What does jitter sound like?

[shenzi]

Supernatural effects makes a change from quantum effects, I suppose.

 

The trouble with a lot of listening tests is that it is differences which are claimed and without references to the original recording, how do you tell which is the improvement? A device may make a piece of music sound hard and clinical and can be modified to sound warmer, more dimensional, etc but what if none of those things were on the original recording? Maybe the producer aimed for hard and clinical.

 

Back to the jitter bugging.

 

[tfarney]

"minutae that means nothing poor old audiophiles who just want their computers to be the main source of their Media and a good sound."

 

Have we met? You seem to know me so well.

 

Actually, I'm thankful for Steve's last response. If jitter mostly effects transient response (which I did not understand is unmeasurable) then I can relax, certain that I need to concentrate on listening. The speed and precision of my system, it's ability to reproduce the impact of the attack of cymbals, bells, drums, etc, is so much better than it was in the old days. Really, I know where to put my money, should I ever come across any - speakers. And then wait patiently for the industry to get over "loudness."

 

Tim

 

[tfarney]

"Worse than that, it may persuade some of them to buy something expensive for one part of a system that has more serious problems elsewhere.

 

It's not a good situation and it's not helpful, but worse still it is likely discourage the wider and considerably larger audience that is currently switching to home media computers and limit the scope of this Forum to the tiny and marginalised minority of audiophiles."

 

Tell it, brother Ashley. Can I get an amen?

 

To all new to computer audio: It is simple and cheap. Take the shortest path, hook it up to your system and listen. Really. The most complicated thing you might need to do is put an inexpensive DAC, outside of your computer, in line on the way to your system.

 

If you really love complications or believe you can tweak it to perfection, there will be plenty of time for that later.

 

Tim

 

[Tog]

No ..you have definately lost me...

When I first started looking at computer audio I was captivated by the new words that sprang up on many of the sites. Those same sites that were brim full of esoteric amps, dacs and tubes that could be rolled if you were really cool. then there was jitter, complete with dire warnings about its pervasive nature and how any fool would know that it must be destroyed at all costs. To do this may involve handing over a sizable wedge of cash to a very nice man with a jitter demodulator (Bel Canto may have one) or a side pod gizmo usb to spdif jitter deregularizor from Empirical.

 

I'm sure jitter is real and may well be evil but if you can hear it you will either be totally mad or have a perfect recording.

 

Me? I'm more concerned about recording quality but I may be tempted by those solid kryptonite isolation platforms from papua New Guinea.

 

Yours with a mild fever

 

Tog

 

 

[drdigital]

Tim, Amen and Hallelujah!!!!!!!

 

[tfarney]

Were we separated at birth?

 

On behalf of our host and the rest of the loonies in the bin, welcome to CA. I love this place as there seems to be room for tweakers and pragmatists alike, with a fair amount of humor preservation in the mix.

 

Tim

 

[Roseval]

If you consider the USB specification which was developed by Compaq, HP, Lucent, Intel, Microsoft, NEC and Philips, plus plus a few more A4 sheets full, that comprise a Who's Who of the Industry, all who are technical leaders in their particular fields and likely to have done a proper job, you may question why anyone of lesser provenance might believe he knows better.

 

Well spoken, I think everybody knows that if any of these companies embark on something like e.g. USB it is always with top quality audio as one of their highest priorities.

The quality of their engineering is unequalled indeed, that's why Microsoft Windows never crashes.

B.t.w. The Who's Who lost a couple of their members years ago (Compaq and Lucent don't exist anymore as independent companies. Hired the wrong engineers?)

 

Might it be that a site called Computer Audiophile is the right a place to discuss Audiophile topics?

 

 

[audioengr]

"I presume you have measured this and therefore have the figures to back this up? If so could we see them for ourselves please."

 

Sure, I make measurements, but there is no standard for transient response measurements, so how can one compare apples-to-apples anyway?

 

The only thing that is done routinely is a square-wave, which is insufficient. As for slew-rate, my new DAC does .24V/usec with a 1kHz square-wave at -12dB. This tells you nothing about how it will sound.

 

Transient response should be measured over a wide variety of stimulus, including:

 

1) different amplitudes

2) different frequencies

3) different loads

 

I believe that when it's consistent for all of these then it starts to sound like real music. If the industry were to adopt standard stimulus and the above three measurements, then we could start making some valid comparsons among equipment.

