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My cable test enterprise - Page 26

post #376 of 438
Quote:
Originally Posted by leeperry View Post

And what would I gain from it? I can DBT my $3 killer sounding shielded composite cable and my Belden 1794A/Canare cable anytime you want. Really. They sound so different that it's not even open for debate....but surely I'm a clueless victim of placebo, and France is rather far from where you currently reside I presume so you'd need to trust me on my good word.

 

All the cables DBT's I've read were done w/ analog cables in non-acoustically treated rooms and without Digital Room Correction. For what I know, the guys were listening to the room more than to the cables....and when you provide links to jitter hearing tests, they're always utterly flawed, like one was using mono signals recorded on tapes, or the other was using $5 headphones. The ppl who enjoy their music have nothing to prove to the non-believers. If everything sounds the same to you, then Hallelujah! one less thing to worry about I'd say[:la buvette]

 

Copper costs $10K a ton, I'm w/ you about the ppl who sell copper for the price of platinum...they use guru-like methods on gullible ppl. A well designed cable doesn't have to carry a 3 figures price tag...it does because the "pricier=better" circular logic is very much at play in the audiophile world.

 

Yeah, we're drinking the Kool-Aid...

 

This is the kind of rebuttal to such tests that does absolutely nothing for the "there is a big difference" crowd.

 

If it is so easy to tell the two cables apart, why don't you set up such a blind test yourself just like you said you can do?  With a helper, it's relatively easy to do - I'm sure someone would be glad to write up a procedure for your facilitator (helper) to follow.  Someone will end up surprised in the end - it's just a matter of whom.

 

If the difference is really a result of the cable and not your mind, you'll find out with enough trials to make a statistically significant conclusion.

 

The people who "believe" do have something to prove, apparently - otherwise you wouldn't be here, and otherwise there wouldn't be any sort of debate over the matter...  One man's icing on the cake is another man's total waste of money...

 

As for the studies you mention, links please to them.  "Five dollar headphones"? "Digital room correction"?  What if you're testing an analog rig?  Perhaps a mono tape, a high quality original eight track...  Like Skylab said, the other factors are not necessarily important at all if they are held constant as a control.  It depends on the particular test system of course - very poor headphones/speakers may indeed mask issues with upstream components.  But without specific examples it's hard to examine exactly what you're trying to say - your point is meaningless without specific study examples.

 

And are there any studies/tests saying there is audibility at the level of accuracy of decent gear?  Show us!

 

If you'd actually read the study I posted....

Quote:
Experiments were carried out in the listening booth or
studio that each listener had offered. The examiner only
brought there a personal computer with a digital audio
interface and a mouse and each listener provided his or her
favorite DAC, amplifiers and loudspeakers.
The sound materials were also selected by each
listener. Materials that had been repeatedly heard by the
listener could be used.

A total of 23 audio professionals or semi-professionals
participated as the listeners. They were audio engineers,
audio critics, sound engineers, and musicians. Some of
them were volunteers and the others were paid for their
participation. All of them were willing to participate in the
experiments.

 

So two dozen professionals and semi-professionals who were listening on their own intimately familiar equipment in their own intimately familiar listening spot could not hear random jitter at all when it was as high as 250 ns.  Only 6/23 participants detected jitter at 500 ns, 11/23 at 1000 ns, and at 2000 ns all 23 could detect it.

 

If you bother to read it, they go on to relate to the results of other studies, including those performed in more controlled listening environments (the same system for all listeners).  Now, this study isn't perfect - more trials would always be useful, and more rigorous statistical analysis as well - but the procedure is very rigorous otherwise, as it's actually a follow-up of a particular controlled listening condition test.  The results are comparable to another study using random jitter, and they explained why a different study with lower results would do so (sinusoidal jitter, and listeners who decided for themselves when they could no longer hear jitter - definitely not a scientifically valid method for determining audibility of the phenomenon).

