[SlimDevices: Audiophiles] what is jitter
I have been confused on the subject of jitter for a while and recently came across some answers that i though i would post here in case it helps others (or maybe everyone knows this already). If i am wrong let me know! There are two types of jitter the Squeezebox users should be aware of: (1) Jitter introduced to the CD when it is ripped due to errors in the digital audio extraction. You can hear this clearly as clicks in the playback. Programs like EAC and dBpoweramp should remove jitter to some extent and will report it back to you as checksum errors in the rip. (2) Jitter introduced by the SPDIF cable when you attach your Squeezebox to an external DAC. I recently bought a 1995 DAP Little Bit Dac and connected it to my squeezebox but found the playback quality much lower than my modern Yamaha CDR-HD1500 hard-drive / CD player. Inside the music I could hear faults, added confused complexity that was clearly incorrect. A more modern DAC I bought didn't have this problem. from: http://www.stereophile.com/digitalprocessors/825/index.html The standalone digital/analog converter emerged as a product category in 1987 with the appearance of the Arcam Black Box and the Marantz CDA-94, closely followed by the PS Audio Link. The idea was that putting the sensitive D/A-conversion and analog stages in a separate enclosure with its own power supply would maximize the sound quality when compared with packing these circuits in the same box as the transport. However, it turned out that the routing of the digital data between transport and processor in the form of an S/PDIF- or AES/EBU-encoded bitstream could introduce word-clock jitterwhich undid much of the sonic advantages (See this for more: http://www.stereophile.com/features/396bits/index.html). By 1997 jitter reduction technology (Digital Signal Processing Techniques) overcame many of the limitations of SPDIF input. However, advances in CD DACs made it extremely difficult for external DACs to outperform quality CD Players and today the external DAC market is quite small. -- willyhoops willyhoops's Profile: http://forums.slimdevices.com/member.php?userid=10563 View this thread: http://forums.slimdevices.com/showthread.php?t=35261 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] what is jitter
I'm afraid that much of what you've posted is inaccurate - it's the same myths and wrong conclusions that have been stated on audio forums many times. Firstly, jitter is not heard as pops and clicks. Pops and clicks are caused by bit errors - errors in the data itself. Jitter is purely a timing error - the correct data arriving at the DAC, but fractionally earlier or later than it should. When the CD is ripped, it's either right or it's wrong. If a program like EAC reports the wrong checksum, it's because of bit errors. The phenomenon of jitter simply does not exist at this stage. Consider as an analogy someone copying out a book by hand. If he gets a letter or word wrong (bit errors), that results in an error in the copy. If he gets up and goes for a wizz part way through, that makes no difference to the copy at all. The ripping process is just the same - timing makes no difference. Jitter is irregularity in the timing at the A/D when recording, and at the D/A on playback. It can't be fixed with DSPs - it can be reduced by using better PLLs, or VCXOs, or other high quality clocking technology. Rather than reinvent the wheel, here is a copy of a post I made a while back on the subject. I hope it clears things up once and for all. With any digital data link, there are always two aspects to consider: the data itself, and the associated clock. Let's consider them separately for a moment. The data is the easy bit. It's just ones and zeroes, and as long as there isn't so much noise on the wire that they actually get misinterpreted, it's easy to reliably recover exactly what was transmitted. It doesn't matter whether they originally came from a CD, or a file on a hard disc, or over an Ethernet or wireless connection. Then there's the clock, which is more complicated. In some communications systems, the clock is carried on a separate wire, and the receiver samples the data whenever the clock changes from low to high or from high to low. If all you're doing is storing the data in memory or forwarding it on to another device, that's all there is to it. As long as the clock transitions line up with the data bits, the link works. Zero degradation. In many modern systems (Ethernet, USB, S/PDIF), no separate clock wire is used. Instead the clock is recovered by looking at the timing of transitions in the data. In the case of something like Ethernet, where all you care about is getting the data from A to B reliably, this also works fine. The problem comes when you have to start caring about not just getting the bits from A to B, but also about exactly