Distortion: Acquired Taste or .......

RBFC

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In another thread, Amir related the story of two headphone amps, one tubed and one solid state. Although the tube unit measurably has more distortion than its counterpart, the tubed unit sounds more revealing.

So, is it merely that we "like" distortion? Or, do the fractional components of distortion (odd and even harmonics) exist in a different balance in the two units, thereby causing the perceived differences in sound quality?

Up for discussion!

Lee
 

amirm

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Even though I am the spark for that fire, err, I mean discussion :D, I don't have a ton to offer. But maybe a theory.

We know from Fletcher-Munson curves that our ears are not so sensitive to low and high frequencies. So perhaps, what we like about high distortion products is that they do better in the mid-tones but worse, maybe much worse at the two extremes. These are the curves by the way:



And the thread it came from: http://www.whatsbestforum.com/showthread.php?273-Key-principal-in-human-auditory-system

As to odd vs even harmonics, I have hard that many times but where did that come from? That saying has been around for decades. But was it ever proven?
 

RBFC

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As to odd vs even harmonics, I have hard that many times but where did that come from? That saying has been around for decades. But was it ever proven?

Not being an engineer, I'm just regurgitating a common statement about distortion products.

I like your theory about midband clarity. Even Steve's illustrious system seems to follow the logic of that position, with the great tube midrange and highs coupled with solid state amplification for the subs. Perhaps you're onto something.

Lee
 

Mike Lavigne

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my perspective on audible distortion is that you should use the very best tool possible to determine what is distortion.

which, of course, is our brain interpreting information from our ears and body (we hear with both).

real life imprints reality in our brain. when we hear reproduced music our brain compares those perceptions with previous experiences and we have an 'idea' of what sounds most correct. it is this 'comparing' which we do without intentions that determines what is most real (most lacking distortion).

numbers and graphs tell us stuff. maybe good stuff. but things like differences in levels of vividness of music or whether a drum kit skin sounds real or not. numbers will not help much with that.

so do we like distortion? we like real, and if that happens to have worse numbers then the numbers are wrong; or we are looking at them wrongly. or the measuring protocol is not up to the task. real is right.

the concept of distortion assumes proper judgement of the 'control'. if the measuring approach does not really define the control correctly then any measurment is pointless in terms of an ultimate truth.
 

DWR

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I believe that tube ams/preamps have a predominance of even order harmonic distortion while solid state equipment has a predominance of odd order harmonic distortion. Any distortion in musical instruments is also in the even order harmonics. if I am wrong here I am SURE that I will be corrected. And like anything else it just isn't that simple to say one or the other makes a component sound more revealing than another.
 

amirm

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We can certainly show that the harmonic nature is different in tube vs transistor. My question was not that but rather, who determined that one is worse sound distortion than the other? I once went searching on the net for it after half a day, had not found any studies to show that to be the case. Unfortunately, you get billions of hits in searching that way since so many people mention this characteristic so maybe the data is out there but was hard to get to....
 

RBFC

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RBFC

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Most of the articles I've seen clearly state that distortion products are more easily discerned, and therefore recognized as non-linearities of the playback system, when they are higher-order with a larger difference of frequency from the fundamental. The fundamental is less successful at "masking" the distortion product when that product is farther away in frequency.

So, do solid-state electronics possess a different distortion "spectrum" (while still keeping the absolute level of distortion as measured at a similar specification) than tube electronics? Do solid state components generate more of these objectionable high-order harmonics that are more audible at lower levels beneath the signal?

Lee
 

DonH50

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Oh boy... I actually addressed tube vs. transistor (BJT and FET) distortion in another thread, but I am not sure which one...

1. The intrinsic distortion series for a bipolar transistor is exponential. It is factorial for a tube. That means the distortion products are actually lower for a tube than a transistor, all else being equal. An ideal FET's distortion series (Taylor expansion) ends at the second order -- no higher terms, making it the winner. Of course, in the real world, other things ensure there's plenty of distortion to go around...

2. Tube circuits are most often single-ended with low feedback factors. Transistor circuits tend to be differential (internally if not at the input) with higher feedback. This means a tube circuit tends to exhibit even-order harmonics, and a transistor circuit odd harmonics though at a lower level.

a) There are lots of tests and papers saying we (humans) find even-order harmonics more "pleasing" than odd-order. A rounded sinusoidal pulse has higher even-order terms; a square wave, higher odd-order. The rounded cosine pulse sounds "softer" than the raspy buzzing square wave.

b) Tube circuits tend to saturate "softer" than transistor circuits for a variety of reasons. They tend to round off peaks before hard clipping, where transistor circuits, well, they just clip! This has led to people feeling tube circuits clip "softer" than transistor. This is not fundamentally true, but you will start to hear the distortion a little sooner in a tube circuit and turn it down, while in a transistor circuit it just wops you upside the head. (That's technical talk.)

