How much distortion is too much?

Speakers have far more distortion than electronics yet we seemed obsessed with distortion figures of stereo electronics. How much matters and how much is too much for good sound? Have a question you want to ask Paul? www.psaudio.com/ask-paul/
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[@devwhit]

We like long-winded Paul! ☺️

[@lroy730]

Nice one ! All us engineer types want to see your Function generators, Oscilloscopes, Distortion Analyzer and other test Gear !

[@christophschuermann6512]

I agree. I can add harmonics with my new function generator, but for lowest distortion i use my analog wien bridge oscillator.

[@bigadventure3797]

That was a good explanation. So it sounds like it's the type of feedback, harmonics, and/or distortion that matters not necessarily the actual quantity (to a point) of THD that makes up what we hear as distortion.

[@GrahamAtDesk]

Really enjoyed that Paul, cheers. Light has been shed, as usual...

[@patrickcase2018]

Very, very useful. Thanks, Paul.

[@michaelgaddy8271]

Kickass! I thank you greatly my cool cool friend for all of the knowledge and understanding you have funneled into my crazy brain!!!

[@zippstream]

its taking a while but were gettin there cheers paul....

[@rollstuhlwolf]

Paul, the song you were thinking of was "Hallelujah" by Leonard Cohen. Rufus Wainwright just happened to have a popular cover of the song because it was on the original "Shrek" movie soundtrack.

[@markthomas1225]

The question concerns audible levels of distortion. We want to know if 0.1% or 0.01% or 0.001% is too much. In this case, the distortion arises because the transfer function of the amplifier (or loudspeaker or DAC, or whatever) is not a straight line. That’s why it’s called non-linear distortion. All amplifiers are non-linear to some extent, and the subjective effect of non-linearity appears to depend on the exact nature of the non-linear characteristic. This is one reason why distortion is less noticeable in tube amplifiers; their non-linear characteristic creates distortion that is often less annoying. Paul’s answer fails to point out something that is really important: Harmonic distortion is not a type of distortion or some kind of specific amplifier defect. Rather it is a measurement technique for quantifying the severity of the non-linear distortion. Like Paul said, the test consists of using a pure single tone and then measuring the total level of the harmonics added by the amplifier’s non-linearity. THD is the easiest distortion test to carry out, but it is a blunt instrument that is probably the least useful measurement in terms of correlating results with subjective opinion. The discussion about the harmonics of a single musical note (for example a single piano note) is not helpful, because adding or removing harmonics of a single tone changes the sound in a musical way, and our ears are really not sensitive to that kind of thing. We could add several percent harmonics and not have a problem. The real problem arises when we apply a complex musical signal to the non-linear transfer function, so that the distortion products generated are not musical, and this is when we really appreciate the benefits of low distortion.

[@johnyang799]

What if multitone total distortion plus noise is very low of 0.0001% and frequency response and phase response are flat from 0.01hz to 1Mhz

[@garysmith8455]

May I add............we love our speakers because of their 'distortions' to their inputs ! Can I get a raise of hands ???

[@stephenarmstrong-brown6488]

Thank you

[@michaelkesti3917]

This seems a good time to mention a misconception that I find to be fairly common. Specified amplifier distortion levels typically reflect the amount of distortion at rated power or at some fairly high power level. Amplifiers do not, however, output those levels of distortion at all levels of their dynamic ranges. At lower power levels the distortion is typically far less. This is one of the reasons it is good to have headroom by using amplifiers capable of more power than you might actually use.

[@markthomas1225]

That's true, but crossover distortion in Class AB is more noticeable at lower power, and tends to be less of a problem at higher power.

[@wilcalint]

If you can measure it can you hear it? Is this a good place to do a ABX test?

[@paulphilippart7395]

Many instruments have the same fundamental frequency,its their harmonics and the strengths of them that determine the Timbre of their sound and usually.. what they are or who they are,low harmonic distortion,very important,like phase distortion in speakers,doesn't necessarily manifest as a jagged fuzzy sound but takes away detail and masks it,or has that annoying pulling effect on your ears,all distortions on what was originally there.

