Implications of Esoteric G-0Rb atomic clock

The latest TAS (March 2008) has an excellent piece by Robert Harley: a review of the Esoteric G-0Rb Master Clock Generator, with sidebars on the history and significance of jitter. This Esoteric unit employs an atomic clock (using rubidium) to take timing precision to a new level, at least for consumer gear. It's a good read, I recommend it.

If I am reading all of this correctly, I reach the following conclusions:

(1) Jitter is more important sonically than we might have thought

(2) Better jitter reduction at the A-D side of things will yield significant benefits, which means we can look forward to another of round remasters (of analog tapes) once atomic clock solutions make it into mastering labs

(3) All of the Superclocks, claims of vanishingly low jitter, reclocking DACs -- all of this stuff that's out there now, while probably heading in the right direction, still falls fall short of what's possible and needed if we are to get the best out of digital and fully realize its promise.

(4) We can expect to see atomic clocks in our future DACs and CDPs. Really?

Am I drawing the right conclusions?
Ag insider logo xs@2xdrubin
Let me give this one a bump. Must have chosen the title poorly because I thought this would stimulate some discussion.
I own several Japanese CDs that state they were mastered using a Rubidium atomic clock.
>I read some of the article but the price of the trio left me speechless.

Sure, but that's sort of beside the point. The technology, if worthwhile, should trickle down. What's important, I think, is what this product tells us about the problems with digital today, the merits of various claims being made about vanishingly low jitter, and what we may be able to look forward to in the future.

Rja, that's interesting. Which label? Are they good-sounding CDs?
It's a fascinating product review & survey of the jitter problem. If as Joe Harley observes, the ear can easily discern improvements in word clock accuracy down to +/-0.05 parts per billion (translating into jitter reductions on the order of tens of pico seconds), then it would appear that there's still a long way to go toward true SOTA in digital sound. Better clocks are far from an exercise in diminishing returns.

JH makes interesting observations. Unlike the crystal oscillators found in conventional CDP clocks, the rubidium-based clock in the Esoteric does not exhibit frequency fluctuations as a result of instability in the power supply. This correlates with my own experience that improving the quality of DC power into a VCXO Superclock greatly improves its sound. He recounts the luddite position of the Audio Engineering Society in the early 90's (opposing the very notion of jitter), and the gradual acceptance of the concept in the general community. He provides a nice working definition of the signature sound of jitter as "loss of space & depth; softening of the bass; hardening of timbre; a glassy sound on initial transients (most noticeably on the leading edge of upper-register piano attacks); a metallic sheen overlaying the treble; and an overall flattening of the soundstage & homogenization of instrumental images with the stage." Finally, JH notes that the rubidium clock option elevated the Esoteric P-03/D-03 well above the music servers that he had formerly favored over the Esoteric. Perhaps there is hope after all for ye olde compact disk.
Will jitter be an issue in the future if music is primarily read from music servers?
WARNING: There is a lot of marketing going on here. Please consider the fact that frequency stability is not the issue of Jitter! The issue of Jitter and how that distorts audio at the A/D process is a problem of each sample coming at slightly the wrong time. Frequency stability has nothing to do with this. A small example:

The numbers 3,3,3,3,3,3,3,3 average out as the number 3.

The numbers 2,4,2,4,2,4,2,4 average out as the number 3. (This is as simple as 24 / 8 = 3).

The numbers 1,5,1,5,1,5,1,5 also average out as the number. (This is as simple as 24 / 8 = 3).

However, were these Jitter deviations from perfect timing (fluctuations from the ideal value, which was in this example, 3) you would have had worse and worse audio going down the line.

The marketers of all three pieces of equipment in the above example could easily all have said the same thing without lying: "Our Clock is so stable that you can play it for 3 million years and it will never be off by more than a fraction of a second".

Please notice the significance of this. Be aware of the logical trap that this "frequency stability" terminology is putting people into!

