Aqua Acoustic Quality Aqua Formula xHD D/A processor Measurements

Sidebar 3: Measurements

I measured the Aqua Formula xHD DAC with my Audio Precision SYS2722 system (see the January 2008 As We See It"), using both the Audio Precision's coaxial and AES/EBU digital outputs, and USB data sourced from my MacBook Pro running on battery power with Pure Music 3.0 playing WAV and AIFF test-tone files. Apple's USB Prober utility identified the Formula xHD as "aqua XHD" from "aqua," its serial number as "0 (none)," and confirmed that its USB port operated in the optimal isochronous asynchronous mode. Apple's AudioMIDI utility revealed that, via USB, the Formula xHD accepted 24-bit integer data sampled at all rates up to 768kHz. Its coaxial and AES/EBU inputs accepted PCM datastreams with sample rates up to 192kHz.

The Formula xHD's maximum output level at 1kHz in was 3.84V from its balanced outputs and 2.8V from its unbalanced outputs, the latter 2.9dB higher than the CD standard's 2V. The outputs preserved absolute polarity with the front-panel Phase LED dark. (The XLR jacks are wired with pin 2 hot.) The unbalanced output impedance was higher than the specified 19 ohms, at 100 ohms across the audioband. The balanced output impedance is specified as 600 ohms; I measured 24 ohms at low frequencies, and 68 ohms at the top of the audioband.

The reconstruction filter's impulse response was a perfect pulse (fig.1; ignore the tiny amounts of pre- and post-ringing, which are due to the SYS2722's anti-aliasing filter operating at a sample rate of 200kHz). There is no digital reconstruction filter, and with white noise sampled at 44.1kHz (fig.2, magenta and red traces, footnote 1) there was a slow rolloff above the audioband, disturbed by nulls at 44.1 and 88.2kHz. Consequently, the aliased image of a full-scale 19.1kHz tone (cyan and blue traces) was hardly suppressed at all.

618Aquafig01.jpg

Fig.1 Aqua Formula xHD, impulse response (one sample at 0dBFS, 44.1kHz sampling, 4ms time window).

618Aquafig02.jpg

Fig.2 Aqua Formula xHD, wideband spectrum of white noise at –4dBFS (left channel red, right magenta) and 19.1kHz tone at 0dBFS (left blue, right cyan), with data sampled at 44.1kHz (20dB/vertical div.).

Looking in more detail at the frequency response from the balanced outputs (fig.3): Other than a rolloff below 25Hz, it is flat in the audioband at all sample rates, though there is a very slight rising trend toward 100kHz at the higher sample rates. Measured at the unbalanced outputs, the response was flat from 10Hz up (not shown). The channels were well matched from both sets of outputs.

618Aquafig03.jpg

Fig.3 Aqua Formula xHD, balanced frequency response at –12dBFS into 100k ohms with data sampled at: 44.1kHz (left channel green, right gray), 96kHz (left cyan, right magenta), 192kHz (left blue, right red) (1dB/vertical div.).

The Formula xHD's channel separation was excellent, at >105dB from 100Hz to 10kHz, and the low-frequency noise floor was virtually free from any power-supply–related spuriae (fig.4). One thing I noted during this test was that the 1kHz waveform on my oscilloscope was stepped rather than smooth, which is typical of an NOS (Non-OverSampling) DAC. A relevant issue with resistor-ladder DACs is the linearity error: Will a digital signal at, say, –80dBFS be reproduced at the outputs by an analog signal the same 80dB down from full level? However, the Aqua performed well in this respect. When I examined its linearity (fig.5), the error was negligible down to –80dBFS, and remained below 1dB down to –104dBFS.

618Aquafig04.jpg

Fig.4 Aqua Formula xHD, spectrum, 0Hz–1kHz, of dithered 1kHz tone at 0dBFS (20dB/vertical div.).

618Aquafig05.jpg

Fig.5 Aqua Formula xHD, 1kHz output level vs data level in dBFS (blue, 10dB/vertical div.); linearity error (red, 1dB/vertical div.).

Increasing the bit depth from 16 to 24 with a dithered 1kHz tone at –90dBFS (fig.6) dropped the noise floor by 25dB. However, the many distortion harmonics visible in the 24-bit signal suggest that something is not optimal in the Formula xHD's handling of low-level data with this bit depth. As with the HoloAudio Spring DAC reviewed in May, another resistor-ladder DAC, perhaps the LSBs are being truncated. With undithered data representing a tone at exactly –90.31dBFS (fig.7), the three DC voltage levels described by the data were well resolved. With undithered 24-bit data, the result was a clean sinewave (fig.8).

618Aquafig06.jpg

Fig.6 Aqua Formula xHD, spectrum with noise and spuriae of dithered 1kHz tone at –90dBFS with: 16-bit data (left channel cyan, right magenta), 24-bit data (left blue, right red) (20dB/vertical div.).

618Aquafig07.jpg

Fig.7 Aqua Formula xHD, waveform of undithered 1kHz sinewave at –90.31dBFS, 16-bit TosLink data (left channel blue, right red).

