How can DAC's have a SOUND SIGNATURE if they measure as transparent?

[Doodski]

If you need a sine wave generator for matching levels this works well.

Online Tone Generator - generate pure tones of any frequency

szynalski.com

 

[BDWoody]

I'll confess that I don't fully understand the ASR dashboard. But I believe Amir fully when he ooos and ahhs over low levels of harmonic distortion and signal to noise ratios.

This thread may be helpful to put some of these numbers in the context of audibility:

Audibility thresholds of amp and DAC measurements

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...

www.audiosciencereview.com

This is another way to get a feel for how small the noise and distortion numbers are. Haven't seen it for a while:

The Shoutometer

We've all seen the Sound Pressure Level decibel reference tables where you have "quiet room", "chainsaw", "jet engine" and so on. While that is handy for estimating increased loudness in decibles, it didn't help me when thinking about the measurement levels obtained around here when measuring...

www.audiosciencereview.com

 

[CedarX]

I’m simply hypothesizing that there attributes of the conversion from binary back to continuous waveforms that we don’t yet know how to measure…

The sound produced* by the artists and their instruments was recorded using microphones. (1) (*or synthesized, but it still ends up in a record).

“the conversion from binary back to continuous waveforms”: we could use similar mics (same mankind-developed technology) to record these continuous waveforms—i.e. the sound, as reproduced by your transducers (speakers, headphones, etc.). (2)

If we can record (1), we can measure everything about (1). If we can record (2), we can measure everything about (2).
What would be these attributes that we don’t know yet how to measure? If there are things we don’t know how to measure, I can guarantee they were not recorded in (1) either.

Now… that we don’t measure everything, or that some things are not easy to measure, is a different story. Amir’s tests are limited. However, they are a very good proxy to assess engineering excellence and what matters the most in audio.

 

[BDWoody]

. I’m simply hypothesizing that there attributes of the conversion from binary back to continuous waveforms that we don’t yet know how to measure…

How familiar are you with sampling theory? As long as you are filling in some blanks, this is another great video that gets referenced here maybe more than any other.

 

[donrleonard]

The sound produced* by the artists and their instruments was recorded using microphones. (1) (*or synthesized, but it still ends up in a record).

“the conversion from binary back to continuous waveforms”: we could use similar mics (same mankind-developed technology) to record these continuous waveforms—i.e. the sound, as reproduced by your transducers (speakers, headphones, etc.). (2)

If we can record (1), we can measure everything about (1). If we can record (2), we can measure everything about (2).
What would be these attributes that we don’t know yet how to measure? If there are things we don’t know how to measure, I can guarantee they were not recorded in (1) either.

Now… that we don’t measure everything, or that some things are not easy to measure, is a different story. Amir’s tests are limited. However, they are a very good proxy to assess engineering excellence and what matters the most in audio.

Thanks for the thoughtful reply, @CedarX.

I am now wondering if it's not some mystery thing we don't know how to measure yet, but rather something we don't take the time to measure and interpret properly: the complete distribution of harmonic distortion--the distortion spectrum-- that a given piece of audio equipment produces, rather than simply collapsing these distortion profiles into 1-dimensional measures like THD or SINAD.

TLDR? The reason listeners might favor one DAC over another is the quality of the harmonic distortion introduced by their OP-Amps.

As I wait patiently for an evening when my wife is free to help me run the AB test on my DACs, I’ve been killing time learning about THD. This video of Jon Darko interviewing a guest, starting around minute 8, describes what harmonics are from both an electrical engineering standpoint as well as from the standpoint of music-making.

On the musicality side, it was explained that pianos and guitars don’t sound the same even when they’re playing the same note because of harmonics—these are the frequencies / tones above the basic ground note--ie overtones.

When overtones are intentionally created by musicians and their instruments, we call them harmonies. When they are added to what has been recorded, we call this harmonic distortion. It is virtually impossible to design electronics that do not introduce harmonic distortion, they discuss in the video. What is possible is to minimize it.

This effort to control harmonic distortion introduces two facets that are potentially relevant to our discussion of DACs like the PS200.

First, how one goes about minimizing distortion matters greatly. A common method of achieving extremely low distortion with Class-D amplification, where power (gain) is abundant and so is noise, is to introduce lots of negative feedback in order to push distortion to lower-level, but higher odd-order (ie the15th or the 17th rather than the 3rd or the 5th) harmonics. When these low-level harmonics happen to be high odd-order (15th, 17th, 19th) tones, these can be quite metallic-sounding and objectionable. Though the famous "blue note" in jazz is also an example of such low-level, odd-order harmonics being used deliberately to create music. So is a tube amplifier on a guitar amp that is intended to create screechy distortion.

