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

  1. #31
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    Quote Originally Posted by amirm View Post
    Microframes in USB 2.0 are indeed 125 microseconds which translates to 8 Khz as you say. However your analysis I am afraid is not correct. Here is the graph again:



    The jitter side bands are 4 Khz above and below our 12 Khz signal, not 8 Khz as you said. That means our jitter frequency is likewise 4 Khz, not 8 Khz.

    I would be surprised if John didn't know this simple math about jitter side bands and confused this timing with microframing of USB.
    Why do you assume that all spuriae you see on your plot is related to the jitter signal? Why not use another jitter signal which is not a multiple of 8KHz to see if your assertion or mine is correct?
    And I don't know what power supply graphs have to do with framing of USB packet noise coming out of a DAC.
    I just happen to know that those PS graphs from John W were a ground noise plot coming out of the Regen & his plots clearly show 8KHz & multiples thereof as spurs!!

    In fairness to Uptone/REGEN, let's not put more on their plates without properly analyzing such things. This is a complicated system and doesn't let itself to quick and dirty guesses.
    Well, that is correct, Amir & it's rather a shame that you didn't think of this before posting "For my money, I think a rock from the garden put on top of my DAC may do better than either one of these devices" Don't mistake this as defending the Regen - I just think the measurements & analysis looks rather shoddy & rushed!

    Can I ask did you do your listening before or after doing your measurements?
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  2. #32
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    Quote Originally Posted by amirm View Post
    I like to emphasize something: the increased jitter I have shown with REGEN is completely inconsequential. It is way low at -115 db or so. There are worse offenders from the DAC itself. And those are not bad either from audibility point of view.

    So please let's not put practical blame at their feet on this ground. It is curious, yes. Should it be there if we are saying the device creates a cleaner USB signal, no. But from the end result point of view it is not material.
    As i said in my last post, why not clear up whether these 8KHz spurs are the result of USB protocol noise first before damning with faint praise?
    Manufacturer digital products www.Ciunas.biz
    "The greatest obstacle to discovery is not ignorance – it is the illusion of knowledge." - Daniel J. Boorstin.

  3. #33
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    Quote Originally Posted by jkeny View Post
    Why do you assume that all spuriae you see on your plot is related to jitter? Why not use another jitter signal which is not a multiple of 8KHz to see if your assertion or mine is correct?
    There are two causes of symmetrical side bands: jitter and modulation of reference voltage. I generically call both jitter because that is the term people are familiar with.

    I don't know what you mean by your assertion. 8Khz jitter would have shown up at 12-8 =4 Khz and 12+8 = 20 Khz. There is nothing at those frequencies.

    Well, that is correct, Amir & it's rather a shame that you didn't think of this before posting "For my money, I think a rock from the garden put on top of my DAC may do better than either one of these devices"
    There is a difference between me saying whether I would or would not purchase something than throwing out additional technical faults toward the product as you did that is not substantiated with the data we have.

    Can I ask did you do your listening before or after doing your measurements?
    With AQ I did both, once before the dog chewed it up and once after unboxing and measurements . With Regen I did after. Let me know how the measurements differ due to order of listening.

  4. #34
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    Quote Originally Posted by amirm View Post
    I like to emphasize something: the increased jitter I have shown with REGEN is completely inconsequential. It is way low at -115 db or so. There are worse offenders from the DAC itself. And those are not bad either from audibility point of view.

    So please let's not put practical blame at their feet on this ground. It is curious, yes. Should it be there if we are saying the device creates a cleaner USB signal, no. But from the end result point of view it is not material.
    So then what exactly does explain the opinion of 99+% of the owners who feel the Regen does help to improve SQ (myself included)?

    What did you miss in your measurements? Or do you think it's all placebo, cognitive dissonance, owner's bias and/or mass hysteria?

    PS: I don't blame you using it but most Regen owners know the "short cable" is the least preferred way to connect a Regen to a DAC. The solid connector is -strongly- preferred.

