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ESS claim DAC pushes the boundaries of audio science, They claim results are supported by blind testing
wakibaki
post Jan 23 2013, 04:23
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Apologies if this topic has been posted previously, I did a search but found nothing.

http://www.youtube.com/watch?feature=playe...p;v=1CkyrDIGzOE

The above link shows a youtube video of an ESS presentation at RMAF.

Granted it is a sales presentation, it details advances ESS claim in the design of their sigma-delta DACs.

Foremost in the claims is the fact that some people can evidently hear features well below the noise floor which were previously held by the majority of engineers to be inaudible. This is said to be confirmed in blind testing.

Large changes in the values of variables in the state space are said to contribute to non-periodic steady-state noise normally invisible using conventional measurement techniques. This is visible when instrumentation is used to examine the Noise-vs-DC Offset.

This is said to be minimized in ESS products by techniques designed to control the state-space related noise by rapidly quenching state variable excursions.

ESS also claim that a further artifact of sigma-delta modulators, variable (non-linear) excess phase, which causes oscillation in S-D modulators, has been eliminated by making their devices unconditionally stable, and that this too contributes to greater acceptance of the devices by some listeners, although the reasons for this are apparently not clearly understood.

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saratoga
post Jan 23 2013, 05:28
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DACs were a solved problem ten years ago so I'm not sure how you really push boundaries of the science.
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phofman
post Jan 23 2013, 08:13
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The claim would have been much more credible if they presented information about the DBT they mention.
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wakibaki
post Jan 23 2013, 18:36
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QUOTE (phofman @ Jan 23 2013, 07:13) *
The claim would have been much more credible if they presented information about the DBT they mention.


Granted, but the fact that they do mention DBT is at least a nod in the right direction. I'm not about to rush out and buy an ESS DAC. The claims are, however, a lot more interesting than many others I've seen. They do have some instrumented data too. It could be that they have actually got evidence of a level of human sensitivity previously undocumented, which led them to successfully modify their design. There seems little doubt that they have actually been prompted to modify the design by some factor other than random impulse.

While I was a professional engineer for many years, I cannot claim that my insights will immediately be the most penetrating on every subject under the sun. Therefore, in the same spirit that I would normally expose any design of mine to peer review, so do I request your reasoned comments on this material.

Obviously a DBT is the final arbiter of the truth of any claim, but very often rationale alone suffices to dismiss some.

I'm not interested in any mumbo-jumbo. Evidence is another matter. Let me make it clear, I do not defend these claims, but at the moment, on the balance of probabilities, I think they may actually be defensible, and I would appreciate any analytic input, as opposed to personal attacks on my judgement, or essentially meaningless remarks about the state of development of DACs in the past.

In the circumstances it is difficult to judge the exact nature of the situation, but I would have thought that members here would be keener than most to be aware of any possible developments in the field, and to know the exact nature of the claims, possibly with a view to debunking them. After all, I have witnessed considerable energy being put into dismissing far less convincing propositions than this appears to me.

w

This post has been edited by wakibaki: Jan 23 2013, 18:43


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pdq
post Jan 23 2013, 18:54
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I haven't watched the video, but if the DBT that you refer to is the claim that we can hear features well below the noise floor, then that is hardly news. Human hearing is like a Fourier transform, allowing us to selectively hear certain frequency ranges in the presence of higher level noise in other frequency regions.

Similarly, if the total noise of a DAC is, say -96 dB, a spectrum analysis will show far lower noise as a function of frequency, depending on the chosen bandwidth. This is true of any modern DAC, including the one from ESS.

I would be much more interested if a third party had done a careful, level matched DBT that showed a difference.
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Dynamic
post Jan 23 2013, 19:22
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There's some plausible stuff in there, but then he's been asked to remove all mathematics, meaning it's rather difficult to work out if there's anything of true substance. The man himself claims to have degraded hearing and to be unable to tell the difference.

