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Thread: Flac

  1. #31
    Quote Originally Posted by rblnr View Post
    Gotta say, in a very brief test using the Amarra demo, I didn't hear any difference using it vs. straight out of iTunes.
    Neither did I, but I run USB out of a MacBook Pro to a digital converter that re-clocks, converts and then sends optical to my DAC, and runs on battery power....so I am about as isolated from any noise generated by computer activity as you can get. If that's the difference - jitter created by system activity - I probably wouldn't know it. The thing is, if that's the difference, Amarra shouldn't sound better than iTunes without the isolation and re-clocking.

    Tim
    In high-end audio, you can't even fight an opinion with the facts.

  2. #32
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    Quote Originally Posted by Phelonious Ponk View Post
    By "different loads on the PC," are you talking about PC resource demands during audio playback?
    Yes.

    This is what confuses me. It is the only thing that makes different sounding digital players make sense to me, but by that measure, the darling of the audiophile world, Amarra, should be the worst-sounding player on the market.

    Tim
    Well, not quite. As I said, the problem cannot be characterized.

    Let me explain. Let's say that you peg the CPU to 100% in one scenario. And in the other, you spike once a millisecond. The former may not cause much jitter because the load while high, is constant. The other, will cause power supply spikes proportional to that frequency and create jitter frequency of 1 Khz.

    Now here is the problem. The PC is an insanely complex device. Modern CPUs have multiple cores, we have GPUs, many buses, an operating system that is not real time and is running tasks more or less in a chaotic manner. There is no way as such to characterize what is going on. One can take steps to reduce some of this but what effect it has could be very unpredictable.

    My sense is that subjective impressions of these media players sounding different is probably wrong. I have some experience here. I was playing Foobar2000 to test my iPad remote. As soon as I played one of my reference clips, I was shocked that it sounded "better" than I remembered. So I play the same track with the windows media player and it indeed sounds worse to me. I think at first it has to do with a different audio pipeline. I research and confirmed that it was using the identical pipeline to WMP. With that knowledge, I time aligned WMP and Foobar next to each other so that I could switch over in 1 to 2 seconds. In that situation, I could find no difference at all. Placebo effect was incredibly strong here. I can't explain it in words as to how much better I thought Foobar sounded the first time I started it.

    Now this experience is limited to my system and my audio equipment (NHT monitors, Mark Levinson DAC). So other players and on other platforms perhaps perform better. I remember reading on computer audiophile some timing measurements that were improved by using different playback infrastructure. So I leave the possibility there but I highly encourage some kind of objective testing as I did to rule out placebo.

  3. #33
    Member Sponsor [WBF Founding Member] rblnr's Avatar
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    Though I've seen it denigrated in some places, I'm a fan of the 'live flop' method of subjective testing.

    For example, I recently synced the playback of a pair of Squeezeboxes into a pair of DACs, then each of these was fed into my preamp. Flopping between the two was hitting a button on the remote -- the song continues without missing a beat. Very easy to hear tonal differences, etc. Idea is to take sonic memory, and it's relative the placebo effect, out of the equation as much as possible.

    The Amarra demo has a button to bring it in and out of the playback chain. In some quick, casual listening, I heard no difference flopping it in and out on my Macbook Pro. Would more comprehensive testing reveal differences? Maybe, but when I hear talk of major improvement which I define as something easily discerned -- obvious -- I'm out.

    Amir -- so if I understand you correctly, everyone's computer, because of hardware architecture, installed software, etc. could theoretically sound different. The variables are endless which makes the whole question of what sounds better case by case. Yes?
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  4. #34
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    Quote Originally Posted by rblnr View Post
    Amir -- so if I understand you correctly, everyone's computer, because of hardware architecture, installed software, etc. could theoretically sound different. The variables are endless which makes the whole question of what sounds better case by case. Yes?
    Absolutely right.

  5. #35
    WBF Technical Expert (Speakers & Audio Equipment)/Member Sponsor [Technical Expert] garylkoh's Avatar
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    Quote Originally Posted by Phelonious Ponk View Post
    it is absolutely counter-intuitive, and that's the point. Some of the same audiophiles who are buying or building systems dedicated to music production, in which they are going to great pains and expense to minimize CPU usage to nothing but essential OS functions and playing music files, on the belief that this makes these dedicated computers sound better than others, are hailing Amarra as the best-sounding player on the market. And it is the biggest resource hound on the market. Even Amarra seems to recognize that and is working to trim it down.

    Tim
    May be expectation bias because of the great reviews that Amarra was getting?

