Audibility thresholds of amp and DAC measurements

[krabapple]

Chill. This guy pops up every few months, wordily demonstrates that he doesn't understand Fourier analysis, then disappears to wait for the next round. It's useless to try to explain it to him- we all tried nicely, over and over. Pure crank, not worth the keystrokes.

Lemme guess: Sergei designs/sells some sort of 'high end' audio product based on his insights?

 

[captainbeefheart]

Lemme guess: Sergei designs/sells some sort of 'high end' audio product based on his insights?

The less you know the more you charge.

Mantra for most "high end" equipment "designers".

 

[Plcamp]

Question: Does the research that determined the ‘provably inaudible’ threshold of 120 db SINAD have more nuance than that single number dependent on frequency?

Put another way, if I restricted the frequency range of interest to under 500 hz, would there be a radically different inadibility threshold for that range?

I am trying to understand/estimate just how far off transparency an end to end system is, limited of course by woofers.

 

[Deleted member 50971]

Introduction
A recurring theme on ASR is whether or not the various measured qualities of the devices are audible. In this post, I'll present some clear and visual thresholds for when those imperfections can be considered a potentially audible concern. I will not explain the basics of amp/DAC measurements.
Feel free to comment if you have any issues with the content of this post, be it technical, grammatical, or maybe just something that's poorly communicated.

Orange marks strict limits while green marks lenient limits.
Strict thresholds guarantee that anything measuring better will be transparent.
Lenient thresholds are only lenient relatively to the strict thresholds. They are also "strict" from an audible point of view. Devices measuring worse than the lenient thresholds might still sound fully transparent to you or anyone else for that matter.


Frequency range of human hearing
Humans cannot hear sounds of every frequency. The range of hearing for a healthy young person is 20 to 20,000 hertz.
When pure sine waves are reproduced under ideal conditions and at very high volume, a human listener will be able to identify tones as low as 12 Hz (Olson, Harry F. (1967). Music, Physics and Engineering. p. 249). Below 10 Hz it is possible to perceive the single cycles of the sound, along with a sensation of pressure at the eardrums.
For these reasons, the audibility thresholds will deal with frequencies from 0 to 20 kHz.


Dynamic range, linearity
CDs, with undithered audio, have a maximum dynamic range of 96 dB (16 bits). Studies, such as the one conducted by Meyer and Moran, have shown 96 dB of dynamic range is transparent for any normal listening conditions.
120 dB (20 bits) of dynamic range is required for transparency. Anything below -120 dBFS is inaudible. Amir wrote an in-depth article about the subject.

View attachment 18959
Allo Boss V 1.2 is unable to reproduce undithered audio from CDs (with content that makes full use of the 16 bits) transparently.

View attachment 18960
miniDSP SHD lands between the two targets.

View attachment 18961
SMSL VMV D1 has more dynamic range than the required 120 dB for guaranteed transparency.


View attachment 18963
Benchmark DAC1 USB doesn't reach the -96 dBFS target.

View attachment 18964
Orchard Audio GALA remains flat up to -96 dBFS, but losses linearity before reaching -120.

View attachment 18965
Auralic Vega measures perfectly at -120 dBFS, but due to the analyzer itself introducing some noise, it doesn't show the ideal flat line, which it should be.


FFT
NwAvGuy's Heaphone Amp Measurement Recommendations - In this article, NwAvGuy provides some guidelines for good amplifier design. He is "an electrical engineer by education (BSEE) and career", not a psychoacoustician, and he does not cite his sources, so his limits will be treated as lenient.
NwAvGuy says that "noise needs to be -85dB below the signal to be inaudible which works out to only 0.005% THD+N. But music masks distortion so 0.01% (-80dB) is considered acceptable." Since I make no assumptions about the listener or listening material, I'll disregard the -80 dB threshold and go with -85 dB.
His guideline for distortion is <0.05% equivalent to -66 dBFS.

Disclaimer: The FFT spectrum shows the noise floor as being lower than it actually is. This is called “FFT gain” and it allows us to see distortion products that may be well buried inside the noise floor of the amp or DAC. The gain can be as much as 30 dB to 40 dB lower than reality. Comments on the noise floors for the following graphs are for illustrative purposes only.

