the high cost of tubes and electricity, few leave their tube gear on.

I suspect that Mapman is correct for reasons coming from the other side. I have been surprised how my new Tube guitar amp changes character depending on how long it has been on and such. If I can change the source based on tube temp? than it makes sense that a tube output system may display this as well?

I also tend to believe that practically, in most well thought out real world setups, that a higher % of those using SS amps will sound closer to the real thing to me.

I say this based on the fact that I hear more variations from what sounds rel to me more with tube gear I hear and use than with (good) SS rigs.

Fas42, assuming the goal for all equipment is as much accuracy as possible, I do lay the entire blame on speakers. Solid state electronics can be designed to be, for home audio purposes, perfectly neutral, in that their noise and distortions are inaudible, and their frequency responses are flat regardless of load.

Speakers, on the other hand, are usually "voiced" Sometimes this is because the designer wants to achieve a certain "sound", but they are also voiced to apply judgment of how much high frequency roll-off the designer wants to apply to make the speaker sound natural in a room with certain absorption assumptions. I suppose you could argue voicing in the bass might also be necessary, because of room variations.

The latest speakers, designed with the latest driver technology and sophisticated crossovers designed with the latest software, can produce awesomely flat frequency responses these days. The latest speaker designs seem to have frequency responses that remind me of curves we used to see for amps in the 1960's. (Distortion levels too.) But lots of speakers are still "voiced" to sound a certain way according to a designer's biases, and the best drivers and crossovers (and cabinets too) are actually very expensive, so a lot of high end speakers still have response curves that look like saddles (too much bass and too much treble), and compromised crossovers that produce anomalies at the crossover points.

The differences in solid state electronics are far smaller. With tube electronics, one can design them to be as neutral as SS types (VTL comes to mind), but things like SET amps will have nearly unpredictable interactions with a particular speaker.

How close are we to the real thing ?

I'm in agreement with Irv, there are a lot of speakers with unbalanced frequency bandwidth. SS amps IMO tend to be more accurate in their reproduction of the original signal, have better bandwidth, dynamics, rhythm and pace.

That aside i have heard great sound from both SS and Tubes, so go figure.

Irvrobinson, I would agree with you about those distortion levels, but certainly would not blame the speakers directly. I would suggest rather that the combination of equipment and setup is allowing other distortion mechanisms to intrude, into the electronics of amp and CD player, say. Typically the power supplies of much equipment are pretty hopeless in suppressing interference into sensitive areas, and this is the sort of thing that normal THD measuring never captures.

So, either you boost the quality of the power supply, as, say Naim does, or you cotton wool the power being fed to the gear with filters, special power cords, etc, etc.

Frank

Atmasphere, there is no way that well-designed solid state amplifiers "tend to have these higher odd orders all the time. This is one of the reasons they tend to sound hard or bright. Now its important to note that these harmonics do not have to be very distorted, usually 100th of a percent are audible, simply because these harmonics are so important to the human ear." Total harmonic distortion, meaning any and all spurious frequencies away from the fundamental, is normally at about -70db or better, usually better, and there's no way that such low-level distortions could possibly cause amps to sound hard and bright.

The most likely cause of hard and bright sound are no-so-good speakers, that have too much upper midrange energy when driven by an amp with a low output impedance and flat frequency response. Connect a tube amp with a rising output impedance in the same frequency range, which will cause a roll-off in the overall response, and voila, hardness suddenly gone.

Weseixas, Timlub, thanks for your reaction and comments to Atmasphere and Mapman, they are coming from very close to what my take on the situation is.

What I hope to inject into this conversation is something that for me has been very intriguing and frustrating over many years. That, which all hard core tweakers know, is that fiddling with any and everything makes a difference, and my reaction has been, what the hell is going on ?? Agreed, the topology, or circuit type of the amplifier can make a big difference, but once you improve your amp, then you more clearly hear the effects of making changes to other components, and the impact of everything else becomes more significant. Hmmm... not sounding too good at the moment ... gee, I wonder if that fluorescent light outside in the garage is on or off?