    On another thread, someone pointed out that DPC latency was more important to sound quality than absolute CPU usage. I tried this by adding additional processes until Foobar started to glitch - and you can get CPU near 100% utilization without any noticeable change in sound quality. However, I haven't yet figured out how to increase DPC latency to make SQ worse so I haven't been able to investigate this properly.
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  6. #36
    Amir -- so if I understand you correctly, everyone's computer, because of hardware architecture, installed software, etc. could theoretically sound different. The variables are endless which makes the whole question of what sounds better case by case. Yes?
    If that's it, I guess there's not much point in discussing it, then. This I know: I've shut off everything but the player, run the Mac and the converter off of battery, even turned off the screen, and I've done that with Amarra, Pure Music and iTunes. Is there a difference between that and running the MacBook with Safari, Mail and TuneUp running? Is there a difference between that and running the while downloading, surfing, multi tasking my little semi computer-literate butt off? Maybe. But if there is, it is very, very subtle. I don't deny anyone else their experience, but that's mine, and I'm far from hard of hearing. I can hear the sonic signature of tube mic preamps, the tone of specific makes and models of instruments, a 60-cycle hump, a BBC dip and the lovely, elegant deterioration of Joni Mitchell's voice, but I can't hear resource minimalism or the superiority of Amarra. So I let the time run out on my Amarra and Pure Music demos, deleted them from my hard drive and stopped worrying about what is running on my computer while listening to music.

    I think the worry probably degrades the signal more than CPU activity. Maybe that's what we call placebo.

    Tim
    In high-end audio, you can't even fight an opinion with the facts.

  7. #37
    [WBF Founding Member] Moderator RBFC's Avatar
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    We had both music players ready with the same file. We used Amarra WITHOUT iTunes vs. PureMusic, and Amarra (no iTunes) vs. Audirvana. In both instances, Amarra seemed more realistic in my system and to our ears. This is why I worked so hard to sort out the difficulties I had with Amarra early on. For the cost, I would have certainly passed on Amarra if it were not for these convincing trials. Did we conduct them perfectly enought to guarantee that the results were valid.... don't know, maybe not. However, it sure sounded good.

    iTunes, which some of my friends call a "virus", runs other applications while playing music. These apps include sync programs for other "i" devices, etc. Recently, it was reported that a ".mux" file in iTunes 10.2.1 was degrading sound quality in playback. This was one of those "sync" programs that run while iTunes is open.

    As Amir states, this is a very complex tarpit we've entered, and it will be a while before anyone can definitively state what is going on.

    Lee
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  8. #38
    WBF Technical Expert (Speakers & Audio Equipment)/Member Sponsor [Technical Expert] garylkoh's Avatar
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    Quote Originally Posted by amirm View Post
    Now here is the problem. The PC is an insanely complex device. Modern CPUs have multiple cores, we have GPUs, many buses, an operating system that is not real time and is running tasks more or less in a chaotic manner. There is no way as such to characterize what is going on. One can take steps to reduce some of this but what effect it has could be very unpredictable.

    My sense is that subjective impressions of these media players sounding different is probably wrong. I have some experience here. I was playing Foobar2000 to test my iPad remote. As soon as I played one of my reference clips, I was shocked that it sounded "better" than I remembered. So I play the same track with the media player and it indeed sounds worse to me. I think at first it has to do with a different audio pipeline. I research and confirmed that it was using the identical pipeline to WMP. With that knowledge, I time aligned WMP and Foobar next to each other so that I could switch over in 1 to 2 seconds. In that situation, I could find no difference at all. Placebo effect was incredibly strong here. I can't explain it in words as to how much better I thought Foobar sounded the first time I started it.
    Insanely complex is right. If you play a track twice in Foobar, it can sound different, and it can sound better the first time around, or better the second time around. I did this some time ago, so the details are a little hazy, but it has to do with disk hardware buffer, the way Windows memory management buffers, and the Foobar playback buffer working together and against each other. When I noticed it, I pulled up the Windows Resource Monitor.

    The first time the track was played, disk activity was very spiky and CPU activity was very flat. The second time the same track was played, there was NO disk activity but the CPU activity was spiky. Cutting down on the size of the Foobar buffer output buffer length made disk activity less spiky, and subjectively makes Foobar sound better on the first play of the track. On the PNWAS music server, a buffer length of between 530ms and 650ms sounds best.
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  9. #39
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    Ah, you gave me another theory to chase Gary . One approach I was going to test was with my async USB adapter. In theory, that should eliminate the differences. If I still hear a difference, then I am going to commit suicide

  10. #40
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    Quote Originally Posted by amirm View Post
    If I still hear a difference, then I am going to commit suicide
    Before you do, check if there is a galvanic isolation between the PC and the DAC.
    A async protocol sec might be insufficient if stray signals still can enter the DAC.

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