Rubidium is not necessary for timing accuracy, but it makes sense that a commercial rubidium reference oscillator would pay special attention to close-in phase noise in the vicinity of the main carrier, which is what's improtant in regard to jitter.
To put the frequency accuracy issue to rest, here are the facts. Standard (i.e. cheap) crystals are guaranteed within 100 PPM (parts per million) in the proper circuit. Add another 100 PPM for extreme temperature/humidity and circuit voltage variations. The total is 200 PPM or 0.02% of frequency accuracy. For a 1 KHz signal it will be off by 0.2 Hz. Even an acute dog wouldn't be able to tell the difference...
It's a joke when some manufacturers offer an "upgrade" to a TCXO option. How about upgrade to a low-noise oscillator? I'll take that option any day!
I'm having a little trouble following this, but I wonder if "frequency accuracy" is not being used in the same way by all of the posters above. Just to be clear, we are not talking about audio frequency response, at least as I understand what RH is talking about. Dgarretson's summary is excellent.
Jitter occurs all over the place. It is of no significance except at the real-time A/D process or the real-time D/A process, which is when the distortion takes place.

Drubin: The point that Serus and I are both making is that frequency accuracy means nothing regarding audio quality. It is used by some marketers of digital audio technologies to introduce new numbers with flying colors (they look really good on the ads). However, the point in Jitter is not whether the frequency is accurate, it is however the point whether the SAMPLES are accurate. And that's what I am trying to show in my example: samples can be way off and cause massive distortion at the D/A or A/D process but the frequency can be right on target. Frequency is a total amount of oscillations per unit time. Jitter is how much each sample is off time target each and every time. And with clocks, this can be 33 million times a second. So potentially, a clock can make 33 million little mistakes a second and still be accurate to a fraction of a second within years and years of running.

These two things must be differentiated. And it is important to understand that Bach sounds great, whether the music is tuned to A=440 Hz or A=440.2 Hz. Nobody, not even Bach himself, would ever notice the difference. But I think it's safe to say he wouldn't have liked Jitter.

JH's point regarding frequency is that a crystal clock is subject to transient fluctuations in output frequency caused by power supply variations & ripple, whereas the output frequency of a rubidium clock is inherently stable. He states that a transient variation in clock output frequency is "the very definition of jitter." Timing errors in the clock translate directly into a misshapen waveform and amplitude errors in the reconstructed analog signal, as well as introduction of spurious sideband frequencies unrelated harmonically to the original signal.

While I accept the benefits of ultra low-jitter clocks, I wonder whether some jitter in clock frequency is reintroduced in the clock-link cables that connect the G-ORb to the transport & DAC.
Do you really think jitter is the only reason for awful digital sound? The P-01 transport has very low jitter but still benefits from the Rubidium clock. There are other transport that have more jitter but sound as musical and with the same detail resolution as the P-01.

The P-01 transport has very low jitter but still benefits from the Rubidium clock.

I wonder whether some jitter in clock frequency is reintroduced in the clock-link cables that connect the G-ORb to the transport & DAC.

In digital, distance is very important. If a P-01 transport sounds better using an outboard clock, it speaks volumes about the low quality of the internal clock of that unit. The best scenario is when the low jitter clock is running the whole show at the very DAC chip. This way, data reclocking can be done right before conversion. If ever there is a better sound from using an external clock vs. an internal clock, it proves that the internal clock is of poor quality. Think about all the RCA and BNC connectors on the market. Think about all the digital cables. Why do they exist? Think about Eichmann, WBT, small metal contacts, 75 Ohm impedance plugs, balanced AES/EBU format, etc. etc. All of these differences are audible because Jitter is the result of a pulsating high frequency clock signal interacting with reflections as well as intermodulation with other induced ambient electromagnetic fields.

The aether is a chaotic sea of electromagnetic fluctuations going in every possible direction and at all possible frequencies. Just try to introduce a single frequency through this electromagnetic chaos without it even touching another airborne frequency -- and you will see that this is nearly impossible due to inductance and intermodulation. Therefore, shielding is of utmost importance.

