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Topic: Is jitter audible and what does it sound like? (Read 46809 times) previous topic - next topic
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Is jitter audible and what does it sound like?

Reply #25
As I've mentioned here in other threads, the proper way to ABX test direct, live vinyl to a digitized version of it is via a nearly instantaneous (low latency) A>DA>A loop, the exact same methodology used by Meyer and Moran to compare the live, analog out of an SACD player to a digitized version it via a standalone CD recorder put in "record monitor" mode. Pops, ticks, and clicks won't give away which source is being played because you are hearing the exact same playback session of the vinyl either way.


So maybe that's why I don't reach a transcendent state of blissful nirvana and enlightenment when I play my LPs, rather I just enjoy them as I would the same music in any other format.

It's that blasted A>D>A DSP crossover I'm using, surely that must be robbing me of pure audiophile bliss

Good point though, that's obviously the best way to do that ABX test.

Is jitter audible and what does it sound like?

Reply #26
Apologies if it was on this very site, I clicked a link and saved the PDF --- and I cannot remember where I saw the link.

No doubt familiar to many here, it looks like a vital piece of education for a recovering audiophile*, so being one (although I have never subscribed to the analogue/digital divide) I read it and saved it...

The Dawn of Commercial DIgital Recording, Thomas Fine,  ARSC Journal.

Amazing, how so many audiophiles seem to think that digital audio was an assault on the very basis of music, whereas it was actually adopted and further developed by the recording companies to improve their results. "...Denon's stated purpose: "To produce recordings that were not compromised by the weaknesses of magnetic tape recorder." (p3: Pre-Dawn: Denon Introduces Music to Digital)



*or, even, people interested in digital history rather than myth
The most important audio cables are the ones in the brain

Is jitter audible and what does it sound like?

Reply #27
No doubt familiar to many here, it looks like a vital piece of education for a recovering audiophile*, so being one (although I have never subscribed to the analogue/digital divide) I read it and saved it...

The Dawn of Commercial DIgital Recording, Thomas Fine,  ARSC Journal.

Amazing, how so many audiophiles seem to think that digital audio was an assault on the very basis of music, whereas it was actually adopted and further developed by the recording companies to improve their results. "...Denon's stated purpose: "To produce recordings that were not compromised by the weaknesses of magnetic tape recorder." (p3: Pre-Dawn: Denon Introduces Music to Digital)


Digital haters who seem to also tend to be analog fan boys, apparently want to forget about that approximate 10 year period near the end of the heyday of analog, and just before the arrival of consumer digital, where just about any self-respecting recording engineer did as much recording and production on digital gear as he could before the final LP master cutting session.

This listening test strongly relates:

Listening Test of digital production gear for analog media

"
The Ampex 16 Bit Digital Delay Line vs. wire comparison was heard in a recording studio control room on time aligned UREI 813 speakers with McIntosh MC-2100 amplifiers. The audio source was a master 2-track 15 IPS tape on a Scully 280. This master tape had been mixed from a 24-track master tape on an Ampex MM-1000. The mixdown and playback was through an API console. The listeners included professional recording engineers with years of experience on major label projects, professional maintenance engineers, and recording engineering students.. For those not familiar with studio equipment, these are some of the most revered pieces of equipment of that day. API consoles are still prized today for their high quality.
"

This was essentially the same test configuration as the Meyer-Moran tests, only about 30+ years earlier  (late 1970s-early 80s).

The Ampex 16 Bit Digital Delay Line was composed of stereo back-to-back ADCs and DACs separated by a digital delay line that preserved every digital data bit, but added a user-adjustable amount of delay. For the bulk of the testing the delay was set to zero, so the converters were back-to-back.

The purpose of the Ampex 16 Bit Digital Delay Line may be instructive of some of the technical details of SOTA vinyl master production.

It is always a challenge to fit a useful amount of wide dynamic range audio on a LP side.  The louder the track, the larger the cutting pitch or groove spacing that is required to avoid damaging the immediately previously cut groove a few thousands of an inch back.

