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Hey guys,
Another blog post up for this week... Objective measurements of my laptops! Native built-in DAC, adaptive USB1 DAC, asynchronous CM6631 USB-SPDIF.
Bottom line: No need for voodoo. Computer audio can be complicated but so long as the software player & drivers are bit-perfect, and you don't have noise polluting the DAC output... Then you're good.
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Archimago's Musings: A 'more objective' audiophile blog.
Follow Ups:
"There are of course some very expensive USB-SPDIF adapters but given the CM6631A results, why spend more from a sonic perspective? As I have also stated before, I still have no good evidence to say that jitter at this low level is ever audible with real music despite what subjective audiophile reviewers or Internet posters generally claim!"
This comment has nothing to do with measurements. It has to do with your particular system and your ears. Doing AB/X testing is only as accurate as the system and the ears used, and the small selection of USB converters tested.
Some of us can easily hear the difference between a digital source with 20psec P-P jitter and one with 60psec P-P jitter. This difference would not even be visible on your plots.
I do have direct jitter measurements (not through a DAC) that clearly show this difference. They are on my forum, so I cant post link here.
Steve N.
I found reading your article to be worthwhile. The screenshots showing the level of noise and distortion from onboard sound and those showing the differences between adaptive and async modes were useful.
Bill
my blog: http://carsmusicandnature.blogspot.com/
That silly - and unprovoked - outburst of yours was truly remarkable. Looks like the moderator agreed.
In fact, it's not clear at all what your measurements show, as far as audibility is concerned.
Your hobby - amateur measurements - is no worse or better than any other, but you shouldn't really reach that far, based on those.
"In fact, it's not clear at all what your measurements show, as far as audibility is concerned."Maybe not - after all it's just a blog post; how can I show you or anyone what the numbers represent qualitatively?
But I do believe they correlate because I've heard enough during the course of testing that show me better gear does give me better numbers (to put it simply). Some of the results are clearly beyond hearing capacity and beyond the needs of any musical performance.
Lower noise floor, better dynamic range, lower THD, cleaner J-test results IMO do direct my decision making around the best configuration for my listening with line level devices. For examples, listening by itself I do not believe would have allowed me to realize that the LSB for the 2008 MacBook DAC was never going to be bit-perfect with 16-bit input.
Also, for relatively straight forward line level devices, I see no need for expensive pro measurement equipment as a hobbyist. Time and again, what I'm using is good enough to differentiate gear that otherwise sound very close. Since manufacturers rarely publish detailed measurements, nor many reviewers seem to take the time either, why not a hobbyist give it a try and (hopefully) show others how to also do it for themselves? Everyone has a choice to accept the findings or not. It's not like there's any great mystery surrounding the electrical output from a 2-channel DAC!
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Archimago's Musings: A 'more objective' audiophile blog.
Edits: 04/14/13
You should at least validate the Rightmark results against a suite of free pro measurement tools.Rightmaark is the favourite tool for low end card makers gives more than favourable numbers.
The time you have spent is worth far more than buying proper meaurement software.
Another quote from your Conclusions:
''I cannot tell the difference at least up to ~2ms peak-to-peak jitter''
Terribly 'objective'
Edits: 04/14/13
Low-end or not; tell (show) me how it matters. The calculations are straight forward. No magic algorithms. I'm happy to reconsider with evidence.Just re-read and I apologize for the error - I meant 2ns (nanosecond) jitter IN MUSIC.
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Archimago's Musings: A 'more objective' audiophile blog.
Edits: 04/21/13
There seems to be a rather large gap between jitter that some people say they can't hear, 2 nanoseconds, and jitter that other people say that they can hear, 2 picoseconds, one thousand times smaller.
I suspect there is more than a little "apples" vs. "oranges" in these numbers. There is no AES standard for measuring jitter.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
the bits are bits approach.
''No need for voodoo. Computer audio can be complicated but so long as the software player & drivers are bit-perfect, and you don't have noise polluting the DAC output... Then you're good''
Use ours ears, and they don't sound the same even when the setup is fairly ordinary
Gang,
The measurements here are well crap. How do you even know your getting bit true output?