3. The type of distortion that people hear/dislike the most is non-harmonic, e.g. intermodulation distortion (IMD). (And, I do mean ergo (e.g. -- for example) as there are other ways to get nonharmonic distortion terms.) Harmonics we can handle better than something not related (or loosely related) to the signal. Two tones generate "sidebands" at the difference frequencies and multiples:

f1 harmonics = 2f1, 3f1, etc.
f2 harmonics = 2f2, 3f2, etc. -- all multiples of the signals, bad but not too bad

IMD = (f1-f2), (f1+f2), (2f1+/-f2), (f1+/-2f2), etc. -- not multiples of the signals, worse

4. Achieving a high damping factor in a tube amp, with its output transformer, is very difficult. The actual culprit (imo) is load regulation; the relatively high and fairly complex output impedance means a tube amp does not produce a well-controlled flat response into a typical (fairly ugly) speaker load. I loved my tube amp (ARC D79) on my relatively benign Maggies; I thought it did poorly on a set of B&W 801s.

5. High feedback in a transistor amp yields impressive THD numbers and excellent IMD as well, but it also tends to cause high-frequency peaking and phase shifts that induce transient IMD (TIM) because the feedback path cannot immediately and precisely correct the output to match the input.

FWIWFM, my 0.000001 cents (microcent), IMO, blah blah blah - Don

p.s. There have been tube amps designed with differential circuits, additional cathode followers (buffers), and direct-coupled inputs and outputs. They provided distortion characteristics more similar to transistor amps, and were of course panned for it as a result.
 

The Smokester

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We can certainly show that the harmonic nature is different in tube vs transistor. My question was not that but rather, who determined that one is worse sound distortion than the other? I once went searching on the net for it after half a day, had not found any studies to show that to be the case. Unfortunately, you get billions of hits in searching that way since so many people mention this characteristic so maybe the data is out there but was hard to get to....

There is some relevant reading on the audiophiliac :D relevance of various kinds of distortion in the DarTZeel NHB-108 Model 1 model one Audiophile's technical manual, starting on page 9, Sections 5, 5.1, 5.1.1, 5.1.2 through 5.1.3.

The pdf download can be found using this link:
http://www.dartzeel.com/PDF_Files/AudioManuEN.pdf
 

Ethan Winer

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So, is it merely that we "like" distortion?

It depends on the recording, instrumentation, and nature of the distortion. All this talk about odd versus even harmonics ignores IM products which always accompany harmonic distortion. IM products are not necessarily musically related as regular distortion (and natural) harmonics are.

From my perspective, distortion is more likely to be pleasing on sparse arrangements. Adding distortion to a dense symphony will probably make the recording sound too thick and muddy. Of course it also depends on how much distortion you add.

About 30 years ago a company called Aphex came up with a distortion box for mix engineers. They called it the Aural Exciter, and its release was intentionally shrouded in mystery by Aphex. They wouldn't even sell the box. You had to rent it, and pay a per-minute license fee based on the length of the recordings it was used on! The first few years they even lied about what it does and how it works. They have since come clean, perhaps after someone else pulled back the curtain.

Anyway, this device filters out the lows, then adds distortion, then mixes just the buzzy sounding stuff above 5 KHz back into the track. The perceived result is one of enhanced clarity and sparkle. This is different from simply boosting 5 KHz and above with EQ, because the Aural Exciter actually generates new content. So you can add high end sparkle to, say, a muddy piano track that has no content that high. It also adds the pleasing aspect of distortion without adding thick sounding low-mid IM products. I can imagine some people who trust their ears too much would think that music with this effect sounds clearer and more natural and more "hi-fi" than without the effect. Of course it's not more hi-fi!

--Ethan
 

Gregadd

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There is always a problem when you try to the prove the rule with an exception. "You can't genralize to the specific." Especially when your example involves an incompetent design or a deliberate attempt to cheat.
I just think it would make for a better argument that we assume we have a competent design operating within its range.
 