View attachment 18966
Audio-gd NFB-28.28 has a "Massive 3rd Harmonic Distortion" spike that puts it above all 3 thresholds.

View attachment 18967
Parks Audio Puffin fails to meet the strict THD+N criteria and the lenient noise criteria, but stays below the lenient distortion limit.

View attachment 19064
JDS Labs The Element stays below the lenient thresholds, but doesn't stay below the strict threshold.

View attachment 18970
Allo Katana measures well enough to stay below all 3 thresholds.


SINAD
SINAD groups distortion and noise into one figure, meaning the lenient noise threshold of -85 dBFS will be used, because it's not clear whether noise or distortion dominates. When converting THD+N to SINAD, one can simply remove the minus sign and 'FS' like so: 85 dB.

View attachment 43569
The 4 DACs to the left of the orange line manage a signal over noise and distortion of 120 dB or more, exceeding the strict threshold. Totaldac d1-six, and all the other DACs to the right of it, don't make the cut for the lenient threshold.


IMD, THD+N vs frequency
For IMD, the same distortion thresholds as for FFT apply: -120 dBFS for the strict and -66 dBFS for the lenient.

View attachment 18971
Audio-gd NFB-28.28 exceeds the lenient threshold and therefore also the strict one.

View attachment 19063
Musical Fidelity V90-DAC stays between the 2 limits.

I've not come across a device that measures better than the strict threshold.


Like with SINAD, it's not always possible to tell the distortion and noise apart in THD+N vs frequency plots, so we have to go with the lenient noise threshold again.

View attachment 25303
Schiit Yggdrasil doesn't manage to stay below the lenient threshold.

View attachment 25304
miniDSP SHD and Benchmark DAC3 measure below the lenient threshold, but above the strict one.

No device measures below the strict threshold on this test.


Crosstalk
-60 dB is NwAvGuy's guideline for crosstalk, so half (numerically) of the strict limit of -120 dB.
As crosstalk measurements are still scarce on ASR, I wasn't able to found one breaching the lenient threshold.

View attachment 18977
Massdrop THX AAA 789 exceeds the strict threshold at all 3 gain settings, but also stays below the lenient threshold.

View attachment 18978
Gustard A20H stays below both thresholds.


Jitter
Jitter is only found in DACs, so I will stray away from the amp guidelines of NwAvGuy for this section. Thankfully, he wrote another article about the subject where he introduces a threshold for jitter:
View attachment 18990
Despite "all the research [he's] done", he doesn't cite his sources here either, so this limit will also be treated as lenient.
NwAvGuy uses a sample rate of 44.1 kHz and a main tone of 11.025 kHz. Amir uses a sample rate of 48 kHz, hence a main tone of 12 kHz. I've adjusted the threshold to fit Amir's graphs.

View attachment 18980
SMSL Sanskrit 10th exceeds both thresholds regardless of input.

View attachment 18981
Topping DX3 Pro exceeds the strict threshold, but not the lenient threshold.

View attachment 18982
Khadas Tone Board doesn't exceed either threshold.


Frequency response, channel balance
Going back to NwAvGuy's amp guidelines, he recommends a maximum of 0.5 dB deviation (from 0) in the frequency response.
Psychoacoustics: Facts and Models by Hugo Fastl and Eberhard Zwicker is not a very quotable book, but on pages 180-181 it makes it clear that a change in SPL of less than 0.2 dB can be heard by humans.
In 'Sound Reproduction: The Acoustics and Psychoacoustics of Loudspeakers and Rooms' Floyd Toole says the following: "The simplest deviation from flat is probably a spectral tilt. There is some evidence that we can detect slopes of about 0.1 dB/octave, which translates into a 1 dB tilt from 20 Hz to 20 kHz — not much."
0.1 dB is therefore the strict limit.

View attachment 18984
The HP Z series laptop's frequency response takes a nosedive right before 20 kHz and exceeds both thresholds.

