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Thread: Science Thread: Review of Audioquest Jitterbug and Uptone Regen USB Conditioners

  1. #101
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    Quote Originally Posted by rbbert View Post
    I don't think that is necessarily what is occurring here. I'm not trying to defend subjective listening tests, but for "measurements" to be useful in assessing anything one has to be measuring the "right" things....
    I am all ears as to what you think the right thing is. I measured three things:

    1. Comparison of USB power coming out of my computer compared to what comes out of these devices.
    2. Noise floor of the analog output of the DAC to see it has gone done as a result of filtering and or regeneration of the bus.
    3. Level of spurious distortions and noise when playing a 12 Khz signal.

    Please explain why these are not useful or "right."

    , one has to be measuring them in a repeatable and meaningful manner and one has to be able to interpret the measurements correctly.
    I have repeated them and did that one more time this morning in response to testing with longer cable. Results are consistent. Why do you say they are not repeatable? Based on what data?

    As for interpretation, I did that too. I explained that while these products seemed to have degraded measured performance some, I consider them to do nothing audibly. Happy to see someone challenge me and explain otherwise. That is what we ultimately want, right? Whether measurements back output of the DAC changing?

    Many posters are pointing out that in this case none of those requirements have been met.
    Many posters? I see a couple of people putting forward arguments. None have remotely been compelling for simple reasons I have explained and continue to explain. Either something changes the output of DAC or not. I have data that shows no improvement came out of the DAC. No data has been put forward to say otherwise. And no argument remotely sticking that we should do some other test like staring at eye patterns. When was the last you cared about the eye pattern of USB bus? And if you did, what do you think of Paul Miller showing almost no difference?

    What was repeatable about JohnW's measurements? Do you know what computer he used? What USB port? What cable? Nothing, right? I provided all of this detail.

    And I'll repeat again, there is nothing "scientific" about this forum so far; no scientists have participated and no accepted scientific method is being used. If you want to be honest call it the "measurement forum", but also be honest about the breadth and depth of ignorance present.
    I am following the standards practiced in professional audio engineering industry. If you come out with a black box that sits before the DAC and claims to make it sound better, they will immediately ask you to show that the electrical signal on the output of the DAC changed. None will care one bit what happened on USB until you demonstrate this point. And that is the test I did. You can call it whatever you want but improper it is not. It is core to analysis of such products.

  2. #102
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    Quote Originally Posted by rbbert View Post
    I'm not sure what the "outcome" is here; perhaps you could state it again. As far as I can tell, you made some measurements; no meaningful correlations were made to their relation to potential audibility (or lack of). Nothing "scientific" about that, any more than someone else's subjective impression that there was (or wasn't) any audible change or improvement with the DUT's. It doesn't become science until you have used your data or observations to formulate a hypothesis, devise and perform an experiment to test that hypothesis, and then analyze those results. In today's world, that must also be followed by peer review and reproducibility, because while you may think that your experimental design and analysis of results (conclusion) is appropriate, your scientific peers may disagree.
    My peers would all agree with what I did as I just wrote to you. If you say sound changes, they want measurements that show sound changed electrically. My measurements show that only a tiny amount of change occurred with these devices but in negative sense, not positive. I explained that such negative change to be too small to be audible so the net result is that the device does nothing audibly.

    If someone has other measurements, let's see them. If you don't have that, and can't critique the work based on accepted industry standards of engineering, then there is nothing to discuss.

  3. #103
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    Perhaps looking at the DAC output with something more than a 12Khz signal might be useful. Maybe a sweep from 20-20Khz might reveal something. Don't know, just a suggestion.
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  4. #104
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    Quote Originally Posted by BlueFox View Post
    Perhaps looking at the DAC output with something more than a 12Khz signal might be useful. Maybe a sweep from 20-20Khz might reveal something. Don't know, just a suggestion.
    I don't expect it to be revealing but sure, when I get back from RMAF I will run that too. Thanks for the suggestion.

  5. #105
    Quote Originally Posted by BlueFox View Post
    Perhaps looking at the DAC output with something more than a 12Khz signal might be useful. Maybe a sweep from 20-20Khz might reveal something. Don't know, just a suggestion.
    Perhaps it would be better a pink noise with complex envelope and high slew rate, at least double the most difficult and dynamic track it exists

  6. #106
    Playing around with different power supplies connected to my audio server computer, I can definitely hear the difference when a beefier supply is used when listening to my DAC via USB. Especially in the bass department. I think the main reason so many claim to hear positive results with the Regen is plainly because of the dedicated supply providing solid power directly to the USB chip very close to the DAC input. Even if other distortions are added, this extra boost catches people's attention.

