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Jitter problem


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What would fit what you are seeing is a group delay problem. How that would occur with PC and not CD I don't know.

 

With group delay a given tone would pass through with flat response, but groups of tones would suffer variable delay of the wave envelope vs frequency. You could check this perhaps by creating a cluster of tones. Say combine 2 khz, 4khz, 6khz and so on up to 20 khz. Measure that and see if it follows the sweep response or the white noise response.

 

You also could see this with just two tones. Combine a 6 and 12 khz tone. Record the result and see if the phase of these has moved in the recording by looking at the waveshape.

 

Also have you tried this with both of the digital filters on your DAC?

 

If you still think it is jitter try a 11,025 hz tone. That much jitter would show up obviously in the result.

And always keep in mind: Cognitive biases, like seeing optical illusions are a sign of a normally functioning brain. We all have them, it’s nothing to be ashamed about, but it is something that affects our objective evaluation of reality. 

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Finally, regarding the specific jitter-test that I use, let's agree that (excessive) digital jitter translates in a clearly audible analogue effect (which is commonly also called jitter). So why is it so strange that jitter can simply be measured in the analogue domain? Using a noise signal that contains all frequencies in known quantities or magnitudes, clock jitter (or clock phase noise) will result in small phase-shifts that will predominantly shift and (partially) cancel higher frequencies. An FFT algorithm then measures what's left of each frequency component in the analogue sound. And although such a noise signal is extremely susceptible to jitter, in my experience this provides a very useful indication of the amount of sound degradation by jitter in the audio chain.

 

I wanted to respond to this as well. As you can see from Mansr's graphs, not all PC sourced files suffer the problem. I have measured a number of devices fed from a computer using both sweeps, spot tones and white noise or pink noise. None have ever exhibited what you are showing.

 

Your results are an interesting problem, but it isn't endemic to PC sources.

And always keep in mind: Cognitive biases, like seeing optical illusions are a sign of a normally functioning brain. We all have them, it’s nothing to be ashamed about, but it is something that affects our objective evaluation of reality. 

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I recorded the noise and sweep tests playing (still from the PC) on one speaker using a Dayton Audio EMM-6 microphone. Spectrum plot (1/6 octave smoothing) below:

noise-sweep-mic.png

 

Note that the sine sweep test signal is quieter than the noise signal by a few dB (refer to graphs posted earlier). Taking this into account, the two recordings are a perfect match. The speakers (B&W CM6 S2) drop off quickly below 50 Hz.

 

Whatever is causing the high-frequency roll-off in Abtr's system, it's not present in mine.

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... Now consider a situation where the digital sound signal is somehow processed and then resampled in the PC. That would encode the PC's jitter into the audio signal (just like recording jitter). The signal is then no longer bit perfect and a J-test, as I understand it, might not detect this if said resampling isn't applied to the played back J-test test file. ...

 

This "encoding of the PC's jitter" does not occur. There is no mechanism within the PC or the processing / resampling software that could be affected by timing variation in the bits being processed. Each sample conversion is an atomic mathematical step, with no concept of time. The resulting bitstream will always be the same regardless of any timing variation within the PC.

"People hear what they see." - Doris Day

The forum would be a much better place if everyone were less convinced of how right they were.

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This "encoding of the PC's jitter" does not occur. There is no mechanism within the PC or the processing / resampling software that could be affected by timing variation in the bits being processed. Each sample conversion is an atomic mathematical step, with no concept of time. The resulting bitstream will always be the same regardless of any timing variation within the PC.

 

Don

Then try explaining the attached, other than insisting that I must be delusional.

The binary data may still be the same according to .md5 checksums etc. but the audible differences are quite obvious through better than average gear.

I have also demonstrated this kind of thing through another C.A. members own system, as well as via his Bricasti M1 at my place where my Oppo 103 was used as the transport via Coax SPDIF.

Alex

 

http://www.computeraudiophile.com/f8-general-forum/few-non-accurate-rips-cd-28221/index2.html reply 35

 

How a Digital Audio file sounds, or a Digital Video file looks, is governed to a large extent by the Power Supply area. All that Identical Checksums gives is the possibility of REGENERATING the file to close to that of the original file.

