Thanks for asking this question. I was just about to post something similar. If one has a decent CD player -- say, for example, a Rega Apollo CDP -- is jitter an issue, or is it safe to assume that the manufacturer has dealt with this in making the one-box unit, making the transport section and DAC function together in a way that keeps jitter to a minimum?
How can I tell if I need a better clock for my DAC?
I was interested in the responses to a related post by leemaze this week, saying that a Synchro Mesh was a good way to improve a DAC with subpar jitter. I have a Cambridge CXU, with an inboard DAC; how could I determine how much jitter it has?
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In layman’s terms, you are referring to jitter correction. Jitter refers to the timing of the data stream (bits, or 0’s and 1’s) and insuring that they all arrive at the same time for processing. The Synchro-mesh and related products insure this correct timing plus can reject noise. No CDP is jitter-free. The design and implementation will determine how well a standalone component or dac/transport will correct jitter. A manufacturer is also dealing with a price point of the component which includes the quality of electronics, vibration control of the transport, the power supply, and function of the laser. Other members, including Steve N. (audioeng) can explain jitter correction in detail. Steve can explain measuring jitter since that’s what he does. I thought I might start things off with the basics since it is complicated subject matter. |
....No CDP is jitter-free... And as you read enough on this forum you'll likely conclude that the interconnect cable between the transport and DAC also introduces jitter, and perhaps other items. This is why I've always maintained that one must rely on their DAC to do its job and reduce or eliminate jitter given its re-clocking and/or other proprietary technology. And in this context, when I write "rely on their DAC to do its job and reduce or eliminate jitter", I don't believe this is a stretch as far as technology capabilities are concerned. This is why many DAC manufacturers proudly advertise this is what their DAC is doing, among other things. Frankly, I don't understand why there is so much hullabaloo regarding jitter. Apparently, it's as ubiquitous as air anyway so at some level you just have to live with it. |
the analogy that could relate would be , everyone has stress in their lives but life is so much better when you reduce that stress to a minimum. @tooblue I agree with you. But in using your analogy, there is more than one way to reduce stress. For instance, one could take prescription medications, practice yoga, or my favorite, listen to music of choice. Similarly, there is more than one way to reduce (or eliminate?) jitter. I don't see the rationale behind trying (whether successful or not) to reduce jitter at the transport (i.e have better clocking at the transport), because a good DAC will re-clock anyway. It is conceivable (not saying this is the case, although it wouldn't surprise me if it is) that a quality DAC will perform its voodoo (jitter reduction, re-clocking, whatever) regardless of the signal it receives and essentially "undo" or "disregard" the voodoo that was performed prior to it receiving the signal. |
Clocking before the DAC can make a huge difference. Not speaking on theory, but experience, which matches many other’s experience as well. Too many voice their opinions, often based on theory, or just a false or incomplete understanding of how things really work, without actual experience. I’m not an expert, but know what I hear. I already have a good DAC, but added an ISO Regen and SOtM clocking device and it made a significant improvement to the sound. (And linear power supplies to the ISO ansd SOtM which brought it up yet another level.) More weight, more body, resolution, improved timbre, more "analog" (though I dislike that term). Of course you also need a downstream system capable of revealing these improvements. Many or most DACs will benefit from these devices, incuding super high-end ones. I’ve heard a few situations where there was not consistent improvement among users, such as PS Audio and Exasound DACs and maybe a few others. Likely all DACs under $2-3000 will benefit and many more over this amount. I’m not really interested in those who say why not buy a better DAC to begin with, or "USB is flawed, why bother", or especially "expectation bias" (that’s BS). Hey it’s my money and I’m having fun. If things don’t work, I sell them, but that’s not the case for these devices. Plenty more info on this topic on the Computer Audiophile forums where users share their actual experiences and what devices brought about (or didn’t, as some work better than others) these improvements. |