If the track has a quiet passage then reducing the track's pitch is good practice. Unfortunately this sort of decision making has to be made before the loud passage is cut. Therefore SOTA tape mastering machines of the day had a "Preview head" that played the music back approximately one revolution of the LP in advance of the tape head that played the music back for the purpose of cutting the groove.  The preview head fed analog cutting head positioning circuits to optimize the groove pitch before the groove was actually cut. Therefore the tape machine had to have two identical sets of tape heads whose performance needed to be optimized and matched.

The Ampex 16 Bit Digital Delay Line eliminated the need for the second tape head, but its sound quality was of paramount importance because it controlled the sound quality of the final LP master, which needed all the help it could get.  If it were indistinguishable from the canonical "Straight Wire With Gain" then it could not be further improved on. 

The recording engineers whose work product would be profoundly affected by the sonic performance of this digital device threw everything at it that they could. Even recordings of the classic "Keys jangling" were used.  It became clear that the SOTA and carefully optimized high speed wide track mastering tape machines were a little less than sonically perfect, but the Ampex delay line shrugged off the most challenging program material.

For those who claim that the digital audio converters that were used 10 years later could not be up to the task at hand, these test results are very challenging.  The unimpeachable sonic performance of this device from a decade earlier tells a different story. In the early days of consumer digital, the existing and past technology was up to the task, and was demonstrably sonically transparent.


Is jitter audible and what does it sound like?

Reply #28
Just a general point concerning white papers - IME I have found that though they are often technically correct, they often leave out important context and can be misleading.

IOW:

Statement A: "this can cause noise"
Statement B: "our process ensures that this noise will never cause a problem"

Though both A and B might be 100% true, the part they hope one infers - that without their process the noise will be a horrific problem - is never actually explicitly stated anywhere. Instead there might be careful dancing around the audibility question and hypothetical statements like, "if this distortion is great enough, it will...".

So I read white papers as technical marketing documents and read carefully for signs they are dancing around saying things explicitly and ask myself, "If it's a problem in the real world, why don't they just say that? Why all the dancing?".

Is jitter audible and what does it sound like?

Reply #29
Though both A and B might be 100% true, the part they hope one infers - that without their process the noise will be a horrific problem - is never actually explicitly stated anywhere. Instead there might be careful dancing around the audibility question and hypothetical statements like, "if this distortion is great enough, it will...".

There's a positive side to this, which IMHO shouldn't be neglected: By doing this, they try to avoid an outright lie. This may of course be an attempt at minimizing legal complications, but some of them might actually have preserved some professional standards that they are reluctant to give up. This is in contrast to others who have absolutely no inhibition to take the piss out of their customers.

The question is how to act in a situation where you know that your business depends on customers who believe that your product delivers better sound quality than your competition. Even worse, telling people the naked truth would be met with disbelief and even opposition, so you would be in danger of alienating your customer base.

Is it any wonder that even the more sincere amongst the manufacturers try to find a compromise which permits their deluded customers to keep their delusions, and the manufacturers to keep their revenues?

I think that Lavry is one of the more sincere amongst the high-end manufacturers. I tend to respect that, even though the customers who want to keep their delusions will find plenty of pretexts and excuses in Lavry's writings that support them in that. Lavry himself, I am confident, knows which part of it is true and which isn't.

Is jitter audible and what does it sound like?

Reply #30
Though both A and B might be 100% true, the part they hope one infers - that without their process the noise will be a horrific problem - is never actually explicitly stated anywhere. Instead there might be careful dancing around the audibility question and hypothetical statements like, "if this distortion is great enough, it will...".


There's a positive side to this, which IMHO shouldn't be neglected: By doing this, they try to avoid an outright lie.


The moral advantage of an intentional deception over an outright lie being exactly what?

I personally favor the outright lie because it may be easier to detect! ;-)

It is sad that so much of audio has come down to this sort of thing. There is real progress yet to be made, but so  much energy is wasted.


Is jitter audible and what does it sound like?

Reply #31
The moral advantage of an intentional deception over an outright lie being exactly what?

It contains at least a tacit admission that the truth matters to the deceiver, even if he's prepared to obfuscate it for profit. Not very much of an advantage, I know.