Without details of the DBT, I'd remain only open to actual valid evidence should any be forthcoming, but unconvinced they have anything to show either that other manufacturer's Sigma Delta DACs are poor or can be ABXed against linear additive DACs.

He did give the name of a colleague who would provide more information by email if requested. Not sure I'm motivated to bother, though.

The analogy of a stock broker whose results you're averaging breaks down in many ways because you're using oversampling deliberately and filtering the sound for proper reconstruction of a signal with defined bandwidth without introducing false staircasing/aliasing artifacts in the analogue output, because the DAC should have upsampled and shaped the noise to eliminate any false frequency content between the input's Nyquist limit and the gentle analogue low-pass reconstruction filter somewhere above 22 kHz. There's no signal that's trying to invert the reconstruction filter to overcome its effect and force through signals of 30kHz, say, to create incorrectly sharpened edge responses that exceed the proper Nyquist limit. Daily closing stock prices do not have an intrinsic frequency response and represent no physical reality, just a record of prices paid with no specific time intervals. He did admit that he thought up that non-mathematic analogy that morning, so I can't blame him for trying, but it's still there on YouTube over a year after the conference and it deserves to be debunked as being non-applicable to the proper band-limited reconstruction of audio signals.

There's a further presentation immediately after, about digital vs analogue volume controls and about jitter, notionally, albeit more to do with failure to synchronise the DAC to the source clock rate and sustain proper synchronisation of the decision time. He admits that the jitter displayed at first is greatly exaggerated to display it clearly on a graph, then fails to say why with real jitter (much smaller time variations) a PLL is insufficient if it actually locks to the PHASE of the signal and thereby follows the true clock frequency and phase (or even an integer multiple of the clock frequency if that's required for synchronising Sigma-Delta operation), as it should.

The only problems arise if you start to insist on synchronizing to a clock that's internal to the DAC but is not itself synchronized to the source clock. That shouldn't be necessary unless you're making the DAC act as a mixer or something, for sources with different clocks. It's definitely not a problem if the DAC is provided with the same source clock directly, as it is in most consumer equipment with internal DACs, which means the exceptions are standalone DACs and those within Receivers provided with digital input, which must use that input to derive their clocks.
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Dynamic
post Jan 23 2013, 20:10
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pdq, it wasn't all about hearing below -96 dB - he mentioned why that is, and the guy seemed to know his stuff and explain a lot of it pretty well to a lay audience, partly by analogy. He also had a decent enough analogy of noise shaping (error-diffusion type of idea) to get the idea across.

It seemed to be about some type of variation in the quantization noise spectrum and amplitude spikes within it as DC level offset slowly adjusts or as you switch from say a 1kHz tone to a 20kHz tone, which the sigma-delta modulators tended to slowly converge upon with an unstable type of feedback loop. There's something plausible there, and it could well be that they've made it inaudible if it was audible before. It's not clear which components they're comparing and the exact nature of the blind tests, but they claimed that different features in their FPGA could be turned on or off, allowing them to select 5 features to control 5 states (modelling it as a state machine), the last of which apparently made it a match for a linear DAC in the blind testing.

There was a 3D plot of their device pictured as a state machine (they couldn't plot all 5 dimensions they controlled for) which seemed to show it tighly constrained, while the device without their magic had a more unconstrained chaotic pattern in the mysterious parameters, and there were spectral plots showing spikes in the noise floor presumably of their modulator without their FPGA's features enabled (or maybe an unnamed competitor's SDM) and a clean spectrum with it enabled. These were at a plausible level for a 16-bit signal with small amounts of inadequate dither to become potentially audibly degraded by quantization noise in the presence of a -30dB test tone, though they ought to be rather well masked in real music, examples of which included an old Frank Sinatra track, an un-named piece and a modern recording where a shaker is used, which somehow it supposed to reveal the difference. The guy claimed that their measurements would get them in the door at the consumer companies, this 3D plot would really pique interest, and the companies would only decide when their 'golden-ear' audiophile gave it the thumbs up.