Second jitter is not a vertical line extending up at the 1/4 fs. That is not what tells you it's has low jitter. Remember there is also a 1 bit transition at 229Hz.
Ok look at figure 14 here, linked below for the QB9 measurements from Sterophile. You see the fundamental and at the base is called the skirt. The closer in that is the better.
But also note the spuriae that happen in a decreasing order. This also is a very good indication of how well the jitter error is controlled.
Writing blogs about what you know is fine, but since you don't know then you are just misleading people who don't know better.
I have to agree with Fred here... at some point you have to listen to the damn thing. None of these bit true apps sound the same and I have ideas why but who has weeks to figure that out.
Misinformation is what is sending most people into shock when they start CA.
Heck do you know how many people ask me what speakers to buy. Come on... I don't go around listening to or have the time to listen to. Go out and do some work. Get off the couch and get together with people at stores and listen to stuff. Go to a show... this stuff is a major purchase.
Would you go to a car dealer and spend money without a test drive? NO!!!!
So why would you here?
Thanks,
Gordon
J. Gordon Rankin
Gordon,
I appreciate your feedback and critique. I used to have the QB9 and indeed it is a nice DAC so was quite happy that Stereophile's measurements concurs.For this article, I believe the data was "bit perfect" since the LSB jitter modulation was evident in the 16-bit tests. Due to the hardware limitations, this was of course not seen in the 24-bit graphs. I did discuss this fact and the issue that the built-in computer DAC's had problems with bit-perfection.
Thank you for bringing up the "skirt" issue. I'm going to have to update my ASUS Essence One measurements because this was worse with the USB input but not the coaxial or TosLink. However, most of what I've seen suggests that this low frequency jitter is masked by the primary signal. Please correct me if this is wrong so that I may pay more attention to it especially if there's a point of audibility.
As for "at some point you have to listen to the damn thing" (I'm directing this to the general viewership, not just to your comments). It is precisely because I've been listening AND reading forums like this for the last 15-20 years that I started doing the measurements and putting up the blog! I don't think it's at all a stretch to say that people are notoriously unreliable in their experience... I have never found an audiophile who could reliably differentiate high bitrate MP3 for example, yet when I ask, everyone seems to say they can (sure there are people who can ABX 320kbps but that's very few). For those who have a copy, listen to track 26 on Stereophile Test CD2 simulating 10ns jitter. I would estimate that half of the audiophiles I've tried this on over 50 years old have difficulty hearing this simulation on a test tone yet they universally claim that a few hundred picosecond jitter is a "problem" audible in actual music.
There's precious little objectivity out there anymore for audiophiles - look at that bizarre 3-part article on computer audio in TAS early 2012; if "everything's possible" (bit-perfect rips sound different if ripped at different CD speeds according to that article) then nothing is known anymore. Just look at the numerous comments when those new to computer audio asks straight forward questions here. IMO, some of the responses border on delusional.
Time is limited but I have spent many many hours listening to cheap to very expensive gear - even owning a few of the more expensive items over the years. It is my belief that "good" sound can be independent of factors like price, or any of the external factors like workmanship, etc. In fact, I've come across situations where high priced gear are just plain inaccurate. For me, accuracy is all that matters, and this can be quantified objectively.
Speaking of "misinformation is what is sending most people into shock when they start CA". Realize that over these months of testing, I have not advocated anything I would consider as "fringe". I've shown that asynchronous DAC's are better with less anomalous J-Test spectra, coaxial and good USB is better than TosLink in the gear I have, shown 'good' DAC's like the Oppo BDP-105 (ESS Sabre) measures superbly. I advocate for "bit perfect" and showed that both Windows and Mac are capable of accurate output, and have interspersed these tests with listening to make sure nothing appears awry - usually spending a couple hours at a time in the evenings listening (eg. when I was doing some cable measurements recently). As I've said in some posts, there is no voodoo or magic here, and the tests are showing me such. How in the world is this shocking anyone out of computer audio!? If anything, it's reassuring that measurements line up with a rational empirical approach that is reproducible.
