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AES Paper Digest: Do Audio Op-amps Sound Different?

SIY

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Imaging from using 'audiophile' filters at the DAC output could be near audible levels and yet result in a fine THD result.

Yes. Ditto frequency response errors. See my review of the ADI-2 Pro for some measurements showing exactly that for the NOS filtering option. Significant imaging errors and very audible frequency response change compared with the normal filter options.
 

Arnold Krueger

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Thank you Don, this really throws some light on my question.

In that context, it doesn't really make much sense to replace my preamp/amp combo with 0.08% THD and IMD with the combo with 0.008% THD and IMD as sound will anyhow be coming from speakers that have 0.3% THD at best.

Your figures also seem to explain why I cannot hear the distortion from my tube amp/preamp which has combined THD of 0.5%.

In that same context, I also cannot really imagine anybody be able to hear the difference between the Sonica DAC which has IMD of 0.004% and any other modern DAC which very often has THD and IMD of less than 0.001%. That also justifies why Topping D10 is being everybody's darling in the DAC arena, considering it's price and specs.

One other thing. As is well known, most good gear has far less nonlinear distortion at typical operating levels, but ratings are usually taken under peak conditions, and even often when the gear is clipping a bit. So an amplifier speced at .1% THD may only be generating a tenth of that most of the time.
 
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Arnold Krueger

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Of course, that makes sense. I didn't fully understand why they did that either, but that seems like the obvious reason.

Doing listening tests by comparing carefully prepared computer files allows greater convenience in both preparing and performing the test. Computer programs for doing double blind comparisons are freely download able from several sources.

I haven't been able to vet them all, but the ABX Plug in for Foobar2000 it's widely used and one that many know well.

The files can be easily emailed so testing can be replicated by listeners around the world, even those with no personal physical access to the gear.

One problem with listening tests is level matching and time-synching and file comparisons can be tidied up after real world data capture with most accurate audio editors which abound these days.

Finally it is not unusual for DACs and ADCs to outperform much audio gear, especially that with tubes so that signals can be passed through gear repeatedly even when there is only one piece of gear, to enhance the audibility of any distortion that it adds.
 

Arnold Krueger

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And doesn’t this reflect the Swedish crowd’s objective bent? They don’t care if the signal was put through an AD stage because electronics are pretty neutral these days. Right?

They don’t believe the AD stage will colour the sound in a way that will mask audible differences if they exist. Agree?

That a piece of gear won't itself bias a test it is used in should be vetted. In the case of ADCs and DACs that can be done by hooking them together back-to-back and re-recording diagnostic musical passages through them a number of times. Some very cheap gear is so bad that just one pass is detectable. A really good set of converters might be able to be looped 10 or more times without detection. YMMV. This is also a good way to vet the design and procedures used. Before the UUT is stuck into the test set up, the biases of the test setup should be scrutinized by several means, both multiple technical tests, and multiple listeners.
 

Krunok

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Yes. Ditto frequency response errors. See my review of the ADI-2 Pro for some measurements showing exactly that for the NOS filtering option. Significant imaging errors and very audible frequency response change compared with the normal filter options.

Most DAC manufacturers set default filter which rolls off after 20kHz not to affect the specifications and independent measurements.
 

Krunok

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@svart-hvitt ,
But his argument isn´t restricted to the use of the ADC but could be expanded to every part of the reproduction chain overall. You need other gear to transform signals into sound and none of this is working in a perfect manner (even if it is considered to be "transparent" ) .

In the playback chain only the speakers are transforming signal from electrical waves to physical movement and doing that is much harder than amplifying the electrical signal because of various nonlinearities in the physical conversion process. The same goes for microphones in the recording chain. And that is the reason why I strongly believe we can pretty much only hear the differences in those devices and much less in a modern electronic equipment. Unless of course there is a flaw in the design, like clicking, roll off in deep bass etc.
 

SIY

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"Most DAC manufacturers set default filter which rolls off after 20kHz not to affect the specifications and independent measurements."

Yes, but clearly not all. In RME's case, it's changeable to a sensible filter. But there were a pile of DACs that I saw at AXPONA that proudly boasted of the NOS ("For those too stupid to understand Shannon-Nyquist") implementations as the only choice.
 

Krunok

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"Most DAC manufacturers set default filter which rolls off after 20kHz not to affect the specifications and independent measurements."

Yes, but clearly not all. In RME's case, it's changeable to a sensible filter. But there were a pile of DACs that I saw at AXPONA that proudly boasted of the NOS ("For those too stupid to understand Shannon-Nyquist") implementations as the only choice.

Ok, but such cases should be noted when doing the test and taken into account when processing results.

Btw, I'm putting this link to remind all of us how a proper test should look like..

https://www.audiosciencereview.com/...-high-sampling-digital-recording-formats.151/
 

SIY

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Of course, I did note it in my review. Nonetheless, this is a factor that IS audible in DAC comparisons, which was my point.
 

