Re: [time-nuts] Clocks for Audio gear
On Fri, May 11, 2012 at 1:27 AM, Chris Albertson albertson.ch...@gmail.comwrote: I've alway have thought that if nanosecond level jitter is bad then breathing while listening must be really bad. If you inhale the path length from your ear to the speaker changes at the microsecond level. You'd think the resulting doppler shift would drive these audiophiles nuts. All that pitch shifting. +1 So my new product for this is the head vice It will have three wooden plates with lead screw clamps in a cast iron frame. The iron frame is to be bolted to a wall of other massive object. This will greatly reduce those annoying microsecond level audio path length variations that are caused by breathing, blood flow and eye blinks. For those sensitive to picosecond level jitter, the wood blocks can be removed and the steel clamp plate applied directly (wood after all is elastic and compressible) ! +1.02104 Permission to resend to all my audiophile friends? -- Sanjeev Gupta +65 98551208 http://www.linkedin.com/in/ghane ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Clocks for Audio gear
Ashihara's tests were with music/voice, taking into account psychoacoustics, for an average group of music savvy listeners, and even music professionals. As uncorrelated jitter is practically raising the noise floor, most of it was masked by the signal, making it more difficult to detect. Benjamin and Gannon used sinusoidal jitter, which isn't appearing normally in signal chains (badly designed ones excepted). In a real case, with higher probability (added) jitter would be correlated with the digital content transmitted over a path - S/PDIF, and AES/EBU are prone to jitter induced by the signal path characteristics, ISI - PSUs, and even external noise sources. A more realistic simulation would take those into account. OTOH there where tests on pure sine tones, with sine jitter, detectable by trained ears at even lower levels of jitter, which might indicate the lowest threshold of hearing, but using artificial conditions. Who would listen to pure sine tones? On 5/10/2012 8:25 PM, Heinzmann, Stefan (ALC NetworX GmbH) wrote: Chris Albertson wrote: If we are to believe the above paper,then those guys who claim to hear pS jitter are wrong. Note that the jitter spectrum matters for its audibility. Ashihara et.al. used random jitter, and it is not very suprising that the sensitivity for random jitter is lower than for jitter that has specially been shaped to improve detectability by human ears. Thus the results by Ashihara are credible, but they are not the lower limit on jitter audibility. Benjamin and Gannon, the first reference in Ashihara's paper, come to lower figures for sinusoidal jitter with carefully selected frequencies relative to the main signal, which is also sinusoidal. Their results reach down to the single figure nanosecond range, and that can be regarded as the real limit of audibility. Of course, that still leaves those who claim to hear jitter in the picoseconds range out in fairy-tale land. And jitter of just a few nanoseconds is still quite easy to achieve with crystal oscillators. No need for special and expensive parts, then. Normal developer diligence is enough. Cheers Stefan ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Clocks for Audio gear
MailLists wrote: Ashihara's tests were with music/voice, taking into account psychoacoustics, for an average group of music savvy listeners, and even music professionals. As uncorrelated jitter is practically raising the noise floor, most of it was masked by the signal, making it more difficult to detect. Benjamin and Gannon used sinusoidal jitter, which isn't appearing normally in signal chains (badly designed ones excepted). In a real case, with higher probability (added) jitter would be correlated with the digital content transmitted over a path - S/PDIF, and AES/EBU are prone to jitter induced by the signal path characteristics, ISI - PSUs, and even external noise sources. A more realistic simulation would take those into account. OTOH there where tests on pure sine tones, with sine jitter, detectable by trained ears at even lower levels of jitter, which might indicate the lowest threshold of hearing, but using artificial conditions. Who would listen to pure sine tones? Ashihara et.al. wanted to find out what level of jitter was likely to be audible under real-world conditions. Those conditions would likely include music as the main signal, and random jitter. Benjamin/Gannon wanted to find out what levels of jitter could be detected if the conditions were as favorable as possible for detecting jitter. That is not the real-world situation, of course, but it can establish a baseline where you may legitimately say that if you stay below this line with jitter of whatever type, the effects are very unlikely to be audible. And, to add a comment towards Attila, one of the results by Benjamin/Gannon was that training matters a lot, and the best sensitivity was by trained listeners. Your comment is therefore warranted, but already accounted for. Hence, even though their results appear to be very different, they are both valid, because it depends on the exact question asked. I would dare to say, that no matter how you set up your realistic simulation, the results are likely to be somewhere between the values by Benjamin/Gannon and by Ashihara et.al. So, for the purpose of this group, I'd say the psychoacoustic stuff would lead too far, but it might be helpful to know at which jitter levels one can assume to be on the safe side in an audio system, regarding audibility of jitter effects. Judging from the mentioned studies, I concluded (for myself at least), that this boundary is somewhere in the single figure nanoseconds, until someone comes forth with hard evidence that it needs to be set lower. Cheers Stefan ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Clocks for Audio gear