when they arrive at their destination. This is the problem with S/PDIF - you need to play the music at the same rate it comes in. A CD is sampled at 44.1kHz. But, no oscillator in the world (and certainly, no oscillator in your hi-fi) ticks at precisely that speed. Standard tolerance on a quartz crystal is +/-50 parts per million, which is no problem in itself - you can't hear the difference if you CDs are played back at 44.1002205kHz instead. However, say your DAC were running 50ppm fast and your CD transport (or whatever) were 50ppm slow. About 4 times per second the DAC won't have a sample to play, and you might hear this as a click. Not very hi-fi, I'm sure you'd agree. So, there has to be a mechanism to ensure that the clock in the DAC runs at precisely the same speed as the one in the source component. Because S/PDIF is unidirectional - it only provides a path from source to DAC and not the other way round - it has to be this way. When music is digitised, samples are taken at precisely determined intervals by very expensive studio equipment, and so to reproduce the original signal as accurately as possible, the output from the DAC has to be updated equally precisely, so that the time interval between successive samples is the same as it was originally. Variation in this period between samples is what we all know and love as jitter. -The only place this jitter matters is at the DAC chip itself.- In a device like a Squeezebox, big bursts of data are sent over the network into a buffer memory, then it's broken into smaller packets and stored in a FIFO (first in, first out) buffer by the CPU, and finally clocked into the DAC a bit at a time at regular intervals. It's only at the point where the last bit is clocked in and the DAC updates that jitter makes any difference whatsoever. If an external DAC is in use, it's only the clock pulse that causes that DAC chip to update that matters. Jitter elsewhere is basically a non-issue. What does this have to do with S/PDIF? This is all down to implementation. For the reasons explained above, a circuit in the DAC has to recover the clock from the S/PDIF signal and, from this, generate a clock to the DAC which is synchronised and yet has the least amount of jitter possible. Typically this is done with a circuit called a Phase-Locked Loop or PLL, and although they're very good at rejecting jitter,
Re: [SlimDevices: Audiophiles] what is jitter
willyhoops wrote: I have been confused on the subject of jitter for a while and recently came across some answers that i though i would post here in case it helps others (or maybe everyone knows this already). I'm not sure where you found those answers but I'm afraid they are wrong. Try this: http://www.maxim-ic.com/appnotes.cfm/appnote_number/1916/CMP/WP-34 A short quote: The SONET standard states that Jitter is defined as the short-term variations of a digital signal's significant instants from their ideal positions in time. Significant instants could be (for example) the optimum sampling instants. The Fiber Channel standard simply defines jitter as The deviation from the ideal timing of an event. In short, the term jitter describes timing errors within a system. In a communications system, the accumulation of jitter will eventually lead to data errors. Addressing your two types of jitter points: 1. Jitter is not a factor in CD ripping 2. Jitter does not only occur when using an external DAC - it is an issue *anywhere* that timing information is extracted from the signal. The SPDIF interface is one example of this. If i am wrong let me know! Oh we will, we will. :) R. ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] what is jitter
have a look at this on wiki... http://en.wikipedia.org/wiki/Jitter In the context of digital audio extraction from CDs jitter causes extracted audio samples to be doubled-up or skipped entirely. The problem occurs because the Philips CD specification doesn't require block-accurate addressing. As a result, the extraction process will restart a few samples early or late, resulting in doubled or omitted samples. These glitches often sound like tiny repeating clicks during playback. An approach that has produced good results is to do jitter correction in software. This involves performing overlapping reads, and then sliding the data around to find overlaps at the edges. Most DAE programs will perform jitter correction. So jitter can and is used in the context of digital audio extraction... Anway, the jitter I am really concerned with is related to the SPDIF connector. As AndyC says it's due to differences in the clocks on the external DAC and the SPDIF source. Use of a phased locked look reduces this... I was interested in to what extent it can eliminate it. From Andy's post it looks like not entirley which makes we worry about finding a decent external DAC. -- willyhoops willyhoops's Profile: http://forums.slimdevices.com/member.php?userid=10563 View this thread: http://forums.slimdevices.com/showthread.php?t=35261 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] what is jitter