Phelonious Ponk

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I think the Aphex Aural Exciter as been replaced by "sparkly" studio monitors with exaggerated trebles to emulate "detail" and fatigue the bejeezus out of engineers. I used to think it had been replaced by metal dome tweeters, but I've since heard some that sound definitively un-metallic. Sparkly, zingy pro monitors are pretty common, by the way, nearly as common as hifi "monitors" with an 80hz hump. They're even pretty common at higher price points, but they are not necessary and are not better "tools." They are distorted. No distortion is better for hearing detail. It is just a bad illusion.

P
 

Ethan Winer

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..."sparkly" studio monitors with exaggerated trebles to emulate "detail" and fatigue the bejeezus out of engineers.

It's even worse than that. A few years ago, an acquaintance of mine measured ten popular pro monitor type speakers at high resolution in an accurate environment. I might have related this story before, I forget. Anyway, most of these "pro" speakers have a moderate to severe dip in the low treble "harshness" range between 2 and 4 KHz. So of course they sound smooth and pleasing. This is a dangerous trend IMO, because while the speakers might sound nice, mixes made on them will be harsher than the mix engineer realizes. Which penalizes people who have more accurate speakers.

--Ethan
 

Phelonious Ponk

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It's even worse than that. A few years ago, an acquaintance of mine measured ten popular pro monitor type speakers at high resolution in an accurate environment. I might have related this story before, I forget. Anyway, most of these "pro" speakers have a moderate to severe dip in the low treble "harshness" range between 2 and 4 KHz. So of course they sound smooth and pleasing. This is a dangerous trend IMO, because while the speakers might sound nice, mixes made on them will be harsher than the mix engineer realizes. Which penalizes people who have more accurate speakers.

--Ethan

Sounds like Dynaudios. And I like Dynas, but you can tell they've been slightly "warmed." They are, for that reason, a great place for audiophiles to be introduced to active monitors. In general, though, I think that tide has turned and the better monitors endeavor to be accurate, sometimes with tweeter controls you can roll back a bit if you like. The cheap ones often go the other way, in my experience, toward the bright and "revealing." But not always. There are some amazing bargains out there.

P
 

DonH50

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"shiver" I hated the Aphex units, one of the few products I really disliked. A lot of recordings were made with it for a while, with various comments about how it brought out and "pepped up" the vocals, but I thought it sounded terrible. I have never really forgiven them for that Emmy Lou LP, an outstanding pressing of a fine voice made obnoxious...

All IMO! - Don
 

Mark (Basspig) Weiss

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Many years ago, I recall reading about some testing where it was found that a little bit of noise added to a recording caused a controlled listener group to vote that they perceived more high frequency content in the music on that noise-added recording than on the same recording without the noise.

I think this is why some of the horrid DACs out there today, like that of the Oppo BDP-83, are so highly rated by listeners looking for 'air' that is otherwise lacking in the rest of their system.

Human psychoacoustics is a funny thing. Sometimes the choice between a live orchestra and a recording results in the listeners preferring the recording over the real thing, because the real thing is relatively dry and neutral in comparison, whereas the recording might have added HF emphasis making it sound more 'airy'. Noise, distortions of certain orders in small amounts, poor damping, resonance, reverberations, etc., all add up to "pleasing" listening for a surprisingly-large number of people. There's a ton of overpriced cables, tube amps, DACs, speakers, etc., out there that claim to offer this ultimate pleasing listening experience. Funny thing is, when I go and listen to one of these setups, I find myself shaking my head in dismay, wondering if the owners have ever attended a live classical concert in their lives.

One of my favorite tricks is me making an O.R.T.F stereo pair recording of me playing my violin (I play about as well as Jack Benny did--please, no jokes!) and then sitting someone down, blindfolded while I alternately play the recording of me playing the violin and then me actually playing the violin, walking back and forth across the stage in front of the speakers. Given the near-anechoic nature of the front "dead" end of my theater/studio, the recording doesn't contain any audible room acoustics, so no doubling of acoustics, one of the tell-tale signs that it's a recording. All other things being good, the listeners make a 50/50 guess on which is which.

There are two schools of thought on hi-fi: one is about accurate reproduction, no matter how dull reality might be. The other is an enhancement of reality, because that version gives more enjoyment. Sometimes it's more enjoyable to listen to a recording that gets down deep into the orchestra pit and lets you hear ever nuance that you can't hear sitting in the 5th row. Equalizers serve a similar purpose and I'll admit that I sometimes use them to enhance certain tactile aspects of music. I have a dbx 500 in my rack. It's purpose is to synthesize fundamental bass energy from the harmonic energy. And even though Four Jacks and a Jill never sounded like that in real life, the oomph that the 500 gives the lower register turns it into an enjoyable experience for me.
 

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