The trouble is, that last sentence is NOT funny, because it's true! Again, everything matters, and why does it matter? Because all the little, little things alter the makeup of my "micro" distortion, and the ear/brain has no trouble, no trouble at all picking up the change. It may sound better or worse, but it will definitely sound different!

Distortion can be linear, that is, altering the frequency response and phase angles, or nonlinear, which is everything else. The latter is the "baddy", big time: my experience is that if you minimise nonlinear distortion then linear distortion becomes totally benign, and the ear/brain can dismiss it as irrelevant. I've had a very ordinary amplifier (Sony) with classic tone controls, and managed to get the overall system working extremely well; then wound the bass and treble fully up and down, and I couldn't hear anything happening to the sound! Why, because the ear/brain could reject those changes as being unimportant to the musical message, enough "good" information was coming out of the speakers to compensate for a change that would normally be very obvious.

Yes, feedback is somewhere in there. But there is correct feedback, and "bad" feedback! If feedback was inherently not good then no piece of recorded music could ever be made to sound good, since every recording device and studio is riddled with feedback design techniques and circuitry, going back to almost the very start of electronic recording.

The quip earlier about the light points to a key factor that people play around with: power supply quality, or maybe, maybe it's RFI!? The trouble is, it's all very messy, but it ALL has to be taken care of!

Why should one? Because, if you do, then the level of "nasty", NOT "nice", micro distortion is reduced to the level that the ear/brain says "Yes! I can now accept this as being a thrilling experience, I won't be fatigued no matter how long I listen, it's magic, it's real!". And the convincing soundstaging, etc, automatically follows ...

Frank

Tubes and transistors seem to act very similar to feedback. I've less experience with class D, but from what I am seeing there are several techniques of using feedback and some work better than others, so it would be unsafe to generalize that feedback works in all class D amps without increasing odd ordered harmonics. In some it seems to work well though.

Not heard one yet that images as well as I am used to but I've not heard them all either.

Mapman, -- "not all distortion is necessarily unpleasant" , I agree with your comments 100%. And, there is definitely "nice" distortion, which is quite easy to do, and is a perfectly valid way of obtaining listening pleasure. One of my earliest high end experiences was listening to a dealer's highly tweaked in home setup, we are talking here of Goldmund Reference TT, Audio Research D250, Infinity columns: of course the playback on a selected LP was absolutely stunning. He didn't like CD, of course, but had a CAL, so I tried one of my "test" CD's. The experience was bizarre, sounded smooth and pleasant enough, but half the sound content had disappeared! My half reasonable setup of the time at home absolutely walloped his in terms of conveying the musical message on that particular CD.

So "nice" distortion works, but it is "horses for courses" ...

Frank

Hello Atmasphere,

Wouldn't such be dependent on the topology being used, Tubes react differently vs SS with regards to negative feedback
(local or global).

Class-D amps run a lot of feedback, "alot" and they don't have issues with sound staging and details, actually they are quite possibly kings of it, but do exhibit a grainy artificial sound IMO vs conventional amplifiers (class-a, a/ab)

Hi Atmasphere,
Ok, no disagreements...Feedback reduces distortion and have seen changing feedback levels change the effects, no arguments....
I guess, what I am questioning is... Labeling Distortion as a catch all phrase. It doesn't work.

Timlub, It looks to me like Fas42 places a lot of importance on soundstage and imaging. There are different types of 'distortion' that affect that- primarily of bandwidth. The better it is the more intact the phase relationships, which are what defines image location.

The ability of the speakers to 'disappear' is equally important to a system's ability to convince as is detail and tonality.

When feedback is applied to an amplifier, low level harmonic noise is injected into the output of the amplifier. This is nearly all high-frequency information. Now it happens that room ambiance in recordings is often also high frequency and is also low level. The result is that by adding feedback, the low level detail associated with room size can be masked by the harmonic noise floor that is present in the amplifier. In fact *all* detail below this level will be masked. That is why amplifiers that run little or no feedback often seem to have bigger, wider and deeper soundstages.