Both Robin and Andy have pointed out that jitter as we understand it in the audio world refers to timing inaccuracy. They have both said that jitter is not involved in CD ripping. However, there is a phenomenon which *used* to be significant during CD ripping. (Modern drives no longer have this problem). This was that it was not always possible for a CD drive to accurately seek to a specific block on an audio CD. As a result, rippers attempting to read sequential blocks from audio CDs sometimes had to cope with this. (They typically used a strategy of reading overlapping block then trying to align them according to the data content). Unfortunately, the term used to describe this phenomenon was jitter, and has led to a lot of confusion. -- cliveb Performers - dozens of mixers and effects - clipped/hypercompressed mastering - you think a few extra ps of jitter matters? cliveb's Profile: http://forums.slimdevices.com/member.php?userid=348 View this thread: http://forums.slimdevices.com/showthread.php?t=35261 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] what is jitter
Note how in the Wikipedia article, the word 'jitter' is placed within bullsh*t marks - punctuation which, when applied to any word or phrase being used to describe an audio phenomenon, means that the author is either clueless, or knows perfectly well that the words they're using are inaccurate. You'll see a lot of them on audio forums and the technical stuff on manufacturers' web sites. Calling block addressing errors jitter was unfortunate - it leads to unnecessary confusion. Certainly it's not the same thing as jitter in the electronic engineering sense. I think you're confused about the different clocks in DAC and source. They always run at the same speed because they have to, otherwise you'd hear pops and clicks as the buffer in the DAC overruns or underruns. The device normally used to synchronise them is the PLL. Jitter is NOT to do with different clocks running at different speeds. It's irregularity in the one, single clock that drives the DAC. Imagine, for example, that you've bought a cheap wristwatch. It might gain a few seconds a day, but that's not jitter. Jitter is the fact that the seconds hand is stiff and jerky, and doesn't tick at precisely even one-second intervals. It is certainly possible for a DAC to buffer up enough data to cope with the difference in clock speeds over the length of a CD. It only requires about 1/2 a second's worth of buffer. The MSB DAC III does this - http://www.msbtech.com/products/dac3.php - for about $6,000. -- AndyC_772 AndyC_772's Profile: http://forums.slimdevices.com/member.php?userid=10472 View this thread: http://forums.slimdevices.com/showthread.php?t=35261 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] what is jitter
No I get exactly what jitter is and how it works- thanks for your article- very good (of course the clock speeds are set the same it's just tiny inaccuracies that cause the problem as you already pointed out). I mentioned jitter in CD extraction to avoid confusion. All I am interested in is SPDIF jitter. I am really not interested in paying $6,000 for a DAC. I am trying to replace a Yamaha CDR-HD1500 hard-drive / CD player with a squeezebox. It cost me about $1,000 a few years ago including 250Gb hard drive and I have been happy with it but Squeezebox with wireless connection and tags is a a much better idea. My frustration is getting the analouge out good enough to match this mid range cd / hard drive player. I was hoping to find a DAC which did good enough PLL or perfect buffering for just a few hundred dollars. We shouldn't need to spend $6,000 to get a half second buffer that removes all jitter. -- willyhoops willyhoops's Profile: http://forums.slimdevices.com/member.php?userid=10563 View this thread: http://forums.slimdevices.com/showthread.php?t=35261 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] what is jitter
willyhoops;201805 Wrote: I am trying to replace a Yamaha CDR-HD1500 hard-drive / CD player with a squeezebox. It cost me about $1,000 a few years ago including 250Gb hard drive and I have been happy with it but Squeezebox with wireless connection and tags is a a much better idea. My frustration is getting the analouge out good enough to match this mid range cd / hard drive player. I was hoping to find a DAC which did good enough PLL or perfect buffering for just a few hundred dollars. We shouldn't need to spend $6,000 to get a half second buffer that removes all jitter. Have you considered the possibility that the difference in analogue performance you hear between the Yamaha and other devices has nothing to do with jitter? stating the bleeding obvious You know, it must just be something to do with the analogue circuitry in the DACs? /stating the bleeding obvious -- cliveb Performers - dozens of mixers and effects - clipped/hypercompressed mastering - you think a few extra ps of jitter matters? cliveb's Profile: http://forums.slimdevices.com/member.php?userid=348 View this thread: http://forums.slimdevices.com/showthread.php?t=35261 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] what is jitter