View attachment 18985
Topping DX3 Pro exceeds the strict threshold in both the bass and treble, but stays within the lenient.

View attachment 18986
SpeaKa USB DAC stays within both thresholds.

The channel balance threshold from NwAvGuy mirrors the frequency response threshold: if the FR rises by 0.5 dB in one area and drops by 0.5 dB in another, the total discrepancy will be 1 dB, which will be the lenient threshold for channel balance.
The strict thresholds remains 0.1 dB.

View attachment 18987
TEAC HA-P50 exceeds both thresholds.

View attachment 18988
Neurochrome HP-1 exceeds the strict threshold, but not the lenient threshold before running out of power.

View attachment 18989
Sabaj Da3 doesn't exceed either threshold before running out of power.


Output impedance
NwAvGuy's guideline for output impedance is based on the 1/8th rule, placing it at 2 ohms with a worst case scenario of 16 ohms headphones.
The basis for the 1/8th rule is that it allows up to a 1 dB variation in the frequency response. For a 0.1 dB variation a 1/100th rule is derived, meaning the output impedance should be 0.16 ohms or less with a 16 ohms load.
Keep in mind the thresholds vary with load impedance and can be disregarded entirely with headphones that have a flat impedance curve.

View attachment 18991
All the amps to the left of Auralic Gemini 2000 exceed the lenient threshold.


Recap of thresholds
Lenient
Dynamic range, linearity: 96 dB
THD, IMD: -66 dBFS / 0.05%
Noise: -85 dBFS / 0.005%
SINAD: 85 dB
Crosstalk: -60 dBFS
Jitter: -110 dBFS, -100 dBFS around the main tone
Frequency response: ±0.5 dB
Channel balance: 1 dB
Output impedance: 2 ohms

Strict
Dynamic range, linearity, SINAD: 120 dB
THD, IMD, noise, crosstalk, jitter: -120 dBFS / 0.0001%
Frequency response, channel balance: ±0.1 dB
Output impedance: 0.16 ohms


Changelog

• UPDATE #1: Elaborated on the meaning of the thresholds.
• UPDATE #2: Based on feedback from @solderdude and @restorer-john, I've decided to get rid of the THD+N vs power graphs.
• The lenient threshold line for the IMD measurement of Musical Fidelity V90-DAC was mistakenly 10 dB lower than it should've been. It has now been fixed.
• UPDATE #3: Dithering was unaccounted for in a couple of descriptions of CD audio. The sentences have been rephrased to accurately reflect the fact that 96 dB is not the maximum dynamic range of 16 bit audio. Thanks to @bennetng and @Francis Vaughan for pointing this out.
• UPDATE #4: A strict threshold for output impedance has been introduced. The graph has not been updated for practical reasons. Big thanks to @dc655321 for helping with the math.
• UPDATE #5: Added SINAD to the 'Recap of thresholds' section.
• UPDATE #6: As pointed out by @daftcombo, the lenient thresholds on the THD+N vs frequency graphs were incorrect. This has now been fixed.
• UPDATE #7: Added SINAD to the main section. Added a disclaimer to the part about FFT. Moved updates to a new changelog section at the bottom.

I did not go over every page in this thread, but it is an interesting read. What does the level of SINAD have to be before it’s above the threshold of hearing? I have heard Amir mention 115 dB and I’ve heard others mention 100 dB.

 

[BDWoody]

I did not go over every page in this thread, but it is an interesting read. What does the level of SINAD have to be before it’s above the threshold of hearing? I have heard Amir mention 115 dB and I’ve heard others mention 100 dB.

There's a lot to digest for sure, but from the end:

"Recap of thresholds
Lenient
Dynamic range, linearity: 96 dB
THD, IMD: -66 dBFS / 0.05%
Noise: -85 dBFS / 0.005%
SINAD: 85 dB
Crosstalk: -60 dBFS
Jitter: -110 dBFS, -100 dBFS around the main tone
Frequency response: ±0.5 dB
Channel balance: 1 dB
Output impedance: 2 ohms

Strict
Dynamic range, linearity, SINAD: 120 dB
THD, IMD, noise, crosstalk, jitter: -120 dBFS / 0.0001%
Frequency response, channel balance: ±0.1 dB
Output impedance: 0.16 ohms"
https://audiosciencereview.com/foru...text=Recap of thresholds,impedance: 0.16 ohms


There is a lot to be learned from reading through these pinned/reference threads.

