[tfarney]

This elusive distortion seems to be the bane of digital audio. Much is done to minimize it, mitigate it, move it to someplace where we can't hear it. But every description of it I've come across seems to boil down to harsh trebles, and there is so much bad mastering in the present and so much bad recording in the past (just listen to some pop records from the 60s), I'm not sure I have any way of differentiating between "jitter" and just badly recorded or mastered material with nasty trebles. Is there a way? Or, with reasonably good equipment, is jitter really much of an issue these days?

Not to be cynical (well, maybe just a bit...), but I seem to be finding two very distinct points of view on harsh trebles and glare in digital audio. One comes from audiophiles and their high-end suppliers who have them running for cover and spending thousands of dollars on cable snd black boxes to eliminate this uniquely digital distortion, thousands more on tube DACs, pre-amps and amps to mask it, and the other is recording and mastering pros who advise us to turn down the treble a bit...

My experience seems to reinforce the latter. I just lived through an example. iTunes was set to global mix and match - randomly picking tunes from my entire collection. It picked the live recording of "Tin Pan Alley" from SRV's "In The Beginning." Harsh trebles. Harsh upper mids. I have my amp set to hinge the treble at 5kz, and the treble knob rolled back about 1/4, so when I run into this issue I can just rech over there and release the tone defeat switch, which I did, but that wasn't enough.

Jitter?

I switched tone defeat back in and played "Tin Pan Alley" off of "Couldn't Stand the Weather" instead. Smooth as a baby's back side. Warm. Sweet. The ride cymbal and the muted pop of the snare drum's rim were still bright and present, but all traces of upper mid and treble harshness were gone.

No, not jitter, not this time -- recording, mastering. And this is with a cheap data-grade USB cable from hard drive to Mac and whatever DAC chip is on my iBook's soundcard.

So what does jitter sound like?

Tim

 

[tfarney]

nevermind. I meant this to be a new thread...

Tim

 

[Chri5peed]

From the numerous, 'Optical is bad' threads, I get the idea it is a physical thing; like a pop or click. Also how it almost kills Optical and make it un-usable.

Surely 'harsh trebles' is pretty subjective and that could easily be accounted to headphone sound-signatures?

 

[nick_charles]

Quote:

Originally Posted by tfarney /img/forum/go_quote.gif So what does jitter sound like? Tim

I wish I could help you but none of my sources have jitter at levels that are humanly detectable according to the best research we have at the moment. However last year I did strike up a correspondence with a Japanese gentleman who has written several papers about jitter thresholds based on human subject testing.

The chap's name is Kaoru Ashihara, and he was very forthcoming, in his papers he just describes it as distortion, but you could ask him if he collected any perceptual data from his subjects about what they heard when supplied with high jitter.

 

[Golden Monkey]

Chris, LOVE the "modded" Opeth logo for your avatar, lol...

Anyway, good question Tim. I've been trying to quantify jitter myself, and I've tried comparing "known good" remastered discs on various equipment I own. Everything from a crappy old Sony portable CD, to my home theater, PC, etc. I can never quite tell if I'm hearing a cheap DAC chip, op amp, or anything else in the signal path. It know that expensive DIPs, upsamplers, reclocking devices etc. WOULD make a difference "intellectually", I just don't know if I can actually hear this to such a degree that it justifies spending a huge amount of cash to achieve these results. Searching around the web, I found various bits of info, and almost all of them relate to A/B testing of jittery vs. "non-jittery" setups. It seems the only conclusions many reach is "unless you compare good vs. bad, you'll most likely not notice anyway", but a summary of comments regarding jitter point to:

Less jitter -
improved ease of listening
increased clarity
improved high frequency response
better instrument separation
more information
better timing
better soundstage
improved overall audio performance


Rather vague and subjective, I know. How do you know if your setup is truly jitter immune? Apparently you can't ever eliminate it completely...unless you eliminate anything digital in the first place.

 

[sacd lover]

Jitter was an issue long before this poorly mastered material appeared. I can tell you whatever they did to dacs after around 1999-2000 made a huge difference in listenability. Supposedly, the frequency of the jitter also has an effect on the sound. Example, jitter can soften and lessen the impact of bass transients and/ or add harshness and glare to treble frequencies. Jitter does not have one sound. The amount of jitter and the frequency both come into play.

I spent a good part of the 1990's trying to address the fatiguing sound of digital. Rolling off the treble seemed to help at first. But, I soon found that the intrinsic glare of digital from that time would soon reappear once my ears adjusted to the treble manipulation. I did not get any relief until I added the old Audio Alchemy DTI Pro to my setup with this units I2S connection to circumvent to the flawed SPDIF connection. Even today, my modded cd players / transports with ultra low low jitter aftermarket clocks are noticeabley better sounding than their stock countetrparts.