I think the manufacturer in this discussion is suffering from what Freud called "Product Envy"
$15,000 for a clock? With that kind of moola one could buy one hell of a turntable set-up and still have $ left over for software. Oh, and jitter removal is on the house...
Dazzdax, The mods I've made to my CDP that have obtained the most audible improvement are refinements to DC power into the digital section: power to master clock, but also separate discrete power circuits into DSPs and motor/servo control throughout the entire digital section. It's conceivable that some manufacturers do a better job than Esoteric to improve performance of the digital section in ways unrelated to accuracy of the master clock. But the benefits that one hears through these improvements to the digital section are still most likely related to a reduction in jitter. If not, how do I account for the audible improvements that I hear in my modded unit? I can rule out upsampling technologies as a consideration, as no changes were made in this area.

Mods to the digital section make digital sound far from awful and in most respects RBCD has surpassed vinyl in my system. My experience confirms JH's finding that short strokes related to banishing jitter really open up the true potential of digital. Problem is this may require heroic efforts like $15K clocks or 300lb. battery supplies.
Audiofeil: "I think the manufacturer in this discussion is suffering from what Freud called 'Product Envy'"

I choose to dissemintate what I hold to be knowledge at opporunities when my conscience is troubled, for I have a general disposition to side with defending any truth when I suspect disinformation being spread. This reflects a type of world view which I attempt to consciously carry. You may choose to examine further any subconscience aspects of this behavior, but please be aware that in the human science of psychology, it is by now generally known that one tends to notice upfront those aspects of others which are in truth deeply embedded in our own subconscious selves.

The Memory Player, produced by the Nova Physics Corp. made clocking obsolete! Here's how it was explained:

"All clocking does is synchronize the laser with the DAC. Clocking synchronizes the beginning of the time the sampler is "open" for the laser to seek & read the bits. So clock & clock again & you only get the sampling period to start exactly when the laser begins reading a new section of the CD.

The problem is the bits can be read at any time during the sample period, and are read randomly. So the bit, a representation of a moment of music, is always late. Sometimes a little, sometimes intolerably late.

So clocking ever more precisely improves an area that is already nearly perfected in $200 DVD players at Walmart.

All Memory Players extract music bits as a mirror of the master. No more clocking to sync to anything, no jitter as nothing moves, only laser reading efficacy & ONLY reading music bits, hence, a mirror of the master.

As you have no error concealment bits to back up a missed bit, Memory Players must reread to capture all bits dropped in the first pass. If we used error correction bits, we're back to synthetics again so the goal is to reread more & more & faster & faster. In this way, very few bits will be lost & the ONLY bits you CAN hear, are MUSIC BITS.

It is not dependent upon a clock. All of the music bits are on memory & just stream off the memory in the order & TIME they were recorded.

The small community that is either copying the MP or designing their own now that the cat is out of the bag, know the CD player as we know it is going extinct. Good riddance. It was a poor compromise they chose in 1982. They had it nearly perfect (& perfect on CDs containing programs instead of music) but relaxed error correction to fit Furtwangler's Beethoven's 9th symphony on it & digital audio was never right again."