Second, sometimes harmonic "distortion" is viewed as desirable even more generally. Even order harmonics (the 2nd, the 4th, ), as well as low odd-order (ie 3rds and 5ths) are experienced by listeners as benign. Even-order harmonics don't rub. They create octaves above the fundamental note that create the auditory sensation of softness and richness. Thick. Dense. Creamy. Full. Pastel.

Lower-level odd-order (5ths and 3rds) will sound fresh, neon, spicey, energetic, brisk in treble.

High-end amplifier builders often bake in low even-order OR low odd-order harmonic flavors into their amps in order to generate pleasing coloration. Some listeners prefer softer/richer even-order amps, some prefer brighter/spicier. The guest found that his musical tastes switched from even- to odd-order harmonics later in life.

This was all fine and dandy. But what might this discussion of amplifiers have to do with DACS like my newly cherished PS200?

The process by which DACs convert digital signals to analog waveforms entails amplification and, thus, creates a harmonic distortion profile.

When we collapse the harmonic distribution or harmonic profile to a single number (THD or SINAD), and when we reduce a piece of audio equipment to an electrical engineering math equation, as those here who view DACs as black boxes do, we fail to understand the musical qualities inherent in the distortion profiles that these electrical circuits inevitably produce. Tonal color. Precision or dullness on attack, sustain, or bloom? Sunny, or grey and muddy?

But don't take my word for it. Check out @amirm's 2018 review of a 2011 paper that demonstrates this point empirically. Or the follow-up paper linked beneath Amir's summary that confirms that it is the distortion profile of Op-amps that produces audible differences.

 

[donrleonard]

Now that science has demonstrated the plausibility that DACs color sound based on choices about how their op-amps shape harmonic distortion, what possible differences do the DAC chips themselves make?

 

[BDWoody]

A bunch of posts moved in.

 

[BDWoody]

Now that science has demonstrated the plausibility that DACs color sound based on choices about how their op-amps shape harmonic distortion, what possible differences do the DAC chips themselves make?

Have you ever seen a video like that with actual evidence rather than a well told story? Any controlled tests? Ever? From anyone?

A common method of achieving extremely low distortion with Class-D amplification, where power (gain) is abundant and so is noise, is to introduce lots of negative feedback

Oh no! Not negative feedback! Negative means bad after all.

...when we reduce a piece of audio equipment to an electrical engineering math equation, as those here who view DACs as black boxes do, we fail to understand the musical qualities inherent in the distortion profiles that these electrical circuits inevitably produce. Tonal color. Precision or dullness on attack, sustain, or bloom? Sunny, or grey and muddy?

Any listening tests to provide any evidence of what we are all missing?

You really should set up a proper test for yourself instead of looking to Darko for enlightenment.

 

[RandomEar]

Thanks for the thoughtful reply, @CedarX.

I am now wondering if it's not some mystery thing we don't know how to measure yet, but rather something we don't take the time to measure and interpret properly: the complete distribution of harmonic distortion--the distortion spectrum-- that a given piece of audio equipment produces, rather than simply collapsing these distortion profiles into 1-dimensional measures like THD or SINAD.

TLDR? The reason listeners might favor one DAC over another is the quality of the harmonic distortion introduced by their OP-Amps.

That's not the reason. DAC distortion on modern (non-bullshit) designs is vanishingly small, typically below -90 dB, often below -110 dB. That's 0.003 to 0.0003%. Now test for yourself where your audibility limit is for distortion.

 

[Beave]

That's not the reason. DAC distortion on modern (non-bullshit) designs is vanishingly small, typically below -90 dB, often below -110 dB. That's 0.003 to 0.0003%. Now test for yourself where your audibility limit is for distortion.

Exactly. When the TOTAL Harmonic Distortion is that low, it doesn't really matter what the components of that distortion are. They're all going to be even lower than the total.

 

[Beave]

Perhaps there's an app for that?

Bingo. I'm sure there'll be error. But we'll do the best we can over here.

View attachment 431976

As mentioned before, you need to do the level-matching with electrical measurements, not acoustical.. Acoustical measurements are not sufficiently precise and can easily be off by a full dB or two.

 

[voodooless]

Perhaps there's an app for that?

Bingo. I'm sure there'll be error. But we'll do the best we can over here.

View attachment 431976

Don't use this for level matching. It's not good enough by a long shot. If you move the phone by more than a few centimeters, it will throw off the measurement enough to invalidate it, never mind the amount of noise that is in this kind of measurement. @Beave , damn you

Just get a cheap DMM. They work well and are reliable enough to do this.