Clocking before the DAC can make a huge difference. Agree. I use a PS Audio PWT transport which, as many of you know, reads the CD and loads it into a buffer. It then clocks the data and sends out a timed bitstream to an external DAC. This is why a good cable is needed to preserve the reduced jitter signal. |
Interface jitter is a fact of life. It doesn’t matter what you do. The only complete solution to interface jitter is to select a DAC device that ignores the incoming clock and uses it own internal asynchronous clock. Note that this will still leave you with the intrinsic jitter of the device itself but at least you won’t have to worry about fancy cables or what length to use. Alternatively, reclockers and a random selection of cables might help reduce interface jitter if you want to stick with a DAC that does a poor job of eliminating incoming jitter itself...kind of a dogs breakfast of a solution as you can never totally get rid of interface jitter and you would not even know if you had. |
What you can do at home is listen. If you hear a good track on another friends system that has superb focus, clarity and liveness and your system makes the vocalist 2 feet wide and the guitar 1 foot wide, then you have jitter. If you hear echoes or "fill" between instruments in your system and not in your friends system, you have jitter. There are standard jitter tests that display the spectrum of the jitter on the D/A output given a standard input signal from a disk. If you were an engineer with the right equipment you could perform these measurements. The problem is that even if you could, the results are not well correlated to listening tests. I mean really bad jitter in the measurements is audible, but more subtle jitter can be just as audible and will not show up in the measurements. This is the problem with the state of our measurement technology today. May improve in the future though. What you can do at home to improve jitter from your transport is: 1) treat the disks with Ultrabit platinum 2) spray-coat the top side on the disk with a rubber coating to reduce vibration - get this at Home Depot or Michaels etc.. Mask it properly with thin card stock. 3) re-write the disk on CDROM using DBpoweramp on PC or XLD on Mac - this improves the pit shape over the commercial disk 4) pay a modder to install a new clock and clock voltage regulator/power supply #4 will make the biggest improvement in a CDP, but you will still benefit from 1-3 even with the modded clock. Steve N. Empirical Audio |
is it safe to assume that the manufacturer has dealt with this in making the one-box unit, making the transport section and DAC function together in a way that keeps jitter to a minimum? Certainly not. If this were the case, I would not have modded CD players for 10 years and got paid handsomely for that. I don't mod anymore. Steve N. Empirical Audio |
A clock is such a small part of the big picture . I have found if you have a external power supply this is vastly more profound an upgrade. The Mojo Illuminati -2 external power supplies are miles ahead of what are stuffed in the stock boxes. i have a Lumin dac- D-1 Player that comes with a crappy smps , evrn a Sbooster Linear supply is much better. The Mojo is on par even the Lumin flagships S-1 Power supply at 3x the moneys . my point is if you can improve your power supply well worth the efforts. |
This Stereophile AES J-test includes a very high level signal mixed with a LSB (smallest signal) and is a great test for interface jitter and any modulation distortion. Ex 1. Benchmark DAC3 HGC, high-resolution jitter spectrum of analog output signal, 11.025kHz at –6dBFS, sampled at 44.1kHz with LSB toggled at 229Hz: 24-bit TosLink data (left channel blue, right red). Center frequency of trace, 11.025kHz; frequency range, ±3.5kHz. https://www.stereophile.com/images/1117BDAC3fig11.jpg There is no jitter (spurious signal) visible above -150 dbfs noise floor on the analog output. This means there is excellent interface jitter rejection. —-&———————— Ex 2. Schiit Yggdrasil, 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. https://www.stereophile.com/images/217Schiitfig12.jpg There is jitter (lots of low level spurious signal at very specific tones).... probably inaudible but it is there. |
This DAC has no reclocker, just an AK4113 receiver. It would benefit greatly from an external reclocker like the Synchro-Mesh if the S/PDIF input is used. Are you certain that the j-test plot was using the S/PDIF input and not the USB input? The Benchmark 3 on the other hand does a good job of rejecting jitter compared to prior models. Reclocker not necessary, however you are stuck with the sound of the master clock in the DAC. If you like that, nothing more to do. Steve N. Empirical Audio |