 

Again, it pays to actually read...

post #377 of 438
Thread Starter 
Quote:
Originally Posted by BlackbeardBen View Post

 

So two dozen professionals and semi-professionals who were listening on their own intimately familiar equipment in their own intimately familiar listening spot could not hear random jitter at all when it was as high as 250 ns.  Only 6/23 participants detected jitter at 500 ns, 11/23 at 1000 ns, and at 2000 ns all 23 could detect it.

 

If you bother to read it, they go on to relate to the results of other studies, including those performed in more controlled listening environments (the same system for all listeners).  Now, this study isn't perfect - more trials would always be useful, and more rigorous statistical analysis as well - but the procedure is very rigorous otherwise, as it's actually a follow-up of a particular controlled listening condition test.  The results are comparable to another study using random jitter, and they explained why a different study with lower results would do so (sinusoidal jitter, and listeners who decided for themselves when they could no longer hear jitter - definitely not a scientifically valid method for determining audibility of the phenomenon).

 

Again, it pays to actually read...


Random jitter (Ashihara et al) will always be less detectable than signal-correlated jitter (Benjamin and Gannon) , the question is which is the type more likely found in commercial audio kit. There is lively debate over this but even if we take the pessimistic view that deterministic jitter is the more likely then that still allows us jitter of at least 10ns not being a problem.

 

Now many jitter-worriers will talk about how and where to simulate jitter and how all these tests are wrong (wrong subjects, wrong methods, wrong conclusions, wrong jitter) , the british forum HD audio had 5 real-world jitter samples mounted that folks could try out, I am proud to say that I am the only human ever to correctly place them all in order of jitter magnitude from 0 to 100ns. How did I manage this feat , I cheated , I ran them through a spectrum analyzer converted the results to text and did some simple maths in Excel. The answer was obvious, but only mathematically. The distortion caused by 100ns of jitter was laughably small, as B and G found in their study where they show the effect of 50 and 300ns jitter on a single instrument fundamental.

 

The bigger question and I mean this most sincerely is, if jitter is such a big problem, why has nobody from the audio industry been able to empirically prove this ?

 

Steve Nugent swears blind that he can not only detect 2ps (yes 2ps) of jitter but the difference between different spectra of 2ps jitter - I'm still awaiting his proof of this, the highly respected Dan Lavry hedges when asked about how to critically measure and evaluate the audibility of jitter, they both maintain it is a problem but neither can provide what we at the back of the bus might consider good empirical evidence. Steve Nugent says it's too complicated , threre are too many variables you'd have to measure it a gazillion times with different spectra, now would be a good time to start then, Dan Lavry also does not think a formal testing routine would be manageable but both INSIST that jitter is an audible problem, how can they possibly know if they have never correlated the magnitude and audibility ?

 

But more interesting is Bob Adams (Analog Devices) take on it , Adams says basically that there is no point in isolating jitter and measuring it as jitter will (almost always) appear downstream in IMD and THD, how much is IMD and THD a problem in competent digital audio kit ?

post #378 of 438

 

Originally Posted by BlackbeardBen View Post

The people who "believe" do have something to prove, apparently - otherwise you wouldn't be here

I mostly came around coz I had those funny links to share, one with the stellar markups on those DIY cables and then the interview of the maker saying that the differences between cables cannot be measured. This was very much on topic.

 

OK, jitter audibility? The best coax receiver on the market has a PDF available here: http://www.wolfsonmicro.com/documents/uploads/misc/en/A_high_performance_SPDIF_receiver_Oct_2006.pdf

 

It links to another AES paper about jitter audibility, that can only be bought on the AES site apparently...can't find it on google.

 

The problem I'm seeing w/ those jitter injecting tests is how good is it to add 200/500/1000ps jitter if the DAC already has 900ps jitter in the first place?