 

Steve N.

 

[Tog]

If there is no standard way to measure something there are no valid comparisons that can be made but a great deal of tail chasing and head scratching will inevitablly result in someone trying to sell us a device to deal with it - whatever it may or may not be....my head hurts.

 

Yours in a spin, tog

 

[tfarney]

Given that the adverse effects of jitter are not measurable, may not be audible, are at least arguable and, if real, likely to only be revealed by the most revealing systems, I'd venture that the practical path would be the one Ashley suggested: Start with an inexpensive DAC and see how it sounds. If it doesn't sound as good or better than your cdp did, use it as a reference when auditioning other DACs, clocks, black boxes, etc, and don't buy any that won't take a return with no questions asked. If it does sound as good or better than you cdp, get off the internet and listen to music.

 

Been there, done that, with the simple 16/44.1 Burr-Brown built into my digital transport.

 

Tim

 

[shenzi]

...currently doing that with a toslink in to the dac in my receiver. A week into the world of computer audio and it sounds fine. Anything more complex will have to work for a living (an A-D as well as a D-A, for example).

 

[DavidJPettifor]

"Given that the adverse effects of jitter are not measurable, may not be audible, are at least arguable and, if real, likely to only be revealed by the most revealing systems, I'd venture that the practical path would be the one Ashley suggested: Start with an inexpensive DAC and see how it sounds. If it doesn't sound as good or better than your cdp did, use it as a reference when auditioning other DACs, clocks, black boxes, etc, and don't buy any that won't take a return with no questions asked. If it does sound as good or better than you cdp, get off the internet and listen to music.

 

I'd suggest this is a definitive answer. Way to go Tim (and Ashley ). I specifically champion the "return with no questions asked" part.

 

--

djp

 

[Tog]

Tim is exactly right but it occurs to me that the sound of your system can be quite be quite fickle anyway. last night whilst listening to a high bitrate VBR MP3 - no alcohol - no cahnges to the system and the sound was perceptably better than the previous night. Now the loons over at extremeaudiophilespending.com would no doubt say that the mains supply may have been cleaner or that my amps had run themselves in and recommend that I rub linseed oil on my toslink ends....but whatever the reasons the sound was much better. Perhaps I imagined the improvement or there was less wax in my ears but I would swear that the sound was much better than the previous night.

 

Does this mean that for all our concerns over jitter there are some very real ambient or psychological factors at work?

 

Indeed does it work both ways ...did I imagine there was a problem with the sound the previous evening?

 

Yours sober, tog

 

 

[Roseval]

My hearing is a constant (except that is slowly degrades over the years).

My perception of what I hear is not a constant, it changes in the long run (taste) and it changes in the short run (mood).

Everything 'fickle' in the sound, I attribute to perception

Everything in the sound which is a constant over time I think is real.

If it sounds great today and dull tomorrow it is me.

If it sounds dull today and tomorrow and does so for 3 month in a row, I have bought the wrong stuff.

 

 

[tfarney]

Mood, energy level, distraction...a million things can change the way you hear the same system from one night to the next. But let's not forget the most important one -- were you listening to the same recordings?

 

Oh, and Shenzi, I have the opportunity to listen to lots of AV receivers daily, most in that zone between the high reaches of mid-fi (a term I really don't accept as valid) and the entry level of hifi (a term which has more to do with price than performance). Most of them sound very good, even through pretty highly-resolving speakers. I don't know what your AV receiver is or what DAC it contains, but I suspect I would make any potential replacements work hard for their money as well.

 

Tim

 

[sastusbulbas]

Some interesting reading here,

http://forums.slimdevices.com/showthread.php?t=56425&page=1

 

As for computer audio, well most of it is pure rubbish, people repeating what someone else speculated without any evidence.

 

My computer experiences still leave me preferring my CD systems, my music is currently playing through a computer, spdif direct from mobo, high jitter, high clock error, etc etc.

 

Thankfully, re-clocking and removing the bloody jitter gives audible results. For the guys who do not hear jitter, and that have superior Macs and AVI kit, instead of stating rubbish such as its all unsubstantiated foo, why not leave teh thread alone. Many companies still address such issues you state as imaginary, why not give em a bell and offer them a sugar pill, LOL.