Quote
I personally favor the outright lie because it may be easier to detect! ;-)

And easier to attack ;-)

Quote
It is sad that so much of audio has come down to this sort of thing. There is real progress yet to be made, but so  much energy is wasted.

That's still nothing compared to the wastage due to other delusions. Truly sad indeed.

Is jitter audible and what does it sound like?

Reply #32

It is sad that so much of audio has come down to this sort of thing. There is real progress yet to be made, but so  much energy is wasted.

That's still nothing compared to the wastage due to other delusions. Truly sad indeed.


But the other wastage is often based on the carefully worded deceptions.

Well-intentioned persons often end up contributing to these deceptions. One classic example of this that I will boldly proffer, full knowing of his good technical work and numerous fans: NWAVGUY.

In my opinion he plied the world of two-orders of magnitude overkill for fun and profit (at least profit for others) and raised concerns that were psychoacoustically questionable to say the least.

Is jitter audible and what does it sound like?

Reply #33
But high fidelity enthusiasts are concerned with the psychoacoustically questionable.

An enthusiast is not interested in equipment that is "just" good enough to satisfy some clear cut psychoacoustic requirements based on the average listener, except if it is e.g. especially cheap. He/she wants more, probably willing to spend a lot more to gain very little.
It's like the computer enthusiast, that buys a more expensive CPU cooler to achieve 1° lower temperature which effectively makes no other difference.

That's why nwav set the bar(s) higher. If you're cynical you may say that he set them higher such that "inferior" products could not meet them, while his projects do... but even that is awesome considering the prices on both sides.

---

A few ns jitter may not be audible with most music, but we should still strive for lower jitter - that is progress. Jitter is just a random example, but what's greater than all those advancements trickling down into cheaper gear, raising the average fidelity?
"I hear it when I see it."

Is jitter audible and what does it sound like?

Reply #34

It is sad that so much of audio has come down to this sort of thing. There is real progress yet to be made, but so  much energy is wasted.

That's still nothing compared to the wastage due to other delusions. Truly sad indeed.


But the other wastage is often based on the carefully worded deceptions.

Well-intentioned persons often end up contributing to these deceptions. One classic example of this that I will boldly proffer, full knowing of his good technical work and numerous fans: NWAVGUY.

In my opinion he plied the world of two-orders of magnitude overkill for fun and profit (at least profit for others) and raised concerns that were psychoacoustically questionable to say the least.


nwavguy wrote an entire article explaining how I am completely wrong for insisting on ABI that you can adequately measure the performance of a 16 bit audio player using RMAA, the pair of headphones you want to use with it and an inexpensive sound card.  His perspective was very much in favor of excessive perfectionism, both in terms of hardware and in terms of measurement. 

On the other hand, I did enjoy the precision with which he measured things.  I don't think it was often necessary, but if you're not doing the work, its great to have a few more decimal places worth of accuracy

Is jitter audible and what does it sound like?

Reply #35
But high fidelity enthusiasts are concerned with the psychoacoustically questionable.

An enthusiast is not interested in equipment that is "just" good enough to satisfy some clear cut psychoacoustic requirements based on the average listener, except if it is e.g. especially cheap. He/she wants more, probably willing to spend a lot more to gain very little.
It's like the computer enthusiast, that buys a more expensive CPU cooler to achieve 1° lower temperature which effectively makes no other difference.

That's why nwav set the bar(s) higher. If you're cynical you may say that he set them higher such that "inferior" products could not meet them, while his projects do... but even that is awesome considering the prices on both sides.

---

A few ns jitter may not be audible with most music, but we should still strive for lower jitter - that is progress. Jitter is just a random example, but what's greater than all those advancements trickling down into cheaper gear, raising the average fidelity?


PICOSECONDS!  Sheesh...

At 170ps in a <$200 sound card, jitter is approaching the limits of measurement, let alone audibility:

http://www.stereophile.com/content/asus-xo...ds-measurements

Edit: Naturally, even though it has less usability problems, the the Xonar doesn't hold up to JA's $2500 Ayre QB-9, for some unknown reason.

