Chord Electronics Qutest DAC - Official Thread
May 27, 2019 at 12:39 PM Post #3,887 of 6,736
Btw I have a question regarding streaming quality using macbook pro running audirvana. Would the quality of streaming be better if the macbook pro is connected through ethernet cable to an airport express extender? Main airport extreme router is in another room. I use a small airport express to a wall plug which runs the ethernet cable to the mbp. Running optical to cut the noise.
 
May 27, 2019 at 12:43 PM Post #3,888 of 6,736
Thanks. Well mine will do 24/192 no issues, so is all good.
Just that some folk say they hear differences between different toslink cables and I don't get why that should be the case.
The reason toslink cables can sound different is because of different amount of jitter that they introduce. Jitter is a time-slot error, simplified: all the bits get there as they should, but not exactly when they should.

I experienced a little smoother higher frequencies with my Lifatec, but the difference wasn't huge. Note that this depends on the DAC as well, and its ability to handle jitter (basically reclock the signal). I have the RME ADI-2 DAC.
 
May 27, 2019 at 12:52 PM Post #3,889 of 6,736
The reason toslink cables can sound different is because of different amount of jitter that they introduce. Jitter is a time-slot error, simplified: all the bits get there as they should, but not exactly when they should.

I experienced a little smoother higher frequencies with my Lifatec, but the difference wasn't huge. Note that this depends on the DAC as well, and its ability to handle jitter (basically reclock the signal). I have the RME ADI-2 DAC.
Thanks for that. Sure I can buy the difference in jitter on the cable being a factor with some DACs and would expect glass to be a better light transmitter, but Rob Watts' designs are jitter free AFAIK, though folk claim a difference with their Qutest. Just trying to understand.
 
May 27, 2019 at 3:38 PM Post #3,890 of 6,736
Thanks for that. Sure I can buy the difference in jitter on the cable being a factor with some DACs and would expect glass to be a better light transmitter, but Rob Watts' designs are jitter free AFAIK, though folk claim a difference with their Qutest. Just trying to understand.
I don't think any DAC is totally free of jitter (for any input), but some DACs are better at handling it than others. I think @Rob Watts puts on his "salesmen-cap" from time to time :)
 
May 28, 2019 at 1:42 AM Post #3,893 of 6,736
I don't think any DAC is totally free of jitter (for any input), but some DACs are better at handling it than others. I think @Rob Watts puts on his "salesmen-cap" from time to time :)

Hmm - the facts are that you can put 2uS of 1kHz jitter on my DACs via SPDIF and can measure absolutely nothing, down to a FFT noise floor of -180dB. 2uS is a thousand times larger than jitter you would normally encounter on SPDIF.

I don't have a "salesmen-cap". Can you buy one on Amazon?

I am a measurement/objective listening based designer, and am driven entirely upon measurements and carefully controlled listening tests. If I can or can't hear a difference, I post on that. If I measure or can't measure a difference, I post on that. And if I find an observation that contradicts things I have posted before, I post that too. Moreover, Head-Fi posts from people using my designs has been incredibly useful in the past, as people finding sensitivities (X sounds different due to Y and Z), and this has allowed me to investigate issues because of these sensitivities - which then results in better performance from new designs - and I post on that too. But source jitter is for sure not one of these issues.

As a scientist/design engineer I deal in realities, and am solely driven on one thing - trying to close the gap in reproduced audio from unamplified live sound. And I post on my understanding of those realities; I certainly don't want or need a salesman's hat...:smile_phones:
 
May 28, 2019 at 1:53 AM Post #3,894 of 6,736
Hmm - the facts are that you can put 2uS of 1kHz jitter on my DACs via SPDIF and can measure absolutely nothing, down to a FFT noise floor of -180dB. 2uS is a thousand times larger than jitter you would normally encounter on SPDIF.

I don't have a "salesmen-cap". Can you buy one on Amazon?

