2020 Jitter Measurements

Even as digital/analog processors were becoming a hot product category in the early 1990s, audiophiles were also learning that timing uncertainties in the AES/EBU and S/PDIF serial datastreams—jitter—would compromise any improvement in sound quality offered by these DACs. Some companies therefore introduced products to reduce or eliminate jitter—in the November 1994 issue of Stereophile, Robert Harley reviewed three such products: the Audio Alchemy DTI Pro, the Digital Domain VSP, and the Sonic Frontiers UltrajitterBug. I still have Stereophile's review samples of the UltraJitterBug and VSP, along with two contemporary DACs: a PS Audio UltraLink and a Parts Connection Assemblage DAC-1.

As our reviews of these products were published before Paul Miller's and the late Julian Dunn's development of the "J-Test" diagnostic signal, I performed J-Test jitter measurements to bring that 1994 review into the 21st Century. You can see what I found here.

Enjoy!

Oh, and the heading image? This is the PS Audio's output spectrum when fed TosLink data representing a full-scale, 16-bit 10kHz tone and corrupted with jitter at 1kHz with an amplitude of 1 nanosecond. The Ultralink can't deal with the jitter, throwing up sidebands at ±1kHz.

COMMENTS
Bogolu Haranath's picture

As a side note ....... May be JA1 could review the Innuos Phoenix USB reclocker ($3,149) .......It is a device used between the server/source and the DAC :-) ........

Bogolu Haranath's picture

For a $300 device, AQ DragonFly Cobalt also has outstandingly low Jitter measurements, some what similar to dCS Bartok :-) .........

Archimago's picture

With asynchronous USB and ethernet (inherently asynchronous), jitter levels have been low for more than a decade. IMO the Dragonfly Cobalt is rather expensive for what it does.

The more important question is - was jitter ever important when it came to audibility; much like the question of whether 24-bit sample depth is ever important given the limitations of the rest of the audio chain and human hearing (obviously 24-bits are useful in production, but we're talking about domestic listening).

I won't post the link here since it's to my blog, but if you're interested, do a Google search for "Archimago jitter demo" and have a listen for yourself and consider the J-Test results. Compare the results here with some of the samples.

My sense is that jitter, while a real phenomenon and should be minimized for hi-fi playback, is more an objective finding than actually a problem unless very severely - literally "broken" equipment!

Jack L's picture

...... it came to audibility; much like the question of whether 24-bit sample depth is ever important given the limitations of the rest of the audio chain and human hearing?" quoted Achimago.

Agreed. Hi-teck stuff, like jitter, audio bit depth & sampling rate are really detectable by our ears thru our home audio ????? I doubt very much. Another marketing schemes to get consumers' money?

Just like Y2k Millennium Scare which burnt billions dollars of commercial institutes worldwide for virtually nothing disastrous ever happened.

A strong case established by Audio Engineering Society New York + Hiroshima City University Japan on the audible difference among 3 audio sampling rates: 48Khz, 96KHZ & 192KHz of a 16-bit digital signal encoded in white noise. Under the lab condition: in an enechoic chamber, 7 young male/female of early twenties (sharp hearing). Audible differences were detected on white noise only. Music was not used as testing medium.

Now back to jitter. I just recently completed an experiment at home, using a no-name DAC of a cheapest ever basic design (USD7.55 each available only on-line) to test if our ears can detect any jitter or whatever digital craps generated by that cheapie DAC.

Digital audio signals were provided by my new basic SONY WIFI Blu-Ray disc player (USD52 from Best Buy!!!!) using coaxial cable & by my 50" 4K UHD WIFI TV using an optical cable come free with the cheapie DAC.
L & R audio analog signals out of the cheap DAC feed directly to my stereo rig.

Very very surprisingly, the music from my Sony Blu-ray player & my 4K UHD TV sounds pretty good!!!! Being a classical music addict owning'1,000+ vinyl LPs & all vacuum tube phono/power amps, I surely know how how fine music should sound. Fast, see-thru transparency & details. I can't complain at all as if that DAC might have cost my thousand of greenbacks.

Till now one months already, honestly I still can't detect any hashness due jitter or whatever digital craps expected to be generated by my 7-buck dirt cheap DAC !!!!!!!!!!!

Listening is believing

Jack L

Bogolu Haranath's picture

Another $400 device ...... Pro-Ject Pre Box S2 also has outstandingly low Jitter measurements :-) ........

jeffhenning's picture

One of the biggest knocks against USB was the jitter it induced.

John Siau of Benchmark had originally written about how this was not a problem with his DAC's since he'd designed a buffer into his USB system that made the use of an asymmetrical USB driver unnecessary.

Well, the term "asymmetrical USB" became a mantra amongst the industry and a year or so later Benchmark's DAC's have them. I'd imagine that it was more for marketing purposes than anything else.

I use a Emotiva XMC-1 for my serious listening and viewing. It has two DSP processors. One sorts all of the signals coming in. They are clocked at the original rate with all of the incoming jitter eliminated (hopefully) and format/listening mode decoding done. Between this DSP and the next is a buffer.

With all the bits in place, the signal then moves onto the second DSP that involves the outputs and their processing. It is after this that the digital data hits the DAC's for output.

I haven't seen any jitter spectrums in reviews, but the thing sure does sound pretty fantastic.