[@bennyjorgensen]

Thanks for the video, but it just opens a new box of questions. If the ear can't hear distortion under 0,1% and the difference we can hear on different amplifiers are because different topologies, feedback level (or no feedback) and so on, then how does this difference come out through the speaker wire? The ear and the speaker doesn't care about feedback and transistor types. It only care about the signal. I have seen university researche that indicates that the ear can here distortion of higher order than 2. and 3. even if it's under 0,1%. There are also indications that the ear can "detect" harmonics way over 20KHz. My own simulation on the different distortion pattern between JFet and BJT transistors indicate that while JFet primarily have distortion in 2. and 3. order, the BJT have distortion up to and over 9. order. Bringing that together it could be fun to see measurements on amplifiers that test higher harmonics than 3. order og compare them with audiophils opinions.

[@ThinkingBetter]

Use a square wave to check the behavior of an amp. An oscilloscope image of a square wave on the output of an amp can be quite revealing. Low THD is somewhat trivial to achieve in an amp but as Paul says, it's not everything. For example, a low TIM (Transient InterModulation distortion) is also essential and I disagree with anyone saying this is a topic that was solved decades ago. TIM is the result of an amplifier that "rings" through a feedback loop, which you can see on a square wave signal. I've measured recently developed products were TIM was absolutely a problem. A poor frequency response limited to near 20kHz is usually a warning sign that something else is not good for an amp, and TIM might be one such thing. Especially class D amplifiers can be more tricky to make produce a nice square wave output.

[@jonathansturm4163]

Bingo! Somewhat oddly, one of the engineer types took me to task on another thread for making much the same points. Back in my yoof, when we could hear, but not name some distortions, we didn't have interwebs. Useful website here: onlinetonegenerator.com/ for generating tones without the need for a Brüel & Kjær tone generator.

[@olerasmussen374]

Try to meassure the output before the zobel network, and poof: no ringing. The output of class D amplifier will never produce a square wave because it has a second order lowpass filter in order to attenuate the output square wave of typical 400kHZ that is pwm modulated. Better quality will come when faster MOS-FETs are developed ie. higher clockrate.

[@ThinkingBetter]

Ole Rasmussen Also for a class D amplifier you can use a square wave to judge how well it behaves. And no, I don’t expect a perfect square wave from a typical class D amplifier.

[@jonathansturm4163]

A _perfect_ squarewave's harmonics extend to infinity. Consequently _perfect_ square waves aren't attainable. Fortunately, most squarewave generators can easily produce harmonics that exceed the response capability of any audio amplifier revealing any obvious shortcomings. Rod Elliott has some useful info for audiophiles unfamiliar with square wave testing here: sound.whsites.net/articles/squarewave.htm

[@ThinkingBetter]

Jonathan Sturm Nice website. I’ve used square wave testing as one of many additional tests that can help evaluate an amplifier. When something sounds better than something else (except speakers) it’s almost always possible to find out why that’s the case through more advanced measurements and often it’s not a matter of some simple THD or frequency response measurements.

[@MichaelLenz1]

Thd raise with power. We always must pay attention on what wattage is that Thd % is measured. If it has around 0.5 - 1% around 20 watts, then it is a great amplifier.

[@wildcat1065]

Good explanation but not sure you answered the question as to whether a tiny bit of distortion in an amplifier matters when speakers are producing gross amounts that would conceal it ?

[@42ssh]

The quality of distortions matters more than the quantity. For example, the distortion caused by jitter in digital audio can be heard even though it is generally very small. We use a percentage number but 1% is not same as another 1 % because we have to consider spectral distributions of distortions. I bet some 0.1% distortion can be heard while another 1% can't be heard depending on the quality of distortions. I believe this is a research topic in psychoacoustics.

[@jamieanderson7757]

Would you be able to cite any sources for your jitter assertion please?

[@ThinkingBetter]

It was published in Snake Oil Magazine!

[@42ssh]

Google is your friend. Google with "digital jitter audible"

[@ThinkingBetter]

bsb Which URL?

[@tucsonorganist]

A long time ago, a knowledgeable friend told me that, typically, THD was not a great worry but IMD (intermodulation distortion) was definitely a concern. Anyone know if there is any truth to that?