The brain uses phase at low frequency and amplitude at higher frequencies to find the direction a signal is coming from. It works better for low frequencies than high when you have a steady tone, but high frequency positioning is better when the signal is pulsed. It is almost impossible to locate the source of a continuous high pitch tone in a confined space because of standing waves. My boat has a piezo buzzer to indicate low oil level. It was completely impossible for me to tell if it was located in the engine compartment or under the dash, or anywhere else, even though the cockpit is wide open. It turns out it was in the engine controller, to the right of the driving position. Someone had to tell me. Didier KO4BB Sent from my BlackBerry Wireless thingy while I do other things... -Original Message- From: Dan Kemppainen d...@irtelemetrics.com Sender: time-nuts-boun...@febo.com Date: Thu, 10 May 2012 16:16:44 To: time-nuts@febo.com Reply-To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] Clocks for Audio gear Don't forget the human mind can compensate for a lot of things. Think of how we can triangulate a sound source in realtime even with the included echos in a small room. The only thing that I can think of that messes with that system is a single tone setting up standing waves. It's impressive if you think about it. So, it's probably not much of a stretch to imagine the mind compensating for a little movement here and there (since we have controls and feedback to monitor that). It may just take a few thousand years for us to evolve to deal with distortion due to jitter in our digital recordings :) All fun aside. This has been a worth while thread in my opinion. I'm learning more this week, than others watching this list! On 5/10/2012 1:49 PM, time-nuts-requ...@febo.com wrote: I've alway have thought that if nanosecond level jitter is bad then breathing while listening must be really bad. If you inhale the path length from your ear to the speaker changes at the microsecond level. You'd think the resulting doppler shift would drive these audiophiles nuts. All that pitch shifting. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Clocks for Audio gear
Breathing and heart beat are filtered out and corrected for by the brain, otherwise we would have difficulties to hear a lot of things. Interestingly, that works well in our natural environment, but not as well when you are somewhere else. When free diving (when there is no noisy scuba gear and breathing), you can hear your own heartbeat and so can the fish, sometimes at significant distances as it propagates well under water. Didier KO4BB Sent from my BlackBerry Wireless thingy while I do other things... -Original Message- From: Attila Kinali att...@kinali.ch Sender: time-nuts-boun...@febo.com Date: Thu, 10 May 2012 23:25:50 To: Discussion of precise time and frequency measurementtime-nuts@febo.com Reply-To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] Clocks for Audio gear On Thu, 10 May 2012 11:36:40 -0700 Hal Murray hmur...@megapathdsl.net wrote: Heartbeats may be more interesting than breathing. Does anybody know of spectrum domain data? It should be possible to collect position info while also monitoring heartbeat and chest diameter and then crunch some numbers do see how much of the position correlates with heartbeat vs breathing and then plot each part in the frequency domain. Please do not forget that there is a quite sofisticated error correction system attached to the hear, which we usually refere to as the brain. Breathing and heart beat are filtered out and corrected for by the brain, otherwise we would have difficulties to hear a lot of things. For more infos, please have a look at perceptual psychology. A not too bad introduction to that field is Sensation and Perception by E. B. Goldstein. But please do not expect mathematical rigor in that field. It's still a subfield of psychology. Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Clocks for Audio gear
Hi, That jitter value, was that one period jitter? Or was it jitter over a large number of periods, thus close by the carrier? Henk MailLists wrote: Ashihara's tests were with music/voice, taking into account psychoacoustics, for an average group of music savvy listeners, and even music professionals. As uncorrelated jitter is practically raising the noise floor, most of it was masked by the signal, making it more difficult to detect. Benjamin and Gannon used sinusoidal jitter, which isn't appearing normally in signal chains (badly designed ones excepted). In a real case, with higher probability (added) jitter would be correlated with the digital content transmitted over a path - S/PDIF, and AES/EBU are prone to jitter induced by the signal path characteristics, ISI - PSUs, and even external noise sources. A more realistic simulation would take those into account. OTOH there where tests on pure sine tones, with sine jitter, detectable by trained ears at even lower levels of jitter, which might indicate the lowest threshold of hearing, but using artificial conditions. Who would listen to pure sine tones? Ashihara et.al. wanted to find out what level of jitter was likely to be audible under real-world conditions. Those conditions would likely include music as the main signal, and random jitter. Benjamin/Gannon wanted to find out what levels of jitter could be detected if the conditions were as favorable as possible for detecting jitter. That is not the real-world situation, of course, but it can establish a baseline where you may legitimately say that if you stay below this line with jitter of whatever type, the effects are very unlikely to be audible. And, to add a comment towards Attila, one of the results by Benjamin/Gannon was that training matters a lot, and the best sensitivity was by trained listeners. Your comment is therefore warranted, but already accounted for. Hence, even though their results appear to be very different, they are both valid, because it depends on the exact question asked. I would dare to say, that no matter how you set up your realistic simulation, the results are likely to be somewhere between the values by Benjamin/Gannon and by Ashihara et.al. So, for the purpose of this group, I'd say the psychoacoustic stuff would lead too far, but it might be helpful to know at which jitter levels one can assume to be on the safe side in an audio system, regarding audibility of jitter effects. Judging from the mentioned studies, I concluded (for myself at least), that this boundary is somewhere in the single figure nanoseconds, until someone comes forth with hard evidence that it needs to be set lower. Cheers Stefan ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Clocks for Audio gear