It all has a mixture of an air of plausibility and reasonableness in the presenter, and a mix of test & measurement plots and computer modelling plots, combined with the secrecy and lack of detail and transparency that leads one to have enough suspicion that it could all just be a blind-them-with-science marketing approach with some superficially plausible theory behind it.

The best approach to truly demonstrate the truth of their claims to skeptical listeners at a conference like that would probably be to provide a digital sound clip and a digital zero source generated on the same clock, two or more DACs with analogue outputs level-matched in a low-noise summing amplifier sent to a single headphone amplifier and a set of high-grade headphones, and send the non-zero digital signal to one DAC or the other DAC one at a time, while the other DAC receives zero, under computer control to provide A/B/X comparisons (potentially with software very much like the software ABX comparators we use here, allowing the choice of a specific revealing part of the clip, such as this shaker). There might need to be time-alignment of the two channels also if switching is allowed during playback.


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Willakan
post Jan 23 2013, 20:40
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During the presentation on jitter, the ESS guy also claims that jitter under 1 ns is audible, which came as a bit of a surprise...perhaps they just have really good blind tests blink.gif ...

This post has been edited by db1989: Jan 23 2013, 22:42
Reason for edit: as per post #15 ;)
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Banned
post Jan 23 2013, 21:01
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QUOTE (Willakan @ Jan 23 2013, 21:40) *
During the presentation on jitter, the ESS guy also claims that jitter under 1ms is audible, which came as a bit of a surprise...perhaps they just have really good blind tests blink.gif ...
One millisecond?
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wakibaki
post Jan 23 2013, 21:04
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One of the 'golden ear' claims that has been hotly disputed is that there are audible features in reproduced music which are not revealed by conventional measurements.

ESS claim (if I interpret the video correctly) that they now measure a feature that was not previously thought significant (not part of a conventional audio measurement suite), and (if you take the claims at face value) that modifying this feature has audible results. If anyone has experience of DAC development I would appreciate their comments on this.

This leads to the possibility that other audible features exist which are not revealed by a conventional audio measurement suite.

ESS moreover claim that they have discovered (in blind testing) a further modification which is audible but for whose audibility they currently have no explanation (and evidently no capacity to detect by measurement, or none that they revealed). This is some way of imposing unconditional stability which they can turn on and off for the purposes of DBT in an FPGA implementation of the DAC.

Ultimately this has no philosophic impact on DBT, but if it is true, it will undoubtedly eventually set the cat among the pigeons, so those who like to depend on the idea that instrumented measurement as it stands, will reveal any audible feature, better be ready for the shitstorm, if and when it arrives.

Thanks for your comments so far, Dynamic.

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Dynamic
post Jan 23 2013, 21:13
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I think inter-aural timing differences under 1ms can be audible, but that shouldn't be exposed by jitter thanks to phase locked loop clock recovery or equivalent (which runs at the baud rate, itself much higher than the sample rate - typically 6MHz or so for S/PDIF). The thing is, jitter of 1 ms would be 6000 cycles on a 6MHz clock. That's ludicrously high jitter. A fair bit less that 1ms still remains ludicrously high.

16-bit, 44.1 kHz PCM can easily encode timing differences below even the sampling period, as you can prove by making a large pulse at some point in both channels in an otherwise silent 192kHz stereo track, then select one channel and insert one sample silence to shift it by about 5.2 microseconds. Then downsample to 44.1 kHz and upsample back to 192 kHz and see that the timing difference is preserved. (Same sort of thing works in photo editing to correct for colour misalignment in scanned printed materials even when it's below one pixel-width of misalignment, as long as you upsample and downsample with proper respect for Nyquist and Shannon)