  5. #35
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    Oh wait. I see what you mean now John. You are saying that there are harmonics of 8Khz travelling through? If so, that could be it. My bad in not realizing that as a possibility.

  6. #36
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    Quote Originally Posted by amirm View Post
    First welcome to the forum .

    Second, what would you like me to say? This is Paul Miller's of HiFi news making a measurement of the eye pattern in his system with and without AQ:



    This is John's:


    Set aside the colors in John's as that is false coloring based on intensity of the graph. In Paul's measurements the eye is completely clear, with or without AQ. It is wide open too. Both of these are characteristics of a compliant USB port that is driving a short cable. John's measurements are nothing like that. As he says, it is pretty messed up eye pattern with lines through the eye. It makes no technical sense that his eye pattern is typical of what comes out of most computers. If so, and you connected a long cable to your printer, there would be hell to pay in potential data losses.

    Maybe John has it right and it is Paul who has it wrong and found the one clean USB port out there. But if I were you, I would not put my money on that . If I were managing a team of hardware engineers there is no way I would let them release a USB port with John's measurement on a short cable.

    Again, there are a ton of USB implementations out there, some of which could pick up the crosstalk that the CPU activity spits their way. In our application, i.e. audio playback, uses almost no CPU on a modern computer. So even if CPU activity causes such issues, it is not typical in our application. I would love to see John repeat his test but this time with just a media player running and playing some music. And at least try it on one other computer.
    Amir, you are really confusing matters here which is not helpful - Paul Miller's plot is of the USB eye pattern before/after Jitterbug insertion - JohnW's plot the eye pattern of the USB signal from his PC.

    Furthermore, I hope I clarified what was meant by JohnW's phrase 'heavy "CPU Process" jitter modulation' & you now can temper your comments about a rogue PC being used

    I believe your dismissal of JohnW's plot is mistaken - here's what he says
    So I dug up a Digital scope - rearranged the lab to make space for it... I think its the first time I've really used it - I hate them, but it proved useful to capture the data.

    https://dl.dropboxusercontent.com/u/...rect%20usb.jpg

    Above is a colour graded eye pattern of the Direct PC USB connection to an XMOS based DAC (streaming 1KHz, 0dB FS) High speed USB.

    Note the multitude of lines, but more importantly that the background is not black (Black means no data points fell in this area) - the background its dark blue because during the acquisition low frequency "Runt" waveforms where sampled in this area - these "Runt"waveforms occurred as the PC / operating system processed other applications / Operating system house keeping tasks etc. On the Analogue scope it was a horrific mess...

    https://dl.dropboxusercontent.com/u/...egen%20usb.jpg

    Now with the ReGen USB Data, notice not only the much cleaner waveform but far more importantly that there is very little "Runt" data - the background is Black. The USB Hub IC in the Regen has for the most part cleanly repackaged the data.

    The colour grade data sample hit size is the same for both plots (20K Hits on the Red).
    And later:
    "The scope timebase was 200pS a Div, so very fast any LF modulation causes the location of the eye pattern to shift in time - so the location of the crossing points fell into other areas which results these hits being colour graded - Lower Frequency events in Blue, more frequent events in light blue etc.

    The Green graded hits indicate "medium frequency events" - so these "odd states" happen frequently - Observing the Waveforms on a very fast Analogue scope "WITH IMAGE INTENSIFIER" to allow LF events to be visible on the CRT at such fast sweep speeds (500pS Div) you can see the "runt" events directly related to the processing tasks of the PC - the frequency of their occurrence is visibly modulated by the operating system workload / operation."
    Manufacturer digital products www.Ciunas.biz
    "The greatest obstacle to discovery is not ignorance – it is the illusion of knowledge." - Daniel J. Boorstin.