Now as for the test gear I use and software like RightMark. You don't need the Hubble telescope to identify Jupiter in the sky. Likewise, why do I need expensive gear like an AP when I just want to make sure the frequency response is relatively flat, or that the dynamic range of a DAC can exceed 16-bit CD quality, or that the Dunn test isn't atrocious? All these things are within reach of what I have and the beauty of computer audio and technological advancement is that stuff that can do this is easily within the consumer's grasp. However, I'm not saying that anyone should do this since it has taken me countless hours to learn how to get the calibration right and make sure the software setup works for me in order to achieve a high level of reliability in the measurements.
When my simple setup can easily demonstrate analogue cable differences, XLR vs. RCA differences, show me the spectral smearing between 320kbps MP3 vs. 400kbps AAC, demonstrate J-Test differences between coaxial vs. TosLink vs. AES/EBU, when I post about this, in what way is this "misinformation"? In fact, my ASUS Essence One measurements showed a disturbing anomaly when upsampling is used resulting in attenuated frequency response which has since been confirmed by ASUS (and hopefully to be remedied)... How come subjective Essence One reviewers missed this when it was so obvious with just a little testing?
Look guys, ultimately either what I say and write about makes sense, or it doesn't. I mention a new post up here once awhile that could be of interest like this one with the laptop tests to outboard DAC's. I have ZERO financial interests or otherwise. I do it for fun, for my own education, and enjoy sharing what I've found with others. Anyone can freely share their thoughts in the comments section (haven't had to censor anyone at this point for nonsense), and I've invited people to give me evidence/reason if they think something I say is wrong. Of course, with my objectivist mindset, "Level 4 or 5" evidence (ie. individual or series of reports) doesn't really impress compared to experimental results or controlled trials.
Cheers,
Arch
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Archimago's Musings: A 'more objective' audiophile blog.
Edits: 04/21/13 04/21/13
The Jtest signal should not be used for testing asynchronous USB DACs. It was specifically designed to detect probable faults in SPDIF signals and a DACs rejection thereof. The faults in a USB connection are different, so a different test ought to be used.
SPDIF is a continuous stream that contains sample clock data mixed with the signal. In Julian Dunn's Jtest signal, the low order bit is toggled to exercise the codes, thereby creating intersymbol interference caused by the encoded bit transitions passing through a cable that has limited bandwidth. This intersymbol interference shifts the transition times of the clock transitions, thereby creating jitter in the recovered sample clock. The DAC can defend against this to a certain extent through the use of a PLL or other "flywheel" mechanism, but the result will be imperfect and the resulting sonic pollution will show up in the analog output.
USB is a packet based system, and the exact timing of the signals on the cable is not related to the audio clock. Furthermore, in the case of asynchronous connections, the relationship between the USB data clock and the sample clock is dynamic, because the DAC clock requests data from the computer under control of its local clock. If the DAC hardware were perfect, the timing and jitter on the input USB signal would be irrelevant. In reality, the DAC hardware is not perfect and the timing and noise on the incoming signal indirectly affect the DAC clock. However, the coupling does not happen in the signal path, it happens through parasitic coupling, typically through the power and ground wiring. If one wants to assess these effects, one will need a different kind of test signal. Also, because they are much lower in magnitude, they will be much more difficult to measure. (Adaptive USB should never be used at the 44.1 family of sample rates, because it has a brutal amount of packet jitter caused by beats from the USB clock and the audio sample clock.)
With either SPDIF or async USB any sonic differences are relatively hard to measure (or hear). This is not the case with 320 mp3 encoding, where the differences are trivial to measure, and are audible on many music recordings when played on a decent system.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
where knowledge & experience take a backseat to the negative speculation of how there can be no difference between less expensive & more expensive components.....
"Asylums with doors open wide,
Where people had paid to see inside,
For entertainment they watch his body twist
Behind his eyes he says, 'I still exist.'"