618Aquafig08.jpg

Fig.8 Aqua Formula xHD, waveform of undithered 1kHz sinewave at –90.31dBFS, 24-bit TosLink data (left channel blue, right red).

When I tested the Formula xHD's harmonic distortion from its balanced outputs, I got a surprise: With the 50Hz tone I usually use, the distortion was extremely high. Even at –3dBFS into 100k ohms (fig.9), the third harmonic lay at just –20dB (10%), which will be very audible. The unbalanced outputs offered very much lower distortion, even into 600 ohms (fig.10). Fig.11 plots the percentage of THD+noise against frequency with a full-scale signal into the high 100k ohms load from both balanced and unbalanced outputs. You can see that while both outputs offer similarly low distortion in the treble, the balanced THD+N percentage increases rapidly below 200Hz, with almost complete waveform clipping below 80Hz. As the distortion from the balanced output is almost completely odd-order harmonics, I suspect that what we are seeing in fig.10 is saturation of the output transformer's core. Fortunately, as Jason Victor Serinus used only the Aqua's unbalanced outputs, he dodged this bullet.

618Aquafig09.jpg

Fig.9 Aqua Formula xHD, balanced output, spectrum of 50Hz sinewave, DC–1kHz, at –3dBFS into 100k ohms (left channel blue, right red; linear frequency scale).

618Aquafig10.jpg

Fig.10 Aqua Formula xHD, unbalanced output, spectrum of 50Hz sinewave, DC–1kHz, at 0dBFS into 600 ohms (left channel blue, right red; linear frequency scale).

618Aquafig11.jpg

Fig.11 Aqua Formula xHD, THD+N (%) vs frequency at 0dBFS: balanced output (left channel blue, right red), unbalanced output (left cyan, right magenta).

The poor ultrasonic rejection visible in fig.2 resulted in a multitude of aliased images with a full-scale mix of 19 and 20kHz tones (fig.12), and reducing the signal level by up to 10dB produced no change in the number of images. Fortunately, music rarely has significant energy toward the top of the audioband.

618Aquafig12.jpg

Fig.12 Aqua Formula xHD, balanced output, HF intermodulation spectrum, DC–30kHz, 19+20kHz at 0dBFS into 600 ohms, 44.1kHz data (left channel blue, right red; linear frequency scale).

When I tested the Formula xHD for its rejection of word-clock jitter, using undithered 16-bit J-Test data fed to its AES/EBU input, the odd-order harmonics of the low-frequency, LSB-level squarewave were much higher than they should have been (fig.13). (The correct levels are indicated by the sloping green line.) This behavior was identical when I repeated the test using the optical and coaxial inputs. However, the picture looked a little cleaner with 24-bit J-Test data sourced via USB (fig.14).

618Aquafig13.jpg

Fig.13 Aqua Formula xHD, high-resolution jitter spectrum of analog output signal, 11.025kHz at –6dBFS, sampled at 44.1kHz with LSB toggled at 229Hz: 16-bit AES/EBU data (left channel blue, right red). Center frequency of trace, 11.025kHz; frequency range, ±3.5kHz.

618Aquafig14.jpg

Fig.14 Aqua Formula xHD, high-resolution jitter spectrum of analog output signal, 11.025kHz at –6dBFS, sampled at 44.1kHz with LSB toggled at 229Hz: 24-bit USB data (left channel blue, right red). Center frequency of trace, 11.025kHz; frequency range, ±3.5kHz.

618Aquafig15.jpg

Fig.15 Aqua Formula xHD, waveform of analog output reproducing 1kHz waveform sampled at 44.1kHz. Note stepped appearance due to the absence of a reconstruction filter.

One of the earliest but incorrect criticisms of CD players was that they produced a "stepped" waveform. The criticism was incorrect because all players back then incorporated an analog or digital high-order, low-pass reconstruction filter that "smoothed" the waveform. Ironically, because D/A processors like the Aqua don't have a reconstruction filter, their output is indeed stepped, as you can see from fig.15.

Most of the questionable aspects of the Aqua Formula xHD's measured performance stem from its lack of a reconstruction filter. But its poor rejection of word-clock jitter, and that inadequate transformer used to implement the balanced outputs, are flaws that should have been avoided.—John Atkinson



Footnote 1: My thanks to Jürgen Reis of MBL for suggesting this test to me.
COMPANY INFO
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US distributor: Well Pleased Audio Vida
1934 Old Gallows Road, Suite 350-R
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COMMENTS
Ortofan's picture

... "questionable aspects of the Aqua Formula xHD's measured performance"? With a price of $17K, it can't be the result of cost cutting. So, do we then conclude that the (substandard) performance as measured is as the designer intended?

Axiom05's picture

This DAC is designed w/o a digital filter. So the answer to your question is "yes" the measured performance is likely as the designer intended. These are typical measurements for a DAC lacking a digital filter. You will have to decide for yourself whether or not the design sounds better than a DAC with a filter.

Indydan's picture

The Aqua gets an extra star, simply for not having MQA.

allhifi's picture

Touche' !

