What Does Jitter Sound Like? Let's Test

[sandyk]

You're getting mixed up between jitter on the bitstream into the DAC and jitter on the DAC clock. Jitter on the bitstream has no effect unless it's so bad that the receiver loses lock. It only matters if the jitter on the bitstream causes jitter on the DAC clock(*), as can happen with poor DAC design or implementation.

Don

I doubt that the original poster was talking about anything more than Jitter as heard by a typical listener.

You guys are discussing how they went about accomplishing that. Perhaps you went down the rabbit hole further than the OP intended ?

Sorry, but I don't agree with you about the second sentence. It can be easily demonstrated that a .3PPM TCXO using a very low noise and highly stable power supply can sound better than an ordinary XO without it losing lock. The effects are even more noticeable with high res material. I wouldn't exactly class an almost textbook design as implemented by Musical Fidelity in their X DAC V3 using a DIR1703E and DSD1792 as being poorly implemented. Both the ultimate stability of the XO and the precision of the "flywheel" components (filter pins) play a part here, unlike with the later replacement DIR9001.

 

Note that "a superimposed 100kHZ sawtooth on top of the DC output voltage" is simply an instance of "accentuated HF ripple".

 

Of course I am aware of that, as they are my own suggestions as to how this kind of thing might be accomplished. A friend of mine has such a PSU which was used for testing the performance of the JLH designed PSU Add-ons after modifications.

[Don Hills]

Don

I doubt that the original poster was talking about anything more than Jitter as heard by a typical listener. You guys are discussing how they went about accomplishing that. Perhaps you went down the rabbit hole further than the OP intended ?

 

Perhaps. Alex WG, please let us know if we're boring you.

 

Sorry, but I don't agree with you about the second sentence. It can be easily demonstrated that a .3PPM TCXO using a very low noise and highly stable power supply can sound better than an ordinary XO without it losing lock.

 

Nope, it's correct. Read it again, in context:

 

"You're getting mixed up between jitter on the bitstream into the DAC and jitter on the DAC clock. Jitter on the bitstream has no effect unless it's so bad that the receiver loses lock. It only matters if the jitter on the bitstream causes jitter on the DAC clock(*), as can happen with poor DAC design or implementation."

 

So, no real disagreement - I said that input datastream jitter matters more if the DAC (including its clock) is poorly designed or implemented and can be influenced by the jitter. This is not at variance with your statement that a well designed clock can sound better.

 

The point is that you need to separate the functions of decoding the incoming bitstream from the function of clocking the DAC. The two functions are at cross purposes - the bitslicing clock needs to readily adjust to the incoming bitstream, the DAC clock needs to be as stable as possible. That's where the "art and science" of DAC design comes in.

[goldendarko]

Ah, the dreaded jitterbug. When I've had the jitterbug into my brain it usually went a-bang-bang-bang til my feet did the same. Hopefully that helps

[sandyk]

Perhaps. Alex WG, please let us know if we're boring you.

 

It still doesn't answer the question that many other members would like to know, which is "What Does Jitter Sound Like?"

[esldude]

It still doesn't answer the question that many other members would like to know, which is "What Does Jitter Sound Like?"

 

Sounds bad. Real bad. It is like the sound you get coming off a 3 day drunk with the shakes and jitters. Really, really bad.

[sandyk]

The attached is from a U.K.based forum with additional points from both John Kenny and myself added to the original.

Alex

 

 

Here are some audible symptoms of jitter that allow us to determine that one source sounds "better" than another with a reasonable degree of scientific backing:

 

It is well known that jitter degrades stereo image, separation, depth, ambience, dynamic range.

 

Therefore, when during a listening comparison, comparing source A versus source B (and both have already been proved to be identical bitwise):

 

The source which exhibits greater stereo ambience and depth is the "better" one.

 

The source which exhibits more apparent dynamic range is the "better" one.

 

The source which is less edgy on the high end (most obvious sonic signature of signal correlated jitter) is the "better" one.

 

And a reply:

The better one, and it is better, is also easier to listen to. . . less fatiguing. I would also add to this that the low end just "feels" bigger and more solid. This is perhaps a psychoacoustic affect more than a measurable one. It may be that the combination of a less edgy high end and greater depth and width makes the bass seem better.

 

All of this makes sense if thought of in terms of timing (that is what we're talking about isn't it ;-]). With minimal jitter nothing is smeared, a note and all its harmonics line up, the sound is more liquid (a term probably from the "audiophile" crowd but one which accurately describes the sound none the less), and images within the soundstage are clearly defined.

