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Thread: Computer Audio: Is isolation as good as optimization?

  1. #1

    Computer Audio: Is isolation as good as optimization?

    There is a pretty lively discussion going on at a computer audio forum I frequent. A gentleman there who sells, among other things, computers optimized as audio sources, firmly believes that the only way to remove the noise from a computer music source is to hunt it down everywhere it occurs and get rid of it: minimize OS operations, hard disk drive, linear power supply, etc. He upgrades computers for this purpose, so he has a stake in it, but I believe he is sincere. The thing is, I've gotten great results from simple isolation. Well, not really simple. I send USB out of my MacBook Pro to a Trends UD 10.1. The Trends galvanically isolates, re-clocks then puts out coax, toslink, AES/EBU and BNC. I believe it is working for two reasons: 1) It sounds great; I'm getting a super clean signal to my active speakers and my headphone system. 2) it makes sense. By isolating and re-clocking outside of the MacBook, I have left behind all the noise, interference and jitter that is in my Mac. Right? Or am I missing something?

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

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    [WBF Founding Member] Moderator RBFC's Avatar
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    Until you've been able to compare your own listening experience with and without the various alterations, it's only a guess.

    Lee
    Lee Aldridge

    I post my own opinions except when posting as a moderator in green.

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    Couple of points: can you shut down the internal DAC of the Trends while passing the digital through to your actives; and have you tried driving it on battery power, as is possible?

    Frank

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    Unless you can modify the operating system and have equipment to confirm the effects of such modifications, the person is shooting in the dark. Here is an example. Let's say you a have a thousand things running in your PC. You optimize it now and it is only two things. Is the latter better? Not necessarily. The many things being different may regenerate a random signature whereas the other, predictable sources of timing jitter. This is the opposite of what someone thinks may be the case.

    While we can argue about the audible effects of such tweaks, the measurements should give us useful data. I realize the equipment is expensive but at some point, there needs to be a data point for us to use as the starting point. Wonder if Stereophile would be open to measuring a few of these systems.

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    What sort of equipment are you thinking of, Amir? For measuring jitter only, or for other forms of noise and interference as well?

    Frank

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    Jitter and electrical isolation. Can't think of anything else that would impact downstream analog conversion.

  7. #7
    Computer Audio [Technical Expert]
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    Less is more.

    This is a very strong sentiment in the audiophile world.
    If an audible difference between WAV and FLAC is reported, invariably WAV is preferred.
    It is umcompressed so it uses less CPU so it is better.
    (That you get about double the I/O is safely ignored)

    Likewise a lot of PC tweaks, if it is less it is better.
    So underclocking is a must.
    What does it do?
    The frequency lowers and the density of the harmonics increases.
    Why would audio improve?
    There is a very nice post by John Swenson about this subject: http://www.audioasylum.com/forums/pc...s/5/56899.html

    Shooting in the dark indeed.

    I must admit the concept of isolating the DAC (galvanic and a asyn protocol) appeals to me.
    But as usual in engineering there is no free lunch.

    Say we have a USB DAC using async protocol and galvanic isolated from the PC using opto-couplers. Sounds great.
    If we phrase it slightly different: a USB DAC with an async USB receiver converting USB to Toslink.
    Does it still sound great?

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    Member Sponsor [WBF Founding Member] FrantzM's Avatar
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    Hi

    Must one use USB at all? It is practical, true, but it seems t be a noisy interface. In the case of a MacPowerbook isn't SPDIF available from the get go?
    Frantz
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  9. #9
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    No, it is an option (but a lot of PCs don't have a Toslink out)
    But if we talk isolation than:
    Yes, the Toslink shields the DAC from the electrical noise going on inside the PC
    No, the clock driving the SPDIF is not shielded from the electrical noise at all.

  10. #10
    Quote Originally Posted by fas42 View Post
    Couple of points: can you shut down the internal DAC of the Trends while passing the digital through to your actives; and have you tried driving it on battery power, as is possible?

    Frank
    It is isolated, anyway, but I don't believe it turns on until you plug something into the analog output.

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

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