Question about the nature of digital signal in HT

Discussion in 'Archived Threads 2001-2004' started by Vince Maskeeper, Mar 22, 2002.

  1. Vince Maskeeper

    Vince Maskeeper Producer

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    Ok, this might be a long one, so grab a cup of coffee and get comfy...
    I have a HTPC with an M-Audio 2496 card. This card passes ("Bit for bit" according to the box) DTS/DD/PCM audio from my PC to my receiver for decoding. The card had a little break-out dongle which has a digital output on an RCA female jack.
    The digital signal is routed to my Denon 3300 receiver via that coax digital input. The input is assigned properly to the DVD input, everything works.
    However- I get drop outs. Not like a DVD player one second drop out on seamless branching, rather the receiver is losing sync and will stay lost forever. The receiver has a row of lights for DD/DTS/LOCK- and the receiver loses the lock light and the format light, and the audio goes silent.
    And it stay silent. That's part of the stumper for me- something is preventing it from regaining signal lock. The only way I can get it to work again is to shut off the receiver and turn it back on.
    Now here are some specific other oddities:
    1) I have tried probably 10 different RCA cables of varying size, shape, brand and color... the problem stays no matter what.
    2) Instead of turning the receiver on/off- I tried pulling the digital connection cable and plugging it back in- but the receiver will not re-sync to the incoming signal.
    3) I have tried 3 different DVD player software programs, all 3 have the same problem.
    4) It seems to be much worse for DTS-- Dolby usually requires I shut off/turn on the receiver 2 or 3 times in the course of a movie to regain sync, with DTS I have never gotten past the first 5 minutes because it loses sync every 20 seconds or so.
    5) I would lean towards the receiver being the "problem" (mostly because powering it down/up fixes the issue) but I had a regular DVD player up until 3 months ago, and had never experienced this problem once! I plan to borrow a stand alone player from a friend this weekend and see what happens.
    6) I have had some phantom problems with the MOBO in the HTPC- namely it loses network connection often (which leads me to question if there isn't power issues with the board). This makes the PC, in my book, at least SUSPECT.
    So, right now, I'm having trouble determining who's problem this is (the PC or the Receiver). I wondering if the receiver is simply in the process of dying- or if the HTPC is not passing enough juice (or maybe is passing errored signal which is throwing off the receiver). I would assume if it were a "lack of level" issue from the PC, that the receiver sync would come and go- but instead once it is lost, it is lost for good.
    What my question came down to was, is it possible to amplify digital coax signal? I am a bit rusty on digital cariers- so I was thinking maybe DD/DTS signal on coax would be badly influenced by amplitude chages (in other words, I wondered if amplitude of the analog signal had an effect on how it was decoded, if it was part of how the signal was recognized...)
    Anyone have any thoughts on the possible cause of this, what I should try to determine the cause, or if it would be possible (or worthwhile) to try to line amp the digital output.
    -Vince
     
  2. Patrick Sun

    Patrick Sun Moderator
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    Could the CPU usage be a problem? Or has the M-Audio bad board gone bad?
     
  3. SteveF

    SteveF Extra

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    I would be hesitant to amplify signals without being very confident as you don't want to damage the digital inputs in any way.

    Some folks successfully run digital coax over long distances, so I would be skeptical if your (presumably) short coax lengths are causing problems. Are you sure that you are using a 75 ohm cable? I believe that many are 50 ohms. Impedance mismatches can most definitely cause dropouts.

    It would also be interesting to look into Patrick's suggestion and watch CPU usage under the task manager while playing audio.

    Does the analog output work fine when playing the same sources?
     
  4. Scott Simonian

    Scott Simonian Screenwriter

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    Maybe you need to get an update patch for the 2496 board. I see this kind of thing alot and usually there is a patch out there to fix it.
     
  5. Vince Maskeeper

    Vince Maskeeper Producer

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  6. Matthew R

    Matthew R Agent

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    I would guess that it's an issue with the M-Audio 2496 driver. When this happens, open the M-Audio control panel and look under the S/PDIF tab. Select the Advanced checkbox, and look at the Audio/Non-Audio radio button selection. If the bitstream is DD or DTS, Non-Audio should be selected. Otherwise, Audio should be selected. (If you're using Consumer mode, this should auto-select.)

    If that looks okay, another issue might be the sample rate... Under the Hardware Settings tab, try selecting the Reset Rate When Idle checkbox and select the 48kHz rate. This may help (although it may create other issues when you play 44.1kHz CDs).

    Finally, you may have to use a different driver version. I think that there's a new beta version for Win2K or XP that's supposed to fix a few issues, but the 9x/ME version isn't ready yet. A recommended version for 9x/ME is 4.1.22.27. (If you change the driver, I'd recommend using the M-Audio Uninstaller to remove the current driver first.)

    I actually used to have a similar problem in WinDVD, but haven't had any trouble with any of the Ravisent-based players (Cineplayer 4.0 audio filter or TheaterTek).