 

[tfarney]

Quote:

Less jitter - improved ease of listening increased clarity improved high frequency response better instrument separation more information better timing better soundstage improved overall audio performance Rather vague and subjective, I know. How do you know if your setup is truly jitter immune? Apparently you can't ever eliminate it completely...unless you eliminate anything digital in the first place.

Yep. Which loosely translated means 'we can't quite put our finger on it. Sounds like anything and everything that could be wrong with audio. We really can't discern jitter from any other distortion that might occur anywhere in your signal chain. But if you just keep spending money, it will just keep going away..."

Tim

 

[nick_charles]

As far as I know no human being in any proper listening test has ever been able to detect the detect the presence of jitter in music at below 30ns for frequency-correlated jitter or at below 250ns for random non-correlated jitter.

Jitter in commercial digital devices just does not get close to that level. The paragon of bad jitter is an Oppo DVD player which has measured jitter at 4ns peak to peak as measured by Stereophile.

Even the worst jitter signals from such a device will produce spikes (sidebands) that are no worse than 80db down on signal, masking takes care of that comfortably.

 

[Know Talent]

the jitter levels in most decent players is below the level where you can percieve a difference.

There's a controlled study using "audiophiles", musicians and recording engineers that concluded once you get down to 150 ppm level any further reductions are imperceptible....unless you have cat ears.

What's interesting is the MBL 15XX Nobel series CDP was tested by the UK Miller Reseach group and measured 860ppm....and the review claimed it to be the most accurate and revealing player the reviewer had ever heard.

Go figure?

clocking upgrades are by-and-large snake-oil IMO
...and I speak from personal experience.

 

[nick_charles]

Quote:

Originally Posted by Know Talent /img/forum/go_quote.gif There's a controlled study using "audiophiles", musicians and recording engineers that concluded once you get down to 150 ppm level any further reductions are imperceptible....unless you have cat ears. What's interesting is the MBL 15XX Nobel series CDP was tested by the UK Miller Reseach group and measured 860ppm....and the review claimed it to be the most accurate and revealing player the reviewer had ever heard.

Do you have a link for that study, I would really like to read it. How does PPM compare with nanoseconds , as for more jitter being perceived as better I have seen several instances of this, though I am skeptical that it is just the jitter that gives rise to this...

 

[sacd lover]

Quote:

Originally Posted by Know Talent /img/forum/go_quote.gif the jitter levels in most decent players is below the level where you can percieve a difference. There's a controlled study using "audiophiles", musicians and recording engineers that concluded once you get down to 150 ppm level any further reductions are imperceptible....unless you have cat ears. What's interesting is the MBL 15XX Nobel series CDP was tested by the UK Miller Reseach group and measured 860ppm....and the review claimed it to be the most accurate and revealing player the reviewer had ever heard. Go figure? clocking upgrades are by-and-large snake-oil IMO ...and I speak from personal experience.

I had the same player, Sony 555es, in modded and unmodded form. The difference the LXO3 clock made was not subtle.

150 ppm figure is quite low. Some of the players back in the 1990's with the Yamaha input receiver had jitter 20 x that amount.

Remember, it is not just the total amount of jitter, but also where the jitter lies in the frequency band.

 

[BayouSlide]

Quote:

Originally Posted by Chri5peed /img/forum/go_quote.gif From the numerous, 'Optical is bad' threads, I get the idea it is a physical thing; like a pop or click.

I think what you are referring to here are "digital overs"...i.e. what happens when your recording levels exceed O dB in digital recording. Once you've heard a digital over, you don't tend to forget it. When running to analog tape you often record so the highest peaks exceed O dB and the resulting "slam" is much more palatable and remains musical, often just a slight roll off unless you really overdo it.

0 dB in digital is a brick wall...in analog it's the beginning of a slope, metaphorically speaking.

 

[Chri5peed]

Quote:

Originally Posted by Know Talent /img/forum/go_quote.gif There's a controlled study using "audiophiles", musicians and recording engineers that concluded once you get down to 150 ppm level any further reductions are imperceptible....unless you have cat ears. .

I have cat-ears grafted on, I hear no jitter.

 

[loddie]

From what I have read, pro audio minimizes jitter by syncing all digital devices with a master clock such as word clock or superclock, not by attenuating the highs.

 

[Know Talent]

Quote:

Originally Posted by nick_charles /img/forum/go_quote.gif Do you have a link for that study, I would really like to read it. How does PPM compare with nanoseconds , as for more jitter being perceived as better I have seen several instances of this, though I am skeptical that it is just the jitter that gives rise to this...

I'll check and see if I have it bookmarked.
If you search on audioholics I think that is where I found the link.