(Although maybe 2 extra stars -sans Mostly Questionable Algorithms )

pj

Psychedelicious's picture

I am posting this from a funeral home because I died of boredom trying to read this review.

dalethorn's picture

It's like reading a mystery story and at the end, a key component of the mystery is still a mystery. It would be good to know if that smoothing or whatever it is is due to lacking the filter. For example, if the possibility exists to sound as good as a much more expensive unit just by adding a digital filter, it might be worth asking the question.

Indydan's picture

John Darko reviewed and loves this DAC. Could Stereophile have gotten a faulty unit?

johnhdarko's picture

I have only reviewed the original La Scala and La Scala Optologic DAC from Aqua. Oh - and the La Voce S2. But never the Formula.

teched58's picture

Jason writes in his review that he had to "break in" the system for 24 hours to ensure that the cables were "settled in" before he began his listening test. What is the scientific basis for this? What engineering school can I go to to learn about this?

CG's picture

Well...

Although not precisely the same thing, cable stability is a bona fide thing at RF and microwaves. For example:

https://www.signalintegrityjournal.com/articles/165-rf-stability-of-cabl...

http://www.mwrf.com/systems/preventing-pim-microwave-systems

Again, these are not consumer oriented web sites nor is the subject about performance at audio frequencies.

I would note that in many ways, the problem is potentially as severe at audio frequencies as at microwaves, albeit the details are different. The frequency range considered to be "audio" spans 10 octaves, if I did the counting on my fingers right. Within that band, there's a zillion tones that are continually being modulated. Microwave systems don't cover nearly that range. The required signal to noise/distortion ratio for higher quality audio is pretty high, at least compared to most microwave systems commonly used.

So, for a specific example, moving cables often generate triboelectric originated noise, which can degrade an audio signal. If the cables are mechanically stressed, they very well might move as the result of loud audio moving the cables one way or another. The way a lot of people set up their subwoofers to be thumping loud comes to mind. Movement as the result of loud bass notes would give a modulated noise floor that's kind of in synchrony with the music.

In addition, audio frequencies are not just audio frequencies nowadays. Just look at figure 2 of the Measurements section for this DAC. Typical audio systems also carry artifacts from digital audio processing way above the audio band, as well as junk from other electronic gadgets attached to the AC mains or that just might be located nearby. These can and often will generate intermodulation and noise products within the audible range.

At low frequencies, shielding is of limited help. (Too long to explain - try Googling "Ott noise cable shielding") So, you have to rely on the cable design to reject the junk as best you can. (Again, Ott...) You can often reduce the effects of this stuff by using proper audio transformers in the system components as well as truly balanced interconnects. These all have their pluses and minuses and don't come for free.

I can't say that Jason's situation or his cables require 24 hours to resolve. No idea. And, it *could* entirely be in his imagination. But, there is scientific basis for the possibility.

Jason Victor Serinus's picture

when Keith O. Johnson visited my home in Oakland years ago, he mentioned that when you twist cables with teflon shielding, which is the shielding that Nordost uses, microscopic cracks appear that take 24 hours or so for recovery. For me, that helped explain what I had already heard.

Jason Victor Serinus's picture

when Keith O. Johnson visited my home in Oakland years ago, he mentioned that when you twist cables with teflon shielding, which is the shielding that Nordost uses, microscopic cracks appear that take 24 hours or so for recovery. For me, that helped explain what I had already heard.

teched58's picture

Keith O. Johnson is an engineer, so he has standing to comment. I would agree with him that microscopic cracks can occur in the copper conductors However, the failure modality induced by such cracks would be of the on-off variety (i.e., cable failure would cut the connection, causing a drop out). At baseband, microscopic cracks will not cause any frequency-related changes in sound (i.e., loss of certain frequencies) so what you're hearing/not hearing is indeed in your head (confirmation bias). As for any cracks repairing themselves in 24 hours, that's a new one on me, though I'm an EE, not a materials scientist.

I should add that, while I think Jason seems to be a very nice guy, my original comment was not meant literally. It was an expression of exasperation at the nonsense that passes for technical reviews on the current lot of audio websites.

As an engineer, I'm embarrassed to see such audiophilic nonsense. (I think the root cause is that the non-engineers who write this stuff don't know what they don't know. That shouldn't be an excuse, just the same as ignorance of the law is no defense.) I've been into audio for 50 years, so that's why I continue to follow Stereophile, but, honestly, there's not going to be a future generation of audiophile. It's become all about the bling.

Jason Victor Serinus's picture

You write: "At baseband, microscopic cracks will not cause any frequency-related changes in sound (i.e., loss of certain frequencies) so what you're hearing/not hearing is indeed in your head (confirmation bias)."

That is not correct. What I'm hearing is what I'm hearing. What you are thinking seems to be that since you have no explanation for what I am hearing, I cannot be hearing it. These are different things.

If a tree falls in the forest, and no one is there to hear it fall, did it make a sound?