So who would pay $15k on a clocker that merely reduce jitter?
Rather than open yet another thread on MP(I've heard MP & yes it does sound good), I'll address the post by observing that the manufacturer's claims concerning MP theory of operation remain opaque & controversial. There has been too much delay bringing MP to market to consider it at present a serious threat to existing technology. Finally, there appear to be questions as to whether its technology is unique and patentable. The latest AA thread below addresses the controversy & also includes Gordon J. Rankin's recipe on how to build a "DIY memory player" in several easy steps. As regards music servers in general, in his review RH elevates the Esoteric with rubidium clock above HD systems like Sooloos & Qsonic. In any event with servers there is still the need for a clock at the DAC.
This is certainly a naive question, but why can't a CD player store the entire contents of a disc in memory, then send them to the DAC, which would be the equivalent of reading a file from a hard drive? Is that the definition of a music memory player? If it is, why is that controversial? Not spoken, of course, as a digital engineer.
Lapaix, having worked for several years trying to get the ultimate jitter-free sound from a computer source, I can say that it remains better, audibly better, to play files from USB RAM rather than from hard drives. Yes, hard drives are read in packets, and yes, they are buffered extensively throughout a computer system's busses and operating system and playback software and hardware drivers, but the sound remains better from a USB RAM. And this remains worse than the sound achieved when slaving a CD player to a master dac synchronously. The ultimate point in buffering is not the size of the buffer, but the quality of the clock signal. And the quality of the clock signal depends ultimately on all of the surrounding factors including: its own power supply, the radiating ambient high frequency EM signals from other quartzes and other busses, vibrations (hard disks vibrate), and many other things knowns and possibly unknown. THere are several forums on the internet where people have been discussing computer audio for years and some have reached a very high end sound this way. However, once you put all the solutions up to the line and really compare, it remains improbable that merely enlarging a buffer will take away all the digital nasties. Another way of looking at it is that a CD already is a buffer. It is the buffer that is holding the DATA which was recorded at the finite moments of A/D sampling (during the recording). Whether CD, DVD, hard disk, ram, or anything else, the playback depends on the quality of clocking it.
The G-0Rb uses a Rubidium clock. That is not an atomic clock. An atmoic clock is a Caesium clock!
Rhagen, WRONG! NASA uses both Rubidium and Caesium atomic clocks. As a matter of fact most of the recent space probes and satellites use the Rubidium Atomic clock that I use in my system, it is built by EG&G.
I believe this is defined more by the time-base("atomic accuracy" as determined by atoms within an element shifting between discrete states of energy) than it is by the element per se. Clocks with atomic accuracy can utilize Rubidium, as stated by European Space Agency in its description of the Galileo satellite:

"The Galileo satellites will carry two types of clocks: rubidium atomic frequency standards and passive hydrogen masers. The stability of the rubidium clock is so good that it would lose only three seconds in one million years, while the passive hydrogen maser is even more stable and it would lose only one second in three million years. However this kind of stability is really needed, since an error of only a few nanoseconds (billionths of a second) on the Galileo measurements would produce a positioning error of metres which would not be acceptable.

An atomic clock works like a conventional clock but the time-base of the clock, instead of being an oscillating mass as in a pendulum clock, is based on the properties of atoms when transitioning between different energy states.

An atom, when excited by an external energy source, goes to a higher energy state. Then, from this state, it goes to a lower energy state. In this transition, the atom releases energy at a very precise frequency which is characteristic of the type of atom. This is like a signature for the type of material used. All that is needed for making a good clock is a way of detecting this frequency and using it as an input to a counter. This is the principle behind an atomic clock.