PROFILE UPDATED 13-11-2020

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Abtr, I just discovered and read through the thread. You seem to have tested for many variables, including different source computers that suffer from the same issues. The only possibility that I do not recall you testing for is the power supply to the source computers. Perhaps it could be a problem with the power cord to the source (if using the same cord for the different sources), or even the power outlet to the computer source. Perhaps test again with different power cords and/or different wall outlet (no power bar, conditioner, UPS, etc).

 

I know many digital components can be very sensitive to power issues. My NAD M2 Integrated specifically warns about this in their documentation.

 

Good luck

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Abtr, I just discovered and read through the thread. You seem to have tested for many variables, including different source computers that suffer from the same issues. The only possibility that I do not recall you testing for is the power supply to the source computers. Perhaps it could be a problem with the power cord to the source (if using the same cord for the different sources), or even the power outlet to the computer source. Perhaps test again with different power cords and/or different wall outlet (no power bar, conditioner, UPS, etc).

 

I know many digital components can be very sensitive to power issues. My NAD M2 Integrated specifically warns about this in their documentation.

 

Good luck

Thanks Spenrock. I know sometimes issues like ground loops and/or power instability can cause issues in audio systems. But that can't be the problem here. The PCs are galvanically isolated from the DAC by an Intona USB isolator, and I tried three different laptops running solely on battery power with the same result, apparent jitter.

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So far the one thing that's caused a change was CD player input via SPDIF, is that right? Was that playing a CD of the same files you used for the USB and USB-to-SPDIF converter inputs?

One never knows, do one? - Fats Waller

The fairest thing we can experience is the mysterious. It is the fundamental emotion which stands at the cradle of true art and true science. - Einstein

Computer, Audirvana -> optical Ethernet to Fitlet3 -> Fibbr Alpha Optical USB -> iFi NEO iDSD DAC -> Apollon Audio 1ET400A Mini (Purifi based) -> Vandersteen 3A Signature.

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I recorded the noise and sweep tests playing (still from the PC) on one speaker using a Dayton Audio EMM-6 microphone. Spectrum plot (1/6 octave smoothing) below:

[ATTACH=CONFIG]25269[/ATTACH]

 

Note that the sine sweep test signal is quieter than the noise signal by a few dB (refer to graphs posted earlier). Taking this into account, the two recordings are a perfect match. The speakers (B&W CM6 S2) drop off quickly below 50 Hz.

 

Whatever is causing the high-frequency roll-off in Abtr's system, it's not present in mine.

The plot looks like you used 1/96th octave smoothing (I used 1/6th octave smoothing to show the relevant differences more clearly). It's strange that you measure a (slightly) different SPL for the noise signal and the sine sweep. Did you use the Dayton Audio tracks? These might be specific for the Omnimic software. I contacted Dayton Audio with some questions about the exact implementation of the frequency response measurements but they didn't respond yet. (Possibly they will ask the designer.) If you have a USB microphone for sound measurement, I can provide you with the Omnimic software. With it you should be able to replicate my results, or not..

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It's strange that you measure a (slightly) different SPL for the noise signal and the sine sweep.

 

Not at all. The sine sweep is a few dB quieter than the noise as you can see from the first set of plots I posted.

 

Did you use the Dayton Audio tracks?

 

Yes, that was the point.

 

These might be specific for the Omnimic software. I contacted Dayton Audio with some questions about the exact implementation of the frequency response measurements but they didn't respond yet. (Possibly they will ask the designer.) If you have a USB microphone for sound measurement, I can provide you with the Omnimic software. With it you should be able to replicate my results, or not..

 

I have a microphone (Dayton Audio EMM-6) and a USB capture interface (Steinberg). No idea if it will work with the Omnimic software, nor if redistributing it is legal.

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So far the one thing that's caused a change was CD player input via SPDIF, is that right? Was that playing a CD of the same files you used for the USB and USB-to-SPDIF converter inputs?

 

It would be interesting to get a capture of the digital output from that CD player. Unfortunately S/PDIF and Toslink inputs on PC sound cards are somewhat rare.

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Not at all. The sine sweep is a few dB quieter than the noise as you can see from the first set of plots I posted.

Then the Omnimic software must correct for this overall difference because I don't see it in my measurements.

 

I have a microphone (Dayton Audio EMM-6) and a USB capture interface (Steinberg). No idea if it will work with the Omnimic software, nor if redistributing it is legal.