You also write, "I think the root cause is that the non-engineers who write this stuff don't know what they don't know." That is an unfounded presumption. Speaking only for myself, I think a more accurate statement might be that at least some non-engineers who write equipment reviews, and who have the love of music, listening skills, and reference system that enable them to hear differences both great and small, talk about what they do know, which is what they hear.

I thank you for sharing your passion.

RH's picture

Jason S wrote: "That is not correct. What I'm hearing is what I'm hearing. What you are thinking seems to be that since you have no explanation for what I am hearing, I cannot be hearing it. These are different things."

Jason, unfortunately that response doesn't accurately characterize the argument given by teched58.
He wasn't simply saying "I have no explanation for what you are hearing."

He was pointing out that the claim about microscopic cracks changing the sound in the way you describe is an explanation that doesn't make technical sense. It's a bad explanation. And then he DID offer an alternative explanation: You were imagining the differences - confirmation bias - a phenomenon with far more experimental confirmation and documentation than the "micro cracks" hypothesis you provided.

So your reply gives the appearance of just blowing off his arguments without really engaging them.

It seems a constant theme in the subjectivist reviewing literature is to essentially ignore or downplay the significance of bias and human imagination in what we perceive and believe.

If you just do even a quick survey of the incredible things people believe - from psychics, to New Age therapies, Alien abductions, to faith healing, to ghosts, to completely unfounded ideas on fringe medical therapies, and on and on.... it's utterly staggering in scope and variety. And much of it derives from what people *think* they have experienced or perceived.

And then there are the large lists of well documented, experimentally verified realms of human biases that are such a strong problem the very scientific method itself requires they are taken in to account.

Given this, it has to be reasonable to question: Do you truly think you could not be mistaken in what you think you heard?

Because your reply essentially relies on not questioning your belief: "What I'm hearing is what I'm hearing" seems stated as if it ought to be accepted on it's face as a given fact. When that is actually a claim - that there were in fact audible differences - one could have very reasonable doubts about. An explanation for "what you were hearing" could be that you imagined it, misperceived it.

Of course this opens up a can of worms for subjective reviewing in general. It's sort of like the Church pastor's dilemma; if one can't speak with a certain level of certainty, then it's hard to preach anyone should believe it or jump on board, so the role of bias and imagination are pushed in to the background as concerns. Publications like Stereophile (and I'm a long time reader and fan!) would have some trouble justifying the reviewing style, if, in a more scientific-style, concerns about the pollution of imagination and bias were kept more fully in view.

I can certainly understand J. G. Holt's despair over the non-scientific nature of many high end audio claims and reviewing methods.

Though I really appreciate that, at least when it comes to speakers, John Atkinson attempts to correlate measurements to their audible effects. Which makes sense as even the most "objectivist" viewpoint acknowledges that pretty indisputable cases have been made for establishing why speakers can sound different from one another.

But it is telling that this correlation seems to fall off the more the item in question enters the "controversial" zone of claims. For instance, in DAC/CD player reviews, there is much less attempt in the measurements section to correlate the measurements with the perceptions of the reviewer. Mostly, the technical performance is simply described and IF there is an anomaly in the measurements that could be audible, John flags that. But otherwise, the correlation of measurements to reviewers claims of "smoothness, transparency, vitality, lushness, bass depth, tightness" and many other descriptors is mostly left vacant.

And when it comes to cable reviews, as far as I've seen measurements are simply abandoned.

This trend has always seemed pretty telling, in terms of the effort to provide substantiation for the effects the reviewers are describing.

Anyway...just to be clear: I still find Stereophile a fun read and have enjoyed it for years, and I understand that there are certain impracticalities involved in trying to make everything scientifically rigorous. And hey, to some extent, maybe that could even make Stereophile a duller read.

But at the same time it seems to me that we should be able to honestly acknowledge the Elephant In The Room when it comes to subjective reviewing (imagination, bias, often enough accepting technical claims on quite flimsy methods of inference, etc). Rather than to pretend it doesn't exist, as if the audio industry and reviewing is somehow magically immune to everything we know about the foibles of human perception.

Finally: Though I may be taking a bit of issue with this particular reply of yours, Jason, and using it to voice some general concerns, I also have to say I really enjoy your writing and especially your Show Reports! You are never afraid to call it as you hear it. If you hear something you didn't like, we know it, and I appreciate it.

Cheers!

Jason Victor Serinus's picture

:-)

NeilS's picture

"Seeing is believing", not "Seeing is truth". I think the subjective experience of what we see also applies to what we hear, smell, taste and feel.

ok's picture

..is always current science; not to be confused with “technology” which is loosely based on theory as well as in practical success. Modern chemistry for example had already been established well before basic atomic structure had even been outlined let alone confirmed. "Science" should also not be confused with scientism; nor perception with "subjectivism" for that matter.

RH's picture

Uh-oh, the bugaboo term "scientism" has appeared! ;-)

How do you think we moved from "alchemy" to modern chemistry? (Hint: an ever more rigorous, scientific approach).

Science should also not be confused with scientism..

In my experience, it's typically people who apply the term "scientism" who are confusing things (and often using it to attack strawmen).