  7. #37
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    Quote Originally Posted by Antoine View Post
    So then what exactly does explain the opinion of 99+% of the owners who feel the Regen does help to improve SQ (myself included)?
    I don't know. My suggestion is to re-test with an assumption that the device can do nothing or even harm the sound. Then see if it improves the sound still. The notion that 99% of other people said it makes thing sound better is a powerful bias.

    What did you miss in your measurements?
    It could be a lot. But not because of the reason you mention . My mission was to verify the technical aspects of the product. It said it cleaned up the USB signal, ergo it cleans up the output of the DAC. That didn't turn out to be the case. If the improvements were as universal as you said, then probabilities would say that it should have occurred in my test system and my listening room. Again I could not arrive at that conclusion based on listening or measurements.

    Or do you think it's all placebo, cognitive dissonance, owner's bias and/or mass hysteria?
    In a science thread I am not digging deeper in this area. We are here to discuss the objective data which cannot be doubted as easily as what I did or did not hear.

    PS: I don't blame you using it but most Regen owners know the "short cable" is the least preferred way to connect a Regen to a DAC. The solid connector is -strongly- preferred.
    Oh? So what was the outcome with the supplied cable? Were those reports not so positive?

    As I post earlier the manufacturer advertises that reduces dependency on cables: "Although the REGEN does not eliminate all sound quality differences between USB cables in a high-end system, it significantly reduces those differences. "

    How is what you say possible when they say that cable should not matter as much and supply a short one instead?

    Do we now have two USB cables we need to tweak to get better sound, one to this device and one to the DAC?

  8. #38
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    Quote Originally Posted by jkeny View Post
    Amir, I hope I clarified what was meant by JohnW's phrase 'heavy "CPU Process" jitter modulation'

    I believe your dismissal of JohnW's plot is mistaken - here's what he says

    And later:
    You have not John. So it is clear, I have read all of those posts. What I am after is him explaining how it is typical for USB to have such poor response in application of playing music. I take at face value that he has a computer and it spits out the performance he is showing. I don't doubt his method of measurement and the graph at all.

    And to be clear, nothing he has post is at odds to what I have reported. Nothing! I take it as a given that the hub in Regen produces a clean signal since it is outside of the computer and regenerates the bus yet again. That he shows this to be case simply confirms my basic assumption.

    As I explained earlier though, we don't listen to USB bus. We listen to the output of the DAC. I measured this response. JohnW did not. So again, what he reported and what I reported are not at odds. It is not like he measured a DAC output and found that profound difference. He did not.

    Unfortunately as we see from the response of the manufacturer and forum posts, everyone is running with that eye chart as that as if that is the sign of what improvements come out of the DAC itself. JohnW himself warns about not doing that later in that thread but it is just a line compared to the pretty graphs.

    So again, there is no conflict between JohnW's measurements and mine. His are measuring USB, I am measuring the DAC output." One doesn't predict the response of the other. You as a listener and buyer need to decide which data is more useful to you. I think it is the DAC output but you are welcome to think otherwise.

  9. #39
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    Quote Originally Posted by amirm View Post
    ....
    With AQ I did both, once before the dog chewed it up and once after unboxing and measurements . With Regen I did after. Let me know how the measurements differ due to order of listening.
    For someone who preaches quite often about bias, I'm surprised that you don't recognise the very high likelihood of a biasing effect when doing measurements before sighted listening? So, in answer to your question - you have gotten the wrong end of the stick - the measurement results affecting your auditory perception is what I'm suggesting
    Last edited by jkeny; 09-29-2015 at 08:58 AM.
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  10. #40
    Quote Originally Posted by amirm View Post
    As I post earlier the manufacturer advertises that reduces dependency on cables: "Although the REGEN does not eliminate all sound quality differences between USB cables in a high-end system, it significantly reduces those differences. "

    How is what you say possible when they say that cable should not matter as much and supply a short one instead?
    I think what they mean is that the cable between computer and REGEN matters less than if it connected directly to the DAC.

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