There is more than one way to skin the proverbial cat. Proper engineering will always win out in the end.

eriks's picture

The less than $2,000 Mytek Brooklyn reviewed by Stereophile in 2017 may be a better way to compare how much better jitter rejection has gotten than the $15,000 dCS Bartok, no?

https://www.stereophile.com/content/mytek-hifi-brooklyn-da-processor%C2%96headphone-amplifier-measurements

John Atkinson's picture
eriks wrote:
The less than $2,000 Mytek Brooklyn reviewed by Stereophile in 2017 may be a better way to compare how much better jitter rejection has gotten than the $15,000 dCS Bartok, no?

The Mytek does have excellent jitter rejection on its serial data inputs. I'll see at what point it gives up with the sinusoidally jittered data stream. And to answer your question in another comment:

eriks wrote:
Here's a challenge for you, JA. Take your vintage DAC's and compare the delta between how they played CDs and how they played high resolution music.

Neither of these vintage DACs will accept data with a bit depth greater than 16 and a sample rate greater than 48kHz. :-(

John Atkinson
Technical Editor, Stereophile

eriks's picture

Then anything before 2000 will do. An old Theta Casanova?

eriks's picture

Here's a challenge for you, JA.

Take your vintage DAC's and compare the delta between how they played CDs and how they played high resolution music.

Then try the same with the Mytek Brooklyn or dCS Bartok.

I think you'll have interesting findings to talk to your readers about. Can we still justify high resolution music at all?

JRT's picture

...device that worked well, but should not likely be useful in most modern setups, was (is?) the Monarchy Audio DIP (digital interface processor). The original DIP was clocked at 44.1_kHz, and that one was renamed DIP Classic after they came out with a 96_kHz version.

Stereophile reviewed the 96_kHz version. Not sure about others.

https://www.stereophile.com/digitalprocessors/339/index.html

Bogolu Haranath's picture

Also see Stereophile review of AQ JitterBug, USB noise filter, $50 :-) ..........

JL77's picture

These days, all but the very cheapest audio clocks should be operating in the sub-pico-second range.

Bogolu Haranath's picture

One pico second is one trillionth of a second :-) ..........

hollowman's picture

Well, jitter entered the audiophile vocabulary (as well as published lab bench metrics ) in the early 90s, as JA noted.
What is less clear is how aware the orig. R&D scientists were of the issue? I.e., the Sony/Philips RedBook team, back in the late 70s.
Ditto with "linearity" -- which entered the audiophile vocabulary a few years earlier.
I have gone thru a few early Philips papers, and found nothing.

Bogolu Haranath's picture

The same people who invented Jitter also invented Twitter :-) .......

MCK22's picture

I am curious. I have been reading about jitter in DACs for years, but I've never seen any reference to scientific evidence as to how much jitter is needed in the signal to be perceptible. Human ears are wonderful things, but they didn't evolve to be jitter detectors, and like all biological systems of perception there are limits of perceptibility. Does anyone have any citations to peer reviewed journal articles? Different DACs can sound different for reasons other than jitter and it would be interesting to see how much of the R&D budget should be allocated to jitter reduction as opposed to, for instance, the analog output parts of the DAC.

skris88's picture

This is because jitter is irrelevant!

Jitter exists in ALL digital transmission. And there is lots of error correction etc algorithms in the design of digital transmission. The DAC receives only perfect data, identical to what the ADC originally created.

Claiming jitter in digital audio is an issue is like saying that there are errors in the monies sent between bank digital transactions!

Yes, there is errors in transmission, but this is exactly why we use digital data and not analogue data. There are checksums and error correction bits and re-transmission of blocks of data going on all the time.

In the old days of the first CD Players, perhaps processors used were not fast enough to manage re-transmission of corrupted data into the DAC. When such errors happen the DAC algorithm determines that there is no more time to lose and so drops or 'assumes' the data it needs (eg. repeat the previous data for that block of data).

As such Red Book audio can be considered as lossy - like MP3s! (and worse, and it changes on each playback unlike MP3s when data is dropped/'lost' only during the compression process).

But these days with even the cheapest of CPUs 1,000s of times faster than the highest audio data being transmitted, digital jitter is an non-issue.

Otherwise, I'd suggest you take all your monies out of your digital bank account NOW (and check for the missing pennies! :-))

hollowman's picture

I can say with certainty that of the digital-audio gear I've personally owned, subjective quality is not correlated with jitter metrics.

For example, Stereophile reviewed/measured both the Musical Fidelity A324 (2002) and Asus Xonar PCI sound card (2010); both measured very well in jitter and other metrics (unsurprising, given their use of S-D dacs). I own both of these units. I also own a few classic (but heavily modified) Philips/Magnavox CD players with their classic SAA/TDA chipsets.
Sterephile has measured some Philips chipset units (Naim, Marantz, Arcam), but IIRC (the reviews are not online yet), the jitter wasn't great.

HINT HINT to JA for re-measuring classic Philips units, when he has time.

In any case, my modded Philips units sound considerably better than the newer MF and Asus devices mentioned above.

====EDIT===
The Naim CD2 cd player (with SAA7220/TDA1541A) was reviewed in Feb 1997, with Measurements by Robert Harley. (Not online, so more work for JA, if he wants it!!). The unit had very good jitter for that ancient chipset. Not sure how Harley's instruments/techniques, from then, would compare against JA and his AP of today.

Forgot to note that I also own a Theta Chroma 396 (reviewed/measured) Stereophile Aug. 1996. The jitter on that unit was only fair.

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