 

 

Now some extra points:

- listener fatigue is reduced or completely eliminated

- the sound can be turned up higher without any distortion being evident

- the sound can also be turned down lower & the full dynamics are still retained but at a lower volume

[Don Hills]

It still doesn't answer the question that many other members would like to know, which is "What Does Jitter Sound Like?"

 

Yes, I've noticed many posts from members anxious to know the answer. And I see in your subsequent post that you've provided the answer. I'm reminded of the phrase "When I want your opinion I'll give it to you."

[sandyk]

Back 2 days ago in post no.3 , I suggested that Barrows should be contacted as some time back he posted an indepth answer to the original question.

Up till now, nobody has bothered to answer the original question. Now you are pissed off because I dared to post some kind of answer to that original question, and interrupted your lesson on how DACs work that nobody asked for.

[Don Hills]

... Now you are pissed off because I dared to post some kind of answer to that original question, and interrupted your lesson on how DACs work that nobody asked for.

 

Actually, I'm amused, as I thought was clear from my comment. I didn't put a smiley on it because I didn't want to be mistaken as trying to be humorous.

[sandyk]

Don

I was quite happy to let you continue on without interruption , and perhaps even learn something, until you said this :

Perhaps. Alex WG, please let us know if we're boring you.

When not communicating face to face, it's not always easy to tell if somebody is having a shot at you or simply poking sly fun.

[esldude]

Don

I was quite happy to let you continue on without interruption , and perhaps even learn something, until you said this :

 

When not communicating face to face, it's not always easy to tell if somebody is having a shot at you or simply poking sly fun.

 

As AlexGWoody was the OP. I am assuming Don's comment was Alex WG (being the OP) will let us know if we are boring him. Nothing to do with Alex (SandyK) that I can read into that comment.

[sandyk]

Your post in Reply 30 is REALLY helpful too. NOT !

[esldude]

Your post in Reply 30 is REALLY helpful too. NOT !

 

Then try this. The real sound of audible levels of jitter as described here:

 

NwAvGuy: Jitter Does it Matter?

 

A REAL LISTENING TEST: I participated in a listening test at an Audio Engineering Society conference where they played test tracks with varying known levels of different kinds of jitter. It wasn't a rigid ABX or double blind test, but it was very enlightening. We, the listeners, didn't know which tracks were which until they were explained later. The most obvious audible effect was high amounts of jitter at certain frequencies sounds much like the old analog "wow and flutter" that is produced by vinyl turntables and tape recorders. Both devices have tiny deviations in speed--they might be slow variations (wow) like a vinyl record with the hole punched off-center. Or they might be fast (flutter) caused by the motor not rotating smoothly or bad bearings. Digital jitter, interestingly, often produces a rather similar end result.

 

PIANOS AND CYMBALS ARE CHALLENGING: Acoustic piano music seems to be an especially sensitive indicator of jitter (and wow and flutter). As the jitter increases, the notes take on a more brittle quality--that expensive Steinway Grand now sounds more like a garage-sale upright piano. And when the jitter is really high at certain frequencies, you can hear a "warble" to sustained piano notes--just like with low quality tape players or turntables. Some also say cymbals are good at revealing jitter.

[Don Hills]

As AlexGWoody was the OP. I am assuming Don's comment was Alex WG (being the OP) will let us know if we are boring him. Nothing to do with Alex (SandyK) that I can read into that comment.

 

Exactly.

[sandyk]

A REAL LISTENING TEST:

 

That sounds like artificially generated Jitter at much higher levels than normally encountered in any well designed equipment.

[Jud]

I seem to recall seeing somewhere a thread where someone wrote a software jitter injector that allowed supplying a user-defined jitter signal. I'm still looking to see if I can find it again. Even if I can't, it'll be a useful coding project. Different jitter signals (noise, deterministic, signal-correlated) generate different artifacts, which become audible at different thresholds. It would make a useful training tool for people interested in identifying the audible effect of various jitter signals.

 

 

I have a link somewhere around here to a program to add simulated jitter to the playback of a file in the quantity desired, in order to get some idea of whether you can hear various levels and how they affect the sound. Subject to some of the same problems you mention, John, though the developer is accessible and can explain what is being done.

 

I'll poke around and have a look for it if anyone is interested in trying it.

 

PM on the way.

