Thanks. I use AI all day professionally and personally. I have it set up to dig deep. The comments about Holo and I2s are not marketing propaganda it is founded on the design. PS Audio, Denafrips, Rockna all specifically champion I2S input in to their DACS. That being said Tim Connors told me that Jeff Zhu doesn’t make specific recommendations for interconnects. He said let your ears guide your decision. Tim said he personally uses USB. So there you go. Tim also said definitely leave PLL ON. It is the most precise clocking Holo has to offer. For me I have high end ethernet and I2S cables. The results are spectacular! I’m sticking with it and not worrying about the 3 sec delay with SR changes. Two thirds of music is 44.1 anyhow. Thanks for all your input and education. I did switch all of my equipment to the same power source to avoid ground loops. Read more about that situation. Good call!
Apparently you believe the Holo May clocking architecture is inept… When you break-down the signal flow from the USB interface, you must understand how the USB interface handles the packetized digital-audio signals it receives and where the clock source of the USB bus controller is derived. USB digital-audio transmission is asynchronous … the delivery of digital-audio packets is not tied to the master clock architecture of the DAC. The digital-audio data signal is unpacked and processed In the FPGA using the proprietary firmware where the unpacked and processed digital-audio data is intrinsically tied to the Holo May clocking topology… PLL is superfluous in the context of USB, because it is acting on the base clock reference that the PLL circuity is intrinsically tied-to, which is the master clock reference of the DAC platform. … Theoretically, you could be introducing operational noise by virtue of the superfluous engagement of PLL on the master clock reference.
Again, I highly doubt that in a blind random assessment you will be able to discern any tangibly audible difference with PLL engaged versus not being engaged… There are more system related factors that have greater influence on the subjective aesthetic appreciation of the output sound-quality.
If you understand the audibility of platform related intrinsic jitter in music playback, you will find a grounded perspective from which to rationalize the subjective psychoacoustic assessment, in the high-quality playback experience of Audirvāna.
The implementation of I²S protocol is contextually based… How the protocol is implemented by a manufacturer is a matter of engineering design rationale. Why it is implemented is a matter of a rationalization of practicality in the context of interface options presented in support of potential and contextual application scenarios… Initially direct input to the DAC component I²S interface was implemented in support of SACD player/transports, so to take advantage of a DAC platform topology performance not available in the SACD player/transport platform DAC architecture, that is made available in the outboard DAC.
More food for thought… 
I feel the Audio Science Review website should be renamed the Audio Vintage Science Review. It bases its interpretation on a few basic tests with one assumption…. We hear with our ears and they are capable of detecting frequencies typically in the range of 20 - 20,000 Hz at volume levels down to -115 dB. This comes from audiology science of 70 years ago from tests with recipients using headphones….
Modern science teaches us that very low frequencies trigger responses also in sensory receptors other than the ear, i.e we “feel” low bass more efficiently than we “hear it”. Also more recent modern advances in hearing devices for deaf mutes has shown that sensitive receptors in the skin can detect sound pressure waves with sound frequencies up to 30,000 Hz triggering a response also that the brain interprets as sound.
The big kicker is that neurological science has only begun to scratch the surface of how the brain translates these electrical signals from sensory receptors into the soundscape in our head. We hear with our brain….. and that is even before you throw in the brains “filtering” stages based on mood/biases.
Until we fully understand what the brain uses and what weightings on these receptor inputs are applied to determine our perceived soundscape it is impossible to design a series of tests to measure how well, or otherwise, a piece of equipment provides all of these inputs.
We all live in an individual reality created by our brain, one day we may fully understand how and why.., until then go with what sounds best to you.
Ultimately we are the arbiters of our interpretations…
Along with the psychoacoustic research, there is a large body of empirical knowledge regarding the influence of cognitive-bias on our aesthetic and qualitative interpretations regarding anything.
What can be measured and examined, should be measured and examined in context, as this gives us tangible reference for determinative certainty, free of ego-bias. The object of measurement is to remove as much cognitive-bias from the observation as possible and to produce empirical fact-based evidence… Yes, a ‘test’ can be biased, however measurable data is what it is… and there is no question as to the accuracy of the measurements, given the tools used in the measurement are considered reference devices with quantifiable performance characteristics by a consensus of qualified authorities on the subject.
Do you believe audio device architectures are designed around subjective opinion and unqualified hyperbole? At the very least, the design topology of any given audio-device is measured in the same way we see (or hope to see) in the tests demonstrated in the video content provided here in this thread. The results of these measurements will not be influenced by subjective interpretive bias, no matter how much a ‘subject’ re-interprets the data to fit a cognitive-bias narrative, the data speaks for itself.