Is jitter audible and what does it sound like?

Reply #36
And I see no problem with products with 2-digit picoseconds jitter for enthusiasts either.

However, there appear to be huge problems in audiophool circles: FUD and focusing just on something like minimizing jitter while ignoring far more important things.
"I hear it when I see it."

Is jitter audible and what does it sound like?

Reply #37
And I see no problem with products with 2-digit picoseconds jitter for enthusiasts either.

However, there appear to be huge problems in audiophool circles: FUD and focusing just on something like minimizing jitter while ignoring far more important things.


Such as?

Is jitter audible and what does it sound like?

Reply #38
And I see no problem with products with 2-digit picoseconds jitter for enthusiasts either.

However, there appear to be huge problems in audiophool circles: FUD and focusing just on something like minimizing jitter while ignoring far more important things.


Such as?


Speakers and room acoustics have been far and away the largest source of noise and distortion in any audio system since we moved beyond analog media.

The noise and distortion in rooms and speakers struggles to be as much as 40-50 dB below listening levels.

Compare that with the noise and distortion in even just mediocre amps and dacs - more like 70-90 dB down.

Is jitter audible and what does it sound like?

Reply #39
Oh, definitely, though ambient room noise probably isn't as likely as computer onboard audio to trick your brain into expecting an imminent insect attack.

Do any of the "Hifi" rags like Stereophile even talk about room acoustics?

Is jitter audible and what does it sound like?

Reply #40
Do any of the "Hifi" rags like Stereophile even talk about room acoustics?

Rarely because there's (almost) nothing to sell.

I've recently made some big improvements to my room by the use of carpeting, drapes, strategic furniture placement, and some modifications to my air ventilation system but how many of these things, I bought, are advertised in rags like Stereophile? None. They cater to their advertisers so pushing overpriced wire, amps, and DACs is their bread and butter, not articles about rugs, drapes, etc. which actually do make a difference.

Is jitter audible and what does it sound like?

Reply #41
And I see no problem with products with 2-digit picoseconds jitter for enthusiasts either.

However, there appear to be huge problems in audiophool circles: FUD and focusing just on something like minimizing jitter while ignoring far more important things.


This article claims jitter can be audible at 20ps:
[a href="http://www.madronadigital.com/Library/AudibilityofSmallDistortions.html" rel="nofollow"]http://www.madronadigital.com/Library/AudibilityofSmallDistortions.html[/a]

All you have to do is slow your pulse and respiration, put on a good pair of headphones and listen to John Cage's 4'33" in a sensory deprivation chamber.  You're bound to get a spurious 2kHz tone eventually.

I am interested in his claim that mass-market AV receivers can have thousands of picoseconds of jitter over HDMI.  Granted, this is also a video connection, which makes you even less likely to notice distortion.  Does anyone know how to convert picoseconds of jitter to a decibel level?

Is jitter audible and what does it sound like?

Reply #42
Most question already answered here.

Btw, the big HDMI jitter problem has been fixed years ago. Products released over 5 years ago did already manage ~300ps and lower total correlated jitter. Arcam had a product back then (maybe still has the same) with essentially unmeasurable jitter.
"I hear it when I see it."

Is jitter audible and what does it sound like?

Reply #43
This article claims jitter can be audible at 20ps:

If you know about the posting history of that author here and at the AVS forum you'd know that he is nothing more than a pompous, insufferable lobbyist for the grossly overpriced DACs and other "high end" snake oil manufacturers which he sells at his retail store. I'd advise avoiding any material he's written, it's a waste of your time.
I exposed him as a liar in post #3 here.

Is jitter audible and what does it sound like?

Reply #44
And I see no problem with products with 2-digit picoseconds jitter for enthusiasts either.

However, there appear to be huge problems in audiophool circles: FUD and focusing just on something like minimizing jitter while ignoring far more important things.


This article claims jitter can be audible at 20ps:
http://www.madronadigital.com/Library/Audi...istortions.html


The author was given the opportunity to back up his claims with a listening test and failed.  His claims are based on other works that themselves were not generally based on reliable listening tests.

