Educate me about Jitter

I found the most enlightening report on jitter to be from a review from...1996!

Remember when people used to say in their technical papers in hi-fi magazines that, although jitter was measurable, you couldn't actually "hear it?" Then, in 1996 the Genesis Digital Lens popped up, designed by Paul McGowan, (now of PS Audio). The Lens was a device you plugged between your 1990's expensive transport and your expensive 1990's DAC. The first of it's kind to address the issue.

This Stereophile review of the Genesis Lens gets to the point without without too much technobabble.

Genesis Technologies Digital Lens

Then the review seems to go on about spatial depth, bass, definition and detail. But that was 1996, not today. So maybe the enthusiasm was warranted.

I have an Oppo 205. And for now, discs sound better than using WiFi to stream files from my Mac. I have a LOT of cables and a crazy amount of other WiFi going on in this very, very big house. When I asked Oppo, and several others, the answer was "maybe the WiFi connection is introducing jitter." This may be true. Streamed files via WiFi just have a little less clarity than playing discs.

 

So a dubious study which we have to take your word for existing from 3 decades ago with an unknown scientific testing methodology and a bunch of customers who can't do blind side-to-side testing of the original and modified peripheral. Yeah, that's an open and shut case.

 

When you are having a hard time finding the start of a song after the first song on an LP.

 

I don't think you can educate most of the people who still don't/won't understand that digital audio is far from perfect.

The only way you can be sure a digital clock is "perfect" is to have a precision crystal oscillator built into a special oven to keep it's frequency constant. Not very practical for most consumers or bedroom audio engineers.

Why are all these weird variables that are found in digital audio still not fully explained? I don't know. I'm not a scientist, but I've worked as an audio engineer for many years and I do trust my ears over my eyes when it comes to sound.

I recently did a transfer of 4 reels of 2" 24 track (30ips) tape to digital for doing a mix . This was on a properly biased and calibrated Studer A800 straight into a Lavry Blue system. Pretty much SOTA in professional digital A/D and certainly one the best analog tape decks ever made. We dumped all the tracks and then level matched the payback. The Lavry sounded great, no doubt. Very analog-like. But... it still came up short when we switched back to monitor directly off the Studer. It lost elements like depth and soundstage and other crazy audiophile intangibles like "organic wholeness" and "flesh and blood". Those magnetic particles replicated with zeros and ones did not sound quite the same. Theoretically, it should. Both sounded really, really good, but the analog easily won out. In 2018.

There you go. Perfect sound forever? We still haven't figured that one out yet.

How can this be you ask? I really don't know. Perhaps the Nyquist theory is wrong or incomplete? I do know that while the human ear can't hear harmonics above 20khz, we sure can feel it. I think this makes a big difference in how we feel/hear the music as an complete picture.

Tape and LPs are very much imperfect mediums, but while digital always "looks" perfect, it still fails to capture some crucial missing essential elements that make up the "complete" audio picture.

In my somewhat informed opinion, that is.

Now back to the deaf leading the blind!

 

Well said, but I don't think it will convince the "deaf leading the blind" around these parts.

Digital artifacts, most notably jitter, cannot be eliminated. They can only be minimized. Many audio components cannot resolve the differences. Nor can some ears.

 

You are lucky in being able to compare the sound from the original tape with the sound from the digitised version.

How close is the sound of LP playback to the tape if the analogue delivery chain were used?

I have a shed load of music that is available to the consumer in digital format only.

Obviously I have no control whatsoever over what happens in the supply chain - presumably ADC plus whatever else. Just as I have no control over what happens in the analogue supply chain to produce the gramophone record.

Does the computer hardware itself make a difference?

Does the software on the computer make a difference?

Does the USB cable make a difference?

Do jitter, timing, taps, upsampling, speed of circuitry, or whatever else in the DAC make any difference?

I am stuck with digital. How do I get the best from it? Simple question.

 

It can. As far as DAWs (digital audio workstations) are concerned, they are all coded differently with the aim of achieving the same end result. Given all the same parameters and holding constant such variables as panning laws, a file created by one DAW may not null completely with one created by another. They may sound broadly the same or they may sound slightly different. Under ideal circumstances, they may even sound remarkably different. A mastering engineer once demonstrated for me (in an admittedly non-blind test) the same stereo file played back from a couple different DAWs (Avid Pro Tools and Magix Sequoia) in her treated studio. The difference in sound was not night-and-day, but it was more than subtle. I'd need to do it blind to be sure, and I'd love to try a null test, too.

 

That is the creation of the digital file that I will be playing back by whatever means?

 

If you are once again going to tell us that you’re an audio engineer and that your opinions matter more than ours (we should trust your authority even though you haven’t told us what work you’ve done) please tell us what titles you’ve worked on. I’ve asked this before and you typically run to the Gorts asking for the thread to be locked and/or my post deleted.

 

Again, cites? Also what you're describing is not a study showing that the human ear can "out-discern any measuring device." In fact, the human hearing is widely variable and relatively sensitive in certain areas, and not so sensitive in others and very much non linear and dependent of frequency and loudness. Most people can tell differences of pitch of low frequency tones that a 1 Hz apart even, but at 2kHz, we couldn't tell the difference between frequencies 8 Hz apart. Now, we certainly could measure those differences with mics and scopes. So there's an area where human hearing is definitely not more sensitive that any machine. Same thing with just noticeable differences in loudness. Humans' ability to recognize loudness differences between two tones is widely variable, depends on pitch, depends on initial loudness, etc. On average we may not be able to tell a 1.5 dB difference in loudness between two tones, starting at 40 dB, but we can certainly easily measure smaller differences than that. There are lots of audio related phenomenon where we can easily measure fine threholds of difference that we can't hear very well.