 

A valid test would be to use a controlled source, such as the TC Electronic Konnekt 6...it's spec'ed at 46ps jitter. Now we're talking: use some analytical headphones and go ahead, inject jitter(if you can, coz it's got the TC jitter rejection DSP biggrin.gif). The only thing I can say is that the USB>coax transport I currently use reclocks the Tenor USB chip I2S outputs through DIR9001, then through WM8804. It sounds amazing! OK, I'll say it: it's a night and day over POF toslink off a Realtek regular_smile%20.gif

 

The Firestone Bravo can be used as a reclocker...try it to reclock toslink to coax if you dare. I'm not the only one who's very happy w/ the unit and hears a major SQ improvement when doing so: the sound is just tighter.


Edited by leeperry - 2/23/11 at 4:00pm
post #379 of 438
Thread Starter 



 

Quote:
Originally Posted by leeperry View Post

 

Originally Posted by BlackbeardBen View Post

The people who "believe" do have something to prove, apparently - otherwise you wouldn't be here

I mostly came around coz I had those funny links to share, one with the stellar markups on those DIY cables and then the interview of the maker saying that the differences between cables cannot be measured. This was very much on topic.

 

OK, jitter audibility? The best coax receiver on the market has a PDF available here: http://www.wolfsonmicro.com/documents/uploads/misc/en/A_high_performance_SPDIF_receiver_Oct_2006.pdf

 

It links to another AES paper about jitter audibility, that can only be bought on the AES site apparently...can't find it on google.

 

It is the Benjamin and Gannon paper, this paper places audibility in the 10s of nanoseconds range, it is well worth reading as they graph the magnitude of distortion sidebands against jitter magnitude, aIso they talk about masking whiich makes jitter less audible, here is a segment...

 

The threshold of audibility for pure tones was found to be about 10 ns rms at 20 kHz and higher at lower frequencies. For nearly all program material no audible

degradation was heard for any amount of jitter added below the level at which the DIR lost lock. Certain program material was found in which an audible degradation due to jitter was heard. The

threshold of audibility for these programs was generally found to be in the range of 30 ns rms to 300 ns rms for sinusoidal jitter. Finally, the audible degradation was found to correspond to measurable changes in the spectrum of the program material.

 

The problem I'm seeing w/ those jitter injecting tests is how good is it to add 200/500/1000ps jitter if the DAC already has 900ps jitter in the first place?

 

It was ns not ps added before it was found to be audible and the setup used by B and G had 80ps jitter.

 

see also

 

Figure 4 shows the spectrum of jitter measured from a laptop PC DVD ROM with optical output. Excellent performance is achieved despite the use of an optical interface. The jitter spectrum is basically white phase noise jitter with a spectrum level of 7 ps rms and small additional sinusoidal components at 250 Hz and 1.3 kHz.

 

 

- this was back in 1998

 

 

 

 

post #380 of 438

 

Originally Posted by BlackbeardBen View Post


they were adding nanoseconds of jitter, not picoseconds.


Yeah, right...the audible improvement when reclocking 800ps jitter to 50ps coax on the Firestone Bravo is illusionary, the spoon doesn't exist...Same goes for 44.1kHz playback on the Asus Essence STX>ST(the latter has a 75ps CS2000 reclocker between the 24.576Mhz PLL and the DSP). In both cases, the improvement is exactly as explained on this webpage: http://www.bursonaudio.com/burson_clock.htm

 

"The effect of the clock is instant; [..] By reducing the jitter error, you will hear clearer positioning, also details are further refined vocally and instrumentally. Sound stage and positioning will improve noticeably and that includes deeper sound stage and darker background. Some said it also improves the control on the bass."

 

Firestone have posted RMAA measurements about reclocking on the Bravo:

http://www.firestone-audio.eu/shop/images/before_520.jpg

http://www.firestone-audio.eu/shop/images/after_520.jpg

 

You may wanna try real world experiments, they're worth a thousand words..or so they say. Do you think TC Electronic strive for low jitter in order to please a bunch of audiophools?