 

[shenzi]

My receiver is a fairly most Teac Legacy 700. I've no idea of the type of DAC inside other than it is 24bit, 96kHz. But as I've said, it sounds fine. Actually the whole receiver sounds fine and I'll be interested to see how the conventional rig compares when it emerges from enforced hibernation.

 

But thanks for the info on what you've heard. I read a while back that Earl Geddes uses a receiver to dem his comparatively high-end speakers, whiich upsets the golden ear brigade no end.

 

I may go into business manufacturing heavy-guage, high-end metal enclosures to retro-fit over the top of a modest stereo to pretend it's something more boutique ...

 

[keithmick]

From the earliest days of cd, right through to the present, the overall sound quality of digital is largely dictated by the absence or presence of jitter. Jitter basically destroys the precision of transient signals, resulting in sound that may be described as harsh, cold, smeared, or any of the manifold adjectives that have been used to describe"digititis".Any digital -to- digital transfer is inherently jitter-prone unless re-clocking or other preventative measures are taken. The removal of jitter brings digital audio into another realm, where musical enjoyment is not only possible but predictable. The maturation of digital can be directly traced to jitter reduction throughout the recording &playback chain today. While there are other factors, if significant amounts of (the bad kind) of jitter are present, quality of analogue circuitry, power supply , etc,. will not matter. Only if jitter is residualised will other design aspects surface as important. Jitter elimination remains the key goal in digital audio. Thank You-CA

 

[The Computer Audiophile]

Hi sastusbulbas - I'm a little slow today as I don't really get what your mean by your statement:

 

"...As for computer audio, well most of it is pure rubbish, people repeating what someone else speculated without any evidence..."

 

I get what you're saying in the rest of your post but I'm really interested in reading an elaboration on the above comments.

 

Thanks sastusbulbas!

 

[John Choate]

Being somewhat familiar with digital data and controls I have always wondered why there was so much press given to the jitter specs of digital transmission devices and protocols. It seems to me that a small bank of dual-ported RAM designed as a FIFO buffer could be used to write the incoming digital data stream, using the transmitting clock for synchronization. Then the data could be read from the FIFO and clocked into the DAC using a very accurate local clock. I believe this would completely eliminate jitter introduced by the digital transmission, leaving only the jitter associated with the local clock, which should not be difficult to minimize below a measurable threshold considered to be acceptable. (Of course any jitter introduced during the sampling of the original audio signal would always be present, but no DAC can overcome that.) Given the cost of medium to high end DACs, I can't imagine that the cost of such a RAM FIFO and local clock would add that much. Perhaps I have oversimplified and overlooked a significant technical issue, can anyone here explain why this approach wouldn't work, or isn't widely used?

 

[The Computer Audiophile]

Hi John - Welcome to Computer Audiophile. Thanks a lot for the nice post. It clearly sounds like you know what your talking about, but I really like the fact you haven't ruled out every other possibility. Those who know more realize there are many things they don't know. Said another way, those who claim to know it all know nothing. I don't have the answer to your question unfortunately. I just want to thank you for the informed post that does leave the door open for other readers to offer a compelling opinion that hasn't already been shattered by sophomoric internet banter.

 

Thanks John!

 

[Roseval]

can anyone here explain why this approach wouldn't work, or isn't widely used?

This is exactly how streaming audio works.

- galvanic isolation (network card or wifi)

- big buffer (to avoid drop outs)

- DAC reading the buffer at its own clock speed (no need to lock on a source)

- strict (TCP/IP) or a less strict protocol (UDP)

 

Yes, it is widely used, any Squeezebox proves this point

No, not in the audiophile world, there stoneage protocols like SPDIF rules.

Same could be observed in case of USB DACs. The first where not from any big name in audio. Now the traditional audio brands are slowly catching up.

 

[sastusbulbas]

Chris asked regarding,

 

"...As for computer audio, well most of it is pure rubbish, people repeating what someone else speculated without any evidence..."

 

I get what you're saying in the rest of your post but I'm really interested in reading an elaboration on the above comments.

 

Thanks.