Hi Fas42,
If you can accept the explanations that Atmasphere, Mapman and Weseixas has added to what you have stated, I find it acceptable(like that matters). Their combined inputs do explain the entire list of questions that I asked about why different items sound different as well as all distortion is unwelcome. I appreciate your input... I noticed that you are fairly new, I am not an oldtimer here either, but I have read back through several threads from the years and there are arguments about the difference of harsh or grainy. We are in a very subjective hobby, we all want to help with input and sound authoritative, but what I have found is...Everyones experiences are different and that doesn't make yours right or wrong, just different... I do try to be careful about seperating fact from opinion, I believe that is where my challange or disagreement came with you, but as you can see after some nice input, your points have been reinforced/corrected. Good Listening, Tim

Good explanation Atmasphere. Agreed
To you and Weseixias also

Mapman,

taken in that context, all hi-fi is distortion and I'm sure we can all agree that when the reproduced signal is different from the original the effect is distortion.

What Frank has stated is that we hear differences in the sound due to an increase or decrease in "distortion" and if there is no distortion change then both systems will sound the same

What we are trying to determine "which distortion" , tim, thd, phase, slew, VCID, maybe Frank is describing the changes in the RLC makeup when switching out wire for eg. changing the original "distortion".

Regards,

FWIW, low ordered distortion is pleasant, but it does obscure detail, and the ear tends to hear it as a fatness or warmth in the sound. Lower orders are the 2nd, 3rd and 4th.

Transistor amps have almost none of these distortions, but they are common with SET amplifiers. P-P tube amps on the other hand tend towards the 3rd and 5th.

Now it is the higher odd orders that our ears use as loudness cues. Anytime they are distorted, the amp will sound louder than it really is. This is why SETs will sound very 'dynamic' for their power, as normally they don't make much distortion, but if you push them (which is what transients do) then the loudness cues appear **but only on the transients**.

Transistor amps tend to have these higher odd orders all the time. This is one of the reasons they tend to sound hard or bright. Now its important to note that these harmonics do not have to be very distorted, usually 100th of a percent are audible, simply because these harmonics are so important to the human ear.

This, BTW, is why two amps can seem to have such different tonal characteristics even though they both measure flat frequency response on the bench. The addition of global negative feedback to any amplifier will increase the odd-ordered distortion slightly, which is why any amp with GNF will tend to sound brighter even though frequency response is unaltered.

(The trick, IMO, is to build an amplifier that does not use feedback, and use other means to eliminate distortion.)

The bottom line here is that distortion is always audible and to nearly anyone. Its just that it does not *sound* like distortion to us, often it sounds like a tonal aberration ('bright' in the case of many transistor amps, 'caramel' in the case of many tube amps).

Its true that by definition a reproduced signal that is not exactly identical to the original source (ie exactly the same as the real thing) is distorted and that the reason no two systems deliver the exact same sound is because each distorts the input signal differently.

So not all distortion is necessarily unpleasant. In fact some may be enticingly pleasant! Others will induce different responses, both positive and negative.

"If you have two widely differing systems that don't distort then they must sound identical".
So, when 2 different cone materials sound different on speakers, one is more distorted or when you roll tubes for a completely different sound, one is distorted, or when a designer changes from bipolar to mosfet or vise versa, they sound different because one has distortion or when we add spikes to a speaker and the sound cleans up a bit, we have lowered distortion or 2 identically spec'd phono cartridges sound completely different, its because of distortion????? Does Silver copper or gold in wire carry more distortion??? They all sound different. I can go on and on.... Your comments do not hold merit. I'm glad that you have a Holodeck, distortion matters overall, no argument, but it is not the one thing catch all.
Sorry Frank, I can't agree on this one.... I've been convinced of a few things on here...Thanks Atmosphere & Almarg, but you've got a long way to go to change my mind on this one. Good Listening, Tim

Weseixas, " ... has a Holodeck" -- nicely put :-)

Timlub, unfortunately the key phrase in your comment is "distortion is so far below our hearing that it was unconceivable to hear" -- of course distortion is easy to hear! My system distorts, your system distorts, everyone's system distorts. That is why every system sounds different from every other system, every time you change something in a system it sounds different, because you have changed the distortion component. If you have two widely differing systems that don't distort then they must sound identical.