 

[Deleted member 50971]

There's a lot to digest for sure, but from the end:

"Recap of thresholds
Lenient
Dynamic range, linearity: 96 dB
THD, IMD: -66 dBFS / 0.05%
Noise: -85 dBFS / 0.005%
SINAD: 85 dB
Crosstalk: -60 dBFS
Jitter: -110 dBFS, -100 dBFS around the main tone
Frequency response: ±0.5 dB
Channel balance: 1 dB
Output impedance: 2 ohms

Strict
Dynamic range, linearity, SINAD: 120 dB
THD, IMD, noise, crosstalk, jitter: -120 dBFS / 0.0001%
Frequency response, channel balance: ±0.1 dB
Output impedance: 0.16 ohms"
https://audiosciencereview.com/forum/index.php?threads/audibility-thresholds-of-amp-and-dac-measurements.5734/#:~:text=Recap of thresholds,impedance: 0.16 ohms


There is a lot to be learned from reading through these pinned/reference threads.

That’s awesome thank you!

 

[dlaloum]

There's a lot to digest for sure, but from the end: "Recap of thresholds Lenient Dynamic range, linearity: 96 dB THD, IMD: -66 dBFS / 0.05% Noise: -85 dBFS / 0.005% SINAD: 85 dB Crosstalk: -60 dBFS Jitter: -110 dBFS, -100 dBFS around the main tone Frequency response: ±0.5 dB Channel balance: 1 dB Output impedance: 2 ohms Strict Dynamic range, linearity, SINAD: 120 dB THD, IMD, noise, crosstalk, jitter: -120 dBFS / 0.0001% Frequency response, channel balance: ±0.1 dB Output impedance: 0.16 ohms" https://audiosciencereview.com/forum/index.php?threads/audibility-thresholds-of-amp-and-dac-measurements.5734/#:~:text=Recap of thresholds,impedance: 0.16 ohms There is a lot to be learned from reading through these pinned/reference threads.

Take this list with a little bit (or a lot) of Caution (!!!)

Lenient Threshold of THD/IMD @ -66dbFS - implies a SINAD of 66

The SINAD referred to here, is being referenced only to the lenient threshold for Noise - in which case it should be the Noise threshold... as the whole point of SINAD is to wrap noise and THD together

What should be kept in mind, is that the audibility threshold for noise is circa 85db, whereas the audibility threshold for THD/IMD is circa 66db

SINAD is a valuable measure of engineering hygiene and rigour - but it is less useful in terms of the specifics of selecting equipment.
Also the SINAD measure is a valid measure of engineering hygiene and rigour TODAY - but it falls down a bit when looking at designs and implementations from 40+ years ago - some of which are very well designed and built... it is applicable to todays newly designed equipment (or say the last decade or so) - as the state of the art in terms of what is possible has shifted.
50 years ago, achieving the threshold of audibility was an engineering/design and manufacturing challenge, today it is a matter hygiene and due process - how to achieve it is well known and documented, components are readily available... but the bar as to what is possible is now way beyond our thresholds of audability - which to a greater or lesser degree, makes values beyond that point somewhat academic.

A designer can make a great sounding amp, and choose manufacturing and component values, that are above and beyond the thresholds of audibility, without being State Of The Art... - eg: the target could be 75db THD and 90db Noise - effectively a SINAD of 75db (and in the eyes of many SINAD chart readers - inadequate) - but 75db THD = 0.018% - is well below the threshold of audibility! - and there might be savings to be made as a result of that design choice, resulting in a more economical component on the market. (or a higher profit for the manufacturer...)

I have multiple amplifiers that fail the audibility threshold on SINAD grounds.... because their THD is above -85db - their noise specs are typically in the 100db+ range - so very good. And these are highly regarded audiophile amps.