Jitter is one of the things that people have pontificated on for about 30 years while either not gathering or ignoring evidence that is contrary to their beliefs.  The beliefs are a kind of a license to pontificate, so they tend to be self-perpetuating.

Quote
All you have to do is slow your pulse and respiration, put on a good pair of headphones and listen to John Cage's 4'33" in a sensory deprivation chamber.  You're bound to get a spurious 2kHz tone eventually.


That there is a 2 KHz tone or audible tone at any other frequency due to real world jitter to hear is generallly a misapprehension. Jitter adds sidebands that while they show up as something like tones on a FFT are generally not heard that way.

Quote
I am interested in his claim that mass-market AV receivers can have thousands of picoseconds of jitter over HDMI.


I would take that to be something that was a fact at one time in some cases. However just because the jitter could be described with scary numbers does not mean that it was a problem. His proposed solution which was ansynch USB converters have some pretty severe-seeming inherent problems of their own, which are generally obfuscated by the industry.  A blogger named Archimalgo has writtten what little there is that has been backed up with even just technical tests. 

Remember, no reliable listening test, and you're just dealing with speculation.

Quote
Granted, this is also a video connection, which makes you even less likely to notice distortion.  Does anyone know how to convert picoseconds of jitter to a decibel level?


You need to know the frequency and amplitude of the jitter and the frequency and amplitude of  signal being jittered to do that. If you know those four things then the conversion is one of those things you learn in an advanced  undergraduate class in modulation theory.


Is jitter audible and what does it sound like?

Reply #45
All you have to do is slow your pulse and respiration, put on a good pair of headphones and listen to John Cage's 4'33" in a sensory deprivation chamber.  You're bound to get a spurious 2kHz tone eventually.

Just tried. The frequency of my tinnitus seems higher than 2khz 

Is jitter audible and what does it sound like?

Reply #46
I am interested in his claim that mass-market AV receivers can have thousands of picoseconds of jitter over HDMI.  Granted, this is also a video connection, which makes you even less likely to notice distortion.

They also have DSP and thus buffer audio data which kills jitter.

Is jitter audible and what does it sound like?

Reply #47
Isn't it an audiophile fact that electrons have memory? Thus, signals which have been exposed to jitter, must surely be left feeling, and sounding... jittery!
The most important audio cables are the ones in the brain

Is jitter audible and what does it sound like?

Reply #48
... All you have to do is slow your pulse and respiration, put on a good pair of headphones and listen to John Cage's 4'33" in a sensory deprivation chamber.  You're bound to get a spurious 2kHz tone eventually. ...


I'm sure you were just having a little fun there, but  some readers don't know that and might take what you said as a fact.
(The sound of jittered silence is... silence.)
Regards,
   Don Hills
"People hear what they see." - Doris Day

Is jitter audible and what does it sound like?

Reply #49
I am interested in his claim that mass-market AV receivers can have thousands of picoseconds of jitter over HDMI.  Granted, this is also a video connection, which makes you even less likely to notice distortion.

They also have DSP and thus buffer audio data which kills jitter.


The high numbers for jitter that were measured were taken at the analog output of the AVR which were downstream of all  of those enhancements. It was real.

The more serious problem is that there is no general knowledge among consumers or technicans about how many (pick a prefix indicating a small division of time)-seconds of what frequency jitter makes an audible difference in which signals at whatever audio frequency.

IME, most consumers can't be relied on to tell you whether a nanosecond was larger or smaller than a picosecond, and by how much. Obviously, the smaller unit of time you choose, the bigger the conventional numbers that describe the actual measurement.  Good practice is to pick a unit of time that gives reasonable numbers, but obviously many in the industry obviously ignore those guidelines and pick very small units of time so as to contrive large numbers > 1,000.

Add to that the perceptual differences in how or whether jitter is audible depending on whether it is random or periodic, and the differences in audibility based on the frequency spectral content of both the audio signal and the jitter itself.

How much jitter is audible is thus not an question with a simple single number answer. Consumers generally lack the background and interest to manage just a single number.  Reality is that large numbers of numbers are needed to describe the problem.