 

If the DAC's they used in those tests already had a medium to high jitter, anything on top of it won't make an audible difference until you'll reach ridiculous amounts(and good luck generating random jitter)...this is rather easy to understand, but keep thinking that jitter isn't audible on headphones w/ good gear until 500ns if you like[:mcyrb]

 

At this point, we're rather OT as I understand it...let's not make another pointless thread about jitter if any possible...noone's willing to change his mind anyway.

post #381 of 438
Sorry, cleaned up.

Quote:
Originally Posted by leeperry View Post

 

Originally Posted by BlackbeardBen View Post

The people who "believe" do have something to prove, apparently - otherwise you wouldn't be here

I mostly came around coz I had those funny links to share, one with the stellar markups on those DIY cables and then the interview of the maker saying that the differences between cables cannot be measured. This was very much on topic.

 

OK, jitter audibility? The best coax receiver on the market has a PDF available here: http://www.wolfsonmicro.com/documents/uploads/misc/en/A_high_performance_SPDIF_receiver_Oct_2006.pdf

 

It links to another AES paper about jitter audibility, that can only be bought on the AES site apparently...can't find it on google.

 

The problem I'm seeing w/ those jitter injecting tests is that how good is it to add 200/500/1000ps jitter if the DAC already has 900ps jitter in the first place?

 

A valid test would be to use a controlled source, such as the TC Electronic Konnekt 6...it's spec'ed at 46ps jitter. Now we're talking: use some analytical headphones and go ahead, inject jitter(if you can, coz it's got the TC jitter rejection DSP biggrin.gif). The only thing I can say is that the USB>coax transport I currently use reclocks the Tenor USB chip I2S outputs through DIR9001, then through WM8804. It sounds amazing! OK, I'll say it: it's a night and day over POF toslink off a Realtek regular_smile .gif

 

The Firestone Bravo can be used as a reclocker...try it to reclock toslink to coax if you dare. I'm not the only one who's very happy w/ the unit and hears a major SQ improvement when doing so: the sound is just tighter.



They were adding nanoseconds of jitter, not picoseconds, as I stated.  That's on the order of 250 to 1000 times more than the jitter of nick_charles's DAC - which is not the ones used in any of those tests.

 

The listeners, industry professionals, were using their own equipment.  The particular equipment for each of the 23 listeners (and each listener's results) wasn't published.  I hope that as industry professionals they were using equal or better equipment than a casual tester, but of course it can't be confirmed.  It would of course be better if it could...  Not that it is relevant anyway with the jitter of typical DACs being three to four orders of magnitude less than the detectable threshold in this case.

 



Quote:
Originally Posted by nick_charles View Post




Random jitter (Ashihara et al) will always be less detectable than signal-correlated jitter (Benjamin and Gannon) , the question is which is the type more likely found in commercial audio kit. There is lively debate over this but even if we take the pessimistic view that deterministic jitter is the more likely then that still allows us jitter of at least 10ns not being a problem.

 

Now many jitter-worriers will talk about how and where to simulate jitter and how all these tests are wrong (wrong subjects, wrong methods, wrong conclusions, wrong jitter) , the british forum HD audio had 5 real-world jitter samples mounted that folks could try out, I am proud to say that I am the only human ever to correctly place them all in order of jitter magnitude from 0 to 100ns. How did I manage this feat , I cheated , I ran them through a spectrum analyzer converted the results to text and did some simple maths in Excel. The answer was obvious, but only mathematically. The distortion caused by 100ns of jitter was laughably small, as B and G found in their study where they show the effect of 50 and 300ns jitter on a single instrument fundamental.

 

The bigger question and I mean this most sincerely is, if jitter is such a big problem, why has nobody from the audio industry been able to empirically prove this ?