Dropped or repeated samples might also be audible if you fail to synchronise clocks and thus mess up the PCM signal.
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db1989
post Jan 23 2013, 21:25
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QUOTE (wakibaki @ Jan 23 2013, 20:04) *
Ultimately this has no philosophic impact on DBT, but if it is true, it will undoubtedly eventually set the cat among the pigeons, so those who like to depend on the idea that instrumented measurement as it stands, will reveal any audible feature, better be ready for the shitstorm, if and when it arrives.
I expect that academic concepts regarding highly specific scenarios will be twisted into an argument that DBT is always flawed, and therefore $2000 cables. :/
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greynol
post Jan 23 2013, 21:38
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Until positive DBT results can be repeated by an independent body, I don't think people will need to embrace themselves for an impending shitstorm.

This post has been edited by greynol: Jan 23 2013, 22:35


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Dynamic
post Jan 23 2013, 21:49
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QUOTE (wakibaki @ Jan 23 2013, 20:04) *
Ultimately this has no philosophic impact on DBT, but if it is true, it will undoubtedly eventually set the cat among the pigeons, so those who like to depend on the idea that instrumented measurement as it stands, will reveal any audible feature, better be ready for the shitstorm, if and when it arrives.


I think these are the sorts of extraordinary claims that require at least ordinary evidence to be taken very seriously. By ordinary, I mean DBT with some details of methodology and identification of the equipment under test. We can't simply accept it on authority and claim to be skeptically astute.

Some of the talk may inadvertently have set up straw men and demolished them, some of it may have genuine evidence behind it that hasn't been sufficiently revealed to allow an objective assessment of its merits or otherwise.

They have provided some measurements (e.g varying the DC offset level - not sure where they're doing so and whether it's in sub-LSB amounts or what) that provided some measurable spikes, so the idea that it's beyond measurement is not necessarily supported. Whether it's simply a failure to apply adequate dither or some other flaw that they're displaying, I really can't guess. They don't provide enough information, though they hint that it's often fleeting and dynamic during transitions, not often visible in steady state conditions and not especially visible on waveform plots either. I dare say it would be visible with appropriate FFT comparisons of a good ADC capture of the DAC output (e.g. an digital sampling oscilloscope or a good audio ADC running at, say 48 kHz 24-bit). Having a digitized capture would allow a variety of FFT lengths and alignments to identify features in question.

Perhaps someone needs to take a few screen captures and timings from the YouTube video to help us discuss certain points without making everyone sit through an hour's lecture. Then again, without enough evidence, perhaps it's not worth pursuing unless ESS substantiate it further.

The guy sounds for the most part like someone who really knows what he's talking about but is trying not to reveal trade secrets and not to use any mathematics in front of a lay audience. He does mention some patent numbers on some of the points he bring up in one of the two videos, but I forget which of them it was. He says that ESS normally don't present to enthusiasts as they're usually involved only with industry and don't produce products sold directly to consumers. He might also be loathe to go into details that might normally be discussed only under a commercial non-disclosure agreement.

Personally, I'm not that inclined to take it that seriously for now, as there are so many audio companies providing measurements that are irrelevant to audibility and I've no clue whether any DAC I'm using would potential sound like the un-named purpordetly less-than-transparent sigma-delta DAC and whether it's enough for me to care either for my own less-than-audiophile use case or out of technical curiosity.

This is an audio forum thankfully devoid of unsubstantiated claims (thankyou TOS#8), and these claims remain tantalizingly short of substantiation from what I've seen. If the fine folks at ESS would care to substantiate them further, they might be worth a look, but we don't even know what devices they're claiming are deficient so they're unsubstantiated and from the information provided unverifiable. If anyone takes a look at the patents mentioned and finds something plausible, I might be interested. I might do so myself if I have time to spare, but I'm not greatly inclined to do so.
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Willakan
post Jan 23 2013, 22:36
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Pretty impressive typo in my earlier post: I meant 1ns...1ms is a great deal of jitter biggrin.gif

21:10 - declares audiophiles can hear silly-small amounts of jitter in http://www.youtube.com/watch?v=JYjHKv2_OqQ

Hey, I was only off by lots of orders of magnitude!

