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The most important parameter of all: overall system integrity

Discussion in 'General Audio Discussions' started by fas42, Oct 17, 2016.

  1. RayDunzl

    RayDunzl Major Contributor Central Scrutinizer

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    I had this measurement with a UMIK-1 and and 80dB at 815Hz tone on my panels:

    upload_2017-6-18_3-46-23.png

    2nd and 3rd harmonics at .03%/-70dB (harmonics just barely rising out of the noise floor, whatever comprises it)

    Anyway, less than .1% under those conditions with that (quality?) mic
     
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  2. fas42

    fas42 Major Contributor

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    And RogerD has just posted another good sample of solid playback ...

     
  3. fas42

    fas42 Major Contributor

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    Roger's latest effort - very nice ...

     
  4. fas42

    fas42 Major Contributor

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    And Roger's still doing good'uns ...

     
  5. blackmetalboon

    blackmetalboon Member

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    What a lovely video of his ceiling!


    I have seen a few threads on Roger’s system on other forums and decided to have a read. I did find his chassis grounding tweaks interesting as couple of photos of it really stood out to me.


    More on those after a little anecdote (it has some relevance but as it happened a few years ago I don't have the measurements and test readings to back it up!)


    A long time ago in a galaxy far, far away….


    ….whilst carrying out an inspection of an electrical control panel, it was noted that one of the incoming phase conductors inside the panel was showing severe signs of overheating. This conductor had damage and discolouration to the insulation that were an obvious sign of excessive heat. Inspecting the incoming phase conductors with a thermal imaging camera showed a dramatic temperature difference between them but was localised to where it terminated into the MCCB (Moulded Case Circuit Breaker).

    To terminate the cable to the MCCB, a lug with a hole in it, is crimped to the conductor and then bolted to the large flat stubs of the MCCB giving a nice tight connection with a large contact area. Now to cause such localised heat there had to be something wrong with this termination. So I checked the tightness of the bolt, that was fine. I inspected the crimp termination, that was fine and had been done using a crimping tool with a hexagonal die (rather than an indent crimping tool). It wasn't until disconnecting the conductor that I could see the problem.

    This control panel is switched off at the MCCB every night, so to combat the problem of condensation there are couple of small heaters inside the panel. These are connected to the supply side of the MCCB using a conductor of a much smaller gauge and therefore the crimp lug, while retaining the correct size hole to be bolted to the MCCB, is a fraction of the size. This was sandwiched between the crimped lug of the main conductor and the stub significantly reducing the contact area and increasing the resistance of the termination. Well I'm sure you can guess what happens when you have almost 200 Amps passing through it.


    So back to the photos of Rogers system,

    IMG_0303.JPG IMG_0304.JPG

    We have large gauge cables with low resistance but connected with tiny screws, making a minimal contact to the cables crimped lugs, against a painted metal cover which probably provides little to no contact area. I'm happy to be corrected on this, but it just seems to go against all logic.

    If there ever was a clearer audiophile example of a "bottleneck" I'd like to see it!
     
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  6. fas42

    fas42 Major Contributor

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    Because this is a frequency dependent issue, not a current one - IMO. The effect is to provide a lower impedance path for frequencies in the MHz range, which means geometry is everything - the contact area at one point is irrelevant, because capacitance across it will make it a high frequency 'short'.
     
  7. Don Hills

    Don Hills Senior Member

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    Nope. Do the capacitance math for a plate the size of those lugs and the thickness of the paint "dielectric". Now look at the impedance of that capacitance at the frequencies of interest. Finally, look at the wavelengths of those frequencies compared with the length of the wires. Your grasp of the physics involved appears to be no better than Roger's.
     
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  8. fas42

    fas42 Major Contributor

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    Yep. You're right, about the capacitance at that point ... happy now?

    And the wavelength is relevant, how?
     
  9. BE718

    BE718 Major Contributor forum experimenter

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    Omg, what a pointless mess. Frank, he needs a vector network analyser....or more to the point understand why he needs one.

    Frank, why do you post youtube vids of systems playing? They tell us nothing about how the system actually sound.
     
    Last edited: Sep 9, 2017
  10. fas42

    fas42 Major Contributor

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    I most certainly wouldn't do it the way he has - but it's helping him get the system to a place where he's getting full enjoyment from it - what I hearing in the videos is not everything that it's doing right - but the absence of it doing key things wrong - there are endless clips of very promising setups on YouTube, which are clearly getting the sound wrong in some area - that's the journey: an absence of audible defects.

    And Mike Lavigne is getting to a very good place; his latest posts on what his digital source is providing is ticking the boxes - convincing sound is in the room, or very close to it. The difference there is that he has taken a very expensive journey to make it happen ...
     
  11. RayDunzl

    RayDunzl Major Contributor Central Scrutinizer

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  12. BE718

    BE718 Major Contributor forum experimenter

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    Looks like uninformed tweaking which is feeding his imagination from the photos. Ooh look, I am convinced I have got rid of RF, of course it sounds better.....

    Audio recorded that way played on youtube will tell you almost nothing about the system. It will only demonstrate the most gross of problems. As I pointed out in the other thread, are you hearing the recording setup or the room or the actual system sound?
     
    Last edited: Sep 9, 2017
  13. fas42

    fas42 Major Contributor

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  14. fas42

    fas42 Major Contributor

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    It will always be a combination of those things - the system "sound" should be minimal, the room sound will typically add more reverb in the mix; and the most important is the "sound of the recording". A good system will "sound like the recording" - as in, listen to a YouTube clip of the actual recording, then listen to the YouTube clip of the recording of a system playing that recording - if it's jarringly different, then something is really messing up the sound. In key areas there should be excellent agreement, subjectively - there are plenty of clips in YouTube channels of the same recording being played on multiple systems, which were recorded using the same equipment. Huge differences are obvious, way beyond FR and similar "subtleties".
     
  15. BE718

    BE718 Major Contributor forum experimenter

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    And this is where your reality seems to diverge from most people's.

    Those YouTube clips sound nothing like hearing the system in person. Jarringly different in all aspects; spatial, timbral, whatever. It concerns me that you believe key areas similar, I have no idea what these areas are. It's also concerning as to why you still don't understand the many reasons why a recording will sound different, especially performed in different rooms with different mics, despite the conversation in the other thread. It's just willfull ignorance on your behalf.

    Your reality is at odds with mine, so far removed from mine in fact that there is no further basis for discussion.
     
    Last edited: Sep 9, 2017
  16. fas42

    fas42 Major Contributor

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    As you say, we live in different sound worlds - I listen for different things from what you do, and there is little common ground ... so, leave it be ...
     
  17. Don Hills

    Don Hills Senior Member

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    At the frequencies at which the impedance of that small capacitance becomes low enough to be significant, the wavelengths are going to be in the same range as the length of the wire. You therefore have a bunch of random LC resonant circuits instead of a grounding scheme.
     
  18. fas42

    fas42 Major Contributor

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    And if the connection is actually DC shorted, ie. the person ensured that there was metal to metal contact, well secured, do we still have a problem?
     
  19. BE718

    BE718 Major Contributor forum experimenter

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    Yes. Low dc resistance is not the same as low rf impedance. With a TDR you can easily see where joints, connectors are.
     
  20. fas42

    fas42 Major Contributor

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    Will TDR do this for a single conductor, in free space?
     

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