 

Steve Nugent swears blind that he can not only detect 2ps (yes 2ps) of jitter but the difference between different spectra of 2ps jitter - I'm still awaiting his proof of this, the highly respected Dan Lavry hedges when asked about how to critically measure and evaluate the audibility of jitter, they both maintain it is a problem but neither can provide what we at the back of the bus might consider good empirical evidence. Steve Nugent says it's too complicated , threre are too many variables you'd have to measure it a gazillion times with different spectra, now would be a good time to start then, Dan Lavry also does not think a formal testing routine would be manageable but both INSIST that jitter is an audible problem, how can they possibly know if they have never correlated the magnitude and audibility ?

 

But more interesting is Bob Adams (Analog Devices) take on it , Adams says basically that there is no point in isolating jitter and measuring it as jitter will (almost always) appear downstream in IMD and THD, how much is IMD and THD a problem in competent digital audio kit ?


Yes, it is clear that structured jitter is an entirely different animal - I haven't spent too much time looking at jitter myself as all the previous evidence I have seen says it's below audible thresholds.

 

I also agree that if it is so audible, why isn't there any evidence (concerning reasonable systems) beyond subjective, visually aided testimonials?  I'd be glad to see something - but as far as I'm aware of there's nothing.

post #382 of 438
Quote:
Originally Posted by leeperry View Post

 


Yeah, right...the audible improvement when reclocking 800ps jitter to 50ps coax on the Firestone Bravo is illusionary, the spoon doesn't exist...Same goes for 44.1kHz playback on the Asus Essence STX>ST(the latter has a 75ps CS2000 reclocker between the 24.576Mhz PLL and the DSP). In both cases, the improvement is exactly as explained on this webpage: http://www.bursonaudio.com/burson_clock.htm

 

"The effect of the clock is instant; [..] By reducing the jitter error, you will hear clearer positioning, also details are further refined vocally and instrumentally. Sound stage and positioning will improve noticeably and that includes deeper sound stage and darker background. Some said it also improves the control on the bass."

 

Again, there's that "science-y" talk - no empirical evidence of audibility whatsoever.  Just unsubstantiated claims of improvement with no link establishing proof of correlation of audibility with the reduction in jitter.

 

 

 

Firestone have posted RMAA measurements about reclocking on the Bravo:

http://www.firestone-audio.eu/shop/images/before_520.jpg

http://www.firestone-audio.eu/shop/images/after_520.jpg

 

I admire that you're trying to come up with empirical evidence - and it's true, there is certainly a measurable difference.  But measurable does not automatically mean audible - the reduction in noise is from -120 dB peaks to -130 dB peaks.  You do realize how incredibly low that is already, right?  The absolute best recordings available have a dynamic range of around 60-70 dB, so we're looking at noise that is another 60-70 dB below the noise floor of the recording...

 

In other words, that, while it looks like a major improvement (and it is in technical terms), means absolutely nothing at all in terms of human hearing.

 

 

 

You may wanna try real world experiments, they're worth a thousand words..or so they say. Do you think TC Electronic strive for low jitter in order to please a bunch of audiophools?

 

No, they do it to make money off of a bunch of audiophools.  Or they're audiophools themselves.  I'm not sure which is is, and I'm not sure which is worse either.  One is unethical but craftily evil-genius, and the other is stubbornly ignorant but meaning no real harm (except to peoples' wallets!).

 

 

 

If the DAC's they used in those tests already had a medium to high jitter, anything on top of it won't make an audible difference until you'll reach ridiculous amounts(and good luck generating random jitter)...this is rather easy to understand, but keep thinking that jitter isn't audible on headphones w/ good gear until 500ns if you like[:mcyrb]

 

Yes, they are generating ridiculous amounts of jitter.  250-1000 times the jitter of the so-called "high-jitter" DACs used.  I don't get what's so hard about that to understand.  250 ns of jitter compared to jitter on the order of 1 ns from the system alone.  So the jitter of the system is irrelevant when compared to the induced jitter.

 

And if you think there's no such thing as truly random...  There's plenty of commercial products out there to generate genuine random numbers.  You can get PCI cards with thermal number generators for just that - but their main purpose (outside of science use, for which artificial random numbers are often just fine) is for generating one-time-pad numbers for secure transmission of data.