    Hope this helps,

    Matthew
     
  7. Vince Maskeeper

    Vince Maskeeper Producer

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    Okay, I'm stumped.

    Over the past 6 months, I have had continued "uneven" audio from my Maudio 2496 card. Most often, I got drop outs [as described above]- particularly with DTS. When the signal would drop, i would have to shut off the receiver (Denon 3300) and turn it back on for the pair to resync. In the course of a film, this usually meant 3-4 restarts with DD, and usually 10+ with DTS before I would give up and just go DD.

    I thought, since the power down/up of the receiver "fixed" the problem, that maybe the receiver was at fault. I broke out my old Panasonic RV-80, and it sync'd up with the receiver just fine.

    After another few months of problems, I was tinkering around and found that the digital COAX jack on the receiver was damaged. The rca connector seemed to have broken loose from the board and was spinning-- and it required being set in a specific position for audio to work.

    "Bingo" I figured, the whole time all the sync problems were being caused by this physically bad connection-- the working RV-80 must have just been luck.

    I sent the Denon off to the repair facility and had it fixed. Came back yesterday- and I reconnected the HTPC- and could get no audio. It wouldn't see the digital signal (all the inputs on the DENON are assigned correctly, etc). It had worked on/off previously, but now I've got nothing.

    I drug out another set-top player (A Phillips this time)- and again- the DENON sync'd into that unit immediately- and was able to hold the sync with DD and DTS material, no problem.

    After some experimentation, I managed to get some Maudio settings together that allowed the receiver to recognize the DD signal, but the moment I switched to DTS, it lost the sync (and would only regain when I returned to HTPC to a dolby stream). I tried more experimentation with settings, and have once again rendered the card silent.

    At this point, I have once again lost all audio from the card. The denon will not see any digital audio from the HTPC, no matter the format. The denon has zero problem syncing to other sources, like set top DVD. The HTPC only has coax output, so I have been unable to find out if optical would make any difference.

    The TheaterTek player controls are set to allow SPDIF pass, the multimedia panel in Windows is set to treat the SPDIF as the default output. I have the latest drivers for the card (updated yesterday).

    I'm beginning to wonder if the signal isn't just so errored comeing from the Maudio that the denon can't read it. Once in a while it wavers back and forth between analog/digital on the autodetection- but cannot lock to the signal.

    I'm considering trying to get a converter to change the HTPC output from COAX to optical as an experiment. I'm also considering taking the PC to a friend's house, and trying to see if his outlaw will sync to the damn thing.

    Any thoughts?

    Thanks

    Vince Maskeeper
     
  8. Ned

    Ned Supporting Actor

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    Personally I would borrow an sblive and just see if it's the Maudio card. I setup an htpc on the cheap with mostly leftover parts and it works great
    p3 450
    256mb pc100
    sblive 5.1 oem
    It passes AC3 and DTS without any trouble (except DTS CD which is a well documented problem for many cards).
    If the problem persists with a different card then you can think about trying another receiver to see if the 3300 is the problem.
    The best/worst thing about an HTPC is that it's a computer [​IMG] Lots of potential, for good and bad.
     
  9. Jeff Rosz

    Jeff Rosz Second Unit

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    hello vince,
    there may be some tips for you in this thread..
    or maybe you could at least ask those members who replied in the thread for advice. anyway, good luck.
    oh ya,
    something else i found: does the denon have an auto-detect funtion for selecting the digital audio input format? if it does(i am 95% sure that it does), and it is enabled, you may try turning this feature off and going to manual input mode. in other words...force the denon to take the digital signal you want, not what it thinks it wants.
    edit: i am now 100% sure it has auto-detect.
     
  10. Greg_R

    Greg_R Screenwriter

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    Vince,

    I seem to remember a few threads (over at AVS) about studdering issues with one of the Via chipsets. Power delivery is also a frequent culprit with HTPC problems. I assume you've tried reseating the card and looking it over for any obvious damage? To me (not an M-Audio expert) it sounds like an intermittent power issue (either a card, power supply, or Motherboard issue)...
     
  11. Vince Maskeeper

    Vince Maskeeper Producer

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    Well, an interesting development on this issue:

    I tried my HTPC (VIA chipset with Maudio card) with an Outlaw receiver, and it sync'd up just fine.

    Someone on AVS posted this:



    This sounds exactly like the issue I've had- and I've always been suspect of the electricity possibility.

    I guess my options are to ditch the Denon and move to something else... Unless anyone here has any thoughts on how I could stabalize the power (but it sounds like this guy has dedicated circuits and a conditioner and still has problems).

    -Vince
     
  12. Pete Mazz

    Pete Mazz Supporting Actor

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    Any chance you could swap out the PCs power supply with another one? The newer stuff requires a lot more power these days(~350 W). I've even tested stuff by using an old PS while the existing one is installed, and just unplugging all but the MB.

    Pete
     

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