Case in point: insofar as "scientism" would be a critique, how does that term apply to what I wrote?

ok's picture

..should also not be confused with irony either :-)

RH's picture

...I may certainly be confused!

It's just that I have so often seen the term "scientism" raised in the way I interpreted it.

Did I misinterpret your initial reply to me somehow, and if so could you clarify?

Thanks!

ok's picture

..nothing more than what I’ve already wrote – and certainly nothing personal whatsoever.

dalethorn's picture

"He was pointing out that the claim about microscopic cracks changing the sound in the way you describe is an explanation that doesn't make technical sense. It's a bad explanation. And then he DID offer an alternative explanation: You were imagining the differences - confirmation bias - a phenomenon with far more experimental confirmation and documentation than the "micro cracks" hypothesis you provided. So your reply gives the appearance of just blowing off his arguments without really engaging them."

Pure imagination is not really an alternate explanation, unless it were imagined once and not repeated after, say, a cup of coffee or glass of wine. A better alternate explanation would be something like "In a system of that complexity, it could be a lot of things."

RH's picture

Pure imagination is not really an alternate explanation,

Sure it is, in the form of expectation bias (and other forms of fallible inferences).

Why do you think medical studies are so often done with placebos and control groups? It's to help rule out the always present alternative explanation of human imagination/bias/misattribution.

unless it were imagined once and not repeated after, say, a cup of coffee or glass of wine.

That's not really how human bias works, at least the type that could be in play here. Some biases can change based on imbibing the drinks you mention, others can easily run through all those situations. We are talking about specific types of perceptual inferences - e.g. that there's a difference between A or B, or that a cable changed it's sound due to being moved or whatever. I've never, ever seen any study support the idea that, for instance, people become immune to expectation bias (e.g. expecting a more expensive cable to sound better) by drinking coffee or spirits.

A better alternate explanation would be something like "In a system of that complexity, it could be a lot of things."

I agree that we shouldn't restrict the explanation ONLY to one or two possibilities. However, that's different from saying that pointing to perceptual biases as a possible explanation isn't really an alternative explanation. It's actually a very well-supported, and hence very plausible explanation, and if one's method doesn't account for this, it seems to me we should scale our confidence accordingly.

As for other explanations: sure someone can propose some other explanations - e.g. some other technical claim that would account for Jason hearing the difference. But then we'd ask: Ok, is that a sound explanation? What's the technical basis or evidence in it's favour? Because if it's just another speculation without much behind it, then the alternative explanation appealing to human bias is still the front-runner, as we have so much evidence for these effects.

dalethorn's picture

Medical studies are rigidly controlled, and you cannot just stop drug A in the middle of a test to see what drug B would do, unless so ordered by the test administrator. On the other hand, an experienced reviewer already knows where his expectation biases etc. are, and he knows how to get around them.

Forgive me for a possibly weird analogy, but there are philosophical arguments about whether true altruism is possible, or at some level we always do what benefits us even if we're not specifically aware of it. But it is possible to stop onesself in a moment and say "I'm going to make a conscious decision to do something I have absolutely no motivation to do, if for no other reason than to prove to myself by experiment that it's feasible to do."

And so the experienced reviewer creates tests that are specifically designed to filter out biases. We could suggest that so-and-so doesn't, or isn't capable of it or practiced at it, but it's better addressed with a question than with an either-or assertion.

RH's picture

On the other hand, an experienced reviewer
already knows where his expectation biases etc. are, and he knows how to get
around them.

If you actually thinks this applies to subjective audio reviewing, then you do not seem acquainted with how bias actually works. Because that just doesn't fly.

You can't just sort of "power through" some of the well known biases. Do you think doctors who design medical studies - fully aware of the biases they are controlling for - would absolve themselves from the experimental controls if THEY were subjects in a study? Like "don't bother putting me in a study with placebos or blinding or control groups, I know how bias works so I won't be affected."

Of course not. As Feynman famously said: The first principle is that you must not fool yourself – and you are the easiest person to fool.

We are all susceptible, no matter how confident or clever we think we are. As someone who believes in the usefulness of blind testing (when practical/applicable) I feel very cognizant of my biases. Yet some blind testing of some of my own equipment showed how easily susceptible I have been to fooling myself.

And so the experienced reviewer creates tests that are specifically designed to filter out biases.

How?

I certainly have not seen that in the subjective reviewing community for the most part, far from being designed to filter out biases, actually are designed to ensure they can easily come in to play, if not outright invite them to the party.

There are rare exceptions, where a reviewer attempts to bring a bit more rigour to his review, such as Jim Austin's fairly recent Benchmark DAC3 stereophile review, in which he tried to control variables as much as possible in a head to head DAC switching scheme - and at that point found no sonic difference! (Though it still wasn't a blind listener test as I understand it, so it leaves that variable on the table).

dalethorn's picture

I won't argue that you can "power through" every bias, since we all have to breathe and eat, and remember to lock our doors. But testing past a simple confirmation bias is infinitely easier than trying to get control of autonomic body processes so we can fool a drug etc.