 

Hi Chris, a little elaboration, I guess what I am getting at is some of the sweeping statements and sliding remarks made against various areas of performance. Looking through various threads shows a bit of speculation not to mention what seems like the dismissal of jitter (amongst other things) as having any relevance and of anyone who thinks it relevant seeming to be "wrong" regardless. Of course this also includes me, I also repeat others writings, as most only post what they have re-read elsewhere, which is why many question dismissive comment, hence my comment. Stuff such as below,

 

"Interestingly, purveyors of so called jitter busters never seem to publish such measurements."

 

"Hifi gurus often spout theories and scientific fact without any quantitative data to demonstrate the magnitude of the effect especially if they have a magic product to sell."

 

"Given that the adverse effects of jitter are not measurable."

 

If my memory serves me correctly, many "jitter buster" producers DID provide measurable data backed up with audible benefits, I also think that considering this development really took off during the 90's when manufacturers were starting to get to grips with digital audio, it seems a little naive to dismiss jitter when may companies still seem to be attempting to address it during product design, and many magazines seem to be quite capable of producing measured results. In fact in the late 90's many "jitter busters" were found to only address narrow band jitter at certain frequencies, companies such as Meridian, Genesis and such clearly showed there could be improvements and I think much of this early work helped pioneer development, as many of today's equipment is reported to deal well with jitter.

As companies are prepared to still work on this area, AV equipment for example having extremely high jitter levels via spdif and HDMI, with some speculation as to detrimental performance, 50psec versus 7660psec via HDMI in one recent article stated as debilitating then clearly some still put some importance into what people here are dismissing due to some other guys opinion.

I consider some reason must exist for CD manufacturers to address so many issues of playback performance, clock accuracy, jitter levels, build quality, chip choices, careful circuit layout, power supplies etc, all chosen in many cases for beneficial reasons, and at times cost implementation. Yet so many seem to give variables in measured and audible performance.

 

Computers have only recently gained in popularity as audio devices, many attempted as early as the mid 90's with audio and computers at home, I still remember hospitality boards on the first PowerMacs allowing connection to a HiFi, with costly CD drive hardware and software such as Toast, and the staggering cost of HD storage, and the subsequent loss of interest during late years due to various detrimental issues regarding SMPs, RFI, and other such things. These days things have moved on, but I think little has been done with computer hardware with regard to audio performance. Hence why I think Macs are popular, there are less variables with performance in comparison to PC, though it is only in recent years Macs have caught up to PC with regards to OS and storage and such. I still remember limited hardware for Macs, and they are still limited in comparison cost to PC spec.

Though no one will specify jitter or clock accuracy, the effect of a SMPS or a GPU interface, which now seem to be dismissed as having no bearing on performance, we seem to have as many opinions as facts with no absolutes or factual evidence.

 

Don't get me wrong, computer audio is going somewhere, what else is giving such a head start in HD audio and high res music for such costs! and sites such as this help considerably, but I think there is still a lack of knowledge and little naivety in place. The more we see them used for audio at home, the more product may be developed with Audio performance in mind, and teh more people will investigate component performance, for now though just about every Mac and PC is a compromise with the product developed with many other areas in mind.

 

I myself play with older equipment, we do not all use the same equipment and such, I mainly use 16/44.4 and I prefer an old NOS DAC in my system. I have used Mac and PC through the years, but always preferred my CD transports. I am currently interested in turning an old PC into a music box for upstairs (for 16/44.4) as both my (Old) Macs have failed in succession (HD failures). I will continue to use Mac and PC even though they have higher jitter and clock errors than my CD transports. And even after jitter removal and re-clocking I prefer the CD transports.

 

Of course this may change if I build a better computer for the audio, not sure what performance increase I will get with a decent sound card instead of spdif direct with this old PC. When more 24/192 music of my liking is available I will go down that route.

 

 

 

 

 

[Tog]

There is a danger that computer audio will be hijacked by those to whom cash is a substitute for sound and pseudo science is a replacement for sense. I like good design and great sounds and that is it. I am not going to obsess about bit oversampling jitter creep when listening to music.

 

yours jitter free, tog

 

[Ashley James]

I think these discussions are ignoring the progress that has been made over the last few years. Firstly DACs that are extremely resistant to jitter were developed and now receiver chips that reduce it to below levels of significance, and if you want more SRC will eliminate it altogether. May I suggest that those interested Google the part numbers of the different DACs available and read the application notes to see how each cope with it.

 

We're also of the opinion that if a DAC doesn't sound right, a punter will not know why, only that he doesn't like it.

 

Ash