In response to the OP, jitter never goes away; in the best DACs it is reduced to a minimum. The best way to keep jitter to a minimum is to see that your component has one of the high quality, high specification, clocks. If it doesn’t, sell it and buy one that has a great clock. At the moment the best clocks used in very high quality consumer units are referred to as a femtoclocks with about 80 femtoseconds of jitter.* At least one manufacturer, Wyred4Sound, makes a femtoclock available as an upgrade to existing DACs. Reports are that the clock change alone makes for better SQ. That being said, there seems to be little doubt that the quality of the incoming digital signal (jitter, noise) will affect the amount of correction the DAC has to do and so affects SQ. That’s why, for example, some disk players can sound better than others feeding the same DAC, and why some use reclockers in front of their DAC. As to whether you need a better clock, that's hard to say. Do you need better SQ? Will your associated equipment allow a better clock's effect to be heard? How critically do you listen? Can you afford? No one can answer for you. *There are more accurate clocks but they are used in the space and defense industries and are very, very expensive. |
The best way to keep jitter to a minimum is to see that your component has one of the high quality, high specification, clocks. If it doesn’t, sell it and buy one that has a great clock. A good oscillator is a good start, however, there are a lot of other things that take that 80 Fsec and turn it into 200psec. These things include: 1) bad choices for logic family for the associated circuitry 2) poor board design, sliced-up ground-planes and crosstalk 3) Poor power delivery and decoupling caps choices and locations 4) slow reacting power supply and regulators 5) too much sharing of the power between oscillator and other circuits 6) no clever circuit design to minimize jitter It turns out that these things are actually more important than having an oscillator with 80Fsec of jitter or one with 1psec of jitter. there seems to be little doubt that the quality of the incoming digital signal (jitter, noise) will affect the amount of correction the DAC has to do and so affects SQ. Yes, but it’s not correction, it’s simple D/A distortion. It’s not so much the accuracy of the clock that is important, its the jitter and phase noise specs. Steve N. Empirical Audio |
This Stereophile AES J-test includes a very high level signal mixed with a LSB (smallest signal) and is a great test for interface jitter and any modulation distortion. But which sounds better? :) |
I suppose my response was an "all things being equal" one. Of course if the rest of the circuit is screwed up, the best jitter clock in the world will be of little use. So I assumed the circuit was otherwise competently designed and executed. A good example of the importance of the clock in an otherwise pretty well designed circuit is the optional upgrade to the femto clock by Wred4Sound. Apparently the improvement is SQ is undeniable just by going to a better clock. Yes, "a good oscillator (clock) is a good start". Without a good start, you have nowhere good to go. So what is this argument about? I'm not here to show off what I know about bad circuits. |
The issue is implying that only a good oscillator is required. That's what the argument is about. It purveys the wrong impression. This is like saying that only a good D/A chip is required and you have the perfect DAC. Not by a long shot. Like most things, the devil is in the details. Steve N. Empirical Audio |
The issue posed by the OP was about a better clock. So my response was about clocks. At the current state of the art, a femtoclock, while not a sufficient condition is IMO a necessary condition to the best possible SQ. Also, generally speaking, if a maker implements a femtoclock, chances are the rest of the unit compliments it. In other words, it's a good sign of quality . . . generally. If Steve N. wants to provide exceptions that he knows of, I'm all ears. |
Proper spdif connection between transport and dac should be made using 75ohm bnc. rca is not true 75ohm and this can also introduce jitter. https://www.markertek.com/productImage/450X450/B-PF.JPG https://www.amphenolrf.com/media/catalog/product/cache/1/image/9df78eab33525d08d6e5fb8d27136e95/0/3/... Cheers George |
Here's an article that touches om the subject even though ge talks more about usb inputs. He also has a list of components he recomends, including dacs. https://darko.audio/2013/07/when-should-you-use-an-external-usb-spdif-converter/ I suspect a lot of new dacs sound better than your Cambridge but it doesn't have to do with just jitter. |