    Although there's been over 1700 satisfied Regen users, the % of satisfied users among the professional crowd seems to be much smaller.

    Let's not forget "my pet rock" made the inventor rich as well.
    Last edited by Blizzard; 09-29-2015 at 10:52 PM.

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    Quote Originally Posted by rbbert View Post
    but also be honest about the breadth and depth of ignorance present.
    You best look in the mirror for the direction of those shortcomings.

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    Quote Originally Posted by amirm View Post
    This is incorrect. The DAC has a PLL which filters jitter. If you measure the jitter prior to that at the clock input, you will be misrepresenting how much jitter will appear in the output of the DAC.
    Again, Amir, I believe you are confusing matters. The DAC you used for testing was the Merdian Explorer - what PLL does this use?

    Let's clarify what I believe Alex is talking about - there are 2 distinctly different clock domains in any asynch USB device - the USB clock (12MHz or multiple of) & the audio clocks (usually a pair - one for each speed family) which are the ones where jitter matters. Jitter is only important at the D to A conversion step & the audio clock is directly used in this step (not a PLL derived clock). What Alex was suggesting is that the jitter at the audio clocks input to the DAC chip is indeed the one that should be measured - it will directly affect the output from this chip. Now could this output be corrupted by the output stage after the DAC chip - yes it could. What you are measuring is this downstream output (which will differ from DAC to DAC) & looking for signs of jitter here. Does Alex's suggestion not have merit? Furthermore, to do this, you are using a jitter test which is somewhat imprecise & general.

    Seeing as the main element of change in the USB signal seems to be low frequency fluctuations (as per JohnW's measurements), should you not use a jitter test with some more sensitivity to close-in phase noise?

    It is like saying let's ignore a car has suspension and then see how good it rides. The car has suspension and you can't judge its ride without it. Same with the DAC.
    Sorry, but it's nothing like your analogy - there is no suspension (PLL) in operation in the DAC unless it is receiving SPDIF signal. What Alex is saying, to use your analogy, is to measure the bumpiness of the road because you have no suspension (PLL)

    Importantly, what we hear is the analog signal of the DAC. We don't listen to the clock. We have hard enough time convincing people to pay attention to the measurements of the DAC waveform. How would it then be a better approach to then try to get them to understand correlation between some digital clock source and audio???

    So no, we don't deviate from industry standards such as measuring the analog output of the DAC. It is the right thing to do.

    Now if you are a designer, sure, you instrument the DAC clock jitter. But we are not. We are customers and care about what comes out of our DAC.
    I'm sorry, Amir but there are mixed messages here - are you doing a consumer report or a technical investigation - you seem to be flip-flopping between the two?

    When a device is being analysed, it's the output of the device that is first & foremost of interest - do you analyse a turntable's performance by looking at the output from the speakers?

    Do you see any of the prior "industry standard" investigations into the Regen only looking at the output of a DAC when analysing these devices?
    Last edited by jkeny; 09-30-2015 at 02:50 AM.
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  9. #109
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    Quote Originally Posted by amirm View Post
    My peers would all agree with what I did as I just wrote to you. If you say sound changes, they want measurements that show sound changed electrically. My measurements show that only a tiny amount of change occurred with these devices but in negative sense, not positive. I explained that such negative change to be too small to be audible so the net result is that the device does nothing audibly.

    If someone has other measurements, let's see them. If you don't have that, and can't critique the work based on accepted industry standards of engineering, then there is nothing to discuss.
    The name of the forum is "science thread"; if you actually mean "engineering", or "measurements", then change the name to the appropriate one; your choice. As "site founder and administrator", you should have higher standards. As I posted before, engineering is not a science.

    As far as "peer review", read post #62 again. As far as reproducibility, I must have missed that. Who else has reproduced your results?

  10. #110
    Quote Originally Posted by jkeny View Post
    Again, Amir, I believe you are confusing matters. The DAC you used for testing was the Merdian Explorer - what PLL does this use?
    Whatever PLL is integrated in the PCM5102 DAC chip it contains.

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