On 5/11/12 12:48 AM, MailLists wrote: Who would listen to pure sine tones? As a youth, I listened to WWV, which is a pure sine tone, in between the ticks. Drove my parents batty. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Clocks for Audio gear
- Original Message - From: Jim Lux jim...@earthlink.net To: time-nuts@febo.com Sent: Friday, May 11, 2012 8:10 AM Subject: Re: [time-nuts] Clocks for Audio gear On 5/11/12 12:48 AM, MailLists wrote: Who would listen to pure sine tones? As a youth, I listened to WWV, which is a pure sine tone, in between the ticks. Drove my parents batty. me too, I think replaying this in my head is a better way to measure time than the 1 thousand, 2 ... trick, having low music skills would wonder what the limit of human time keeping is ? Director , Drummer ... how would we collect data to produce a Allan variance graph ? Does a timing savant exist ? http://discovermagazine.com/2002/feb/featsavant Stanley ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Clocks for Audio gear
Two things 1) - people in anechoic chambers will really notice the sound of their heartbeats as well as the s-sh-s-sh sound of the blood flowing through their heads. http://en.wikipedia.org/wiki/Anechoic_chamber They are designed to have complete sound absorption and are dead quiet. Very spooky to be in -- used to live in Boston and Harvard University had one that I was able to visit for an hour. 2) - an interesting experiment in brain filtering is to stand near a broadband noise source (fan or air conditioner or radio with someone talking) and talk with someone. Have a recorder going and record your conversation. You can understand the other person perfectly while face to face but listening to the recorded conversation, it will be hard to hear them over all that noise. Dave -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of shali...@gmail.com Sent: Friday, May 11, 2012 04:27 To: Time-Nuts Subject: Re: [time-nuts] Clocks for Audio gear Breathing and heart beat are filtered out and corrected for by the brain, otherwise we would have difficulties to hear a lot of things. Interestingly, that works well in our natural environment, but not as well when you are somewhere else. When free diving (when there is no noisy scuba gear and breathing), you can hear your own heartbeat and so can the fish, sometimes at significant distances as it propagates well under water. Didier KO4BB Sent from my BlackBerry Wireless thingy while I do other things... -Original Message- From: Attila Kinali att...@kinali.ch Sender: time-nuts-boun...@febo.com Date: Thu, 10 May 2012 23:25:50 To: Discussion of precise time and frequency measurementtime-nuts@febo.com Reply-To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] Clocks for Audio gear On Thu, 10 May 2012 11:36:40 -0700 Hal Murray hmur...@megapathdsl.net wrote: Heartbeats may be more interesting than breathing. Does anybody know of spectrum domain data? It should be possible to collect position info while also monitoring heartbeat and chest diameter and then crunch some numbers do see how much of the position correlates with heartbeat vs breathing and then plot each part in the frequency domain. Please do not forget that there is a quite sofisticated error correction system attached to the hear, which we usually refere to as the brain. Breathing and heart beat are filtered out and corrected for by the brain, otherwise we would have difficulties to hear a lot of things. For more infos, please have a look at perceptual psychology. A not too bad introduction to that field is Sensation and Perception by E. B. Goldstein. But please do not expect mathematical rigor in that field. It's still a subfield of psychology. Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Clocks for Audio gear
On Wed, 09 May 2012 14:25:34 -0700 Hal Murray hmur...@megapathdsl.net wrote: Back to technical stuff... As a practical matter, is clock jitter or phase noise from a typical low cost crystal and decent board layout a significant problem in audio gear? How hard is it to measure? Depends on how accurate it should be ;-) But for audio purposes, the crystal itself has low enough noise. The Problem is the oscillator circuit and the power supply. That's where most designs mess up. Video geeks solved their clock distribution problems by using frame buffers. Is there a similar trick for audio? Is there a need for it? Video is a lot less sensitive to jitter. An A/V desync starts to be noticable from 10ms upwards for most people. Trained people notice it even below 5ms. I guess that 1ms is beyond what anyone can notice. But imagine you've a 1ms gap in your audio... People will scream at the poor quality. Part of the problem is that they are doing magic down conversion in the ADC. (I can't think of the term.) Direct downconversion using sampling :-) Suppose you have a 100 MHz signal with a 1 MHz bandwidth. You don't have to sample at 200 MHz. You can sample at 2 MHz and your signal will alias down. It's turning what is normally a bug into a feature. It's not a bug. It's a feature of the sampling process itself. Think of sampling as multiplication of an comp of dirac pulses with your input signal. Now remember that mixing is a multiplication of two signalsAnd the idea doing that is actually quite old, but it wasn't feasible with main stream components until a few years back. Attila Kinali -- The trouble with you, Shev, is you don't say anything until you've saved up a whole truckload of damned heavy brick arguments and then you dump them all out and never look at the bleeding body mangled beneath the heap -- Tirin, The Dispossessed, U. Le Guin ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Clocks for Audio gear