"Use ours ears, and they don't sound the same even when the setup is fairly ordinary"
But the lack of consistency in these observations once you control the variables and biases in many (most?) situation is a bit inconvenient, don't you think?
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Archimago's Musings : A 'more objective' audiophile blog.
sound of the component, - ever.
For we never listen to a component, but whole systems in different rooms. Measurements, (when isolated in the appropriate, somewhat limited context), can be of use when determining certain types of component matching characteristics, but those values are easily determined by specs.
there is no substitute for listening experiences.
"Asylums with doors open wide,
Where people had paid to see inside,
For entertainment they watch his body twist
Behind his eyes he says, 'I still exist.'"
"But the lack of consistency in these observations once you control the variables and biases in many (most?) situation is a bit inconvenient, don't you think?"
Who said it was supposed to be convenient?
Measurements are not able to resolve down to the level of bits, even down to 16 bits. There is no sufficiently accurate ADC. Try digitizing the analog out of a DAC and trying to recover the original bits. (As you would if the DAC and ADC were being used as a modem.) You won't be able to do it. Even if you were to remove the actual analog converters in the DAC and ADC and work at the level of the output of the DAC's DSP and the input of the ADC's DSP you wouldn't be able to get back the original bits. Ditto for commonly used sample rate converters.
You are correct about how flaky our hearing is. Our hearing has evolved over millions of years, but ability to select audio components has to do with survival of the fittest. We tend to over detect differences in sound, and if that were not the case our ancestors would have been eaten and we wouldn't be here. However, our flaky hearing system has vastly more computational horsepower going on between the ears than any DSP processing in audio equipment or audio test equipment. Perhaps if the computer power were up to the standards of Deep Blue the situation could be different.
Objective measurements can be a useful engineering tool or method of production line quality control, but they are not an effective way of assessing sound quality.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
If you assume bits are bits you can put together a very good sounding system but you can make it better if you go beyond the bit perfect point of view
Alan
"If you assume bits are bits you can put together a very good sounding system but you can make it better if you go beyond the bit perfect point of view
Alan"
Got an example of where it does beyond bits (and timing as I endeavoured to explore with the J-Test results)?
I assume you're talking about the direct DAC output since I agree that room correction for example is an example of how one can make the system sound even better.
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Archimago's Musings : A 'more objective' audiophile blog.
As Archimago is measuring the analog out, no reason to accuse him of the ‘bits are bits’ approach.
The Well Tempered Computer
he is using amateur software; study the numbers. I am just quoting what he said and commenting.
"he is using amateur software; study the numbers. I am just quoting what he said and commenting."
So what? See my response to carcass. It's not like there's some kind of big trade secret on how dynamic range is measured!
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Archimago's Musings : A 'more objective' audiophile blog.
sweeping conclusions like yours cannot be drawn from measurements the way you did them and the way you analysed them.
Edits: 04/14/13
"sweeping conclusions like yours cannot be drawn from measurements"
That about says it all Fred, I reckon that's the only reason this is still an interesting hobby.
I'm at heart objective, but the interactions in complex systems make it tough to reliably map measurements to a particular user's system and experiences. Just not enough control. I've worked on other stuff that suffers much the same fate and food manufacturers face it daily. Their solution is usually to just add more sugar but we don't really have an electronic equivalent other than maybe "turn it up"
However going the other way, i.e. trying to find measurable differences that correlate with what a single user experiences in his system in his home is much easier and more useful.
So my take on it that audiophiles should do everything in their power to try and measure electrical differences that correlate with what they hear. There are so many less variables at that point that measurements can really help find and fix problems and optimize happiness.
Rick
''So my take on it that audiophiles should do everything in their power to try and measure electrical differences that correlate with what they hear''
But those measurements need to be correlated with listening and not derived from 'thin air'.
There is actually much better correlation between signal transmission integrity and SQ than amongst rows of dB value tabulated thru suspect measurement software. Jitter is another factor which needs to be measured correctly and statements such as +-2mS peak jitter makes no difference to SQ are rubbish. Even RME, with rather poor sounding hardware only claims 1 nS to be 'low' jitter.
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