 

 

 

At this point, we're rather OT as I understand it...let's not make another pointless thread about jitter if any possible...noone's willing to change his mind anyway.

 

That much is clear.


 

post #383 of 438



nm.

post #384 of 438
Quote:
Originally Posted by leeperry View Post
I don't have any point to make, just that saying that all cables sound the same doesn't match MANY ppl's *real world* experience...using lofi gear will never allow you to hear any difference. But keep on thinking that all perceived differences are due to placebo, and that the ppl who hear them are stray sheeps that require guidance badly if you like [:icon12]


So because many people think that cables make a difference doesn't mean they are right until they can consistently pass a DBT. I've heard that phrase over and over, that if you can't hear a difference either you have tin ears or your system isn't resolving enough and those people who say those things never passed a DBT themselves so who are we kidding here?

post #385 of 438

A very interesting conversation about jitter, but can i go back a bit.......what in the following cable comparison of cables is in the audible range?

 

        1000x500px-LL-ed1a5738_Cables.png

post #386 of 438
Originally Posted by BlackbeardBen View Post

 

the reduction in noise is from -120 dB peaks to -130 dB peaks.  You do realize how incredibly low that is already, right?

 

The point of those measurements is not to suppress inaudible background noise, it's to prove that the S/PDIF jitter has been lowered: http://www.head-fi.org/forum/thread/446451/jitter-measurement#post_6027819

 

http://www.lessloss.com/page.html?id=42

 

The S/PDIF masterclock is embedded within the signal and has to be extracted: the cleaner it is, the easier it is for your DAC to work it out = less jitter = clearer and less colored sound. DIR9001 does some fancy clock recovery(much like the CS841x chips), but WM8804 discards it completely and creates new timecodes altogether: http://hifiduino.blogspot.com/2010/02/programming-wm8804.html

 

WM8804 is starting to show up in more and more units because it sounds amazing...it chews the work of the receiver on the other end in a tremendous way, and it's very much audible. It brings the legacy jittery flawed S/PDIF protocol to a whole new level IME.

 

OK, why is S/PDIF flawed? http://www.gearslutz.com/board/so-much-gear-so-little-time/172143-spdif-vs-word-clock-question.html

 

"S/PDIF is a horrendously poorly designed interface. This is because it combines the clock and audio coding onto the same signal. The receiver is supposed to recover the clock from this signal as well as extract the audio data. This turns out to be a non-trivial task, and one that almost always leaves the recovered clock contaminated with signal correlated jitter artefacts."

 

Originally Posted by BlackbeardBen View Post

 

they do it to make money off of a bunch of audiophools.  Or they're audiophools themselves.


humm, TC are far from audiophools...they're simply well aware that USB isn't workable because of the bus clock induced jitter, and that the only proper way to connect an audio interface to a computer is to run it in full async firewire + using their (market leading?) jitter rejection DSP. They have an AES paper about audio jitter available here: http://www.tcelectronic.com/techlibrary.asp

 

Clock and Jitter in Audio Systems using Firewire
 

http://www.tcelectronic.com/media/frandsen_travis_2006_clean_clocks_tc(1).pdf

 

Their $199 Konnekt 6 interface jitter is spec'ed at <42ps RMS at the last page of its manual: http://www.tcelectronic.com/media/dt_konnekt_us_0705.pdf

 

But whatever I'll say, you'll always refuse to try all those audiophool pieces of gear and throw at me whatever study you see fit to prove me wrong.

 

My point is that you're listening to the PSU as much as to the masterclock(whatever passive, or better: active). A high ripple SMPS together w/ a jittery clock won't allow much ppl(if any) to hear the subtle differences between cables...so I'm not that OT after all b5534309458a4a97d172f16d51bc9.gif

post #387 of 438
Thread Starter 
Quote:
Originally Posted by Prog Rock Man View Post

A very interesting conversation about jitter, but can i go back a bit.......what in the following cable comparison of cables is in the audible range?