Hearing tests showed the ability to discern jitter above a few hundred nanoseconds rms. http://amorgignitamorem.nl/Audio/Jitter/Detection%20threshold%20for%20distortions%20due%20to%20jitter%20on%20digital%20audio%2026_50.pdf Others claim the ability to detect jitter in the picoseconds range... It would be a conservative assumption that jitter in the range of tens-hundreds of picoseconds will be practically not discernible. Usually integrated oscillators are composed of the classical inverting gate oscillator, with external CQC, and selfbiasing R, which has practically no rejection (~6dB) of the power supply noise. As it's usually on the same die with noisy digital circuitry, the gate threshold will jump around, producing timing errors, also the slew-rate is quite low, which just worsens the situation. As most digital circuitry is less affected by jitter, the best solution is to place a clean oscillator near the D/A conversion, where the most critical timing point is, and through buffers clock the rest of the digital circuits - eventually galvanic isolation might be implemented, to pollute less the analog part with digital noise. To minimize jitter, digital clock inputs should be driven by fast slew-rate circuitry. On 5/10/2012 12:25 AM, Hal Murray wrote: was Subject: Re: [time-nuts] Faster than light of a different type (Probably my fault.) act...@hotmail.com said: What I found funny was that the Audiophlie and light thread drew such attacks when it hit home to me as exactly what the Time-Nuts mission is about. The Audio thread touched on some real world time and freq research ... I too enjoyed the technical discussions. Thanks for your contributions. It's the audiophool bashing that people are complaining about. Sure, it's fun, but only at the right time and it gets old quickly. The problem is that with large groups, there are different opinions of when and how much is appropriate. The long tail on opinions of reasonable can annoy a lot of people. --- Back to technical stuff... As a practical matter, is clock jitter or phase noise from a typical low cost crystal and decent board layout a significant problem in audio gear? How hard is it to measure? Is clock accuracy a practical problem? How good are people with perfect pitch? It wouldn't surprise me if there are a few that are much much better than others, but how good is that relative to 50 PPM which I can get in a low cost crystal? Video geeks solved their clock distribution problems by using frame buffers. Is there a similar trick for audio? Is there a need for it? I know clocking is a serious problem in fancy DSP systems. For example, modern radar has gone digital. In that context, clock jitter can be important. Standard procedure is don't run your clock through a FPGA because it will add jitter. Part of the problem is that they are doing magic down conversion in the ADC. (I can't think of the term.) Suppose you have a 100 MHz signal with a 1 MHz bandwidth. You don't have to sample at 200 MHz. You can sample at 2 MHz and your signal will alias down. It's turning what is normally a bug into a feature. The catch is that the errors/noise due to clock jitter happens at the high frequency, in this case multiplying the noise by 100. (Your sample/hold at the front end has to work at the high frequency and your anti-aliasing filter gets more interesting.) There has been an interesting change in the specs for ADCs and DACs over the past 20(?) years. They used to be specified using terms like DNL and INL and No-missing-codes. Modern high-speed ADCs are specified with terms like ENOB and SFDR. Data sheets often include several plots of a batch of samples run through a DFT so you can see the noise floor and such. Here is a reasonable glossary: http://pdfserv.maxim-ic.com/en/an/AN641.pdf I don't remember comments/specs about clock jitter in the data sheets but I haven't looked at one in a few years. I'll have to keep an eye out the next time I'm browsing. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Clocks for Audio gear
In message 4fab74eb.1050...@medesign.ro, MailLists writes: Others claim the ability to detect jitter in the picoseconds range... It would be a conservative assumption that jitter in the range of tens-hundreds of picoseconds will be practically not discernible. We're probably talking about one of those tripple-blind experiments ? (http://www.cco.caltech.edu/~boyk/sdttest.htm) -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Clocks for Audio gear
Hal Murray wrote: As a practical matter, is clock jitter or phase noise from a typical low cost crystal and decent board layout a significant problem in audio gear? How hard is it to measure? The answer depends a lot on the circumstances (as usual). If you refer to jitter effects on a conversion between analog and digital (either way), and you're interested in whether these can be audible, you will want to measure the effect on the audio signal, and not necessarily the jitter itself. For example, you might want to use a high frequency sine wave close to the upper bandwidth limit as the audio signal, and measure the jitter-related distortions using an FFT analyzer. It may be hard to distinguish jitter-related artifacts from other distortions, but as you are interested in the overall signal fidelity, that's probably what you want anyway. The good thing about that is that you need no extra gear that you don't already have as an audio developer. No expensive phase noise analyzer, for example. If you refer to jitter effects on a digital transmission, you will be interested in what they do to the bit error probability, or whether you are still conformant to some standard that puts a limit to the allowable jitter. In that case you are more likely to find