The transitions between energy states can take place by releasing or absorbing energy at optical or microwave frequencies. An atomic second corresponds to 9 192 631 700 counts of the frequency of the energy detected in the transition of the Cesium 133 isotope when exposed to suitable excitation."
I thought we were talking about the international atomic clock which keeps the official time. That is not a rubidium oscillator but a caesium oscillator. There is now however a new invention unveiled a couple of days ago which breaks new ground.
The new dCS Scarlatti sepearte clock generator has got an option where you can put an antenna on the roof and syncronize the clock with the international world clock by sattelite.
This type of product is already obsolete and I am sure that many audiophiles aren't even aware of it. We are on the verge of a imminent change to USB driven computer front ends that will sonically outclass the traditional CD transport and D/A converters here. Even the cost no-object "Uber" technology products. Here is a short understanding to why: once a CD is properly converted to a computer hard drive (with a true lossless format) there just isn't a need for something like the Esoteric "Superclock". With the hard drive containing the music data in a much purer form, it can then be sent to a USB D/A converter, via a USB cable, without the overlying clocking issues that creates such a headache sonically, i.e. a much purer methodology. In this new methodology, only one decent clock (read not overtly expensive) will be needed inside the D/A converter itself (instead of one at the tranport then another "Uberclock" at the other end attempting to "fix" and "massage" very ugly timing issues). Therefore, in an excellent designed USB D/A converter being driven from a hardrive without the ugly timing issues. We will be able to say "Goodbye!" to typical transmitted jitter problems. Say "Goodbye!" to transport differences! Say "Goodbye!" to CD treatments! And finally, say "Goodbye!" to high dollar "band-aids", uh..errr..."Superclocks" - (such as this Esoteric). We are on the precipice of a very exciting breakthrough with some new upcoming USB dacs that will sound much more analog than most of us have ever imagined. Sorry Esoteric, I'd really like to give you credit for this "breakthrough", but in my opinion, the true sonic breakthrough in digital will be in USB connected products that don't even need a clock such as this.
Since there are already plenty of USB DACs out there, what is the big breakthrough that is coming?
The big breakthrough in upcoming Dacs has much more to it than just if they are USB connected. It's more to how the data is streamed from a hard drive to the USB dac. There are HUGE sonic gains to this methodology ONLY if it is properly executed. At this moment, there are only a few select digital designers that even know how to do this correctly. Most that have a USB connection are not taking advantage of the elegance of streaming the data via a USB to avoid the jitter and many other problematic issues that are inherent in our current way of digital playback. Once we get a digital couple of companies that surface into the mainstream (that actually know how to do this correctly via USB), I think many audiophiles will be STUNNED to hear the analog fluidity that cannot be achieved with any other form of connectivity. Other digital companies will have to notice of this leapfrog improvement in sonics. Subsequently, they will (most likely) just follow suit and copy, i.e someone else does it right first, then the "other" digital companies will copy the "correct" way to do it. I figure we are looking at sometime later this year for the first breakthrough USB dacs to surface. I know, I know... we've all heard these sort of "statements" many times before. This time though, I think we will finally have digital offerings that can actually have most (if not all) of the inherent musicality that was only inherent via an analog front end. It's about time!
C'mon Ehider, tell us who is doing it right today. Whose gear did you hear that convinced you of this rosy future?
Most of this conversation is over my head, but Ehider are you talking about the Asynchronous Mode USB Audio in Gordon Rankin's new DAC's?
I wish I could talk more about what I recently heard (I've been sworn to secrecy). As to my earlier posts, I was not talking about a USB DAC that is currently available to the audiophile public at this very moment. Based on my discussion with the designers, it should be released within the next six months or so. In terms of the question regarding Gordan Rankin's product, this may be part of the "new wave" of revolutionary USB connected products that sonically prevail over typical transports/DACs. Unfortunately, I have yet to hear Gordan's product myself to determine if it also reaches above the levels which we are accustomed from typical "statement" digital offerings. As far as the "Beta" pre-production USB DAC that I heard though (from a company other than Gordan Rankin's) it was a serious jaw dropping experience!
So, now we are finally approaching the pure "bits-are-bits" theory with the USB based digital music reproduction (as was intended from the beginning) and we're leaving the vagueness of the bits-are-bits + something magical concept. This could be a manifesto. To all audiophiles worldwide: Get rid of those mediocre CD transports!

AFAIK any digital signal that requires conversion to analog (which is the format of the sound that we hear) requires a clock. So even USB based DACs will require a clock for the data (asynchronous or otherwise) to be converted to analog. Though not exactly the same, it's like tuning into your FM radio station.. If you're not tuned into the right frequency, you won't get the full sound. If your recording runs at 44.1khz, you need a clock that runs at 44.1khz.. Can't get away from that clock.