[@shayhan6227]

Poor Paul has to constantly explain this to people ;-;

[@cars654]

In the past they used to state that distortion was noticeable for the average listener when approaching 4 %. Today's electronics would never come close to that figure unless there was a severe failure in the electronics.

[@AndyBHome]

Aren't harmonic tones naturally created both above AND below a tone in surrounding objects, (as opposed to in electronic gear)?

[@michaelkesti3917]

No. By definition, if there is a lower frequency tone then that lower frequency tone is the fundamental.

[@jonathansturm4163]

I beg to differ. Stringed instruments such as guitars and pianos generate tones below the note played due to resonances in the carcass of the instrument.

[@kencohagen4967]

With 1% being audible, anything at 1% or higher is too much. .0004% is fine. And in some amps 1% to 10% is where they rate their output. Keeping THD distortion below 1% we can then address the problems associated with our speaker's design. That's what I shoot for.

[@toxlaximus3297]

What we need is a 3.5mm jack on our heads thus sending the pure signal straight to our brains bypassing speakers and ears altogether.

[@michaelkesti3917]

Make that an RJ45 jack.

[@carlosleao1460]

Ahm! Not a Rufus Wainright song, a Leonard Cohen song Sir!

[@PimpinBassie2]

35%

[@carpetcleaningprofessor]

Oh boy the Distortion can of worms You can plug in 10 amplifiers from 10 different manufacturers and they all sound different. What I love about your product is that doesn't change what is coming into it we're so many manufacturers compensate you mindfully leave the signal clean warm and bright.

[@gerritgovaerts8443]

on top of that , we tolerate even order harmonics a lot better than odd order: electric guitar amps are tubes for a reason

[@ThatGuy2042_]

Tubes can generate odd order harmonics well as even ones. Generally asymmetry in the wave (distortion from a single ended tube circuit) will be even order harmonics and compression (from a push pull output stage for example) will be odd order. A fuzz pedal will have lots of odd harmonics as well. So a fuzz pedal driving an amp's power section in to overdrive, commonly used in late 60's and 70's rock, is not going to just be even order harmonics. Jimi Hendrix, Jimmy Page, Tony Iommi and Brian May are all examples of a cranked push pull tube amp with a fuzz pedal driving it. However, what is interpreted as harshness in hifi is seen as an edgy exiting tone in rock. Also most guitar speakers roll of frequencies above 4-6k depending on the speaker, so you are spared the highest and harshest harmonics.

[@jonathansturm4163]

Valve amps are also loud; very loud. Back in the early 70s Billy Thorpe and Lobby Loyde had Strauss amps built by John Woodhead in Melbourne. I remember when Thorpy and Lobby had a gig at a club in Sydney. The club had a huge aquarium full of expensive tropical fish. Back in Melbourne a few days later Mike Chugg regaled us with what had happened: "Billy killed the fuckin' fish!" I can also still recall the smell of burning insulation when they were being overdriven with a Fuzz Face for too long.

[@doylewayne3940]

A 440 hz vs A 432 hz, i've heard different opinions...I'm so confused, thanks Paul.

[@RealAnonymousse]

A is just a name you give to a frequency, or, rather, a set of frequencies, as A can be in a higher/lower octave. Classical compositions preferred 432Hz because it supposedly sound better. It's a matter of taste. The standard is 440Hz, however.

[@InsideOfMyOwnMind]

@@RealAnonymousse And don't EVEN get us started on stretch tuning. I never understood why they did that but here we sit.

[@michaelkesti3917]

Stretch tuning, the sharpening of higher pitched tones and flattening of lower pitched tones on wire stringed instruments accounts for the strings being imperfect due to having mass and width. This results in harmonics not occurring as exact integer multiples of tones' fundament frequencies and therefore sounding out of tune even though the fundamentals are exactly in tune.

[@jonathansturm4163]

Hmmm... I thought it was due to string _stiffness_, but then I only ever tuned guitars, not pianos.

[@michaelkesti3917]

Sure, and stiffness is a result of having mass and width.