well, stating the bleeding obvious, the analogue output from the sb3 i didn't like is not a spdif jitter issue like i said the 1995 DAP Little Bit Dac i am guessing had a jitter issue connected to squeezebox. its an old dac with no jitter protection i believe. andyc was one the one making the remark that pll does not perfectly solve jitter issues only buffering. i am just interested in the subject and also in a good dac for my sb3... sounds like i should try and find a 0.5s buffering new dac for $500 or less. so far have not seen one. buffering dacs all looks real expensive. soon i will try two old pll dacs and see how they fair. -- willyhoops willyhoops's Profile: http://forums.slimdevices.com/member.php?userid=10563 View this thread: http://forums.slimdevices.com/showthread.php?t=35261 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] what is jitter
At risk of stating the bleeding obvious myself: pick a DAC you can afford and which you like the sound of, don't waste time and energy worrying about how it works or what factors might be affecting its performance. That's for the design engineer to worry about, not the customer. A fixation on jitter is, frankly, a bit odd, and certainly not a productive way to choose hi-fi components. -- AndyC_772 AndyC_772's Profile: http://forums.slimdevices.com/member.php?userid=10472 View this thread: http://forums.slimdevices.com/showthread.php?t=35261 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] what is jitter
willyhoops wrote: No I get exactly what jitter is and how it works- thanks for your article- very good (of course the clock speeds are set the same it's just tiny inaccuracies that cause the problem as you already pointed out). I mentioned jitter in CD extraction to avoid confusion. All I am interested in is SPDIF jitter. I am really not interested in paying $6,000 for a DAC. I am trying to replace a Yamaha CDR-HD1500 hard-drive / CD player with a squeezebox. It cost me about $1,000 a few years ago including 250Gb hard drive and I have been happy with it but Squeezebox with wireless connection and tags is a a much better idea. My frustration is getting the analouge out good enough to match this mid range cd / hard drive player. I was hoping to find a DAC which did good enough PLL or perfect buffering for just a few hundred dollars. We shouldn't need to spend $6,000 to get a half second buffer that removes all jitter. Can I suggest you actually try listening to some devices instead of theorising based on their technical specification? You might like to try the Transporter, for example. Or maybe the SB+? I don't use an external DAC any more since I got the Transporter (I used to use an Art DI/O with my SB1/2) so I'll leave others to recommend possible options for external DACs. R. ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] what is jitter
willyhoops wrote: well, stating the bleeding obvious, the analogue output from the sb3 i didn't like is not a spdif jitter issue No but as I said in my initial response jitter is not solely an issue when using SPDIF - it comes into play any time you reconstruct the analogue signal from the digital data, i.e. the SB3 output will be affected by jitter *internal* to the SB3. like i said the 1995 DAP Little Bit Dac i am guessing had a jitter issue connected to squeezebox. its an old dac with no jitter protection i believe. andyc was one the one making the remark that pll does not perfectly solve jitter issues only buffering. i am just interested in the subject and also in a good dac for my sb3... sounds like i should try and find a 0.5s buffering new dac for $500 or less. so far have not seen one. buffering dacs all looks real expensive. soon i will try two old pll dacs and see how they fair. And as I said in my subsequent response, I'd not get hung up on technical specs and just listen to a few different options. R. ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] what is jitter
