tag:blogger.com,1999:blog-6890046273025265768.post7121511668246421689..comments2024-03-18T03:10:30.572-07:00Comments on NwAvGuy: Jitter Does it Matter?NwAvGuyhttp://www.blogger.com/profile/00309644608738074125noreply@blogger.comBlogger47125tag:blogger.com,1999:blog-6890046273025265768.post-49822976434848984842012-08-15T11:12:46.678-07:002012-08-15T11:12:46.678-07:00This is an old review, but belated thanks. I almo...This is an old review, but belated thanks. I almost bought one of these a while back from all the praise, it didn't even occur to me that anything other than Apple would have proprietary usb jacks these days. That alone would be enough for me to write it off, it sounds like it's lacking in many other areas as well.<br /><br />I ended up getting a Sansa Clip, I love some of the options Anonymoushttps://www.blogger.com/profile/09912577000814102779noreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-81457425255704737252012-07-15T08:51:30.581-07:002012-07-15T08:51:30.581-07:00You concern is correct. The common clock would mas...You concern is correct. The common clock would mask many forms of playback jitter making it an invalid test. And if you did observe jitter components you wouldn't know if they were in the D/A or the A/D.<br /><br />For some things, there's just no substitute for proper audio test equipment. Jitter testing is one of those things. The dScope produces its own very low jitter JTEST signal. NwAvGuyhttps://www.blogger.com/profile/00309644608738074125noreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-12860956752994327782012-07-13T16:31:13.755-07:002012-07-13T16:31:13.755-07:00Would simply doing a loopback with a near FS 11.02...Would simply doing a loopback with a near FS 11.025kHz sine wave show<br /><br />- LF spreading<br />- distinct HF sidebands?<br /><br />I'm not hoping for an absolute test but for a cheap 'relative' test.<br /><br />The hope is that the inevitable delay due to anti-aliasing filters is sufficient to allow random jitter (the LF spreading) to muck up the signal.<br /><br />I'm not ricardonoreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-15425896072890896572012-07-09T09:38:49.433-07:002012-07-09T09:38:49.433-07:00I'm inclined to agree about the LF "sprea...I'm inclined to agree about the LF "spread" being more audible in some cases but I don't really have much objective proof to back that up.<br /><br />I haven't run the new dScope summed jitter test on much gear yet. But, judging from the jitter spectrums I've seen in the past, some would be over -90 dBFS. I've seen especially bad jitter from on-board PC audio, an NwAvGuyhttps://www.blogger.com/profile/00309644608738074125noreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-20421014431548876952012-07-07T15:49:34.515-07:002012-07-07T15:49:34.515-07:00My formal Blind Listening Tests on jitter were don...My formal Blind Listening Tests on jitter were done in the early 80s. In da old days, it was the LF 'broadening' at the base of the pure tone that was most audible. I've never encountered the distinct sidebands that the J test comes up with.<br /><br />Have you measured any DACs where the jitter sum exceeds -90dBFS?ricardonoreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-82783207813172247052012-07-06T09:13:22.234-07:002012-07-06T09:13:22.234-07:00The presenter did not quantify the levels of jitte...The presenter did not quantify the levels of jitter we heard, but he did say they were "unusually high" or something to that effect. That said, because jitter is a more dissonant form of distortion, it's reasonable to assume it's generally more audible than mostly harmonic distortion. Still, even if that's the case, it's difficult to imagine jitter being audible if the NwAvGuyhttps://www.blogger.com/profile/00309644608738074125noreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-10070124525444469032012-07-05T22:56:02.065-07:002012-07-05T22:56:02.065-07:00NwAvGuy, I'm surprised the AES convention list...NwAvGuy, I'm surprised the AES convention listening test came up with ANY audibility of jitter. IMHO, this would only be audible with appallingly high levels. Do you have any more details?ricardonoreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-48220469625065974692012-05-15T11:30:29.640-07:002012-05-15T11:30:29.640-07:00To the first question, I honestly don't know. ...To the first question, I honestly don't know. There are so many variables involved I'm not sure you can say one is more jitter prone than the other.<br /><br />I really doubt you're hearing a difference on your NAS tracks with an external DAC. If you use the blind ABX add-on for Foobar you can compare a local track to a NAS track that way. Nearly everything I play is on a NAS NwAvGuyhttps://www.blogger.com/profile/00309644608738074125noreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-29545465779270335262012-05-15T01:45:55.336-07:002012-05-15T01:45:55.336-07:00Just curious about 2 things:
Are single bit DACs (...Just curious about 2 things:<br />Are single bit DACs (bitstream) more sensitive to phase jitter than multibit DACs (R2R)? There was a craze for aftermarket clocks in the 1990s and I could imagine that getting the clock right for a bitstream DAC where the amplitude of the output is critically dependent on the mark/space of the clock could make a difference. Maybe things have improved in the Steve Daviesnoreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-41493652970690677862012-04-27T09:17:02.378-07:002012-04-27T09:17:02.378-07:00The issue is you can't clock out the data at a...The issue is you can't clock out the data at a fixed rate as you suggest when you can't control the source of the data. The playback clock HAS to adjust itself to the incoming data rate. No watch keeps perfect time forever because no crystal is perfectly accurate. The in and out rates have to match or the buffer will always eventually overflow or run dry. So the output clock, by NwAvGuyhttps://www.blogger.com/profile/00309644608738074125noreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-53918734274793972202012-04-26T19:52:17.587-07:002012-04-26T19:52:17.587-07:00Thank you for your confirmation.
