Prologic confusion

Discussion in 'AV Receivers & Amplifiers' started by mandlebrot, Jun 25, 2002.

  1. mandlebrot

    mandlebrot
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    Hi

    Has I understand things the prologic signal is encoded in the stereo signal. If this is the case and I use a prologic/Dolby surround source such as a video, should my amp be able to detect the prologic signal?

    I have a Marantz SR4200 and have just always had in set in prologic II mode for TV/video. Today I had changed the amp setting to auto (can't remember why) and noticed that it said stereo and set itself into stereo mode. This got me thinking so I kept changing digital TV channels looking for something transmitted in surround but on all channels the amp just reported that it had detected a stereo source. I then decided to try it with my nicam video selecting a film that said Dolby surround but the amp still reported a stereo signal, now I'm confused :confused: Should the amp auto detect a prologic signal or is it up to me to manually change the setting to prologic etc.

    Please note when playing the video film the sound signal was outputting from the analogue stereo connections on my TV to the amp e.g. video connected by scart to TV, TV connected to amp with stereo phono's and auto selected on the amp.

    :confused: :confused:
     
  2. Reiner

    Reiner
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    DPL/DPL II cannot be auto-detected, i.e. you must activate the processing manually.
    It is correct that DPL is encoded in a stereo signal, hence it can be received via analog connections from VCR, tuner, CD etc., as well most new TV programs are broadcasted in DPL (e.g. X-Files), given you have a stereo (NICAM) TV / VCR / SAT receiver.
     
  3. MikeK

    MikeK
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    In an analogue signal, Dolby Surround isn't "encoded" as such, it's simply mixed (or matrixed if you prefer). There are no flags to detect, and no digital datastream to contain such flags.
    Hence, your amp (or any amp) can't autodetect it.
    So, as Reiner says, it's a manual selection I'm afraid.

    Many more recent amps will digitize the incoming analogue signal, as this makes it easier to extract the channels (and more accurate), but it can't digitize a ProLogic flag which was never there in the first place, if you see what I mean.

    They can place a ProLogic flag in a DD 2.0 datastream though, and the amp's decoder will detect that (often displaying PROLOGIC on the LED display).
     
  4. mandlebrot

    mandlebrot
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    Cheers guys I had thought that was the case in the past hence I always had my amp set to DPL II, then I read something somewhere which got me a bit confused thinking the amp could detect the PL signal.

    Thks
     

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