Audiophilia has this almost Ptolemaic model of physical phenomena -- each of us as individual humans sits at the center of the physical universe and we convince ourselves that our frail, limited, physical organism and our highly suggestible and manipulable psyches are the be-all and end-all. But in truth human hearing is widely variable from person to person, non linear with respect to pitch and loudness, bandwidth limited and subject to psychological phenomena that don't necessarily represent physical phenomena.

It may well be true that we don't have great correlations between everything we we hear (or we think we hear) and everything we measure. And we certainly don't have a great understanding of the psychological components of hearing in the context of audio -- what is this phenomenon of soundstage depth that we listen to? What aspects of phase response or disperson or something else relate to that? But we know for a fact that there are frequencies and differences of frequency and loudness etc that we can measure that we can't hear very well. The idea that human hearing is broadly and inherently more sensitive than any measuring device, just isn't true. And the fact that thy human mind comes to believe things regardless of physical facts, IS true (like when Jimmy Kimmel hands an old iPhone to a man on the street, tells 'em its the new iPhone, and they start explaining how much faster, lighter, and better performing the "new" phone is).

 

Correct.

 

Jitter was exterminated about 20 years ago now - virtually all modern D/A converters reclock the signal to phenomenal accuracy. In fact, jitter accidentally encoded in an old digital signal will be removed by a modern D/A converter.

 

As I see things, storing data on Solid State Drives is far more reliable than reading a disc with its speed fluctuations, what can fluctuate while reading a solid state memory? Another matter is lossless codecs, as with them the original PCM data stream is reconstructed by an IC and mechanical reading becomes a non-issue subject. Just imagine a real world situation,I actually did it a couple of hours ago, you're playing a Blu ray Audio disc (I played Rush Moving Pictures) that has the same music from the same mastering as Hi Res PCM and lossless DTS-HD Master Audio. What gets more jitter when playing from the player to the receiver via HDMI, the PCM or the DTS-HD MA track? With PCM traveling trough an HDMI interface and cable jitter can be produced, it can't with the same path if you play the DTS-HD MA tracks as what is transmitted via HDMI is not real PCM audio but a data stream that allows INSIDE the receiver to reconstruct the actual PCM data. Am I wrong?

 

There is far less jitter when data is read off a hard drive or memory card than the opto-mechanical CD drive. But most better DACs reclock all the data anyway, which alleviates the jitter.

 

So to sum up, jitter as a problem affecting sound quality has basically been eliminated in modern hi-fi equipment, and it's also a mystically profound and inescapably persistent flaw degrading digital sound in ways that only scientifically illiterate fools ignore as it poisons their supposedly "perfect" digital music.

Sorted!

 

At some point, you have to pick a side. Everyone can read up and then decide whether it's worth it for them to explore the issue in detail and spend whatever amount of money is necessary to address it, if they deem it to be worth fixing.

Myself, I go by the adage if only the odd online person who claims to have golden ears can hear it, either they're making stuff up to appear superior with the cover of anonymity the Internet provides or they really are in the very top 0.1% in hearing and except for them and dogs, nobody would ever be able to tell the difference anyway. I've never tested my hearing but even though it's very good, I doubt it's in the very top "golden ears" range, same as almost everybody.

So in the end, is it really an issue or not? Up for the individual to decide. I've reviewed almost everything posted in this thread and have decided for my own self. Up to others to decide for themselves.

 

We can't hear above 20khz but we feel it, you say....

What do we feel it with? Our arm hairs? Our noses? Please explain what mystical thing you "feel" that scientific instruments cannot detect.

The answer to all this is much more about human psychology than magical feelings.

 

In his defense, even though we can't hear below 20 hertz, we do feel lower frequencies. I too am puzzled by his statement that we feel higher inaudible frequencies but since he flew off the handle (now deleted) when he was simply asked his name, I doubt he'll be inclined to civilly elaborate on this topic.

 

All fair comment. Except, well, yeah, we feel very low frequencies due to the amount of vibration they produce, but really high frequencies won't produce equivalent vibrations.

 

It's called bone conduction. By means of bone conduction we can hear up to 50 kHz. Values up to 150 kHz have been observed in some young people. It's generally agreed on that 20 kHz is the upper acoustical limit through air conduction.

The reason for this is debated, but the transfer function of the ossicle chain in the middle ear is a suspected of setting the upper frequency limit to 20 kHz.

 

The effects of bone conduction are moot if there's no significant coupling of the sound source to bone. Sound in air is attenuated as a function of distance times frequency squared. Headphones, which provide the most physical coupling to the skull, by design minimize bone conduction, as it would result in a grossly unnatural sound.

 

So are you sat on your tweeter?

Or does the sound go through the air first?

 

Phantom, one of Rotel's recent disc spinners (RCD-1570) was reported to have "higher than typical jitter for a player in this class at over 1,000 psec." Is that really a higher than average jitter number for a player which costs a thousand dollars? What range do low jitter usually fall around?

 

I would point out that digital jitter is quantifiable, as well noted by others on this thread, and thus using professional equipment easily measured down to levels that would make the Starship Enterprise's Warp Drive look like it was built with a carpenter's rule. It is not "audiophile" voodoo ( I can easily hear it, it's like glare) it's there at audible levels or it's not (it's not) and is not debatable unless you like irrational debate.

 

I must admit that there are times that people swear to be hearing stuff that I am not hearing. My right ear has tinnitus so I don't think I've truly heard a "black background" in 30 years. That being said, the examples in my post were not subtle changes, especially item 3 . I tested it on my wife -- who has no audiophile pretensions whatsoever -- and she told me about the improvement that she was hearing even before I had a chance to ask her the question.