willyhoops;201812 Wrote: I am not sure if SB3 jitter is below 20ns rms... but if i try this... 20ns = 0.0002 seconds then 1 / 0.0002 = 50,000,000 then andyC's statement Standard tolerance on a quartz crystal is +/-50 parts per million ... [and] you can't hear the difference sounds spot on. I still think you're unclear as to what jitter is. You've certainly misinterpreted the figures in my example above. A clock can have zero jitter and yet still have an inaccurate frequency. In my example, a crystal that's 50ppm too fast would result in a sample rate of 44.102205kHz. But, provided that each and every one of those samples was clocked into the DAC at precise intervals of 1/(44.102205k) seconds, there would be no jitter at all. Jitter is NOT the same thing as a frequency error. Try this: imagine a turntable playing a record. The motor is accurate and smooth, so the stylus tracks the groove at exactly the correct speed all the time. That's accurate frequency and no jitter. Now suppose the motor speeds up fractionally, so that instead of spinning at (say) 45rpm, it now spins smoothly at 45.00225 rpm. That's a frequency error of 50 parts per million, but still no jitter. You can't hear the difference. Now replace the nice, smooth belt drive with a rattly gearbox. The average speed remains the same, but there's torsional vibration as each tooth engages and disengages. So now, as the record turns, sometimes the relative speed between stylus and groove is slightly faster, and sometimes it's slightly slower. That's more like the effect of jitter. MSB confuse the issue slightly by stating that they use a crystal accurate to 2.5ppm. That's all well and good, but the absolute frequency accuracy really doesn't matter - they'll just have found that applications that require low jitter also tend to require an accurate frequency as well, so that's what crystal manufacturers make. Audio, however, is NOT one of those applications. They just mention the frequency spec because it looks good in marketing literature to people who don't really understand the issue. Knowing that their own clock is accurate also minimises the size of buffer they need - they only have to cope with 52.5ppm of mismatch, and not, say, 100ppm. SB3's jitter is way, way less than 20ns. Here's a plot of its digital output: http://www.cawte.nildram.co.uk/Jitter/sb3.jpg You can see that the transition points between 1 and 0 are very well defined in time - I actually struggled to see any jitter at all with my 'scope, and I suspect that what I did see was instability in the scope itself. -- AndyC_772 AndyC_772's Profile: http://forums.slimdevices.com/member.php?userid=10472 View this thread: http://forums.slimdevices.com/showthread.php?t=35261 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] what is jitter
Jitter is a measurement of temporal uncertainty. With regard to digital audio, and CDs in specific, there are 3 common places where jitter is measured: 1. RF jitter. This is timing uncertainty of the bit transitions in the RF recovered from the CD. This is caused by, among other things, the pit length of the disc, which is affected by many variables in the burning and molding process. The data is encoded with EFM (8 to 14 modulation), so there are 14 possible transitions per byte. RF jitter becomes a problem when it becomes large enough to cause mistaken bits, which results in the need for error correction (Reed-Solomon) or error conceilment. 2. DAC clock jitter. Since data from the CD is buffered in RAM and clocked out to the DAC, DAC clock jitter is a measure of the stability of the clock circuitry driving the DAC. Instability is often caused by insufficient power supply regulation or mechanical vibration. 3. DAE (digital audio extraction) jitter. This occurs when an audio CD is read by a computer drive. This was not contemplated when CD standards were set; the CD was designed with a long spiral groove to be played continuously by an audio player, so it does not have the sector identification needed for the true random access that digital audio extraction programs require. To overcome this problem, DAE programs perform overlapping reads and use pattern matching techniquews to align the result to generate a continuous data stream. DAE jitter is a measure of the seek uncertainty of the drive. EAC reports a Synchroniation error when the pattern match fails. Jitter of type (1) and (3) will often not affect the audio quality until they reach a threshold where they cause unrecoverable errors. These types of jitter occur in the drive mechanism, not in a device such as the SB and TP. However DAC clock jitter of any ammount will degrade the audio quality, so high end equipment often goes to extreme lengths to reduce it to an absolute minimum. -- Timothy Stockman Timothy Stockman's Profile: http://forums.slimdevices.com/member.php?userid=8867 View this thread: http://forums.slimdevices.com/showthread.php?t=35261 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] what is jitter