yourself looking at eye diagrams on an oscilloscope, or perhaps using a bit error analyzer. There is little use for a proper phase noise analyzer in audio, and RD labs of most manufacturers I know don't have one. Is clock accuracy a practical problem? How good are people with perfect pitch? It wouldn't surprise me if there are a few that are much much better than others, but how good is that relative to 50 PPM which I can get in a low cost crystal? Clock accuracy can be a problem, but not because of pitch perception. Crystal oscillators are easily accurate enough for human perception, even the crappy ones. Clock accuracy does matter in system applications, when pieces of gear need to lock to each other, or to a house clock. Here, the clock accuracy needs to match the lock range of downstream PLLs, or else you can't lock reliably. The AES11 standard has rules for that. Video geeks solved their clock distribution problems by using frame buffers. Is there a similar trick for audio? Is there a need for it? A sample buffer of at least one sample is contained in pretty much every S/P-DIF or AES/EBU receiver chip, so the answer to your question would be yes. Storing a sample is cheap, however, compared to storing a video frame. Cheers Stefan ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Clocks for Audio gear
On Thu, May 10, 2012 at 12:57 AM, MailLists li...@medesign.ro wrote: Hearing tests showed the ability to discern jitter above a few hundred nanoseconds rms. http://amorgignitamorem.nl/Audio/Jitter/Detection%20threshold%20for%20distortions%20due%20to%20jitter%20on%20digital%20audio%2026_50.pdf Others claim the ability to detect jitter in the picoseconds range... If we are to believe the above paper,then those guys who claim to hear pS jitter are wrong. Likely they can also here is a fuse is is place in the holder backwards. So by the above, no now can hear 250 nS of jitter.I really doubt any decent system other then the most low-cost consumer level junk has jitter at the 250 nS level. Even a TTL can oscillator is better than that. A TTL can that is marked 4.096 MHz costs about $2 and will make a square wave with a period of very close to 250 nS. Then they divide this down to the sample rate of 96KHz. In order to see a 250 nS jitter in the 96K signal the TTL can would have to skip a beat. 250 nS is is a huge error and you don't get there with digital noise Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Clocks for Audio gear
In fact, I do believe the paper is a voice of rationality in an ocean oh hype. Very expensive hype, promoted by shameless hucksters. -John === On Thu, May 10, 2012 at 12:57 AM, MailLists li...@medesign.ro wrote: Hearing tests showed the ability to discern jitter above a few hundred nanoseconds rms. http://amorgignitamorem.nl/Audio/Jitter/Detection%20threshold%20for%20distortions%20due%20to%20jitter%20on%20digital%20audio%2026_50.pdf Others claim the ability to detect jitter in the picoseconds range... If we are to believe the above paper,then those guys who claim to hear pS jitter are wrong. Likely they can also here is a fuse is is place in the holder backwards. So by the above, no now can hear 250 nS of jitter.I really doubt any decent system other then the most low-cost consumer level junk has jitter at the 250 nS level. Even a TTL can oscillator is better than that. A TTL can that is marked 4.096 MHz costs about $2 and will make a square wave with a period of very close to 250 nS. Then they divide this down to the sample rate of 96KHz. In order to see a 250 nS jitter in the 96K signal the TTL can would have to skip a beat. 250 nS is is a huge error and you don't get there with digital noise Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Clocks for Audio gear
Chris Albertson wrote: If we are to believe the above paper,then those guys who claim to hear pS jitter are wrong. Note that the jitter spectrum matters for its audibility. Ashihara et.al. used random jitter, and it is not very suprising that the sensitivity for random jitter is lower than for jitter that has specially been shaped to improve detectability by human ears. Thus the results by Ashihara are credible, but they are not the lower limit on jitter audibility. Benjamin and Gannon, the first reference in Ashihara's paper, come to lower figures for sinusoidal jitter with carefully selected frequencies relative to the main signal, which is also sinusoidal. Their results reach down to the single figure nanosecond range, and that can be regarded as the real limit of audibility. Of course, that still leaves those who claim to hear jitter in the picoseconds range out in fairy-tale land. And jitter of just a few nanoseconds is still quite easy to achieve with crystal oscillators. No need for special and expensive parts, then. Normal developer diligence is enough. Cheers Stefan ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Clocks for Audio gear
I've alway have thought that if nanosecond level jitter is bad then breathing while listening must be really bad. If you inhale the path length from your ear to the speaker changes at the microsecond level. You'd think the resulting doppler shift would drive these audiophiles nuts. All that pitch shifting. So my new product for this is the head vice It will have three wooden plates with lead screw clamps in a cast iron frame. The iron frame is to be bolted to a wall of other massive object. This will greatly reduce those annoying microsecond level audio path length variations that are caused by breathing, blood flow and eye blinks. For those sensitive to picosecond level jitter, the wood blocks can be removed and the steel clamp plate applied directly (wood after all is elastic and compressible) On Thu, May 10, 2012 at 10:03 AM, J. Forster j...@quikus.com wrote: In fact, I do believe the paper is a voice of rationality in an ocean oh hype. Very expensive hype, promoted by shameless hucksters. -John === On Thu, May 10, 2012 at 12:57 AM, MailLists li...