Bottom line: bits can be bits until the point where it's converted to analog, at which point you would need the most accurately constant (i.e. lowest jitter) clock possible to ensure the sound's integrity with the lowest jitter. One solution?...the atomic clock.
Kamil is correct about the need of some sort of "clock" . The point I've been making with my posts is that the synchronization of TWO clocking signals, between a "traditional" type of transport and a DAC, is completely eliminated with USB connectivity (provided it is designed correctly). With USB, we are down to just ONE clock at the DAC. With a hardrive having the ability to stream perfect music data and NOT having to carry an overlying clocking signal on the USB cable, the improvement is substantial. The sonic benefits are HUGE. Most importantly, the need for a "bank account breaking" UBER clock like the Esoteric is eliminated altogether. The sonic potential of the USB approach is way cheaper (no need for an UBER clock) and yields a superior sonic result to boot. This is the future of the best digital sound.
Ehider ... you don't need USB, you just need a buffering and reclocking DAC, like the Lavry 924. A relatively small RAM buffer will allow for any drift between the transport clock and the DAC master clock.

Of course, the more stable the DAC master clock the better. This may be where a rubidium type clock is useful .... I don't know.

I'm not sure where current technology is with respect to the relative influence of clock imperfections versus DAC non-linearity (both are probably an order of magnitude better than current speaker technology).

One last thought ... it's true that ADC clocks are equally important, and therefore a better ADC clock will lead to a better remaster. However, the implication is that all early digital recordings (ADAT) are forever unrecoverably distorted by the relatively poor clocks used at the time.
Sean, is it possible once jitter is introduced into a specific recording to remaster this recording in such a way that the jitter could be eliminated? If this is not possible, why not? Are those early digital recordings sounding bad because of the high jitter content? There are also oldskool digital recordings (from 1980/1981/1982) that sound great, how could you explain that? Pure luck?

Perhaps a re-iteration of my explanation is in order. All SPDIF digital connections (read "traditional") cannot sonically compete with a properly designed USB Dac (being driven by a hardrive). Even if the traditional digital connection is being "buffered" or "re-clocking" the data, etc. The traditional digital connection scheme was seriously flawed from the get-go. UBER designed "re-clockers" or "buffering" schemes are only band-aids. They work to a point, but still don't quite give us the true analog purity we were all hoping to achieve. Closer yes. Perfection, not by a country mile! Too many of these "band-aids" are damn expensive at that. Of course the proof is in the pudding. The recent USB Dac I heard comes so close to sounding like analog that I was shocked that ANY digital could sound this good. No other digital scheme I've heard comes nearly as close (and I've heard way too many to count).
Ehider, I'm reluctant to open this can of worms, but have you heard the Nova Physics Memory Player? If so, how does it compare to the USB DAC you heard?
Ehider ... USB DACs are RAM buffered because USB does not stream the data at the bit rate required by the DAC.

Since it's possible to buffer for USB then it's possible to do the exact same for SPDIF.

A more likely explanation is that the USB DAC you heard happened to be a better designed DAC (or more to your taste) than any other SPDIF DAC you'd previously heard.
Chris, I can't imagine how you could remove jitter from an existing digital recording as there's no inherent information that would allow you to determine the jitter in order to subtract it.

I think a bad digital recording is destined to remain a bad digital recording. However I hope to be proven wrong, because a lot of good music is otherwise beyond salvation.
Sean; the USB DAC that I have been citing does NOT connect to a CD transport, It connects directly to a computer i.e. my posts statements regarding the "hard drive" . With this methodology, the computer does not have a SPDIF (traditional) connection whatsoever. It streams pure data directly from the hard drive, WITHOUT the subsequent clock data. It is much different with this methodology. (It is also much more elegant). This is the ONLY way the sonic improvements that I am discussing can have any meaning. If there was a "traditional" CD transport involved, the USB carrying the data wouldn't yield any sonic improvements whatsoever (BTW: this is where your assumptions would be absolutely spot on). So, the complete elimination of having to carry clocking information from the CD transport to the DAC is where the huge jump factor relies (remember, the music data is now on a hard drive). With this in mind, any simplification of transferring the music data from point A to point B really does yield sonic wonders.