Andy sorry for the confusion... Point taken: a crystal that's 50ppm too fast would result in a sample rate of 44.102205kHz. But, provided that each and every one of those samples was clocked into the DAC at precise intervals of 1/(44.102205k) seconds, there would be no jitter at all. Ok. But in this paper is that what he is referring to? Eg if I play music from a clock that's 100ppm too fast then maybe he is saying some people will be able to hear the difference between it and a clock which is absolutely correct. In this paper the term jitter is used to mean: #8220;Deviation in timing of transitions when measured with respect to an ideal clock.#8221; If so, was my calculation right anyway?... the quartz in the squeezebox is accurate to 50ppm (unlike say the expensive temperature adjusted $6,000 DAC oscilators) but still good enough. -- willyhoops willyhoops's Profile: http://forums.slimdevices.com/member.php?userid=10563 View this thread: http://forums.slimdevices.com/showthread.php?t=35261 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] what is jitter
willyhoops;201812 Wrote: I am not sure if SB3 jitter is below 20ns rms... but if i try this... 20ns = 0.0002 seconds then 1 / 0.0002 = 50,000,000 then andyC's statement Standard tolerance on a quartz crystal is +/-50 parts per million ... [and] you can't hear the difference sounds spot on. The rms jitter for the SB2 measured at the S/PDIF out is around 65 ps (=.065 ns) rms. Of course if you insist on using an external DAC the digital cable, DAC, and connections will increase that, but that's your fault, not the SBs. http://forums.slimdevices.com/showthread.php?t=15882 -- opaqueice opaqueice's Profile: http://forums.slimdevices.com/member.php?userid=4234 View this thread: http://forums.slimdevices.com/showthread.php?t=35261 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] what is jitter
willyhoops;201838 Wrote: Ok. But in this paper is that what he is referring to? Eg if I play music from a clock that's 100ppm too fast then maybe he is saying some people will be able to hear the difference between it and a clock which is absolutely correct. That would be really remarkable, considering there's no way instruments can be tuned to each other that accurately. Such people would probably find it hard to listen to any music, as it would always be terribly out of tune... Look, changing the overall clock rate just shifts the absolute pitch of the sound (by an incredibly tiny amount). It doesn't introduce any distortion. That amound of shift is equivalent to the Doppler shift from moving at about .03 m/s towards or away from the music. Listen to your stereo and try moving your head slowly backwards or forwards - do you hear the pitch of the music change? -- opaqueice opaqueice's Profile: http://forums.slimdevices.com/member.php?userid=4234 View this thread: http://forums.slimdevices.com/showthread.php?t=35261 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] what is jitter
That makes sense but remember that the difference between note c0 and c#0 is 16.35kHz and 17.32kHz. Thats sounds like a small difference... -- willyhoops willyhoops's Profile: http://forums.slimdevices.com/member.php?userid=10563 View this thread: http://forums.slimdevices.com/showthread.php?t=35261 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] what is jitter
I think that by ideal they mean perfectly regular - not necessarily perfectly accurate in frequency. I very much doubt that the human ear can perceive a shift in pitch as small as 100ppm (0.01%) - and even if you could, there's no reason why it should actually affect your enjoyment of the music. (Think of an orchestra tuning up - does it really matter exactly the pitch or tempo they play at, provided they're in tune and in time?) Your calculation doesn't really mean anything, I'm afraid. 1/20ns is 50MHz, but so what? The fact that there's a 50 there somewhere is just coincidence. -- AndyC_772 AndyC_772's Profile: http://forums.slimdevices.com/member.php?userid=10472 View this thread: http://forums.slimdevices.com/showthread.php?t=35261 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] what is jitter
willyhoops wrote: That makes sense but remember that the difference between note c0 and c#0 is 16.35kHz and 17.32kHz. Thats sounds like a small difference... Er, I think you mean 16.35 Hz and 17.32 Hz This is still large compared to the change induced by a clock running 100ppm fast. R. ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] what is jitter
opaqueice;201844 Wrote: Listen to your stereo and try moving your head slowly backwards or forwards - do you hear the pitch of the music change? That explains what head-banging is for. Those metalheads must be trying to add a vibrato effect to their music. -- cliveb Performers - dozens of mixers and effects - clipped/hypercompressed mastering - you think a few extra ps of jitter matters? cliveb's Profile: http://forums.slimdevices.com/member.php?userid=348 View this thread: http://forums.slimdevices.com/showthread.php?t=35261 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] what is jitter