I think the problem area is in the use of this word "distortion". One dictionary says "a change in the wave form of the original signal", which sounds fair enough to me. The argument would then be how MUCH change is allowed before you would call it distortion; I would say only so much that you can hear a difference between the original signal and the distorted one: if you can hear a difference between the original and the altered signal then you can hear the distortion! Two systems sound different, which is the distorting one? Both, of course, as compared to the original waveform.

Another way of looking at it, is that there are 2 tiers of distortion, let's call it "macro" distortion and "micro" distortion -- sounds familiar ... :-). Everyone knows macro distortion: boomboxes overloading, speaker cone rattling, treble ripping layers of skin off your eardrum, you could even include really bad digital playback here; all very easy to pick.

Micro distortion unfortunately is everywhere, it's all that low level stuff that makes one system sound different from the next. But everyone normally calls it the million and one other things, see J. Gordon Holt's Audio Glossary. Interestingly he includes "distortion" in its own right, firstly as a "true" definition: "1) Any unintentional or undesirable change in an audio signal." and then to highlight most people's concept of "macro" distortion: "2) An overlay of spurious roughness, fuzziness, harshness, or stridency in reproduced sound." But in the majority of the other, sound related terms in his glossary he specifies virtually every other type of "micro" distortion: dry, forward, haze, liquid, etc, etc. Talking of THD and IMD, these are just straightforward ways of putting numbers to the distortion in a very specific setup, somewhere between maximum "macro" and minimal "micro" ...

So, what to do? My "solution" is to eliminate, obviously, "macro" distortion, and then as much of the unpleasant, AUDIBLE "micro" distortion as I possibly can, which is, very, very difficult. How do I know I've got there? When I can change something on the system and from the point of the auditory experience nothing changes! And, at this point the sound becomes "real" ...

Frank

Timlub ,

Franky has an Holodeck, you will never match his soundstage

:):):)::)

Al, My gosh, that was hard to find, Searched literally 50 sites, But I found it and bought it, Thanks, I'll be listening in about a week. Tim

I am loaded with Jazz and only a couple of classical recordings, Can you give me 3 recordings that I can't live without?

Hi Tim,

Obviously a virtually unlimited number of recordings could be named, but I'll suggest exactly one, although I'm not sure if it is still readily findable:

Chesky CD31: Dvorak's Symphony No. 9, "From the New World," The Royal Philharmonic Orchestra conducted by Jascha Horenstein. You will not believe that it was recorded in 1962!

Best regards,
-- Al

I'm not the best one to recommend Classical music.The majority of mine was passed down to me from my family.I listen to it more to hear a full orchestra perform.That seems to be the best part I enjoy.

Thanks Hifihvn, you might be right, I was using old Sumo gear. In July I bought a Coda CL preamp. It is so superior in so many ways. I have an MHZS cd player that I've modded so many times that I have finally tore a solder trace. I had bought a NAD C515BEE for $50.00 broken and a new laser was only $30.00...fixed, so I haven't even tried to repair my tubed cd player with my new Coda. I really need to get off my duff and finish this. I'll try to lay my hands on a decent dac also, thanks for the suggestion And I'm with you specs mean little or nothing to me. Also, Hifihvn, i've noticed in some old threads that you have alot of classical music, I am loaded with Jazz and only a couple of classical recordings, Can you give me 3 recordings that I can't live without?
Good Listening, Tim