 

        1000x500px-LL-ed1a5738_Cables.png


The correct answer is that it is highly unlikely that any of these differences would be audible under normal listening conditions and that until someone does (yes you guessed) proper DBTs that the cables tested above in the above setting would have to be regarded as undifferentiable in the above setting. 100+ years of psychophysics research suggests that none of those differences above would be humanly detectable, so until someone proves otherwise...

post #388 of 438
Quote:
Originally Posted by leeperry View Post

Originally Posted by BlackbeardBen View Post

 

the reduction in noise is from -120 dB peaks to -130 dB peaks.  You do realize how incredibly low that is already, right?

 

The point of those measurements is not to suppress inaudible background noise, it's to prove that the S/PDIF jitter has been lowered: http://www.head-fi.org/forum/thread/446451/jitter-measurement#post_6027819

 

http://www.lessloss.com/page.html?id=42

 

The S/PDIF masterclock is embedded within the signal and has to be extracted: the cleaner it is, the easier it is for your DAC to work it out = less jitter = clearer and less colored sound. DIR9001 does some fancy clock recovery(much like the CS841x chips), but WM8804 discards it completely and creates new timecodes altogether: http://hifiduino.blogspot.com/2010/02/programming-wm8804.html

 

WM8804 is starting to show up in more and more units because it sounds amazing...it chews the work of the receiver on the other end in a tremendous way, and it's very much audible. It brings the legacy jittery flawed S/PDIF protocol to a whole new level IME.

 

OK, why is S/PDIF flawed? http://www.gearslutz.com/board/so-much-gear-so-little-time/172143-spdif-vs-word-clock-question.html

 

"S/PDIF is a horrendously poorly designed interface. This is because it combines the clock and audio coding onto the same signal. The receiver is supposed to recover the clock from this signal as well as extract the audio data. This turns out to be a non-trivial task, and one that almost always leaves the recovered clock contaminated with signal correlated jitter artefacts."

 

Originally Posted by BlackbeardBen View Post

 

they do it to make money off of a bunch of audiophools.  Or they're audiophools themselves.


humm, TC are far from audiophools...they're simply well aware that USB isn't workable because of the bus clock induced jitter, and that the only proper way to connect an audio interface to a computer is to run it in full async firewire + using their (market leading?) jitter rejection DSP. They have an AES paper about audio jitter available here: http://www.tcelectronic.com/techlibrary.asp

 

Clock and Jitter in Audio Systems using Firewire
 

http://www.tcelectronic.com/media/frandsen_travis_2006_clean_clocks_tc(1).pdf

 

Their $199 Konnekt 6 interface jitter is spec'ed at <42ps RMS at the last page of its manual: http://www.tcelectronic.com/media/dt_konnekt_us_0705.pdf

 

But whatever I'll say, you'll always refuse to try all those audiophool pieces of gear and throw at me whatever study you see fit to prove me wrong.

 

My point is that you're listening to the PSU as much as to the masterclock(whatever passive, or better: active). A high ripple SMPS together w/ a jittery clock won't allow much ppl(if any) to hear the subtle differences between cables...so I'm not that OT after all b5534309458a4a97d172f16d51bc9.gif


Okay, thanks - I appreciate the clarification.  But you should have made that clear from the beginning instead of posting those measurements unqualified, thus misleading any readers.

 

Also, could you explain to me, explicitly, how the end result of jitter (lateral movement in the time domain of amplitude values) differs from general noise?  Yes, due to its nature it may (or may not) be patterned in a unique manner, and it of course arises in a unique manner - but how does the time domain movement of sample values differ from small random changes in amplitude?  Each potentially has the same effect on the waveform, does it not (i.e. moving a sampling point up/down in amplitude a certain amount could be similarly represented by moving the point forward/backwards in time)?  You're changing the waveform slightly in a random or unwanted pattern - that's exactly what noise is!