Wombat

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Concerning wines, it is not totally correct that there is zero correlation between quality and price, or that expensive wines cannot be differentiated from cheaper wines. I looked into the research on this some time ago, spurred by the fact that blind-testing of wines sometimes became a part of some hifi discussions. I found that some of the media coverage on this was somewhat incorrect.

In short: Individual cases of ratings of wine are heavily influenced by things like color, reputation, prices, etc. Nevertheless, there does seem to be a modest correlation between wine prices and quality ratings in blind tests. Which means that there are objective quality differences between wines after all. This article sums up much of the evidence:
https://academic.oup.com/ajae/article-abstract/97/1/103/2737501

I found this article interesting too:
https://www.cambridge.org/core/jour...d-replicates/BBF3DCCD599F587F4E7AE19F72EAE412

Even though individual wine judges are far from having a perfect replicability score, there is nevertheless a higher probability that they will rate a "good" wine as better than a "bad" wine. Which means that a 0-result in an individual blind test between two wines doesn't invalidate that one of the wines may in fact be better, and that it's somewhat more likely that wine drinkers will prefer that one over the other.

For me, this seems roughly on a par with where I think things stand in audio. I trust measurements and objective data over sighted listening, and even though I like DBTs, I don't think individual negative results in a blind test is the final word (if there are in fact substantive objective differences that can be measured).



I didn't say there is zero correlation between quality and price. For heaven's sake, refer to my post, #130, above.. o_O
 

SIY

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I didn't say there is zero correlation between quality and price. For heaven's sake. o_O

The correlation is, however, loose, especially because there's no agreement on what constitutes "quality." What is indisputable is that nearly any two wines, regardless of relative price, can be distinguished in blind tasting.

/former wine judge who had to pass numerous blind tasting evaluations
 

Krunok

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Of course, I did note it in my review. Nonetheless, this is a factor that IS audible in DAC comparisons, which was my point.

And my point is if you have a DAC which doesn't have a single filter with roll off after 20kHz that falls into the category of flawed design.
 

Krunok

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The correlation is, however, loose, especially because there's no agreement on what constitutes "quality." What is indisputable is that nearly any two wines, regardless of relative price, can be distinguished in blind tasting.

/former wine judge who had to pass numerous blind tasting evaluations

You being a former wine judge doesn't make that indisputable. What would make it closer to become indisputable is a properly done blind test, so if you have at least one I suggest you open a separate topic and we will be happy to discuss it. ;)
 

Wombat

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The correlation is, however, loose, especially because there's no agreement on what constitutes "quality." What is indisputable is that nearly any two wines, regardless of relative price, can be distinguished in blind tasting.

/former wine judge who had to pass numerous blind tasting evaluations
The correlation is, however, loose, especially because there's no agreement on what constitutes "quality." What is indisputable is that nearly any two wines, regardless of relative price, can be distinguished in blind tasting.

/former wine judge who had to pass numerous blind tasting evaluations


As a retired accredited ISO 9000 series QMS Senior Auditor I am well versed on the subject of 'quality'. The technical definition of quality is that something meets its specification. If its specification is low-level and the 'product' complies then it meets its quality criteria.

Popular ideas of quality are nebulous and generally are built on shifting, less tangible and somewhat subjective criteria and judgement.
Modern wine composition analysis could replace wine tasting judges but, like in audio, individuals put their taste(hearing) perceptions on a pedestal.
 
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Krunok

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As an accredited ISO 9000 series QMS Senior Auditor I am well versed on the subject of 'quality'. The technical definition of quality is that something meets its specification. If its specification is low-level and the 'product' complies then it meets its quality criteria.

I agree with this definition. At least for DACs and other audio equipment.

P.S. not so with wines, but that's completely different story. :D
 

Wombat

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You being a former wine judge doesn't make that indisputable. What would make it closer to become indisputable is a properly done blind test, so if you have at least one I suggest you open a separate topic and we will be happy to discuss it. ;)

That is a test I would like to participate in. :rolleyes:
 

Wombat

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I
I agree with this definition. At least for DACs and other audio equipment.

P.S. not so with wines, but that's completely different story. :D

I added/edited my post while you were replying. FYI. ;)
 

Jakob1863

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In the playback chain only the speakers are transforming signal from electrical waves to physical movement and doing that is much harder than amplifying the electrical signal because of various nonlinearities in the physical conversion process. The same goes for microphones in the recording chain. And that is the reason why I strongly believe we can pretty much only hear the differences in those devices and much less in a modern electronic equipment. Unless of course there is a flaw in the design, like clicking, roll off in deep bass etc.

Which misses imo the point that i tried to address (while strangely supporting it nevertheless).

If you question the use of the ADC in the mentioned test setup, because it might mask differences between the DUTs, you´ve to suspect that all the other parts of the reproduction environment could provide the same (or similar) kind of masking . So it´s an inherent problem of the perceptual sensory test approach for audio.

Therefore we should always be hesitant/careful (when)/ to draw far reaching categorical conclusions from test results.

Edit: Nothing wrong with (even) strong beliefs provided that you keep in mind that it is a belief.
"Much less" leaves room in a sufficiently way, although from my experience it depends if "much less" also might mean "i can´t stand it" .
 
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