[@ThinkingBetter]

Yes, distortion is often a real problem for speakers much more than for amps and ironically, amp vendors publish these numbers while speaker vendors don't. Lots of speakers have horrible distortion and you can absolutely hear it if you know how to check it. For example, many speakers have a bass port that yield a lot of wind noise. If you do a sine wave sweep at moderate to loud sound volumes in the bass, you will often realize the bass is not very pure. But distortion can be anywhere in the frequency response and behave in many different ways depending on origin. You can easily learn how to check for such problems by your ears and actually it's easier to find out with your ears using test signals than using music what is going on. Just yesterday I did exactly that in my home theatre. I noticed the left rear channel had some new tiny distortion while watching a movie. But it only occurred at very specific scenes in the movie. Then I applied a sine wave generator (using Studio6Digital app on iOS) and found out that the distortion peaked at around 730Hz. I took off the front grill of the speaker and to my surprise I noticed the surround ring was cracked in a small area. Apparently the rubber had hardened and a small crack had occurred creating a small "flute" through the rubber. I then used some liquid tape (Gardner Bender, find it in Home Depot) to fix it and now the problem is gone. Yes, maybe the material of the surround is starting to show signs of aging and this problem might show up elsewhere when playing loud.

[@jonathansturm4163]

I performed some sound sweeps through my system a couple of days ago. My aging ears can only hear to 8 kHz these days. Do you think liquid tape might help?

[@ThinkingBetter]

Jonathan Sturm It’s a great question what it takes to regain your hearing in the treble but adding any weight to your eardrums is not the answer as it would result in the opposite effect 🤔

[@jonathansturm4163]

As I understand it, the hearing loss is caused by hair cells breaking off the inner ear. I figured that some glue might help retain the few I have left ;-)

[@ThinkingBetter]

Good luck applying the glue in there. While you are at it, perhaps a few drops of Rogaine might help.

[@jonathansturm4163]

If I did that I'm sure my friends wouldn't be at all surprised. "There's no follicle like an old follicle," they'd say ;-)

[@flex-cx9bi]

I do not agree. Harmonics in a amplifier is very much involved in defining the "sound" from an amplifier. Most just look at the harmonic distortion at the output, but all stages in an amplifier handles distortion and one need to look at each stage and keep it lower than detectable. Many amplifers with a great amount of feedback can have low distortion at the output, but at the feedback point in the input stage the distortion increases with the feedback. Up to levels that are easily detectable and that is what creates the problem and the "sound" signature of the amplifier. Have seens amplifiers with 5-30% distortion at the input stage when playing at listening levels and of course it sounds bad and not true to the source. That level of distortion at the input stage is most common in low bias class AB that starts to get into crossover region in the output stage. Also read Nelson Pass paper on Feedback and distortion. Very interesting to read about "perfect storm" of distortion when many different distortions adds to higher distortion levels. All THD measurement is normally done with sinus waves, and those levels of distortion is not representative for how much distortion that actually is created by complex music with a lot of different instruments all having their own harmonic signature. Add crossover to that mix and send it back to the input stage. Then the input stage are by no means linear. It distorts a lot and IMHO set the sonic singnature of an amplifier.

[@TheSourceReport]

I’m allergic to sinus waves

[@supergwizzo]

00.015@ 8 ohm from 5hz to 20kz

[@chrisvinicombe9947]

Yes that's true. Must be the extra currant being drawn to push lower impedance. The extra heat being generated probably doesn't help either.

[@michaelkesti3917]

Correlation is not causation in this case. Without knowing the amounts of power at which these measurements were taken, and perhaps other parameters as well, one cannot know whether lower impedance ("ohms") is the determining factor.

[@supergwizzo]

Yes left out wattage 200 @8 and 400 @ 4 thats spec on one of my amps.

[@MrMarantzman]

I just didn't understand what u where trying to say today... ( Perhaps next time a chalkboard instead)..

[@vincentbroms667]

Thus the distortion isn't necessarily bad per say unless you're looking for absolute high fidelity. If you like the sound of tubes or like me, a fairly warm sound, that if I understand it correctly is still considered distortion, could actually sound "good" if it, let's say adds some warmth to the sound?