You may need something like a Dayton Audio UMM-6, but possibly the USB interface will work. And I don't see the legal problem if I just want to measure your sound system using your (Windows) PC running my Omnimic software. After that the Omnimic software must of course be removed from the PC..

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Don

Then try explaining the attached, other than insisting that I must be delusional. ...

 

No thanks. Having weighed all the arguments to date, I'll stick with my current opinion.

"People hear what they see." - Doris Day

The forum would be a much better place if everyone were less convinced of how right they were.

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This "encoding of the PC's jitter" does not occur. There is no mechanism within the PC or the processing / resampling software that could be affected by timing variation in the bits being processed. Each sample conversion is an atomic mathematical step, with no concept of time. The resulting bitstream will always be the same regardless of any timing variation within the PC.

Yes, I'm also perplexed by this phenomenon and (as yet) I can't explain it. The cause should be outside the PC, but I really don't see it.. By the way, I don't think this problem is quite the same as Sandyk's problem..

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Yes, I'm also perplexed by this phenomenon and (as yet) I can't explain it. The cause should be outside the PC, but I really don't see it.. By the way, I don't think this problem is quite the same as Sandyk's problem..

I think Don is trying to get across that the difference is not caused by timing in the PC. The difference would appear to be in the PC, but that difference isn't timing. So if you stop looking for something the PC can't cause ( timing changes in the playback), you then have a far better chance to find what is going on with the PC input.

And always keep in mind: Cognitive biases, like seeing optical illusions are a sign of a normally functioning brain. We all have them, it’s nothing to be ashamed about, but it is something that affects our objective evaluation of reality. 

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So if you stop looking for something the PC can't cause ( timing changes in the playback),

 

The PC can however inject RF/EMI and Jitter into the playback ,as evidenced by the large number of members who use Uptone USB Regens, Intona Isolators etc.

Internal power supplies aren't perfect either, and there will always be some degree of interaction between various sub sections via the PSU, even with a Linear PSU.

 

How a Digital Audio file sounds, or a Digital Video file looks, is governed to a large extent by the Power Supply area. All that Identical Checksums gives is the possibility of REGENERATING the file to close to that of the original file.

PROFILE UPDATED 13-11-2020

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The PC can however inject RF/EMI and Jitter into the playback ,as evidenced by the large number of members who use Uptone USB Regens, Intona Isolators etc.

Internal power supplies aren't perfect either, and there will always be some degree of interaction between various sub sections via the PSU, even with a Linear PSU.

 

Well the evidence that large numbers of people have those various USB conditioning devices is evidence many believe it.

And always keep in mind: Cognitive biases, like seeing optical illusions are a sign of a normally functioning brain. We all have them, it’s nothing to be ashamed about, but it is something that affects our objective evaluation of reality. 

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Well the evidence that large numbers of people have those various USB conditioning devices is evidence many believe it.

 

I'm happy with mine, but sure, it could all be in my head.

 

Reminds me a little of the joke about the parents whose kid thinks she's a chicken, but they don't want her seeing a psychiatrist 'cause they like the eggs.

One never knows, do one? - Fats Waller

The fairest thing we can experience is the mysterious. It is the fundamental emotion which stands at the cradle of true art and true science. - Einstein

Computer, Audirvana -> optical Ethernet to Fitlet3 -> Fibbr Alpha Optical USB -> iFi NEO iDSD DAC -> Apollon Audio 1ET400A Mini (Purifi based) -> Vandersteen 3A Signature.

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I'm happy with mine, but sure, it could all be in my head.

 

Jud

I can't imagine that somebody like you hasn't tried with and without these items under non sighted conditions, other than perhaps if the differences are so marked that you don't feel the need to !

Regards

Alex

 

How a Digital Audio file sounds, or a Digital Video file looks, is governed to a large extent by the Power Supply area. All that Identical Checksums gives is the possibility of REGENERATING the file to close to that of the original file.

PROFILE UPDATED 13-11-2020

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The PC can however inject RF/EMI and Jitter into the playback ,as evidenced by the large number of members who use Uptone USB Regens, Intona Isolators etc.

Internal power supplies aren't perfect either, and there will always be some degree of interaction between various sub sections via the PSU, even with a Linear PSU.

 

PC noise can be a problem, but it won't cause this problem. We're looking at a supposed 10 dB drop in high frequencies, and there's no way noise can cause that.

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