 

[Blumlein 88]

Take this list with a little bit (or a lot) of Caution (!!!)

Lenient Threshold of THD/IMD @ -66dbFS - implies a SINAD of 66

The SINAD referred to here, is being referenced only to the lenient threshold for Noise - in which case it should be the Noise threshold... as the whole point of SINAD is to wrap noise and THD together

What should be kept in mind, is that the audibility threshold for noise is circa 85db, whereas the audibility threshold for THD/IMD is circa 66db

SINAD is a valuable measure of engineering hygiene and rigour - but it is less useful in terms of the specifics of selecting equipment.
Also the SINAD measure is a valid measure of engineering hygiene and rigour TODAY - but it falls down a bit when looking at designs and implementations from 40+ years ago - some of which are very well designed and built... it is applicable to todays newly designed equipment (or say the last decade or so) - as the state of the art in terms of what is possible has shifted.
50 years ago, achieving the threshold of audibility was an engineering/design and manufacturing challenge, today it is a matter hygiene and due process - how to achieve it is well known and documented, components are readily available... but the bar as to what is possible is now way beyond our thresholds of audability - which to a greater or lesser degree, makes values beyond that point somewhat academic.

A designer can make a great sounding amp, and choose manufacturing and component values, that are above and beyond the thresholds of audibility, without being State Of The Art... - eg: the target could be 75db THD and 90db Noise - effectively a SINAD of 75db (and in the eyes of many SINAD chart readers - inadequate) - but 75db THD = 0.018% - is well below the threshold of audibility! - and there might be savings to be made as a result of that design choice, resulting in a more economical component on the market. (or a higher profit for the manufacturer...)

I have multiple amplifiers that fail the audibility threshold on SINAD grounds.... because their THD is above -85db - their noise specs are typically in the 100db+ range - so very good. And these are highly regarded audiophile amps.

I basically agree with your post. However.......

Lenient Threshold of THD/IMD @ -66dbFS - implies a SINAD of 66

A THD rating doesn't imply SINAD anything. That is the point. You can have SINAD of -66 where it has very low noise and is mostly distortion you'll not hear. Or you can have SINAD of -66 db where it has very low distortion and mostly noise in which case the noise will be ever present and audible. The two SINADs are true, but not comparable. If SINAD is low enough no worries either way. But as you say with gears from 40 years ago or more you need to separate out THD and noise to know if something is going to sound okay. Mediocre SINAD numbers need parsing out to be useful.

 

[dlaloum]

I basically agree with your post. However.......

Lenient Threshold of THD/IMD @ -66dbFS - implies a SINAD of 66

A THD rating doesn't imply SINAD anything. That is the point. You can have SINAD of -66 where it has very low noise and is mostly distortion you'll not hear. Or you can have SINAD of -66 db where it has very low distortion and mostly noise in which case the noise will be ever present and audible. The two SINADs are true, but not comparable. If SINAD is low enough no worries either way. But as you say with gears from 40 years ago or more you need to separate out THD and noise to know if something is going to sound okay. Mediocre SINAD numbers need parsing out to be useful.

OK ... yes - that is only the THD part of it, but with that level of Noise, the SINAD could be no better than 66...

I think for people to get some sense of reality the SINAD of speakers should be quoted too....

Then the penny might drop... I have a SINAD of 100 !!! but I am putting it through speakers with a SINAD of 46 (0.5% THD - which is damn good for a speaker!).... - cognitive dissonance anyone?

 

[majingotan]

OK ... yes - that is only the THD part of it, but with that level of Noise, the SINAD could be no better than 66...

I think for people to get some sense of reality the SINAD of speakers should be quoted too....

Then the penny might drop... I have a SINAD of 100 !!! but I am putting it through speakers with a SINAD of 46 (0.5% THD - which is damn good for a speaker!).... - cognitive dissonance anyone?