In the world of audio and especially consumer audio, narratives carry a lot of cognitive weight when there is little to no understanding of the underlying technologies being employed by any give audio device by a subjective observation. The potential for coercive influence that may feed into the cognitive perceptions of the subject is amplified when lack of knowledge and insight is the case.
In the real-world of audio recording and reproduction today, we are bound to some very quantifiable limitations involved in the technologies that are employed to create and playback the music productions we listen to.
I have long argued that the perception of the real-world around us, is the reference for all things to do with music recording and playback. We can measure these things just as we can measure Quantum Entanglement. The measuring devices, test criteria and interpretive biases are the limiting factors. But we hang our hats on the quantifiable results.
Unfortunately, our DACs and other devices are not analogous to the human psychoacoustic neurophysiology of hearing and the cognitive interpretations of those signals. They are machines that have quantifiable characteristics that translate into tangibly audible energy that can be measured, observed and assessed in juxtaposition to the quantifiable natural-world around us. Like it or not, this is the reality we face.. The amalgamation of fundamental factors that are brought-together to make a DAC platform, are not whims of subjectiveness and hyperbole… they are intrinsically tied to the body of science that has evolved to allow this mechanism to exist…
Subjective observation must be quantified through a process of removing influential cognitive-biases… This is done scientifically, otherwise the subjective observation(s) are tainted and fall into the category of opinion… We are all subject to influential bias. The more we know about a subject the better we can mitigate biased interpretation…
Without juxtaposition, there is no quantifiable evidence to refute subjective observation and the influential bias of hyperbole and conjecture (presumption, assumption and ignorance) in contextual narratives..
Agree with the majority of what you are saying, I have listened to quite a few system designers on the topic. They utilise measurement to get to acceptable levels of performance, but then they tend to conduct 1000’s of hours of tweaks and subjective listening to the tweaks before finally arriving at the completed product. As such it seems clear to me that the measurements only take you part of the way interms of sound quality and are insufficient to realise the whole picture. Subjectivity and tweaks from professional listeners takes you the rest of the way.
I can cite my experience. In my demi-decade volume matched blind test of audio players (which the wife tolerates conducting on the grounds she gets her compensation in improved gifting) I first wanted to test out the new Chord DAVE purchased as part of my retirement system versus my Hugo2 which I took specifically for the purpose of benchmarking. In ASR tests the DAVE is crap, the Hugo2 much better. In my blind test picked the DAVE 75% per cent as being the better sounding device.
My point on all of this is an individuals brain, even in blind testing which removes some variables, determines the outcome for them. And anyone picking a device based on measurements rather than their own perception of SQ is depriving themselves of the best possible outcome.
The methodology of a blind test is integral to the results… I’m not arguing that your perceptions are right or wrong… they are what they are, and intrinsic to your interpretations of the experience… If you or ASR measurements were the arbiter of truth for all of us regarding the Chord DAVE, how is this determined? … A better measurement of aesthetic preference is to juxtapose DAVE to a highly rated state-of-the-art $200 ASR recommended DAC, in a blind comparison… this is primarily then speaking to the design architecture that Chord attaches value to…
Agreed on that point but in this case i lived with what I had and the Hugo2 was from a measurement perspective and cost perspective significantly different to the DAVE. In this case my test came out favouring the higher cost yet significantly worse measuring device, sight unseen. I did test the DAVE/Etude Combo against a dCS setup in the dealers however as I prefer the Chord sound signature I knew the outcome of that test was bound to be a preference for the Chord. The dealer was pushing me to go the dCS route, had to get him to adjust the volume output from the dCS as he was clearly trying to steer my interpretation!
I appreciate your determinations… Again, we are the arbiter of our aesthetic interpretations…
Bringing this back to the nature of the Holo May + Holo Red synergy and the fundamentals of DAC platform design in relationship to interface protocol technologies.
There are fundamental scientific concepts being implemented and we can see that in the Holo May USB architecture of the platform, a lot of attention is being placed on very fundamental digital-audio truths about intrinsic noise (jitter) and the perception of the analog distortion that is relative to digital signal jitter, that are corroborated by the ASR videos.
The design architecture of the Holo May and Holo Red are addressing the most fundamental elements that translate into lower intrinsic-noise, which translates into the analog signal energy that we ultimately perceive in the psychoacoustic interpretation… these things are measurable… but do they actually translate into a perceivable aesthetic? This is the subjective side and this must be distilled and quantified through a process of removing cognitive-bias.