@medesign.ro wrote: Hearing tests showed the ability to discern jitter above a few hundred nanoseconds rms. http://amorgignitamorem.nl/Audio/Jitter/Detection%20threshold%20for%20distortions%20due%20to%20jitter%20on%20digital%20audio%2026_50.pdf Others claim the ability to detect jitter in the picoseconds range... If we are to believe the above paper,then those guys who claim to hear pS jitter are wrong. Likely they can also here is a fuse is is place in the holder backwards. So by the above, no now can hear 250 nS of jitter. I really doubt any decent system other then the most low-cost consumer level junk has jitter at the 250 nS level. Even a TTL can oscillator is better than that. A TTL can that is marked 4.096 MHz costs about $2 and will make a square wave with a period of very close to 250 nS. Then they divide this down to the sample rate of 96KHz. In order to see a 250 nS jitter in the 96K signal the TTL can would have to skip a beat. 250 nS is is a huge error and you don't get there with digital noise Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Clocks for Audio gear
Great dialog. The Time Nuts form can be very humbling and often has me questioning my own knowledge base. This thread is no exception. My take on the effect of jitter is when an d toA converter is reproducing a pure sine wave even a single point of slight jitter will show up in the FFT as false analog content. In a complex wave it can easily change the relationship between a fundamental and harmonics. This is a major problem in speaker crossovers design where drivers with different masses can only be aligned at one freq. It has been my experience this relationship between fundmentals and harmonics is noticeably audible at levels that are difficult to measure. To me, it is this difficulty to mathematically define certain aspects of audible distortion that makes audio design fascinating. (It also makes some voodoo science and snake oil products difficult to disprove, especially to those lacking an electronics or physics background) Will timing improvements affect sound quality, because of the complexity of human hearing it seems to me still worthy of investigation. Time will tell. Best Wishes; Thomas Knox From: albertson.ch...@gmail.com Date: Thu, 10 May 2012 09:48:21 -0700 To: time-nuts@febo.com Subject: Re: [time-nuts] Clocks for Audio gear On Thu, May 10, 2012 at 12:57 AM, MailLists li...@medesign.ro wrote: Hearing tests showed the ability to discern jitter above a few hundred nanoseconds rms. http://amorgignitamorem.nl/Audio/Jitter/Detection%20threshold%20for%20distortions%20due%20to%20jitter%20on%20digital%20audio%2026_50.pdf Others claim the ability to detect jitter in the picoseconds range... If we are to believe the above paper,then those guys who claim to hear pS jitter are wrong. Likely they can also here is a fuse is is place in the holder backwards. So by the above, no now can hear 250 nS of jitter.I really doubt any decent system other then the most low-cost consumer level junk has jitter at the 250 nS level. Even a TTL can oscillator is better than that. A TTL can that is marked 4.096 MHz costs about $2 and will make a square wave with a period of very close to 250 nS. Then they divide this down to the sample rate of 96KHz. In order to see a 250 nS jitter in the 96K signal the TTL can would have to skip a beat. 250 nS is is a huge error and you don't get there with digital noise Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Clocks for Audio gear
albertson.ch...@gmail.com said: I've alway have thought that if nanosecond level jitter is bad then breathing while listening must be really bad. If you inhale the path length from your ear to the speaker changes at the microsecond level. You'd think the resulting doppler shift would drive these audiophiles nuts. All that pitch shifting. Perhaps the spectrum of the jitter matters. If the frequency is low enough, I call it wander rather than jitter. Audio doesn't need DC or low frequencies so wander is easy to filter out with a simple high-pass filter. Heartbeats may be more interesting than breathing. Does anybody know of spectrum domain data? It should be possible to collect position info while also monitoring heartbeat and chest diameter and then crunch some numbers do see how much of the position correlates with heartbeat vs breathing and then plot each part in the frequency domain. -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Clocks for Audio gear
One interesting note however. Years ago we had a standard old 4040 ripple counter in our shop that displayed a low occurrence of jitter of several times it's input frequency period at it's lowest frequency output (Sort of what you are describing below). I wish I had the numbers handy, but the output would be good for most of the time, then every once in a while it would jump to a longer delay. It was hard to catch with a scope, but when we measured every single pulse width it showed up fairly well. The high speed clock (A TTL OSC in a can) never skipped, as far as we know. We never did figure that one out. From what I remember we switched IC manufacturers, and the problem when away. Dan On 5/10/2012 1:49 PM, time-nuts-requ...@febo.com wrote: A TTL can that is marked 4.096 MHz costs about $2 and will make a square wave with a period of very close to 250 nS. Then they divide this down to the sample rate of 96KHz. In order to see a 250 nS jitter in the 96K signal the TTL can would have to skip a beat. 250 nS is is a huge error and you don't get there with digital noise Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Clocks for Audio gear