[Jud]

(*) As John Swenson has pointed out, in a poor design jitter or other noise on the input can also result in variations of the supply or reference voltages of the DAC chip, but we're getting well down the rabbit hole now.

 

Can't resist responding to this. One of John's comments over at Computer Audio Asylum makes it clear that he thinks (1) this type of problem is pretty ubiquitous among DACs, and (2) resolving it is no easy matter. So I'm not sure it's fair to call all DACs subject to the problem (in whatever degree and at whatever price point) poor designs.

[wisnon]

Tastes like phase error.

Smells like a rat. LoL

[Don Hills]

Can't resist responding to this. One of John's comments over at Computer Audio Asylum makes it clear that he thinks (1) this type of problem is pretty ubiquitous among DACs, and (2) resolving it is no easy matter. So I'm not sure it's fair to call all DACs subject to the problem (in whatever degree and at whatever price point) poor designs.

 

I get the impression John is pursuing vanishingly small levels of improvement. There's nothing wrong with that. I do it myself, because it's fun to push the envelope. But for a commercially viable product, I'd settle for levels well below the generally accepted levels of audibility. As for "poor design", the mechanisms are well understood. There's no reason for a mid-price DAC to have less than acceptable performance. The real cutting edge is in improving chip and supporting circuitry design to bring the same levels of performance to low-cost DACs.

[Jud]

I get the impression John is pursuing vanishingly small levels of improvement. There's nothing wrong with that. I do it myself, because it's fun to push the envelope. But for a commercially viable product, I'd settle for levels well below the generally accepted levels of audibility. As for "poor design", the mechanisms are well understood. There's no reason for a mid-price DAC to have less than acceptable performance. The real cutting edge is in improving chip and supporting circuitry design to bring the same levels of performance to low-cost DACs.

 

But Superdad and I heard the same "vanishingly small" differences between two versions of a bit-perfect software player on two different DACs 3000 miles apart, yada yada yada you know the rest....

[Don Hills]

PM on the way.

 

(Your mailbox is full.)

 

Thanks, Jud. I'll take a look. At this stage it doesn't quite do what I had in mind, but I'll ask if he might implement it. That is, instead of applying "canned" jitter types, I'd like to add a jitter signal from an external file - for example, a file containing noise, or a tone, or a recording of PSU rail noise from a real DAC, or even a copy of the original signal.

 

Regards,

Don.

[Don Hills]

But Superdad and I heard the same "vanishingly small" differences between two versions of a bit-perfect software player on two different DACs 3000 miles apart, yada yada yada you know the rest....

 

How do you know that the DACs you were using were competently designed? Do you have anything to indicate that the designers paid special attention to jitter and noise rejection? (Not jumping down your throat here, just pointing out that it is possible to reduce the effects to levels well below accepted levels of audibility in a reasonably priced DAC. If Benchmark can do it, so can anyone.)

[sandyk]

How do you know that the DACs you were using were competently designed? Do you have anything to indicate that the designers paid special attention to jitter and noise rejection?

 

Are you admitting that there may be such a thing as software jitter, or more noise generated by one software version than another , and that it can be heard via typical commercial DACs , except perhaps for those designed by Benchmark and yourself ? (grin)

[Don Hills]

Are you admitting that there may be such a thing as software jitter, or more noise generated by one software version than another , and that it can be heard via typical commercial DACs , except perhaps for those designed by Benchmark and yourself ? (grin)

 

I don't argue that "software jitter" can't exist. Rather, I argue that it should have no effect on a competently designed and built DAC. If you hear a difference, it's the DAC's fault, not the software. All of this tweaking software parameters, USB cables and linear power supplies is just putting money into other people's pockets instead of the DAC manufacturers. Once people understand that a DAC's jitter and noise immunity will provide better sound than a milled-from-billet case, the state of the art will advance.

 

(I'm no stranger to "software jitter". I first dealt with it many years ago when porting some Z80 code to 8086. The Z80 processor had a fixed number of clock cycles per instruction. The 8086 clock cycles per instruction could vary. Software based timing loops could thus vary in length.)

[sandyk]

Don

It's a shame that you are so far away from Jud in Aotearoa, as otherwise he could try these different software versions with one of your DACs. It's also refreshing to see Software Jittter acknowledged. We shouldn't need to go to extremes with add-on Linear PSUs etc. or further PSU improvements in most commercial DACs. Perhaps we can blame the "bean counters" for most of this, or is it that the typical consumer doesn't know any better than MP3 ?

 

Alex