HT Audio Problem

Discussion in 'Archived Threads 2001-2004' started by Bob U, Apr 26, 2002.

  1. Bob U

    Bob U Stunt Coordinator

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    I have had a problem for about the last 10 days. I'm hearing distortion that is frequency dependent as opposed to level dependent and primarily on digital cable.

    I swapped digital converter boxes today and problem is the same or worse. It happens only on the lower register of male voices, both speakers, and sounds like clipping, but is NOT a gain staging problem nor is it level dependent.

    So, after a week of trying to track this down, I may now be hearing things. I'm trying to be sure it is cable only and not DVD or CD as well, so that I can start to really isolate.

    Would someone with a high end audio system be so kind as to play Chapter 6 on the Matrix at 17:45 or so and let me know if the is distortion (raspiness) on the agent's voice in that scene? It would be appreciated.

    And secondly, do you folks with digital cable notice LARGE (6-10dB) variations in audio level from channel to channel?

    These things might help me figure things out. If the Matrix is a bit raspy, then it is cable only. Since the box change didn't fix it, it might be the incoming line amp, or the cable signal itself. If the Matrix is clean for you all, then its either my processor, power amp or speakers, all a bit tough to swap around and test and impossible with the proc unless I send it in for service.

    I'm just baffled. Open to any suggestions and all feedback.

    Thanks!

    -=Bob=-
     
  2. Selden Ball

    Selden Ball Second Unit

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    Selden
    Bob,

    I wouldn't call my system high end, (Pioneer F727, Marantz AV9000 & MM9000, NHT 2.9 & AC2 fronts) but I don't hear any distortion in that scene on the DVD, just some slight room echoes.

    Have you tried listening to the analog output of your DVD player to see if it sounds any different? That would compare the decoder in the player with the one in your processor.

    I've noticed that some digital channels have slightly diferent sound levels, but there don't seem to be any dramatic differences on our local cable system (Time Warner with Scientific Atlanta Explorer 2000 stb with coax digital audio output).

    Are there any channels in particular you noticed?

    I'm sure the digital audio levels are set by the originating program supplier, not by the cable company. My understanding is that the cable companies just pass along whaever digital signals they downlink from the satellites. I'd expect there to be some slight variations, but nothing dramatic, even if the digital stb only has analog outputs.

    However, don't forget that the lower channels (below channel 50 or 100 depending on the cable company) are still analog. Their audio levels do have to be adjusted locally and can vary quite a bit.
     
  3. Bob U

    Bob U Stunt Coordinator

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    Thanks for checking that and posting, Selden. If that dialog is clean, then it has to be proc, power or speakers and I suspect the proc.

    I'm not setup to use the decoder in the DVD player. I could try the 2 channel analog outs easily enough, but I don't think that would be a conclusive test.The "distortion" is most noticeable on cable, though, and less so on DVD or CD. But my proc digitizes everything including analog ins, so it could well be the proc.

    As to channels, that is very interesting. The worst for me is channel 13 which is 8-10dB hotter than anything else. On the HBO's, channels 58-64, there is maybe 3-4dB difference among them, maybe less, but just noticeable.

    I swapped Digital Cable Converter boxes yesterday hoping that was the problem, but it wasn't. Still, *might* be the line amp incoming at my house connection, but I doubt that as picture is just fine. The audio from the converter loops through the TV and then the TV audio monitor out to the proc. I bypassed the TV, as well yesterday, and no change, so I can take that out of the questionable loop.

    I doubt two channels of an amp or both speakers would do this at the same time. And it is so frequency dependent, which is so strange. Just lower range of male vocals/ dialogs - maybe rarely a female voice. And it does sound like clipping, but even at very low signal levels, which makes me more think it is a digitizing problem.

    As as you might imagine, the more I concentrate on listening for this, the more I *think* I hear it on other sources such as DVD and CD. That Matrix scene is the closest to any DVD source that I am *almost* sure I hear it every time.

    -=Bob=-
     

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