 

In the case of those measurements, you're seeing the real artifacts that are resulting from jitter of a sine wave - do you really think that you can hear those artifacts even at -100 dB?

 

I'd be interested to hear about this from someone knowledgeable in the matter.

 

 

 

I don't have any disagreement with saying that reducing jitter is a technical improvement... Or the methods to do so.  But I still utterly fail to see any empirical evidence that it matters for human hearing at all.  You can continue to show me all the charts and technical documents you want that show the technical achievement of reducing jitter - that's great.  It's an impressive technological breakthrough.

 

But it means nothing whatsoever except in the lab unless we can hear the difference - and proof of that is what I'm looking for.  You're talking of jitter in the low hundreds and tens of picoseconds -  100 to 1000 times smaller than listening tests have shown is audible for structured jitter, and as much as 1000 times less than for random jitter.  Show me studies or tests of any sort (not sighted, of course) that show that such jitter at such levels you're talking about is in fact audible, and I'll gladly review them.  Show me.  I want to see evidence for the audibility of jitter at levels of under one nanosecond.

post #389 of 438
Thread Starter 
Quote:
Originally Posted by BlackbeardBen View Post

 

But it means nothing whatsoever except in the lab unless we can hear the difference - and proof of that is what I'm looking for.  You're talking of jitter in the low hundreds and tens of picoseconds -  100 to 1000 times smaller than listening tests have shown is audible for structured jitter, and as much as 1000 times less than for random jitter.  Show me studies or tests of any sort (not sighted, of course) that show that such jitter at such levels you're talking about is in fact audible, and I'll gladly review them.  Show me.  I want to see evidence for the audibility of jitter at levels of under one nanosecond.



 

I've spent over 4 years researching this topic, I even joined the AES so I could trawl their library of papers. I've harrangued manufacturers and audio experts alike. Let us be quite clear, there is not one credible shred of empirical evidence to suggest that jitter in the magnitude and patterns as found in barely competent commercially available digital audio kit is in any way audible as a separate artifact. Random jitter adds noise which effectively lowers the resolution, signal correlated jitter adds distinct distortion sidebands. The only piece of audio kit that has verified jitter that even gets close to the most pessimistic threshold of audibility is the piss-poor McIntosh music server which Stereophile helpfully measured

 

http://www.stereophile.com/content/mcintosh-ms750-music-server-measurements

 

If ps of jitter are important then a system with this much jitter (14ns) should be utterly unlistenable. In fact while it is an awful piece of kit in absolute terms jitter is the least of its problems , it has IMD and THD 20 - 24db worse than its jitter distortion, still the Stereophile reviewer liked it until he was told how just how badly it measured then when he went back and compared it to another system and he then thought it a let-down - if I know it is bad I will hear it as bad - these golden ears crack me up right enough !

 

post #390 of 438

 

Originally Posted by BlackbeardBen View Post

 

Show me.  I want to see evidence for the audibility of jitter


Get a Firestone Bravo from any reseller, you got 1 or 2 weeks to get a refund...try to reclock Realtek POF toslink(worst case scenario, use a long cable too) to a short coax(4/5ft), and you'll hear what it's all about. That's the only hard clue I can provide...The sound will be clearer and tighter, less distorted and less colored...more punchy too.

 

I would lend you my Bravo but I reside overseas, and I kinda use it everyday ^^

 

That's the only PNP WM8804 reclocker on the market AFAIK, otherwise there's this board(I've seen it selling for $50 second hand here on head-fi): http://www.twistedpearaudio.com/digital/wm8804.aspx

 

I don't see how anyone could say that WM8804's effect on jitter is inaudible. Other owners in the Bravo thread have confirmed that going toslink>coax was quite a blast. S/PDIF jitter is nasty because it compromises the clock extraction..as quoted above, it "leaves the recovered clock contaminated with signal correlated jitter artefacts".

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