Ah reading about it more that paper is not talking about what i though I think. It is talking about jitter in exactly the sense that AndyC is... except they are adding a twist between edge to edge jitter (typically 500ps and which we get published figures for) and ideal clock jitter which takes into account the shape of the square wave compared to the ideal. Confusing stuff. I can't see any articles about how important clock accuracy is (eg the 2.5ppm $6,000 DAC figure compared to the 50ppm normal quartz clock accuracy). I am giving up and finishing where I started - which is that built in dacs eg on cd players/sb3/transporter don't suffer audible jitter and have a big advantage over problematic spdif connections, and PLL or buffering are vital features in an external DAC. -- willyhoops willyhoops's Profile: http://forums.slimdevices.com/member.php?userid=10563 View this thread: http://forums.slimdevices.com/showthread.php?t=35261 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] what is jitter
willyhoops wrote: I am giving up and finishing where I started - which is that built in dacs eg on cd players/sb3/transporter don't suffer audible jitter and have a big advantage over problematic spdif connections, and PLL or buffering are vital features in an external DAC. sigh You really don't listen to what anyone else has to say, do you? As long as you're happy. R. ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] what is jitter
Phil Leigh;201943 Wrote: Jitter is the uncomfortable feeling I get when someone mentions jitter... Are you sure that's not constipation? -- Patrick Dixon www.at-tunes.co.uk Patrick Dixon's Profile: http://forums.slimdevices.com/member.php?userid=90 View this thread: http://forums.slimdevices.com/showthread.php?t=35261 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] what is jitter
Whatever jitter is... it's obviously not the be all and end all of good sound. There is more... we just not sure what it is yet. MC -- ModelCitizen It is far better to grasp the Universe as it really is than to persist in delusion, however satisfying and reassuring. Transporter Bryston 4B ST PMC OB1s SB3 NAIM NAC 102 NAIM NAP 180 Shahinian Arcs http://www.last.fm/user/ModelCitizen ModelCitizen's Profile: http://forums.slimdevices.com/member.php?userid=446 View this thread: http://forums.slimdevices.com/showthread.php?t=35261 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] what is jitter
The Enlightened Audio Designs DSP-7000 series III uses a propietary circuit called digital flywheel which reduces jitter in the data stream to 10 nanoseconds or less. Excellent performance for a unit made in 1996. It was $2500 back then, though. Excellent value in the used market and easy to modify or upgrade. -- crooner Customized dual chassis Super Squeezebox EAD DSP-7000 MKIII DAC with HDCD VPI Scout with Benz Micro Glider M2 Audio Research PH3, SP16L and VS110 Vandersteen 2Ce signatures, 2W subwoofer. crooner's Profile: http://forums.slimdevices.com/member.php?userid=3379 View this thread: http://forums.slimdevices.com/showthread.php?t=35261 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] what is jitter
I was reading the specs on my Enlightened Audio Designs DSP-7000 series III DAC and the maximum jitter is listed at less than 10 picoseconds RMS (20 kHz). Impressive performance by any standard. The EAD uses a propietary circuit called Digital Flywheel which is responsible for this low jitter figure. I'm sure this was state-of-the-art back in the late 1990s and still superb today. The unit retailed for $2500. A great value in the used market today, and easy to modify and/or upgrade. I replaced a Lite Audio DAC60 with the DSP-7000 III and couldn't be happier! -- crooner Customized dual chassis Super Squeezebox EAD DSP-7000 MKIII DAC with HDCD VPI Scout with Benz Micro Glider M2 Audio Research PH3, SP16L and VS110 Vandersteen 2Ce signatures, 2W subwoofer. crooner's Profile: http://forums.slimdevices.com/member.php?userid=3379 View this thread: http://forums.slimdevices.com/showthread.php?t=35261 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
Re: [SlimDevices: Audiophiles] what is jitter
ModelCitizen;202004 Wrote: There is more... we're just not sure what it is yet. Strikes me that is not really in line with your sig, MC ;) -- adamslim Those are my principles, and if you don't like them... well, I have others http://www.last.fm/user/AdamSlim/ 'Last.fm group: people who don't listen to any of last.fm's top artists' (http://www.last.fm/group/People+who+don%27t+listen+to+any+of+last.fm%27s+top+artists) To occupy Iraq would instantly shatter our coalition, turning the whole Arab world against us ... condemning [young soldiers] to fight in what would be an un-winnable urban guerrilla war. It could only plunge that part of the world into even greater instability - George Bush Snr, 1998 adamslim's Profile: http://forums.slimdevices.com/member.php?userid=7355 View this thread: http://forums.slimdevices.com/showthread.php?t=35261 ___ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
