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sound lag on Panasonic Home Theatre toslink input/ouput?

Discussion in 'Electronic Repair' started by Amanda Riphnykhazova, Sep 7, 2012.

  1. Hoping this is a sci.electronics.repair problem: This concerns a Panasonic SAPT760 home theatre system which has been repaired once under warranty andsuddenly new problems have appeared. (most of which I can live with but I was wondering if anyone here recognised the symptoms).

    There is an annoying half-second lag on sound output when played through the SAPT-760. Panasonic HT tech support said it is caused by the (Panasonic)Plasma TV. TV Tech support at first agreed and sent me a BIOS upgrade. The lag reduced to about a tenth of a second or less (this was almost definitely a coincidence) and has since increased back to about a half second again. If I play the TV sound at the same time as the digital HT, sound, you can hear the marked lag, with the TV sound being, of course lag-less.

    Other problems with the HT setup which may or may not be relevant are that when I first got it, my Nano played and charged through the built in dock. Now it shows incompatibility which Panasonic confirms! But I am wondering how it played and charged formerly??

    More importantly perhaps, on initial turn-on, when switching to the Toslinkinput, I initially get no sound whatsoever. Leaving it on digital input, after a few minutes, I start to hear a low frequency (3-4 hertz?) popping which slowly increases to about 10-15 Hz before the unit starts to recognisethe popping as the light based sound it is supposed to be decoding and then the sound quality is generally OK with no popping. But with that annoyinglag. All other inputs (including the DVD) are OK, which told Panasonic Tech support that the unit is performing properly and that the problem must bewith the signal coming out of the TV.

    On one call, the TV people said they found some reference to an adjustable lag on the HT system but the HT people deny that any adjustment on this (orresetting to defaults) exists. There IS a time delay adjustment on the DVDside but it is set to zero.

    Yes I DO know that there is some millisecond adjustment on individual speakers but this problem concerns a general half second lag on all speakers andall speakers seem to be set up OK on the in-built DVD system.

    One last thing: The lag isn't always there: Sometimes the toslink sound (i.e. the sound from the tv into the HT) dissolves into a generalised crackling.
     
  2. : JeffLiebermann

    This problem has persisted now for 6-8 months with differing degrees of intensity but since I posted, the digital sound first disappeared completely, then the next day came back when I turned off the Dolby (and without any real noticeable lag) and then today the lag came back with such a vengeance that I thought that the HT unit had defaulted back to Dolby (no, it hadn't).
     
  3. I never thought about this before.

    Does that mean that any old surround sound-ish system could in theory have
    audio horribly lagged and off from the video from the source such a DVD?

    I've noticed there are delay settings on most audio decodes but, I've not
    noticed or though about there being sync issues with the audio as a whole.

    MiniDV was another story, and a complete waste of my time when I used it.
     
  4. I'm still living in the past with a 1998 sony DVP S500D DVD player and
    some sort of equally old Technics sourround sound decoder. They connect
    with some sort of toslink-ish fiber optic cable, and pretty much work with
    anything but the movie Hellraiser 2.

    I just added WD Live media player box to the museum of 1990s home thatre
    and it mostly works with the same surround sound decoder, but will freeze
    things up requiring a reboot from time to time. I've not noticed audio
    sync problems, and I watch video over component video or svideo with the
    DVD player and HDMI to a projector with the WD live box. I've never used
    audio over HDMI, and have no idea where you'd even intercept the audio
    signals and listen to them in the first place.
    crappy videotape format with unsynced audio and video streams on the same
    tape. Audio could and would drift from the video if you played the tapes
    back on a computer, but from the analog ports on a player, they were
    always OK.

    I'm still trying to figure out how that was even possible, but it was, and
    the non-consumer DV tape formats never had that problem as they had some
    sort of time sync info between the streams.
     
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