Maybe I'm u...Thank you for your confirmation. <br /><br />Maybe I'm underestimating the issue and the amounts of jitter involed, but I thought the clock averaged out to the specified frequency over time? So for a 44.1k signal you have ~88 samples in a 2ms buffer and can tollerate 87 samples of jitter (i.e. the total available buffer space would be 4ms). Since the clock of the carrier signal will have to Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-73743032317958645962012-04-25T16:51:03.526-07:002012-04-25T16:51:03.526-07:00You're welcome and you essentially have it fig...You're welcome and you essentially have it figured out except for a few pieces. If you think about it, a USB or S/PDIF DAC doesn't usually have any control over the source. USB and S/PDIF are like a water hose pouring out water and the DAC can't control the flow. Under those circumstances you can't use a buffer in the normal way. If you slow down the music even slightly (lower theNwAvGuyhttps://www.blogger.com/profile/00309644608738074125noreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-5462618947480450542012-04-25T16:22:09.951-07:002012-04-25T16:22:09.951-07:00I think I may have finally understood what jitter ...I think I may have finally understood what jitter is .. after all these months.<br /><br />The problem is the DAC is relying on the "carrier signal" of S/PDIF (or USB) to drive its DAC-chip, rather having its own dedicated clock for that purpose - right? Or did I get it wrong? It would at least explain why jitter looks so weird and pattern-less (on charts), since a DAC running at the Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-78074356958252154992012-01-15T10:31:41.347-08:002012-01-15T10:31:41.347-08:00http://www.diymobileaudio.com/forum/how-articles-p...http://www.diymobileaudio.com/forum/how-articles-provided-our-members/78465-mathematics-jitter.html<br /><br />Above is a thread from Jeff (AKA Werewolf, Lycan). He used to be VP at Cystal and helped design one of the first multibit DAC chips (IIRC). The thread explains jitter and further into the thread there was an attempt to create a clean test file and add jitter to it, don't think it Frank (T3sn4f2)noreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-50717202241253938332011-12-29T08:04:49.720-08:002011-12-29T08:04:49.720-08:00@Alexium, I don't have such recordings but I&#...@Alexium, I don't have such recordings but I've thought about contacting the conference presenter and seeing if he would share a couple excerpts of what he played for us. If I come across something I'll do a quick article on the subject. I agree it would be useful for people to hear.<br /><br />I'm not aware of a way to assess jitter by itself without using something like the NwAvGuyhttps://www.blogger.com/profile/00309644608738074125noreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-74422649245665548552011-12-28T13:33:26.250-08:002011-12-28T13:33:26.250-08:00Do you, by any chance, have any recording similar ...Do you, by any chance, have any recording similar to that you've listened on a conference? Indicating how jitter sounds?<br />Also, is it possible to assess jitter level without any equipment (I'm not saying "measure", obviously, but assess if jitter exceeds the audibility threshold or not)?Alexiumnoreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-26847455535218906762011-12-03T12:50:31.727-08:002011-12-03T12:50:31.727-08:00So much for "low impedance headphone output&q...So much for "low impedance headphone output"! Welcome to the world of pro gear headphone jacks :(<br /><br />Your mixer breaks Behringer tradition if it's really around 19 ohms. Even their headphone amps are 47 ohms (right in the datasheets) as is the UCA202 and other Behringer gear I've checked. But even 19 ohms still means only headphones around 150 ohms or greater. <br /><br NwAvGuyhttps://www.blogger.com/profile/00309644608738074125noreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-19422316976762699742011-12-03T12:13:33.074-08:002011-12-03T12:13:33.074-08:00You're exactly right.
