Keeping computer noise out of DACs

September 23, 2021
 by Paul McGowan

15 comments on “Keeping computer noise out of DACs”

  1. USB noise should not be a concern unless you are hearing hum from a ground loop. If your DAC is receiving data asynchronously and has good clock precision you should be fine. The EMI/RFI noise from the PC should not be an issue. The length of the USB cable is important, keep it as short as possible.

  2. Hey Paul!
    Thank you for telling us about Audovonna!
    I don’t own a Mack as of yet, but I have been looking for something that works on Windows like Bit Perfict does for Macks.
    Again, thank you for telling us about that!
    Now, I will go and look for it.
    PS. will I need to bypass my integrated motherboard sound card to a DAC that can decode DSD?
    I’ve never heard of any integrated motherboard that can decode DSD without converting it in to PCM before your ears can hear it.

  3. The path from my computer to the DSD DAC goes through an ordinary USB hub (to meet USB standards for distance) and then to a pretty good reclocker fed by an “ultra-low noise” power adapter. The DAC is 10′ from the computer and the cables total maybe 15′. How much of a concern is computer noise in this kind of setup?

  4. My take on this topic is aligned with Paul’s thoughts. My current understanding, and paraphrasing his comments, is as follows.

    There are three important areas on which to focus our efforts to optimize audio from a computer/DAC source.

    1. Assuming that the bit stream is already bit-perfect, minimize timing distortions (‘jitter’) in the stream before it gets to the DAC by imposing super accurate clocking to the stream
    2. Bypass the computer system’s native digital audio ‘mixing’ process such that the playing software outputs directly to the DAC
    3. Minimize radio or electromagnetic interference (RFI/EMI) with the DAC.

    My current approach to resolving these issues is as follows.

    1. Interupt the normal computer/DAC USB connection by placing an independent, high-quality reclocker/protocol converter between the computer and the DAC. (USB is converted to I2S)
    2. Use a software player that makes use of an Audio Stream Input Output (ASIO) driver in order to bypass the (Windows) computer audio subsystem and output directly to the reclocker/protocol converter in native (non-DoP) format. (An added bonus is that this enables the transfer of a native DSD bit stream)
    3. ‘Distance is my friend’. This is based on the premise that the strength of an electromagnetic field eminating from a point source is inversely proportional to the sqaure of the distance from the source. So, keep computer, reclocker/converter and DAC as far away from each other as is practicable.

    Of course, YMMV 🙂

    1. Good morning MikeK!
      Perhaps you can tell a blind Audiophile that uses Windows how to do something here.
      Paul said something in his video yesterday, about something about a thing that works just like Bit Perfick for Macks, that’s called Audovonna.
      That is, if I’m spellingg that word correctly.
      But however, I couldn’t find it.
      I have quite a collection of DSD files on this computer.
      Some of them, I copied from data DVD’s that came with some SACD’s that I ordered from PS Audio.
      Others, I created myself.
      I would like to get bit perfick audio out of this Windows machine to any hifi system I hook it up to.
      Email me offline at:
      [email protected]
      that is, if you don’t mind helping me with it.
      Thank you in advance!

      1. Hi John,

        The idea of ‘bit-perfectness’ is somewhat of a curiosity to me as well! I’m guilty of not knowing a great deal about it and, after reading your comment, did a little research myself.

        From what I found, I think ‘bit-perfectness’ is more a concept rather than a product and I believe there are a number of products out there that will allow you to deliver a bit-perfect bit stream to your DAC.

        One important feature of the BitPerfect product about which I was not previously aware is that it appears to also bypass the computer’s internal audio subsystem. Someone more knowledgable may care to chip in here.

        At any rate, I’ve sent you a PM with the limited help I may be able to provide you.

  5. Hello MikeK

    I have just watched Paul’s video about computer noise. You recommend ” an independent, high-quality reclocker/protocol converter between the computer and the DAC. (USB is converted to I2S)” It makes me dizzy only to read the name of this tool.
    Neither Paul nor you mention where to get this product and what it is called.

    Another thing is, how to avoid PC noise by using Audirvana.
    I have listened to Audirvana for years and acording to me you need a PC (In my case a Macmini) to download it to and play it. So I can’t avoid the PC’S noise?? Audirvana is in the middle of it an it is not a tool that one can take out of the PC.

    Please help me I am falling,

    Gommie

  6. Hi Gommie,

    Apologies about the wordiness of my comment. I’m by no means expert in this area but I’ll put it another way to the best of my understanding.

    As Paul says, the ‘noise’ from computers is usually a big problem for audio. It can be acoustic and electronic. Some of it can be greatly reduced by locating your computer in another room from your DAC, amps and speakers. Some of it can be addressed by modifying the computer and optimizing its operation for just the audio function. However, one of the main contributors to the ‘noise’ is due to the way the bits are transmitted through the USB connection to your DAC. You may get the biggest ‘bang for you buck’ by focusing on this aspect.