Drubin; Yes i have heard the Nova Physics player. I think it is an admirable attempt at solving many of CD issues. Like other offerings though, it is still a band-aid approach that doesn't simplify the transfer of music data as well as the USB approach . Again, the proof is in the pudding though. And this player doesn't actually stand at a complete different level above other UBER priced digital products. It is really good, yes. Revolutionary, well if so, then it should absolutely crush any other digital offering IMHO (which it doesn't achieve).

BTW: Even though my posts have been heavy handed technological discussions, I will always favor the digital product that sonically comes closest to a top level analog rig. IMHO way too many technological assumptions, WITHOUT direct comparison to a source of great music perfection (in my case, a great analog rig) are one of the reasons we are now accepting the crazy expensive digital mess and these inherent "band-aids".

Even if the best sounding digital front end turns out to be a Donkey spinning a CD, using a fifty cent flashlight, connected to an electronic slide rule, amplifying via a megaphone. If this "front end" truly sounds closer to a great analog rig, I'm buying it! ....and alot of Donkey food ;-)
This might answer all your questions.

I believe that the reactions of all the reviewers that first heard the Memory Player were NOT all hype. For Harry Pearson to say "He was in AWE" is huge. If his statement was hype, well he must be a "silent" investor in Nova Physics Group.

To be able to explain the shortcomings of the CD playback system and the approach they took to mitigate it is simply not a band aid approach, in my opinion.

Sounds like you are talking about a music server which utilizes USB because you mentioned streaming? If not, what about the playback software and EMI/RF issues with PC playback. These have a huge impact on sound. Will there be a special PC with this new USB wonder device? I thought music servers utilizing network protocols may have been the future?

I can't wait to replace my transport/dac with an HD based system. Seems like not much can beat the Meitner/Esoteric stuff yet, but it certainly seems close. Do you have experience with these transports and would you say this new device bests them? I hope so.
Rgt; I seriously applaud the Nova player designers. They are solving issues that most other digital solutions fail to address. I have no doubt that the Nova is very close to the "top of the heap" digital offerings at this point in time. Much closer to analog, absolutely. Close your eyes and absolutely match analog though, just a smidgent short (but the Nova is very special sonically IMHO). From a technical analysis, the USB solution (that sonically amazed me) avoids interleaving the clock data with the streaming digital information (as compared to the Nova and others). I should note that there are many similarities here with both the Nova and USB solutions. They both address the read error issues which I suspect are part of the sonic 'breakthrough" toward analog. I still hold the direct comparison to analog as my final "tool", i.e. the digital solution that comes closest to sounding like a great analog rig or a master tape deserves the "top of the heap" moniker.

Askat; I think you are correct to assume we need to watch out for EMI/RF issues in the computer. I myself was wary of sonic gremlins associated with a computer's hard drive as the digital transport. Thankfully, the potential problematic gremlins seemed to be entirely absent when I heard the computer to USB DAC solution. (The computer was a current generation Apple computer with the CDs transferred to the computer's hard drive via Apple's internal error correction enabled). Are Apple computers inherently low EMI/RF designs? I have no idea. I do know that the particular Apple to USB DAC was the best digital solution that I've ever heard in terms of managing to sonically emulate a great analog front end.
Why is it not possible to repair a jitterized recording? Jitter is the minute variations in the time intervals between the bits, so if you remaster the recording using some form of reclocking device, you can get rid of these minute variations. How would a jitterized recording sound if it was remastered using the atomic clock in the reclocking circuit?

All of this sounds promising and something to look forward to. I'm wondering about any improvement here that can possibly address the limitations of red book brick wall filtering at the high freq. level , or will that still be the final impassable frontier to analog comparisons.