RH's picture

dalethorn,

You keep saying this, but....how?

Confirmation (and other biases) are not simply at work on some autonomic level...whatever that even means. First, biases run through almost every one of our endevourrs - it can be found in racism, religion, bad science, psuedo science, astrology, which arguments we believe, what products we buy...you name it.

Placebos are used, even in medical trials, to wee out the variable of our MENTAL bias effects. That is the way our perception can change when we think we are doing something different. You could look at a group taking a new medication, and look at another similar group placed in a similar condition as a control group, and then you've controlled some of the variables. But what the placebo does is controle for the additional variable of TAKING a purported medicine, or simply adding "taking a pill" to someone's routine. JUST the fact of taking a pill (or similar) is known to influence people's reactions in of itself. It's a psychological variable that has consequences on perception and experience ; it's not merely autonomic.

But, again, various biases are at play in practically any instance of human perception or inference from our experience. If as you keep saying it's "easy" to "test past" confirmation bias - and the subject here is obviously audio reviewing - can you please give an example of what you mean?

dalethorn's picture

I have lots of biases, and I'm perfectly capable of acting outside of every one of them when called to do so. Unless of course doing so threatens my well-being. It's not even that difficult. All you have to do is make a list and then develop the bypasses as needed.

I don't necessarily try to work around my biases when just enjoying music, although in some cases if I'm curious about this or that, I will as an experiment. But when testing gear or music, it's too easy to get past biases by use of volume controls, EQs and other filters, or even haranguing the occasional friend and neighbor for their opinion.

So let's say that I find a particular recording on a particular system to be too edgy on certain instruments - maybe a piano sounds too glassy. My instinct says it's a combination of things, probably a slight emphasis in the upper mids, possibly a surface reflection (speakers, windows), the recording itself, maybe even dirty contacts somewhere. If I really wanted to blame a particular component, I could make excuses along that line and that would be acting on a bias, intentionally or subconsciously. If I strongly suspected a window reflection in the past, but didn't take action because it didn't happen with other music, then I could blame the problem on the window out of laziness, not wanting to take the time to validate it.

But if I have a new component at hand and I hear something that doesn't seem right, it's not just the irritation however minor that makes me want to investigate - it's curiosity too. There's a practical aspect to human nature that involves work effort and available time that can bias a person toward taking shortcuts and making excuses, but if you're reporting to the public, you have to be pretty careful you don't get caught, especially if it's more than once.

Subjects like racism, religion, and dubious science certainly involve biases when people are operating in their normal comfort zones, but I can tell you without doubt that regardless of my biases, I'm capable of thinking and speaking outside of those biases when necessary. I call it the "atoms and molecules" approach to thinking - instead of making assumptions up front, begin the process at the most basic level possible and examine everything. That might seem very time-consuming, but it's a learned process, and with practice it can usually be kept within reasonable limits, at least to establish facts and rules at a given level of inquiry.

ok's picture

Addressing real differences (and that’s what placebo/nocebo effect is all about) to one’s benign/malicious “imagination” is just another way of saying: “I don’t get it!”

RH's picture

Well, I think you at least have one thing right: I don't get your posts ;-)

I'd ask for some clarification...that seems pretty garbled in it's meaning....but I guess as per the last time, I shouldn't expect any.

ok's picture

..people fall in three basic categories: 1. those who understand by themselves 2. those who understand by instruction and 3. those who do not understand either way; I always thought the second as the rarest of them all – so please excuse on my part any further unwillingness to explain [:=))

RH's picture

You missed another category:

4. Those who are not understood because they do not write either clearly or coherently.

Yet think they are profound when not understood.

"Those who would like to seem profound to the crowd strive for obscurity. For the crowd believes that if it cannot see to the bottom of something it must be profound.”

- Friedrich Nietzsche

;-)

It's too bad you take the route of obscurantism, rather than a dialogue in which we clarify for each other what we mean. But...that's comboxes for ya....

CG's picture

First, think logically for just a minute.

Whatever cable Jason may be using uses Teflon as an insulator, with some metal (probably) probably as the conductor. So, any cracks or other flaws in the Teflon would have no sudden on-off effect on the signal, unless there was somehow a shorting situation in the insulation. Any cracks - if that is the underlying condition - would only change the dielectric characteristics of the cable.

However, Teflon is known to have really severe triboelectric characteristics. Googling "triboelectric Teflon" yielded this as the very first hit:

https://www.alphalabinc.com/triboelectric-series/

This article describes actual measurements of triboelectric properties of various plastics and other materials, as performed by a company that makes test equipment for measuring charge. There's about 480,392 more links available on the subject as well. Wikipedia has a simple explanation of the triboelectric effect here:

https://en.wikipedia.org/wiki/Triboelectric_effect

So, it seems that physically moving or bending cables made with Teflon insulation (and others) can cause a charge effect inside that cable that could last for a time until it discharges. How that affects perceived audio performance probably depends on the system in which it's used - there's a lot of variables just in that alone.

