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Dolby Pro Logic 2 problems

Discussion in 'AV Receivers & Amplifiers' started by waterhousej, Jul 6, 2003.

  1. waterhousej

    waterhousej
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    I am currently experiencing problems with sound through a Marantz SR7300 when using a Sky Digital source. I have used the phono outputs from the Digibox and selected the Dolby Pro Logic 2 Movie sound mode; most of the time the sound is fine with clear sound through all front and rear speakers. On some Sky channels however, the sound through the centre speaker is fine but the left and right front speakers produce a distorted sound. The only way I have found to overcome this problem on these channels is to set the sound mode to 'Auto' which then just outputs sound to the front left and right speakers with no centre or rear sound.

    Is this supposed to happen? I thought that as long as the source was stereo that selecting the Pro Logic 2 mode would convert the signal into 5 channel sound with clear sound through all speakers.

    Jamie
     
  2. Merritt

    Merritt
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    No - that doesn't sound right. Im guessing the problem is coming from the digi box tho (have you every had PLII working properly from another source with your existing amp?). Im thinking that the output level from the 'phono' outputs is wrong for some of the channels. If you can get your hands on one, try using a SCART cable with RCA (phono) output from the digibox - you may (or may not) be able to eliminate the line level audio outputs from the digibox.

    Im afraid thats the only thing coming to mind at the mo, unless of course you have a strange (intermittant) problem with the amp.

    Try another source for the audio as well - you should be able to find out whether its the digi box or not.

    Cheers

    Steve
     
  3. pwiles1968

    pwiles1968
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    Does the noise sound quite worrying? does it sound like one of your speakers cones has popped?

    If it does try the Amp with a Dolby digital EX encoded disc Monsters inc or something similar? Also In the speaker setting try turning the Sub-Woofer On Does this make a difference? I know you probably don’t have a sub connected it does not matter for the purpose of the test.
     
  4. Andywilliams

    Andywilliams
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    Hi waterhousej
    If you do a search on this problem you will see that during pro-logic 11 the proccesing goes funny on certain channels when on sky tv i got fuzzy sounds coming out of the rears that sounded like a radio not tuned in properley alot of forum members noticed this too all on different receivers.The thing is it only does it in pro-logic11 i found itv and bbc1 to be the worst for it .I never got the problem in anyother mode though just pro-logic11.
    Gonzo.
     
  5. dsw182

    dsw182
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    I too have noticed this problem. I'm using a Marantz SR4200 with a Panasonic digibox, using the phono outputs.

    Apparently some of the lower budget or independent channels don't even broadcast in stereo yet (for some reason) so pro logic processing sounds terrible.

    Also, some programs don't have good enough quality soundtracks eg. older shows, music videos etc

    Looks like something we just have to put up with.
     
  6. waterhousej

    waterhousej
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    Cheers for all of the replies. I have since tried using the Dolby Pro Logic 2 Music setting rather than Pro Logic 2 Movie - this works fine through all speakers.

    At least using Pro Logic 2 Music setting gives better sound than just using the 'Auto' setting which only switches the amp into stereo mode. Shame that no Sky Digiboxes (apart from Sky +) have a digital output as I think a digital signal would allow the Auto setting to automatically select the most appropriate setting.

    Thanks

    Jamie
     
  7. mick23

    mick23
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    i have had same problem as regards sky, can sometimes watch program on sky one, througn nicam tv sound ok, switch to pl2 movie on av amp , only get center channel, switch to 5 channel sterio, sound from all five speakers, its though it sometimes mono only signal although fairly new programes.

    i have output from sky box to vdp input on av amp but i doubt if thats causing the problems re sound.
     
  8. graxxor

    graxxor
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    DQMOT but I think that it has to do with the compression levels.
    When you compress a signal, it distorts and loses fidelity (i.e. information). The amount of distortion depends on the quality/amount of compression.

    I have experimented with surround sound and MP3. Using a decent encoder, you can retain Prologic surround signals to around 128kbps (YMMV). Below that, you get random bursts of sound and spotty stuff coming from all over the show. PL2 is a lot more sensitive. Even 160kbps starts to get a bit strange with more aggressive soundtracks.

    Some digital channels sound like 96kbps MP3s with watery treble and bass cut outs... God knows what freeware encoder they're using in the studio. If they can't even retain the primary signal components, they'll be hard pressed to retain decent phase coherence.

    Also, PL2 Cinema is designed for modern HIFI stereo signals (such as PCM) and pushes matrix encoding to the limit. It is really sensitive to distortion. Try playing in PL2 mode with a graphic equaliser between the source and the receiver for a bit of fun.

    I think digital broadcasts have a lot to answer for regarding their shoddy quality.:mad:


    Grax
     
  9. fuglyface

    fuglyface
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    I have a Sony Sky box that has a digital optical out. I use it straight into my amp and I get no problems with DPII

    Sony have stopped manufacturing these boxes now but you can pick them up on ebay thats where I got mine from.
     

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