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Pro-Logic II problem?

Discussion in 'AV Receivers & Amplifiers' started by mij, Nov 3, 2002.

  1. mij

    mij
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    Listening to Digital TV on my Marantz 5200 in Pro-Logic II movie mode I can hear a distorted squealy noise on the rear speakers, I only noticed when the volume was low and when people were talking.
    Getting to the point, this noise is only there on Sky Digital & BBC Freeview (any Channel), if I switch to analogue TV the sound is perfect, to check it was not my set-up I phoned my brother and his Denon 3802 did exactly the same thing with Sky and Pro-logic II, although it was perfect using Neo:6.
    Has anyone any idea what is causing this, and how to cure it.

    Thanks
    mij
     
  2. alex f

    alex f
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    It's funny you should mention this as I have noticed it too. It sounds like a really poor connection on the rear speakers but its fine when I use another source?!
     
  3. mij

    mij
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    Just wanted to add that this is not a regional problem, I live in South London and my brother lives in County Durham, and both of us have the same problem.

    mij
     
  4. Andywilliams

    Andywilliams
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    mij i to have heard this sound on my rear speakers to but only on sky digital. glad somone else has heard it as i too thought i might have a problem with a speaker cable or phono lead.
    gonzo.
     
  5. rowbos

    rowbos
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    I have also noticed this effect using NTL digital and a Denon 1603 amp using DPL II.

    I await with interest some explanation/resolution for this...it has not really bothered me as i can only hear it if i stand right next to the rear speakers.

    Steve.
     
  6. Nobber22

    Nobber22
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    Which model Satellite box do you guys use? Pace, Sony, other? I have the Panasonic and PLII is perfect.
     
  7. mij

    mij
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    I have the new silver Panasonic Sky box and the Sony DX100 IDTV.

    mij
     
  8. Andywilliams

    Andywilliams
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    nobber22 i have pace digi box but it must be said i only get this problem on certain channels mainly itv on sky.
    gonzo
     
  9. rowbos

    rowbos
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    I have the Pace digital cable box - but dont get me wrong - DPL II sounds excellent - BUT on certain programs, mainly with dialogue, if i put my head next to the rear speakers i can hear this strange squeaking noise as words are spoken.

    I think it must be some sound leaking through the decoding algorithms to the rear channels?

    Steve.
     
  10. klnc

    klnc
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    just to add my 2 pittance, i also get it... only noticed it a few weeks ago but using denon a1sr, panasonic sky digibox and B&W 600s2s. Also conscious of it on the front speakers. I thought it might be a wiring thing, but it doesn't do it with dvds etc, although i'll check tonight re DTS NEO for sky etc. Given the different brands of amps etc, sounds like a software issue?
     
  11. EvilMudge

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    Nothing to do with the amps I'm afraid- what you are hearing sounds just like one of the unfortunate side effects of the MPEG-2 audio system. Although human hearing supposedly can't hear this very well (which is why you need to be very close to the surrounds to hear it and it only appears on dialogue), the Pro-Logic II alogorithm is treating it as ambient sound and outputting it to the surround. As far as I know there isn't a fix for it - and as you may have noticed Neo6 doesn't do this because it's a different algorithm.

    Sorry if this disappoints anyone.
     
  12. Biggles

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    I seem to remember there was a thread discussing this problem a few months ago's

    If my memory is correct it's not a problem but related to how the "source" is decoded by DPL II

    DPL II is trying to take stereo and turn it into 5.1ish sound.

    DPL II has a problem seperating voice from music.

    Again this was discussed a while ago and my memory isn't that good but some receivers were better/worse than other

    This might shed some more light on the issue

    http://www.extremetech.com/article2/0,3973,10064,00.asp
     
  13. EvilMudge

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    You are correct that Pro-Logic II has problems seperating music from dialogue - most matrix algorithms have this. However most people are hearing this squealing only on programmes which are almost entirely dialogue - which makes me think this is the lossy compression of DVB-Audio causing the problem.
    The best way to check it out would be to MP3 a talking book at a fairly low data rate - such as 128Kbps - and play this back in PLII.
     
  14. Biggles

    Biggles
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    EvilMudge

    In what I've read ( guessed and added up) if the signel is transmitted in DP the DPII decoder will do a better job than "stereo".

    I also remember reading that some digital transmission companies remove the DP signal and use a standard stereo.

    It would be intering to lisen to a program with nicam etc via a standard aerial and then compare it to say the SKY transmission and see if you hear a diference

    (Maybe I should get a life)

    The long a short of it is from the sounds of it, nothing's wrong with the receiver, that's just the way it is.
     
  15. EvilMudge

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    I quite agree. Almost certainly nothing to do with the receiver, just in case anyone was worried.
     
  16. mij

    mij
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    Thanks everyone for the info, yet another example of a new and improved service (I mean Digital TV)

    cheers
    mij
     

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