I find it funny that my Dan Clark Aeon Open X has better 20-20KHz THD than my headphone amplifier and yet, I am firmly confident that I won't be able to tell a difference between my 30-50dB SINAD headphone amplifier and a 120 dB SINAD SOTA headphone amplifier on a DBT volume matched test with 90% hit rate.

 

[Jimster480]

I find it funny that my Dan Clark Aeon Open X has better 20-20KHz THD than my headphone amplifier and yet, I am firmly confident that I won't be able to tell a difference between my 30-50dB SINAD headphone amplifier and a 120 dB SINAD SOTA headphone amplifier on a DBT volume matched test with 90% hit rate.

Seems like it bad at listening then.
I could tell the difference between many different products even with reasonably high performance.
Now recently I haven't really been able to tell this recent high measuring stuff apart, but that is to be expected when we hit the scientific limits of audible performance.
However below like 105 sinad? You should be able to tell lots of stuff apart with well recorded music.

 

[Deleted member 50971]

Good morning guys, I’ve been tinkering with audio a long time, but SINAD is new to me. Other than seeing it posted here for the last couple of years I always went off of the THD and SNR specs. Mainly because that’s what the manufacturers gave us, so please help me to understand SINAD a little better.

I’m old-school, I like separates, I have a couple of DAC’s that measure very well, a preamp that measures very well. But what about the amplifier? It consistently seems to have the highest noise and distortion in the audio chain, if we leave our music out of it, and speakers out of it.

How good is good enough compared to the distortion that’s in the music? I know that SINAD is not a one stop shop for showing the quality of a specific piece of our gear, but I believe it is a good indicator, and according to everything I read on ASR there’s no better single measurement for letting us know what’s going on.

What about the distortion in the speakers, that’s a measurement that I don’t believe I’ve ever seen from any manufacturer. As for as I can tell from researching online, our speakers have at least 1% distortion, and maybe up to 5%.

To recap my questions for you guys that know our;

What about my amplifier SINAD? I run 2 D-Sonic Pascal based class D amps, and I expect they measure reasonably well.

I also have a set of nearly 30 year old Classe Audio monoblocks that are .1% THD at full power. These are on spec by the way and they just came back from service at United Radio.

Am I really going to hear .1% THD?

What about the distortion in my speakers?

What if my electronics are below the distortion in my speakers, will i ever hear it?

Here’s the 800 pound gorilla in the room I’m assuming;

The music, what about the distortion that’s inevitable in all music? I’ve heard a range from 5% to 10% distortion just in the music we listen to.

I know there are other measurements also, and SINAD is one (or two actually) measurements that we go by. I see the lenient, and I see the strict measurements, but what about everything in between?

Is it really that cut and dry?

I really appreciate someone answering that has the knowledge, thank you.

 

[SIY]

Nothing mysterious, SINAD is just the inverse of THD+N.

"[T]he distortion that’s inevitable in all music" doesn't really have any meaning. By definition, the original musical signal is not distorted, though it certainly has harmonic and anharmonic components. But it is the original signal. We want the electronics to get it from point A and level V to point B and level W without significantly altering. And that's trivially easy to accomplish.

 

[DSJR]

Squinting a little, I'd suggest SINAD is a *general guide* as to the *overall* behaviour of an amplifier, but of course it's but one of a number of things to look for. My *thing* is for low output impedance, a done deal decades ago but it's amazing how deliberately poor some 'audiophile' amps can be, especially valve/tube ones. All this started I think in the 80's rise of 'audiophool mentalities' generated by a handful of reviewers trying to make gurus of themselves (I can think of one UK designer/engineer/consultant/reviewer in particular who raved about then high end amp confections with distortions in the -40's [often costly-unreliable in UK mains voltages] and the routine 'best buys' had IMD at -60dB typical but that didn't matter as he climbed the greasy international high-end reviewer pole). I'd also suggest out of band behaviour is also useful to watch and again, a done deal in the more competent designs which always sound 'boring' to this year's fashion audiophools.