EDIT: Thanks for the correction above, db1989.

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wakibaki
post Jan 23 2013, 23:14
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QUOTE (greynol @ Jan 23 2013, 20:38) *
Until positive DBT test results are shown to be repeatable, I don't think people will need to embrace themselves for an impending shitstorm.


If I was sure that it was coming, I wouldn't have said 'if and when', but nobody thus far has said anything to convince me that the claims are fallacious, which is not always the case with audio claims.

It's customary, however, for claimants to ignore the existence of DB testing, or to downplay it's significance, rather than to fly in the face of the likelihood that an inaccurate claim will be exposed. Of course it could be a ruse, but at what cost to the company's reputation when exposed?

It could just be a mistake, but it's a pretty lucky mistake that exposes a feature in your product that you can modify with visible results and for which you can claim an audible benefit. It's the cumulative serendipity that makes dissembling seem less probable. Still, stranger things have happened at sea.

It may not make you think, but it makes me think.

w


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greynol
post Jan 23 2013, 23:25
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QUOTE (wakibaki @ Jan 23 2013, 14:14) *
If I was sure that it was coming, I wouldn't have said 'if and when', but nobody thus far has said anything to convince me that the claims are fallacious, which is not always the case with audio claims.

Fallacy of the Flying Spaghetti Monster is duly noted.

QUOTE (wakibaki @ Jan 23 2013, 14:14) *
It's customary, however, for claimants to ignore the existence of DB testing, or to downplay it's significance, rather than to fly in the face of the likelihood that an inaccurate claim will be exposed.

Customary, perhaps, but certainly not the way it always goes down. Case in point: Steve Hoffman's insistence that he can ABX his DACs, which was discussed a few years ago.

QUOTE (wakibaki @ Jan 23 2013, 14:14) *
Of course it could be a ruse, but at what cost to the company's reputation when exposed?

Likely minimal. Those who insist they can tell the difference between DACs are generally not interested in DBT except when it is convenient for them.

QUOTE (wakibaki @ Jan 23 2013, 14:14) *
It could just be a mistake, but it's a pretty lucky mistake that exposes a feature in your product that you can modify with visible results and for which you can claim an audible benefit. It's the cumulative serendipity that makes dissembling seem less probable. Still, stranger things have happened at sea.

It could be something entirely different from the claimed mechanism that may cause a legitimate and repeatable audible difference. It also begs the question, does this "difference" result in better sound, or just different sound?

Look, I don't necessarily hold traditional measurements as sacrosanct and am happy that DBT is rightfully being held as the supreme metric. I will not jump to the conclusion that we have a smoking gun when the results have not been vetted, however. IMO, that would make me gullible.

This post has been edited by greynol: Jan 24 2013, 00:17


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wakibaki
post Jan 24 2013, 02:09
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QUOTE (greynol @ Jan 23 2013, 22:25) *
Fallacy of the Flying Spaghetti Monster is duly noted.


No fallacy has been demonstrated yet. If you believe that one has, please state it clearly.

QUOTE (greynol @ Jan 23 2013, 22:25) *
Case in point: Steve Hoffman's insistence that he can ABX his DACs, which was discussed a few years ago.


A single swallow doth not a summer make. Unless of course you have a list of such occurrences. In which case I'm sure I can find an overwhelming majority of contradictory examples.

QUOTE (greynol @ Jan 23 2013, 22:25) *
Likely minimal. Those who insist they can tell the difference between DACs are generally not interested in DBT except when it is convenient for them.


Generally. But not inevitably. I've accepted that it could be a ruse. There's no necessity to labour the point. Are you trying to prejudice the issue?

QUOTE (greynol @ Jan 23 2013, 22:25) *
It could be something entirely different from the claimed mechanism that may cause a legitimate and repeatable audible difference. It also begs the question, does this "difference" result in better sound, or just different sound?