On 5/10/12 11:36 AM, Hal Murray wrote: albertson.ch...@gmail.com said: I've alway have thought that if nanosecond level jitter is bad then breathing while listening must be really bad. If you inhale the path length from your ear to the speaker changes at the microsecond level. You'd think the resulting doppler shift would drive these audiophiles nuts. All that pitch shifting. Perhaps the spectrum of the jitter matters. If the frequency is low enough, I call it wander rather than jitter. Audio doesn't need DC or low frequencies so wander is easy to filter out with a simple high-pass filter. Heartbeats may be more interesting than breathing. Does anybody know of spectrum domain data? It should be possible to collect position info while also monitoring heartbeat and chest diameter and then crunch some numbers do see how much of the position correlates with heartbeat vs breathing and then plot each part in the frequency domain. oddly, I happen to have just that data to hand, having been looking at ballistocardiography. If you put someone in a bed, suspended by 4 wires (one at each corner), your heart beat results in about 1mm displacement (head to foot). 1 degree phase shift at 1 kHz, or thereabouts. in terms of displacement in general, breathing is on the order of 1cm (at 0.1 Hz) and heartbeat is on the order of 0.1-1mm, depending on where you look. (look up microwave cardiography for instance) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Clocks for Audio gear
On 5/10/12 12:44 PM, Chris Albertson wrote: On Thu, May 10, 2012 at 10:25 AM, Heinzmann, Stefan (ALC NetworX GmbH)stefan.heinzm...@alcnetworx.de wrote: Benjamin and Gannon, the first reference in Ashihara's paper, come to lower figures for sinusoidal jitter with carefully selected frequencies relative to the main signal, which is also sinusoidal. Their results reach down to the single figure nanosecond range, and that can be regarded as the real limit of audibility. Are there any real audio systems with sinusoidal jitter. powerline ripple on a signal going into a threshold detector that drive the sample clock would be a nice way to generate sinusoidal jitter. I've got a nice example where 66MHz processor clock modulates a 49MHz sample clock (well, it's not perfectly sinusoidal, but if you digitize a clean sine wave, you get nice aliases of the modulation frequency). I'd goes that it would all be random. I can see where I could build a system with that defect if I wanted to but are there any systems on the market like this? Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Clocks for Audio gear
Don't forget the human mind can compensate for a lot of things. Think of how we can triangulate a sound source in realtime even with the included echos in a small room. The only thing that I can think of that messes with that system is a single tone setting up standing waves. It's impressive if you think about it. So, it's probably not much of a stretch to imagine the mind compensating for a little movement here and there (since we have controls and feedback to monitor that). It may just take a few thousand years for us to evolve to deal with distortion due to jitter in our digital recordings :) All fun aside. This has been a worth while thread in my opinion. I'm learning more this week, than others watching this list! On 5/10/2012 1:49 PM, time-nuts-requ...@febo.com wrote: I've alway have thought that if nanosecond level jitter is bad then breathing while listening must be really bad. If you inhale the path length from your ear to the speaker changes at the microsecond level. You'd think the resulting doppler shift would drive these audiophiles nuts. All that pitch shifting. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Clocks for Audio gear
On Thu, May 10, 2012 at 1:09 PM, Jim Lux jim...@earthlink.net wrote: On 5/10/12 12:44 PM, Chris Albertson wrote: powerline ripple on a signal going into a threshold detector that drive the sample clock would be a nice way to generate sinusoidal jitter. I can think of other ways to design a defective system. But what I was wondering if there are in fact any audio systems on the market like this. The real reason that a recording studio will use a master clock is not because you can hear nS level jitter. It's that they like to use a sample accurate editor and they want to be able to over dub tracks recorded at different times, maybe months apart Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Clocks for Audio gear
Are there any real audio systems with sinusoidal jitter. I'd goes that it would all be random. I can see where I could build a system with that defect if I wanted to but are there any systems on the market like this? I could easily imagine jitter with a significant sinusoidal component. Consider noise from the power supply leaking through. If you think of it as phase noise rather than jitter it would show up as a spike and harmonics. -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Clocks for Audio gear
d...@irtelemetrics.com said: One interesting note however. Years ago we had a standard old 4040 ripple counter in our shop that displayed a low occurrence of jitter of several times it's input frequency period at it's lowest frequency output (Sort of what you are describing below). I wish I had the numbers handy, but the output would be good for most of the time, then every once in a while it would jump to a longer delay. It was hard to catch with a scope, but when we measured every single pulse width it showed up fairly well. The high speed clock (A TTL OSC in a can) never skipped, as far as we know. We never did figure that one out. From what I remember we switched IC manufacturers, and the problem when away. I expect ever old timer who did serious glitch chasing 25-30 years ago has similar stories. Mine involved a dual port RAM, 16x4. I think it was a 74S189. It was made by many companies. Chips from one vendor just occasionally screwed up. We were using them in FIFOs on ethernet boards. (They were probably used other other places too. I was worked on networking.) Back then, most large electronics companies had incoming inspection and qualification groups. I remember stories of somebody contacting that group for help and getting a response of roughly That's why we didn't qualify them. (We were a research group. We purchased small batches of chips wherever we could get them without going through the official qualified list.) -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Clocks for Audio gear