I think this site is an excellent 'melting pot' of the highly technical, as in many posts further up this thread going out right on the academic edge, coupled with simple bods like me trying to distil the concepts into something we can use to improve our own listening experiences via our sound systems. Long may it continue

As for how good is good enough, I'd suggest that varies from person to person and especially, as all the senses and wallet-size is involved in a subjective choice of audio equipment (it's never just the ears, hence the outlandish snake-oil products out there), I'd use the reviews here as a decent sensible starting point and then choose on facilities, cost, service availability at sensible money (the Classe amps hopefully didn't cost a bomb to check over?) and so on. Forget the boxes then and listen to some music...

 

[Deleted member 50971]

Nothing mysterious, SINAD is just the inverse of THD+N.

"[T]he distortion that’s inevitable in all music" doesn't really have any meaning. By definition, the original musical signal is not distorted, though it certainly has harmonic and anharmonic components. But it is the original signal. We want the electronics to get it from point A and level V to point B and level W without significantly altering. And that's trivially easy to accomplish.

Thanks.

Can I or a trained listener hear the difference between these two, or isn’t it that cut and dry?

.1% TDH with an SNR of 100 dB

VS

.0005% THD with an SNR of 120 dB

 

[Deleted member 50971]

Squinting a little, I'd suggest SINAD is a *general guide* as to the *overall* behaviour of an amplifier, but of course it's but one of a number of things to look for. My *thing* is for low output impedance, a done deal decades ago but it's amazing how deliberately poor some 'audiophile' amps can be, especially valve/tube ones. All this started I think in the 80's rise of 'audiophool mentalities' generated by a handful of reviewers trying to make gurus of themselves (I can think of one UK designer/engineer/consultant/reviewer in particular who raved about then high end amp confections with distortions in the -40's [often costly-unreliable in UK mains voltages] and the routine 'best buys' had IMD at -60dB typical but that didn't matter as he climbed the greasy international high-end reviewer pole). I'd also suggest out of band behaviour is also useful to watch and again, a done deal in the more competent designs which always sound 'boring' to this year's fashion audiophools.

I think this site is an excellent 'melting pot' of the highly technical, as in many posts further up this thread going out right on the academic edge, coupled with simple bods like me trying to distil the concepts into something we can use to improve our own listening experiences via our sound systems. Long may it continue

As for how good is good enough, I'd suggest that varies from person to person and especially, as all the senses and wallet-size is involved in a subjective choice of audio equipment (it's never just the ears, hence the outlandish snake-oil products out there), I'd use the reviews here as a decent sensible starting point and then choose on facilities, cost, service availability at sensible money (the Classe amps hopefully didn't cost a bomb to check over?) and so on. Forget the boxes then and listen to some music...

I have to get ready for work, but at what measurement threshold do you consider a low output impedance?

Only one amp has the out impedance spec of 6Mohms listed.

70 Kohms on one amp, and 60 Kohms on my other one, and that’s input impedance.

 

[Lambda]

Can I or a trained listener hear the difference between these two, or isn’t it that cut and dry?

why would you mix dB and % in one sentence?!

 

[SIY]

Thanks.

Can I or a trained listener hear the difference between these two, or isn’t it that cut and dry?

.1% TDH with an SNR of 100 dB

VS

.0005% THD with an SNR of 120 dB

It’s not that cut and dry. If the number is high, it doesn’t matter. If the number is low, then you need to go past the raw number to predict audibility.

There’s a great and understandable desire for some sort of unidimensional metric for ranking components. Unfortunately, that metric doesn’t exist, and using SINAD as a proxy for this nonexistent number is highly misleading. That said, if SINAD is, say, 100, you’re not going to be hearing any issues.

 

[Lambda]

Am I really going to hear .1% THD?

I cant speak for you but some can with the right test signal.

I’ve heard a range from 5% to 10% distortion just in the music we listen to.

How would you measure this?
If its in the music it is the music. its not distortion it is the signal.

There are vastly different thresholds of hearing for distortion and for noise.
And they are extremely depended listening level/ playback gain. on of cause the type of signal.

 

[Deleted member 50971]

why would you mix dB and % in one sentence?!

I’d appreciate a constructive answer.

If I’m wrong show me, thanks