Thanks, everyone, for your inputs. Unfortunately, much of what was said went over my head.... You’re welcome. Honestly I think you may be over thinking this. Go with whatever your monetary budget allows, your personal listening impressions, manufacturer reputation and other customer testimonials. After all that then consider jitter and other technical measurements. Just my recommendation. |
Here is a video I often recommend with a simple explanation of what can go wrong with a digital signal fed into a DAC. It includes the topic of jitter. While discussing the signal passing into the DAC, its principles can also apply to the signal within the DAC unit. Please let us know if this helps. https://www.youtube.com/watch?v=grzoqEb2KMk&t=2s |
Proper spdif connection between transport and dac should be made using 75ohm bnc. George - You are dead right. Just buying a 75 ohm cable with BNC's does not guarantee that the BNC connectors are 75 ohms either, particularly from Marketertek. I have 75 ohms cables with 50 ohm BNC on the ends from Marketertek. Also, BNC to RCA adapters should be 75 ohms as well. Here are some cable jitter measurements, including some from Markertek: http://www.audiocircle.com/index.php?topic=154425.0 Steve N. Empirical Audio |
I suspect a lot of new dacs sound better than your Cambridge but it doesn't have to do with just jitter.Thanks for the additional references on dacs -- that's a good start! As for the quoted comment, @headphonedreams may be right about that, but it leads to a more basic question. By my standards, the Cambridge is a fairly expensive (and well-reviewed) unit, but the sound it gives to a Redbook CD doesn't compete with that of my more modest phono (Technics SL-D2 with a Nagoka MP-110). Can I expect to get comparable sound quality with a CD player and DAC, without spending well over $1000, or is this the unavoidable result of the 44/16 format? |
Sorry that first 75ohm bnc plug link, was a bnc to rca adapter, not a plug. what I meant to put up was this. https://www.bhphotovideo.com/images/images2000x2000/Comprehensive_BP_2C7559P_BP2C7559P_75_Ohm_Male_2... Cheers George |
By my standards, the Cambridge is a fairly expensive (and well-reviewed) unit, but the sound it gives to a Redbook CD doesn’t compete with that of my more modest phono (Technics SL-D2 with a Nagoka MP-110). Can I expect to get comparable sound quality with a CD player and DAC, without spending well over $1000, or is this the unavoidable result of the 44/16 format? A confirmed analog guy, I have learned, but only within the past year, that Redbook CD can be as good (if not exactly the same) as a very good vinyl set-up. With more consistency as well as the usual digital advantages, digital has come a long, long way. I also learned a long time ago that "well reviewed" in the audio press means practically nothing. Better to spend some time and energy on the forums. This one and head-fi and computer audiophile, for ex. I did 2 things that brought my CD listening to a higher level than I ever thought possible. One cost a bit of money; one cost me nothing. First I sourced a high performing DAC* directly from China. Not very expensive from my point of view, but still just a bit more than you may want to spend. But I think one can do well for less. Second, rather than use a CDP, I ripped all of my CDs to a portable hard disk which I had hanging around and played them through my (also hanging around) laptop directly into the DAC (easiest if the DAC has a USB input). Sound is better than using my Oppo to play disks through the new DAC. Also, using JRIver I can control my digital listening entirely from my phone. *And yes it has a femtoclock, in fact three of them. |
My DAC is an LKS MH-DA004. There’s a thread about this DAC on this forum. Owning a Chinese DAC is a bit of an adventure, but worth it IMO. I believe there are other Chinese DACs out there for less money that also offer extraordinary value. It’s definitely the road less traveled though. As for ripping CDs and getting better SQ, I think my experience is shared by many others. Your CDP has a severe limitation in that it does not support asynchronous USB, usually evidenced by a USB "b" port . See https://www.youtube.com/watch?v=dBLto-DlGJo You might also look here and in the PC Audio forum for advice in getting improved SQ from ripping. |
Seems like even a dCs dac gets better with a better clock. Better clocks and cleaner power can probably help almost any dac. https://forum.audiogon.com/discussions/dcs-puccini-clock |
@cheeg, Installing a better clock in your CXU would likely be cost prohibitive. Also, there's no telling if the rest of the CXU circuitry would reveal what a new clock would offer. If you want better digital performance then you get from the CXU, better to sell it and start over. Or you can begin by adding a separate DAC and using the CXU as a CD front end. |