It could be something entirely different. What is the difference between an illegitimate difference and a legitimate difference? I hope there is a difference. Or perhaps this is a case of, as they say, a difference that makes no difference is no difference at all.

No, it doesn't beg the question. The issue is one of difference and its detectability, not quality. Please do not attempt to introduce red herrings.

QUOTE (greynol @ Jan 23 2013, 22:25) *
Look, I don't necessarily hold traditional measurements as sacrosanct and am happy that DBT is rightfully being held as the supreme metric. I will not jump to the conclusion that we have a smoking gun when the results have not been vetted, however.


Good. Nor will I.

w


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greynol
post Jan 24 2013, 02:46
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Funny how it is you who gets to rely on words like could, if, likely and sometimes, where I am held to a different standard. Anyway, thanks for trying to bait me into an uninteresting game of nitpicking and selective quoting. If that's the best you can do then I will happily and safely continue to serve my self-appointed position as skeptic as well as stand on the validity of my contributions to this discussion (inexact language not withstanding).

That you appear eager to believe will not be my problem; my purpose in life is not to attempt to change your mind. smile.gif

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saratoga
post Jan 24 2013, 02:56
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QUOTE (wakibaki @ Jan 23 2013, 17:14) *
If I was sure that it was coming, I wouldn't have said 'if and when', but nobody thus far has said anything to convince me that the claims are fallacious, which is not always the case with audio claims.


Seems like it would be a waste of yours and my time trying to convince you given that you have already made up your mind.
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greynol
post Jan 24 2013, 03:06
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...until it is disproved that the Flying Spaghetti Monster exists, I shall accept that He does.

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pdq
post Jan 24 2013, 03:06
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QUOTE (wakibaki @ Jan 23 2013, 20:09) *
No, it doesn't beg the question. The issue is one of difference and its detectability, not quality. Please do not attempt to introduce red herrings.

So what are you saying, that it doesn't matter if the difference makes it better or worse, as long as it is detectable? Last I knew, it wasn't that hard to make a DAC audibly worse.
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Arnold B. Kruege...
post Jan 24 2013, 14:12
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QUOTE (wakibaki @ Jan 23 2013, 15:04) *
ESS moreover claim that they have discovered (in blind testing) a further modification which is audible but for whose audibility they currently have no explanation (and evidently no capacity to detect by measurement, or none that they revealed). This is some way of imposing unconditional stability which they can turn on and off for the purposes of DBT in an FPGA implementation of the DAC.

Ultimately this has no philosophic impact on DBT, but if it is true, it will undoubtedly eventually set the cat among the pigeons, so those who like to depend on the idea that instrumented measurement as it stands, will reveal any audible feature, better be ready for the shitstorm, if and when it arrives.


IME it is not uncommon for golden ears to try to pass off some pretty poorly done evaluations as being "blind". In many cases requests for even general details of the alleged "blind test" are sloughed off. After all, if you don't understand what it means, blind is just another word...
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Arnold B. Kruege...
post Jan 24 2013, 14:28
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QUOTE (wakibaki @ Jan 22 2013, 22:23) *
Apologies if this topic has been posted previously, I did a search but found nothing.

http://www.youtube.com/watch?feature=playe...p;v=1CkyrDIGzOE

The above link shows a youtube video of an ESS presentation at RMAF.


About 10 minutes into the presentation it misidentifies dither as noise shaping. How many more serious simple errors do I have to tally up before I justify not wasting any more time with it?
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Nessuno
post Jan 24 2013, 18:00
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QUOTE (pdq @ Jan 24 2013, 03:06) *
Last I knew, it wasn't that hard to make a DAC audibly worse.

Or just more "euphonic"... wink.gif

Anyway, I'm not holding my breath, actually, but should a proven difference exists, then judging its quality as positive or negative would be rather subjective for lack of a reference to compare to.


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