I ran a 1 kHz sine wave...You're exactly right.<br /><br />I ran a 1 kHz sine wave into my Traktor Audio 2 and got 2.847 V open and 2.331 V into 470 Ohms, and the resulting output resistance is 105 Ohms. This is obviously disappointing. Their specs recommend phones with 8 Ohms and up, go figure.<br /><br />My Denon AH-D2000 headphones DC resistance is 23 Ohms.<br /><br />Off my Behringer Xenix 502 mixer, I measured anAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-23764275513850851022011-12-03T07:04:15.969-08:002011-12-03T07:04:15.969-08:00I have a feeling the less expensive FiiO E10 will ...I have a feeling the less expensive FiiO E10 will easily beat the Traktor 2 as a headphone DAC but that's just a hunch. NI obviously spent most of their budget on other things (like the giant control surface, etc.). Also, I've yet to measure any piece of semi-pro or pro sound gear that had a headphone output impedance under 10 ohms. Most are 22 or 47 ohms. Even Asus can't manage to doNwAvGuyhttps://www.blogger.com/profile/00309644608738074125noreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-55926521548582985092011-12-02T20:28:56.334-08:002011-12-02T20:28:56.334-08:00Thank you for the insight on the signal waveforms....Thank you for the insight on the signal waveforms. I did realize that you do this on your own time and money and I had a vague idea of the amount of time involved. About the Traktor, it's a low cost USB soundcard with built in low impedance headphone amp and volume control. I think it's worthy for your platform but I respect your choice. Thanks so much again. EE10000Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-52622499250647411672011-12-02T20:04:45.275-08:002011-12-02T20:04:45.275-08:00No, the interfaces in question do not use sine wav...No, the interfaces in question do not use sine waves although the signal at the other end can sometimes resemble one after having gone through the cable version of a low-pass filter. The outputs of the chips that drive say a USB bus can be described as "controlled rise time rectangular waves". The rise times are slowed to ease power consumption and reduce RFI/EMI for FCC and CE reasons.NwAvGuyhttps://www.blogger.com/profile/00309644608738074125noreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-80220342285048975402011-12-02T19:27:25.578-08:002011-12-02T19:27:25.578-08:00About high frequency roll off through cables. Don&...About high frequency roll off through cables. Don't modern data interfaces use sinusoidal waveforms? The spectrum of the signal should ideally be bandwidth limited both at the top and the bottom. So that even cheap cables won't affect the edge detection.<br /><br />Analog audio does not use matched<br />impedance cabling. The cable is just a capacitor. With increased cable length, the Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-30619924315461559952011-12-02T19:12:17.052-08:002011-12-02T19:12:17.052-08:00Comparing DACs is very hard. A possibility to swit...Comparing DACs is very hard. A possibility to switch between them while playing the same sound is required and their levels need to be matches do 0.1 dB or better, which is 1 percent in Voltage, well within the accuracy of a regular digital multimeter.<br /><br />Ideally, there would be blind testing with ABX hardware. I considered making one, but there are just so many other things to do. Like Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-66719876083665435192011-12-02T18:56:40.821-08:002011-12-02T18:56:40.821-08:00Thanks for your comments. I'm mostly in agreem...Thanks for your comments. I'm mostly in agreement but it's worth pointing out nearly all USB DACs, especially reasonably priced ones, use adaptive mode and are not genuinely asynchronous. I've read/heard mixed things about HRT's async using the TI TAS1020B and I have not personally tested one. I know TI is discontinuing that chip in favor of newer designs. But the MS2 seems like aNwAvGuyhttps://www.blogger.com/profile/00309644608738074125noreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-15627301953434299012011-12-02T18:46:03.224-08:002011-12-02T18:46:03.224-08:00It's very important to distinguish data integr...It's very important to distinguish data integrity and jitter. Data integrity means that sample for sample, the same data arrives at the DAC that is contained on the storage media.<br /><br />Jitter means that the ADC's or DAC's clock is frequency modulated. Or, that a sample rate conversion is based on erroneous phase detection.<br /><br />It amazes me that data integrity is even an Anonymousnoreply@blogger.com