The idea of engaging PLL on the Holo May master clock architecture, in the context of USB protocol transmission does not make sense… And leaving it engaged, because of a rhetorical statement and subjective observation and ignoring the facts about asynchronous USB audio transfer and the attention paid to this architecture in Holo May, is adding needless playback latency to the experience and potentially adding operational noise.
I don’t second-guess the design acumen imbued in the Holo May DAC, nor do I do this for the Chord DAVE (although the USB interface has been questioned as well as the power-supply… I have close knowledge of these factors)… I would like to read about a subjective blind comparison of Holo May versus DAVE… this could go on and on…
There are lots of peer reviewed published scientific experiments leading to this same conclusion. I have a book and website by a leading scientist in the field to recommend in case you’re interested. (I happen to find the area fascinating. Fortunately the book and website are written for the layperson.)
Before that, there’s a Wikipedia article about blind testing versus matching a familiar pattern that feels “right,” regarding the sense of taste rather than hearing, which I think is interesting and informative: New Coke - Wikipedia
OK, now the website and book:
Corollary…
“Influence of context effects on sound quality assessments”
Comprehensive reference:
AUDITORY PERCEPTION AND COGNITIVE PERFORMANCE
Angélique A. Scharine
Kara D. Cave
Tomasz R. Letowski
The book:
https://www.tandfonline.com/journals/rpac20
Excerpt:
Audition
Audition is the act of hearing a sound in response to acoustic waves or mechanical vibrations acting on a body.
Sound also may result from direct electrical stimulation of the nervous system. The physical stimuli that are, or may become, the sources of sound are called auditory stimuli. The human response to the presence of auditory stimulus and its basic physical characteristics of sound intensity, frequency, and duration is called auditory sensation. The three basic auditory sensations are loudness, pitch, and perceived duration, but there are many others. Auditory sensation forms the basis for discrimination between two or more sounds and may lead to some forms of sound classification (e.g., labeling sounds as pleasant or unpleasant). However, auditory sensation does not involve sound recognition, which requires a higher level of cognitive processing of the auditory stimuli. This higher level processing forms a conceptual interpretation of the auditory stimulus and is referred to as auditory perception.
Auditory perception involves association with previous experience and depends on the adaptation to the environment and expected utility of the observation. Depending on the level of cognitive processing, auditory perception may involve processes of sound classification, e.g., on speech and non-speech sounds, sound recognition, or sound identification. More complex cognitive processing also may include acts of reasoning, selection, mental synthesis, and concept building involving auditory stimuli but extends beyond the realm of audition.
The study of audition is called psychoacoustics (psychological acoustics). Psychoacoustics falls within the domain of cognitive psychophysics, which is the study of the relationship between the physical world and its mental interpretation. Cognitive psychophysics is an interdisciplinary field that integrates classical psychophysics (Fechner, 1860), which deals with the relationships between physical stimuli and sensory response (sensation), and with elements of cognitive psychology, which involve interpretation of acting stimuli (perception). In general, cognitive psychophysics is concerned with how living organisms respond to the surrounding environment (Stevens, 1972b). For the above reasons, Neuhoff (2004) refers to modern psychoacoustics as ecological psychoacoustics.
In general, all content of our experience can be ordered by quantity, quality, relation, and modality (Kant, 1781). These experiences are reflected in perceptual thresholds, various forms of comparative judgments, magnitude estimation, emotional judgments, and scaling. These characteristics define the realm of psychoacoustics and, more generally, psychophysics. Various types of cognitive measurements and methodological issues addressing psychophysical relationships are described in Chapter 15, Cognitive Factors in Helmet-Mounted Displays, and are not repeated here. The current chapter presents psychoacoustic relationships and builds upon the information on the anatomy and physiology of the auditory system presented in Chapter 8, Basic Anatomy of the Hearing System, and Chapter 9, Auditory Function. It describes a variety of auditory cues and metrics that are used to derive an understanding of the surrounding acoustic space and the sound sources operating within its limits.
Understanding how a particular sound is likely to be perceived in a particular environment is necessary for the design of effective auditory signals and to minimize the effects of environmental noise and distracters on performance of audio helmet-mounted displays (HMDs). Psychoacoustics provides the basic conceptual framework and measurement tools (thresholds and scales) for the discussion and understanding of these effects.
Thanks, I too find this area fascinating. Always keen to digest the latest research on this topic!