That's the real problem with measurements. Almost exclusively these are performed under test bench conditions for each component of the system. I have rarely seen any consideration to how these components performed when connected to other components as a system. (If anybody can point me to some, I'd love to investigate!) Not only that, but the usual test condition is to apply a continuous sine wave test signal for most of the analyses. It's certainly true that music and other complex signals are composed of combinations of sine waves, but it's also true that changes of these combinations over time also contribute additional modulation that is ignored in most audio tests. (How is the coherence time of a saxophone's sound taken into account?) This is especially true when averaging is used in the test system to eliminate what might be considered as "noise". Not as random events tend to get "averaged out" in the test and lost in the measurement. But, these can be just as audible as any steady state signal. (Yet another parenthetical statement - Serious engineers who work on and analyze communications systems have learned that it's not complete to just look at averaged values of SNR or MER. You also need to pass actual data through the system over a period of time to catch flaws that only appear on a random basis. These count, too.)

dalethorn's picture

I seem to remember there was a suggestion that maybe the teflon was the source of the anomaly, not that a measurement pointed specifically to the teflon covering. Unless I'm mistaken, the teflon was suggested as a possible cause, and bias was suggested as the only alternative.

On the coherence time of saxophone sound, I might miss it and the next guy pick up on it - who knows?

There was a review here a couple of years ago where someone mentioned that a particular tweeter could resolve a faint high-hat cymbal sound in a track (possibly Luminol by Steven Wilson), and while I had a few of the best headphones lying around and obtained a CD and high-res download of that track, I couldn't hear the high-hat even with the volume turned up where a 16 khz tone hurt my ears. I dunno - maybe my copies were bad or the wrong master, or I just couldn't hear what the reviewer heard, but I still don't doubt that it exists and the reviewer heard it. It would be interesting to resolve that issue as much as the teflon issue, so who knows? Maybe someone familiar with that cable could weigh in.

CG's picture

I cannot speak to whatever Keith Johnson may have said. Nor, can I speak to whatever Jason may or may not be hearing.

However, as a physicist slash electrical engineer - I don't know if that gives me standing or not - I'm always embarrassed when engineers insist on taking the short cut of relying on simple approximations that are used to make engineering calculations and analysis simple. Engineering approximations work for a lot of things, but they are not the complete and entire story. This is not only true with regard to the actual physics of the situation (which, in the end, may turn out to be such a low order effect that it practically doesn't matter - or maybe not) but especially with regard to the perception of sound by human listeners.

Simple linear amplitude response may not be affected by cable changes as measured by a network analyzer or similar device. But, as an example, if there are non-linearities in the cable and system, a change in the characteristics might cause a resulting change in the spectrum of the distortion products. This could easily be perceived as a frequency related change in sound. They can also be measured, although it takes a certain amount of resources and desire to do so.

My own personal opinion is that if there turns out to be no future generation of audiophiles, it would be because of two main things. One is that modern music - whatever that may be for potential future listeners - is not recorded or engineered in a way that lends itself to where high fidelity playback adds anything to the experience. The other is that high fidelity playback really by nature is a focused activity. To make it worthwhile to pursue, you have to be able and willing to sit down and listen to music for more than a few minutes, and not as just a catchy background beat to whatever else you might be doing. That's not the current trend.

Finally, no, I'm not connected with the cable industry (except as an occasional customer) nor with Stereophile (except as an occasional customer).

dalethorn's picture

"....modern music - whatever that may be for potential future listeners - is not recorded or engineered in a way that lends itself to where high fidelity playback adds anything to the experience."

Are you thinking of popular music, or does that include jazz and classical?

"....high fidelity playback really by nature is a focused activity. To make it worthwhile to pursue, you have to be able and willing to sit down and listen to music for more than a few minutes, and not as just a catchy background beat to whatever else you might be doing."

Seems to me it's always been that way, and audiophiles as I know them were always the curious types who poked their fingers into things that others would not bother with. I can't speak about large systems with speakers since I've been out of that for years, but if you look around on some of the portable audio and headphones forums, you'll encounter lots and lots of audiophiles who are very picky about sound.

allhifi's picture

tech58: Do you have a name ? Firstly, identify yourself.

You know, you so-called "engineers" are a typical bunch (much like today's physician's) that somehow feel your education gives you some type of "advanced" understanding. It's actually, quite laughable -the attitude, arrogance.

You say:

" ... As an engineer, I'm embarrassed to see such audiophilic nonsense. (I think the root cause is that the non-engineers who write this stuff don't know what they don't know"

Just so you understand, you have it reversed (i.e. "non-engineers who write this stuff don't know what they don't know")

It's you dufus's that don't know what you should. Have you (and your types) ever thought, considered, and asked yourself: "Damn, what am I missing, what coud acount for such 'characteristics/ qualities/observations?"

The answer is clear: NO.

Please understand (and learn) that the finest minds in the world, as much as their impressive credentials entail, humbly acknowledge they need to learn/discover more. Far more.

But not you, Mr. Engineer. Perhaps you should both identify yourself along with your credentials. When someone hides behind anonyimity, they can't be (shouldn't) be taken seriously. And so it stands here, your useless reply(s).