 

[JeremyFife]

Steady cowboy! I'm a newbie and don't want to be scared off this forum. If you have listened to the Chord kit I have no grumble. If not and merely relying on the measurements (I have read the ASR review piece) I am suggesting (that in my humble experience) they do not tell the whole story.

Welcome to ASR

You've gone in head first, but don't be put off by the responses .. look at what is being said rather than how. We can be a bit blunt, but this is a fantastic resource for learning and re-learning.

Something that helped me: if anyone here said they had measured a DAC with a new piece of measurement equipment the first thing we'd do would be to ask about that new measurement equipment. If it was not standard, not calibrated, DIY or just unknown then we wouldn't accept the measurements. We'd look for evidence, for comparison against a known measure and we'd want to know what controls are in place. Only after we understood that could we begin to look at the actual measurements.
That's normal, scientific / engineering / common-sense practice.

Our ears are exactly that: unknown, (pretty unreliable) and uncalibrated instruments. Before we can share our listening experience in any meaningful way, we must apply listening controls (calibrate our instruments).
That means level matching (+/- 0.1dB), double blind, preferably ABX, quick switching and multiple repetitions.

Without controls, an opinion based on listening is simply flawed and really tells us nothing. Our brain, our subconscious biases, process what we hear and have been proven again and again to be deeply unreliable

It's your system, you can like anything you want to - no issue with that. Do accept though that uncontrolled listening tests are pretty useless.

 

[DSJR]

I'll confess that I don't fully understand the ASR dashboard. But I believe Amir fully when he ooos and ahhs over low levels of harmonic distortion and signal to noise ratios. I just wonder whether there are other aspects to the quality of a sound wave that are not captured by this model---a model that puts a $9 apple dongle on par with much more elaborate DAC implementations.

Is it possible that there variables that relate to the qualities of a sound wave that are not captured by these measurements? Variables that impact how an analog sound wave creates the illusion of soundstage width and depth?

Have you actually LISTENED to the Apple dongle having corrected for the large difference in output level? Inaudible jitter levels aside, I'd say myself that the Apple is all but indistinguishable subjectively as a line output tool to conventional dacs as long as the output levels are adjusted to match, the signal path (if that matters still these days of miniaturisation) lacking an output buffer to boost output from 0.5V (EU) or 1V (US) to a typical 2V single ended level.

I'd suggest that soundstage width and depth can be messed with (Naim did this with the Snaic interconnects and also using three core mains cable as interconnect from power supply to power amp, this totally ballsing up the perceived soundstage - over-wide central image and limited L-R I remember when I compared to a proper twin screened cable). Modern sensible gear shouldn't do this at all if the separation is greater than, say a suggested 80dB across the range and the two channels are matched in performance.

 

[antcollinet]

but rather something we don't take the time to measure and interpret properly: the complete distribution of harmonic distortion--the distortion spectrum

Have a look at the multitone test. Exactly what it does.

And I'm going to repeat.

Why go searching for some mysterious thing unknown to current science**, when we have known science that fully explains what you are hearing?

** or just - in this version of your argument - not measured, when so many engineers here are either happy with the measurements done, or are unable to put up a sufficiently convincing argument for others to be done.

Remember - every decent piece of audio equipment on the market has been engineered by engineers. Not conjured up from a cauldron of mystery and magic by grand wizards.

The measurements done here are exactly the same as the ones those engineers (if they have any competency at all) are using to validate the quality of their designs.

 

[JustJones]

I love this thread it reminds me of my youth and old records that skipped. You'd have to nudge the arm every now and then.
Dacs are commodities
Yes, you may find one that's muffled and sounds different ( shows up in measurements)
Move on to speakers, DSP and your room.
Awaiting the next influx of , "My wife heard it from the kitchen! ".

 

[donrleonard]

That's not the reason. DAC distortion on modern (non-bullshit) designs is vanishingly small, typically below -90 dB, often below -110 dB. That's 0.003 to 0.0003%. Now test for yourself where your audibility limit is for distortion.

Have you ever seen a video like that with actual evidence rather than a well told story? Any controlled tests? Ever? From anyone?