[@bernhardmichaelfux308]

Harmonics ? You mean the Oszillation of the Amplitude itself i think.... Edit: In German, we say: "Amplitudenoszillation", and that describes the Oszillation that is carried on top of the Sinewave itselve. Therefor we can different a Voice from another Voice, or a Sexophone from a Piano. We use this also (worldwide, not just in German, lol) for carriing a Voice over microwave. The microwave with, rule of thumb, 2,4 Ghz, is oszillated on the Wave itselve to transmit the Human voice, and the demodulator takes out only this oszillation and leads it to an analog device, so we could hear people talk via a Smartphone (in the analog Cellphone aera..)

[@johndii2194]

All that talk and not one audio example. I want to hear this THD you are talking about. I want to see it on an oscilloscope. I don't think it exist.

[@baconbyte4065]

A good example are fire bottle amplifiers. Especially those used for guitars. Crank everything up to 11 and it clips which causes distortion.

[@voiceofreason9238]

I think you're just kidding John D, but just in case you're not, put on any recording. Turn the tone controls up as high as they will go, then turn your amp as high as it will go. I guarantee you are hearing distortion, at least for a short while until it blows the speakers.

[@gerritgovaerts8443]

the question as such can not be answered : the human ear has a frequency dependent tolerance for distortion

[@bernhardmichaelfux308]

I think it can be answered: As soon as the Distortion disturbes you Enjoying music, it`s to much... ^^

[@InsideOfMyOwnMind]

@@bernhardmichaelfux308 And as such music will cause the amp to have a very dynamic distortion characteristic. I suppose it could be quantified pseudo-dynamically with impulse tests but it would add a few dimensions to the measurement to account for slew, damping, IM etc. There's no reason it can't be done but would all that info really help the buyer?

[@bernhardmichaelfux308]

InsideOfMyOwnMind certainly not... if one`s a true audiophile. I (must lough when i) watch myselve even when i lay down the needle to the Vinyl. It depends a lot on the routine, or better the celebration, of the moment when the needle touches the record. The right amount and temperature of damping Silicone-oil in the arm-lift can sometimes enhance my joy due the soft "plop" i aspect going through the Speakers from this move. Who could measure that ? What i want to say - its all about the celebration and the feelings - certainly depending on a good Equipment - and the taste of the listener. Just, as the old romans knew : de gustibus non est desputandum.... ^^

[@InsideOfMyOwnMind]

@@bernhardmichaelfux308 Certainly I wouldn't try to argue with your taste in music or sound even if I knew what it was. Also I respect your sense for ritual as long as you keep it yours. I have my own and it happens to be more about deciding what to listen to. However it seems the "scientists" among us demand all the data they can get whether they know what to do with it or not. (Go buy more tools. It will make you a better craftsman.) I just think that if we did try measuring the mundane parameters in different ways there are most likely things to learn from it.

[@jonathansturm4163]

"However it seems the "scientists" among us demand all the data they can get whether they know what to do with it or not." A very important observation.

[@scotts7017]

Any distortion is too much.

[@jonathansturm4163]

It was that attitude that led to some really shit amps back in the early 70s. Insanely low THD, but huge amounts of very audible intermodulation distortion. Acceptable THD level depends on musical content, but I suspect that you'd need to be a full-on golden-ears to hear 0.1% THD.

[@scotts7017]

Touché my friend. I like your retort. I hate hearing distortion on anything else but my guitar amps.

[@jonathansturm4163]

I'm rather fond of the voice distortions that Laurie Anderson creates. Then there's Walter Carlos's distortions of Rachel Elkind-Tourre's voice on the albums Switched on Bach and The Well-Tempered Synthesiser.

[@scotts7017]

Jonathan Sturm thank you.

[@scotts7017]

I will concede that intended distortion can be desirable.

[@baconbyte4065]

Thats why I don't use tube amps for listening to music. I like my music clean with no noticeable distortion. Can't have that with antiquated firebottles.

[@machintelligence]

Back in my high school days (early 1960's) I built a single ended (not push-pull) tube amplifier with about 5 % THD. It really didn't sound too good to my ears.

[@tothemax324]

No noticeable dist with my tube preamp infact the sound is better than any SS preamp I ever heard

[@machintelligence]

Preamps and power amps are really different kettles of fish.

[@apollorobb]

.000000000001% is too much if your amp isnt this clean its junk lol