I am a measurement/objective listening based designer, and am driven entirely upon measurements and carefully controlled listening tests. If I can or can't hear a difference, I post on that. If I measure or can't measure a difference, I post on that. And if I find an observation that contradicts things I have posted before, I post that too. Moreover, Head-Fi posts from people using my designs has been incredibly useful in the past, as people finding sensitivities (X sounds different due to Y and Z), and this has allowed me to investigate issues because of these sensitivities - which then results in better performance from new designs - and I post on that too. But source jitter is for sure not one of these issues.

As a scientist/design engineer I deal in realities, and am solely driven on one thing - trying to close the gap in reproduced audio from unamplified live sound. And I post on my understanding of those realities; I certainly don't want or need a salesman's hat...:smile_phones:
Well said @Rob Watts thank you for creating qutest I am having a blast!
 
May 28, 2019 at 2:50 AM Post #3,895 of 6,736
Hmm - the facts are that you can put 2uS of 1kHz jitter on my DACs via SPDIF and can measure absolutely nothing, down to a FFT noise floor of -180dB. 2uS is a thousand times larger than jitter you would normally encounter on SPDIF.

I don't have a "salesmen-cap". Can you buy one on Amazon?

Audiosciencereview: no jitter whatsoever
Stereophile measurement: no jitter whatsoever
-180dB seems a little exaggerated though. So you do have a salesman cap :) :)

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1218ChoQutfig15.jpg
 
May 28, 2019 at 3:52 AM Post #3,896 of 6,736
Audiosciencereview: no jitter whatsoever
Stereophile measurement: no jitter whatsoever
-180dB seems a little exaggerated though. So you do have a salesman cap :) :)

Have you considered that Rob might have better measuring equipment than the reviewers?
 
May 28, 2019 at 4:12 AM Post #3,898 of 6,736
Hmm - the facts are that you can put 2uS of 1kHz jitter on my DACs via SPDIF and can measure absolutely nothing, down to a FFT noise floor of -180dB. 2uS is a thousand times larger than jitter you would normally encounter on SPDIF.

I don't have a "salesmen-cap". Can you buy one on Amazon?

I am a measurement/objective listening based designer, and am driven entirely upon measurements and carefully controlled listening tests. If I can or can't hear a difference, I post on that. If I measure or can't measure a difference, I post on that. And if I find an observation that contradicts things I have posted before, I post that too. Moreover, Head-Fi posts from people using my designs has been incredibly useful in the past, as people finding sensitivities (X sounds different due to Y and Z), and this has allowed me to investigate issues because of these sensitivities - which then results in better performance from new designs - and I post on that too. But source jitter is for sure not one of these issues.

As a scientist/design engineer I deal in realities, and am solely driven on one thing - trying to close the gap in reproduced audio from unamplified live sound. And I post on my understanding of those realities; I certainly don't want or need a salesman's hat...:smile_phones:
Thanks Rob, I'm satisfied that jitter is of no concern.
I guess the other issue that could arise would be a poor cable producing data transmission errors, which the DAC can't fix as in the signal already, but this would be clearly audible as clicks or pops AFAIK. As my cable does not have these issues I conclude that an upgrade is likely not needed (though I will look forward to @kerisabe doing a comparison :))
 
May 28, 2019 at 7:55 AM Post #3,900 of 6,736
Thanks Rob, I'm satisfied that jitter is of no concern.
I guess the other issue that could arise would be a poor cable producing data transmission errors, which the DAC can't fix as in the signal already, but this would be clearly audible as clicks or pops AFAIK. As my cable does not have these issues I conclude that an upgrade is likely not needed (though I will look forward to @kerisabe doing a comparison :))

Or maybe, like USB, the tranceivers that interpret the incoming signal generate noise internal to the receiving device, and the harder it is to interpret a jittery signal the more noise they generate. The digital data you hear is reclocked so no jitter there, but is there electrical noise from the tranceivers that can be heard?
 

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