In 2018, Amir examined a peer-reviewed conference paper published in the 2011 proceedings of the Audio Engineering Society. The author is a faculty member at a well-regarded audio engineering program at McGill University in Canada. This study demonstrated, through a double-blind AB preference test, that a statistically significant number of listeners were able to express preference for one DAC over another:

• "While the differences were slight, the op-amps in this test were capable of producing levels of distortion within their normal, unclipped operational range that were detectable by listeners. It is possible for listeners to differentiate between op-amps based on distortion characteristics alone. The ability to distinguish between the distortion characteristics of op-amps appears to be dependent on a complex interaction of the THD vs. Frequency, THD vs. Amplitude, and the harmonic spectrum of the distortion. This low-level distortion is enough to alter the character of the sound but does not necessarily reduce listener preference."

As you can see, 9 of the 24 listener-observations (some listeners tested more than once) were able to express a statistically significant (column 1 p<.05) preference for one DAC over another even though both the A and B DACs had THD+N ratios well below 0.1% (columns 2 & 3).

In a follow-up 2014 study, the author finds that

• "Due to the gain-bandwidth characteristics of operational amplifiers, their nonlinearities are frequency dependent, showing a rise in distortion at higher frequencies. Depending on the circuit and system implementations, this distortion can be significant to listener perception of sonic character and quality and is therefore relevant to models of op amp-based analog equipment."

Finally, a 2019 masters thesis out of the University of Huddersfield (UK) cites these McGill studies and was able to reproduce their general findings.

• "This thesis presents and discusses research undertaken into the detection and measurement of colouration produced by audio transformers. It is common for transformers to be subjectively described by audio professionals as ‘warm’, ‘fat’, ‘smooth’, etc. however there is little evidence to show if there is an audible difference and if there is a correlation between these levels of perceptual attributes and the performance of the device. Therefore, the research question was defined as: is there an audible difference with a transformer?
• "A review of the objective and subjective elements of the study was conducted. First the history, application and operation of the audio transformer with an aim to understand the objective measures and performance of the device with focus on the nonlinear distortion response. This also includes the design and testing of a suitable test circuit used in the measurement method. The subjective review concerns perception of distortion and testing methodologies for investigating audible differences. The conclusion of the review is that few pieces of research exist showing the relationship between device, distortion and perception
• "The testing of each transformer involved the use of a specially designed test circuit using a variety of measures including THD+N and frequency domain analysis, to provide the most information about the operation of the device. Using the same setup, the device responses to a variety of samples were recorded and implemented in a double-blind triple-stimulus with hidden reference test using trained listeners in accordance with the ITU-R BS.1116-3 recommendation. The test results were then analysed for a random distribution using a 1-tailed binomial test. The results of the analysis show a high likelihood that the bass samples were audibly different shown by the significant p-values of all 3 samples at less than 0.001. A slight correlation seems to exist with THD+N, 3rd harmonic distortion and level however with no other obvious trends, it was concluded that the distortion and therefore the audibility is programme dependent.
• "It was concluded that transformers are likely to produce a level of distortion deemed audible although the effect is considered to be programme dependent."

None of these tests "prove" that I (or anyone) can tell the difference between two operational amplifiers with otherwise similar measurements of THD. But the statistical significance of these seemingly well thought out experiments should increase our confidence in the plausibility that I--and myriad other audio professionals and enthusiasts--aren't suffering from some mass delusion when we hear qualitative differences between opamps.

Audio enthusiasts and technicians should be less-dismissive of claims that individuals can hear such qualitative differences between DACs. There may be quantifiable differences in the way low-level operational amplifier distortion generates audible even- or odd-order harmonics.

 

[voodooless]

Is it just me or are these a bunch of very poorly performing opamps

 

[donrleonard]

Have a look at the multitone test. Exactly what it does.

Thanks for this suggestion, Ant. This is exactly the kind of feedback I was looking for.

This was Amir's multitone test for the DAC originally in question - the PS200.

And this was his multitone test for the Wiim Ultra that I did the most extensive (within my humble limitations) impressionistic comparison testing of.

In both cases, multitone performance was noted as "great". But are they identical?

I know even less about music theory than I do about electronics, terrifying though that may be. Can this test indicate whether even- or odd-order harmonics are present in these distortion profiles?

 

[Jimbob54]

Thanks for this suggestion, Ant. This is exactly the kind of feedback I was looking for.

This was Amir's multitone test for the DAC originally in question - the PS200.
View attachment 432175

And this was his multitone test for the Wiim Ultra that I did the most extensive (within my humble limitations) impressionistic comparison testing of.
View attachment 432179

In both cases, multitone performance was noted as "great". But are they identical?

I know even less about music theory than I do about electronics, terrifying though that may be. Can this test indicate whether even- or odd-order harmonics are present in these distortion profiles?

Both are below 130db . One slightly more so .

Do either dac have a variable volume and a display showing it? Turn it down as low as it will go above silence to you. It will probably be around -90db .