On Thu, 10 May 2012 19:25:33 +0200 Heinzmann, Stefan (ALC NetworX GmbH) stefan.heinzm...@alcnetworx.de wrote: Benjamin and Gannon, the first reference in Ashihara's paper, come to lower figures for sinusoidal jitter with carefully selected frequencies relative to the main signal, which is also sinusoidal. Their results reach down to the single figure nanosecond range, and that can be regarded as the real limit of audibility. Of course, that still leaves those who claim to hear jitter in the picoseconds range out in fairy-tale land. I'm not so sure there. Having been active in the video coding scene for quite a while i know that a trained ear/eye can be easily a factor 10 better than the average. Eg, after a couple of months of hunting for bugs in the A/V sync code, i got sensitive to A/V desync down to 3-5ms. Yes, i know this is below the frame rate. But i cannot otherwise explain it as something started to feel odd, when the desync got over that limit. From somewhere between 5 and 10ms i could usually tell in which direction the desync was. Yes.. still below the frame rate. And i know that there are eyes and ears out there that are much better trained than mine ever could be. So i wouldnt imediatly dismiss it, if someone would tell me he could detect a A/V desync of 1ms (given proper frame rate). So, if someone proves that 1ns jitter is audiable for an average person, i would definitly not decline the possibility that a trained ear can hear 100ps jitter. But that is still a jitter level you can get with an crystall quite easily. You need to take care of a few things to not introduce any jitter from power supply or bad shielding, but nothing too difficult. Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Clocks for Audio gear
On Thu, 10 May 2012 11:36:40 -0700 Hal Murray hmur...@megapathdsl.net wrote: Heartbeats may be more interesting than breathing. Does anybody know of spectrum domain data? It should be possible to collect position info while also monitoring heartbeat and chest diameter and then crunch some numbers do see how much of the position correlates with heartbeat vs breathing and then plot each part in the frequency domain. Please do not forget that there is a quite sofisticated error correction system attached to the hear, which we usually refere to as the brain. Breathing and heart beat are filtered out and corrected for by the brain, otherwise we would have difficulties to hear a lot of things. For more infos, please have a look at perceptual psychology. A not too bad introduction to that field is Sensation and Perception by E. B. Goldstein. But please do not expect mathematical rigor in that field. It's still a subfield of psychology. Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Clocks for Audio gear
This audio thread had some interesting information; thank you. Now I welcome you to get back to the focus of the group; please. Thanks, /tvb p.s. If we need to start another mailing list that includes audio let me know; contact me off-line. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Clocks for Audio gear
You can refer to this for a relation between SFDR and INL: http://www-inst.eecs.berkeley.edu/~ee247/fa07/files07/lectures/L14_f07.pdf On Wed, May 9, 2012 at 11:25 PM, Hal Murray hmur...@megapathdsl.net wrote: was Subject: Re: [time-nuts] Faster than light of a different type (Probably my fault.) act...@hotmail.com said: What I found funny was that the Audiophlie and light thread drew such attacks when it hit home to me as exactly what the Time-Nuts mission is about. The Audio thread touched on some real world time and freq research ... I too enjoyed the technical discussions. Thanks for your contributions. It's the audiophool bashing that people are complaining about. Sure, it's fun, but only at the right time and it gets old quickly. The problem is that with large groups, there are different opinions of when and how much is appropriate. The long tail on opinions of reasonable can annoy a lot of people. --- Back to technical stuff... As a practical matter, is clock jitter or phase noise from a typical low cost crystal and decent board layout a significant problem in audio gear? How hard is it to measure? Is clock accuracy a practical problem? How good are people with perfect pitch? It wouldn't surprise me if there are a few that are much much better than others, but how good is that relative to 50 PPM which I can get in a low cost crystal? Video geeks solved their clock distribution problems by using frame buffers. Is there a similar trick for audio? Is there a need for it? I know clocking is a serious problem in fancy DSP systems. For example, modern radar has gone digital. In that context, clock jitter can be important. Standard procedure is don't run your clock through a FPGA because it will add jitter. Part of the problem is that they are doing magic down conversion in the ADC. (I can't think of the term.) Suppose you have a 100 MHz signal with a 1 MHz bandwidth. You don't have to sample at 200 MHz. You can sample at 2 MHz and your signal will alias down. It's turning what is normally a bug into a feature. The catch is that the errors/noise due to clock jitter happens at the high frequency, in this case multiplying the noise by 100. (Your sample/hold at the front end has to work at the high frequency and your anti-aliasing filter gets more interesting.) There has been an interesting change in the specs for ADCs and DACs over the past 20(?) years. They used to be specified using terms like DNL and INL and No-missing-codes. Modern high-speed ADCs are specified with terms like ENOB and SFDR. Data sheets often include several plots of a batch of samples run through a DFT so you can see the noise floor and such. Here is a reasonable glossary: http://pdfserv.maxim-ic.com/en/an/AN641.pdf I don't remember comments/specs about clock jitter in the data sheets but I haven't looked at one in a few years. I'll have to keep an eye out the next time I'm browsing. -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
