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Sorting apples

Paul's Posts — 20 September 2012

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Sorting apples

If you’ve been following along with our series on networking you now understand that regardless of how data gets out of your computer to your DAC – USB or over a network – the path it takes is a shared one used by more than just the music we want to send.

In fact, USB stands for Universal Serial Bus and the very name itself is a clue for us to understand this shared architecture: the last two words specific keys.  ”Serial” refers to a single conduit where everything marches along in series, one followed by the other.  ”Bus”, represents a group of items together; the actual word derived from “Omnibus” which, in literary terms, refers to a book of collected stories or volumes.  The point is that USB is a single shared path in the same way that our network is and all the “traffic” on either the network or the USB is traffic shared with many others.

I am keeping us focused on the shared nature of traffic on these exit paths from your computer because it is this shared quality that is the essence of how a computer and a network works – and once you get your arms around how and why the computer is such a sharing and caring machine, the rest will be child’s play.

Have you ever seen how a machine sorts apples?  Picture a long single conveyor with thousands of apples traveling down the path in single file.  Along the way, apples leave the path – like cars exiting the freeway – while others continue on their way and leave by different exits.  At the end of the conveyor there are no apples left.  The apples get off at various exits because of their size or weight: large ones first, then the next size down, finally ending with the smallest apples.  In this way, the farmer can simply dump a basket of multiple sized apples into a hopper and, though the apples are mixed up, each finds its way to where it needs to go following a shared path.  Think of this as the apple network where many different types of apples can all journey down the same path; yet each has a different final destination.

This analogy isn’t too far off from how data travels down our shared paths but, instead of apples, we have another enclosure called a packet.  These packets are data enclosures and identified not by their size but with little “notes” pinned on their “shirts” in the same way that a line of grade school children can be sorted out by their teachers: using these little name tags.

Tomorrow, the Packet Racket.

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About Author

Paul McGowan

Paul McGowan is the CEO and co-founder of PS Audio Inc. a Boulder Colorado design and manufacturing company of high-end audio products and services. McGowan has been designing and building high-end products for nearly 40 years. Hobbies include skiing, music, hiking, artisan bread baking, kick boxing and cooking. He lives in Boulder Colorado with his wife Terri and his 4 sons.

(4) Readers Comments

  1. Soundminded

    September 20, 2012 at 5:35 pm

    Okay, I just gotta ask. I don’t get it. When it comes to anything digital I’m swimming in well over my head….at least sometimes. I know you’re going to tell me that the audio signal is distorted. One way or another that’s what it’s going to boil down to. But how? Think of all that is transmitted digitally every second of every day. Countless financial transactions, every kind of data in every field. No problems, rarely a glitch. So you’d say that’s all digital. It starts digital, it ends up digital. We’re talking analog to digital and back to analog again. But what about TV signals transmitted over digital communications networks? What about TV that started analog, became digital, and wound up analog? Example? I’ve got a digital cable tuner. Everything sent down the pipe to it is sent digitally. That includes the signals that started out as TV shows decades ago, are converted to digital and then in my house are converted back to analog for my old NTSC CRT TV set. Yep, still got a lot of those. And VCRs too. Each NTSC TV channel signal is over 7 megahertz in analog form. That’s 350 times the bandwidth of an audio signal. Are there any signs of distortions in that signal? No, it’s clearer, sharper, less distorted than when I saw them originally broadcast decades ago. No noise, no artifacts, no ghosts, nice sharp edges, no pincushion or barrel distortion in the geometry, no wiggles, completely stable, no green or purple skinned people (except for the sci-fi movies), in short no distortion. So what gives? Why can not just one but hundreds of these channels be transmitted digitally to me simultaneously over the same wire and every one of them as undistorted as I can ask for (along with hundreds of HD digital channels as well) all on the same network while a single pair of stereo signals can’t? Where is the problem? BTW, I have virtually no experience with streaming audio so I’m learning from your postings and enjoy them along with everyone else.

    • September 21, 2012 at 6:30 am

      Well, I am not quite clear what your question is when you say “distorted”. If you’re asking about keeping all the bits in order and without missing any when they’re transmitted down the network, then no, they are not distorted. There’s never been any dispute about sending bit perfect data over a network. Packets can be lost but it’s rare because of all the checks and balances that go on.

      The fact that your email is rarely ever wrong, or your TV or music – as you point out – is something we take for granted.

      So where’s the problem with audio? Typically in the computer itself or the DAC and how they are either sent or rendered. For example in my article about iTunes and upsampling. I am sure you’re aware that upsampling has sonic consequences and when the computer does this it changes the sound – so even if you send perfect bits from this process, it still is changing the sound. Same problems exist on the other end when you’re receiving them that change the sound.

      You mentioned TV’s – while I agree most of us look at TV and think it’s fine – but when I am at CES Sony and a lot of the big guys continually show us what they can do to the same set of bits to make them look better – and the differences are huge.

      So it isn’t the transmission of the bit streams accurately that’s the problem.

  2. dr.goodears

    September 20, 2012 at 8:49 pm

    Hey Paul,

    I was recently informed that with an Apple Airport Express one can stream music files from i-Tunes while the computer is powered down whereby a Sonos System requires the computer to be powered on. Sonos also recommends NAS to overcome this limitation.

    Sorry for the return to the cheap stuff but having a basic understanding at the entry-level always helps in the technical understanding of the good stuff!

    • September 21, 2012 at 6:32 am

      I don’t think that’s true or possible. Once the computer is shut down so too is the hard drive where your music is stored. Perhaps they are using Apples new Cloud storage? Many people have placed their music in the hands of Apple and stored it in their cloud – which enables Apple products users to play on their products without the use of a computer – something a Sonos can’t do.

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