    Along with ‘data bits’ that represent your music file, the computer also transmits timing information so that the DAC can determine when a bit is ‘on’ or ‘off’. The timing information is supposed to be (and generally is) a very regular, high-frequency pulse, like the ticking of a clock. That ‘regularity’ can be upset or distorted by other electrical functions occuring in the computer. This ‘jitter’ in the data stream can eventually find it’s way into the music that comes out of our speakers. Our ear/brain can often hear the effect of this.

    One way to treat this issue is by intercepting the data being transmitted through the USB connection to the DAC. In this scheme, the computer sends the USB data to a device specifically designed to receive the data from the computer, temporarily store it and then pass it onto the DAC in a more timely manner using its own (more accurate) clock. The bonus part I mentioned in my original comment is that this device also converts from the USB way of transmitting data to another protocol called I2S (or more strictly ‘I squared S’) which is better suited to transmitting audio data by separating the timing information from the music data. The device I use to perform this function is called an ‘X-SPDIF 2’ made by a company called Matrix Audio.

    Regarding Audirvana, I have no experience with it but I believe it addresses point 2 in my original comment in that, like a number of other products, it bypasses the computer’s in-built audio subsystem and outputs directly to your DAC (via USB for example). Unfortunately, what it sends to the DAC will still be affected by the timing issue I described above. So it only addresses one part of the problem.

    Oops! I was again verbose! Apologies for that. 🙂

  7. Hello MikeK,

    No apologies please. You are not “Verbose” (What a beautiful word by the way)

    This was a clear explanation, which I really understood, being an electrical layman.

    I have 2 “I squaredS” (Simple names are rare in Audio!!!) connections on my PS Audio Perfectwave Directstream DAC. One of them I use for my PS Audio Directstream Memory Player. So I have one free connection. So I might use that one for the device you recommend (X SPDF 2)

    Question 1: Are there any other devices doing the same trick?
    Question 2: I also have nucleus. Do I need the device there too?
    Can I download Audirvana and Qobuz on the nucleus too?

    Perhaps you will have time to reply again.

    Thanks in anticipation and enjoy your Sunday

    Gommie

    By the way I am from Holland

    1. Hi Gommie,

      Greetings from Australia on the bottom hemisphere. 🙂

      I note you have a Memory Player. I use only one of the I2S connections on my DS DAC but, from what I read in the PS Audio forum pages, the X-SPDIF 2 solution can provide a similar level of sound quality for ripped CDs and SACDs and downloaded PCM (FLAC or native) and DSD files.

      As for other similar devices, I can’t really advise you. I first read about the X-SPDIF 2 in a PS Audio forum topic in the ‘Accessories’ category called ‘Matrix X-SPDIF 2’ (https://forum.psaudio.com/t/matrix-x-spdif-2/9116/5282). I’m not really an avid tinkerer with my system mainly because I have limited resources to try out different products. I settled on the Matrix after reading the many favourable reports in the forum topic. I did a quick internet search on ‘usb reclocker’ and ‘i2s converter’ but didn’t find that many devices.

      As for (Roon?) Nucleus, again I can’t really advise you having no experience with using it. However, I believe it’s a specialized computer optimized for digital audio, as I mentioned in an earlier comment. It appears to be designed for use as the core component in Roon’s view of a digital audio service, providing an archive for your music files, access to streaming services and serving music data to your DAC. Although it probably goes a long way to cleaning up the USB output to your DAC, it’s still a computer performing a number of different processes and does not exclusively perform the reclocking function as does the X-SPDIF 2. As far as I can tell, it also doesn’t do the conversion from USB to I2S, although it does have an HDMI connector but I think that’s for HDMI data and not for I2S data.

      There may be a way to install Audirvana or Qobuz but I’m not familiar enough with its architecture to say whether or nots that’s possible. Access to Qobuz may already be an available option but I can’t say for sure.

  8. Here are a set of comments influenced only by the engineering. I haven’t done any listening experiments:

    – I can’t see any fundamental benefit in I2C compared with S/PIDF; the two standards transfer the same information, and the multiplexing in S/PIDF is typical of any number of other standards successfully used in communications and networking.

    – Asynchronous USB must surely be the way to go. In this mode, the DAC’s internal clock is used to convert digital data to analogue, while the computer provides information as and when needed by the DAC. In this case, jitter from the computer does not modulate the audio output.

    – I see how the noisy environment of the computer can be a problem. It’s incumbent on DAC designers to ensure that the DAC is well isolated from that noise. However, consider the similar case with an outboard ADC; we can amplify and convert the sub-millivolt signal from a microphone without contaminating it with electrical noise, to it must be possible to do the same with a 2 volt output from a DAC.

    – The “bit-perfect” thing is a no-brainer. It’s essential to transfer the exact digital data to the DAC without processing in the computer’s audio sub-system.

  9. I’ve always had marginal success using a computer but since adding a Digital to Digital Converter, that has all changed. Placing a Pi2AES ahead of my DAC has made a world of difference.

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