I can't help but genuinely laugh at the sheer arrogance -verging on stupidity- when I hear/read this kind of thing. Such idiots (self-proclaimed Engineers) actually believe they "know". What you know is near squat, nada, nilch. What a joke. What a joker.

Get a set of 'ears', leap off your High-Horse and perhaps investigate (find answers) to help explain such phenomenon.
You know what you can do with your 'expectation bias' (and similar crap). Get to work and learn something. Hint: You may wish to consider and investigate Quantum Physics -it may hold the answers you desperately need to discover and then validate -for your own insecure reasons.

peter jasz
P.S. Do you even own a hi-fi. Or listen to music?

allhifi's picture

Hey touched58:

" What engineering school can I go to to learn about this?"

That would be a school you could never even enter -let alone graduate.
(Simply due to your lack of available "resources")

However, fret not, there are many such schools that will gladly take you on -expecting nothing more than a sterile-minded chap that unconditionally professes (to his professor): "You are the best, so amazing, smart, handsome -and sensible.

Until of course, these know-it-all's learn a thing (or one-hundred) by advancing (quantum physics/sciences) research that will re-write the 'textbook' on such matters.

pj
(I honestly thought the dinosaurs died out 60-million years ago?)

dalethorn's picture

"What possessed me to begin with Michael Tilson Thomas and the San Francisco Symphony's download-only recording of Berg's Three Pieces for Orchestra (24/192 FLAC, SFS Media/HDtracks), whose disturbing atonalities seem to presage WWI, I don't know."

I'd suggest it's because it's a fantastic recording.

dalethorn's picture

Adding to my comment above, this lecture on the Three Pieces illustrating the cross-pollination of influences between composers Berg, Schonberg, and Webern was a great find for me.

https://www.opusklassiek.nl/componisten/berglecture/mbberglecture.htm

ok's picture

There’s no physical account or acceptable measurement for the placebo effect – so according to diehard objectivists placebo should not exist by definition..

Archimago's picture

Remember that the placebo effect is a psychological phenomenon. While we may not understand the underlying neuropsychological mechanisms to provide direct objective measurements, the placebo effect can of course be demonstrated!

In fact... Not hard to demonstrate time and again throughout the decades when we observe the differences in outcomes between "open-label" and "blind" research trials where expectation biases can play a role in the results. That effect is "measurable".

ok's picture

Well, hearing itself is also a psychological phenomenon and therefore not prone to direct evaluation: you just have to trust what certain people say for reasons unknown. Even deaf people could actually participate in double blind tests with statistically interesting results provided the coordinator (who should not be allowed to know he’s dealing with deaf, that’s triple blind) is capable enough of manipulating all other significant parameters in order to prove what has already been decided. On the other hand placebo in medical experiments can really heal people from tangible ills – so it’s not purely psychological after all. Neither is merely the "label" thing that accounts for all placebo deviations; as written elsewhere: "listening exclusively to 'perfectly measuring' amplifiers etc is another form of placebo; just like a fussy patient who feels terribly sick till the doctor says the lab tests are 'perfectly fine', even if sometimes this isn’t exactly the actual case.."

jracine's picture

Jason - I love your work and your style of writing.
But there is a problem with this review.
I own this DAC. I started my Aqua journey with a La Scala MKII, then a Formula, then the xHD.
My kit is comprised of Nagra and Magico. I have been an audiophile for 30 years, 19 years with a consequent budget and a custom built room. And my ears are good.

I do NOT recognize my DAC in your review.
I take offense because I am also a business owner and I am very annoyed by the fact that some people might not buy this product from a very reputable company that is _universally_ praised because of a half-baked, botched review.

Your CA test setup is mediocre. Inserting a Jitterbug is a mistake. The whole thing is wrong. You know what the worst part is? I will now doubt your reviews of all the products I don't know.

This DAC DESERVES a second review. Or you should request a second unit.

This DAC, sounds "right". It is dynamic, natural, image is huge in all directions. A true marvel.

Go back to the drawing board. Show us you care about your work.

I officially invite you to visit me in Montréal. Your airfare and hotel are on me.

allhifi's picture

jracine: Your reply to Vicky (Victor) was most appropriate; indeed Vick's set-up (ancillary gear) far from ideal.

Casting out such words/review should be an embarrassment to both schlock writer, editor/publisher.

Yet, jracine, you even offer to invite this schlock to your home -on your dime ? (You are MUCH too generous. Did this reviewer even have the decency/professionalism to reply to you?)

Perhaps unknowingly, but such "writing/reviewing" will be the (impending) demise of such publications based on (partly) the cavalier indifference of inadequate writer's.

I was most pleased to read your passionate, sensible reply.

Enjoy that beautifully engineered/built Aqua 'Formula' DAC !

pj

ToeJam's picture

Those kids are doing that thing again!”
Mommy - “What thing?”
“I dunno what it is Mommy, but they sure look serious!”

Allen Fant's picture

Excellent product coverage as always- JVS.
Hopefully, the price will trickle down to us common folk soon.

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