Does "Dolby System" on cassettes mean I need Dolby B for playback?

Discussion in 'Pro Audio' started by Guest, Oct 22, 2004.

  1. Guest

    Guest Guest

    I am converting a pile of old cassettes to digital form.
    Many, if not most, say "Dolby System" or "A Dolby System"
    with the double-D Dolby logo on it.

    They don't say "Dolby B" or anything like that.

    Can I happily assume that that means they were encoded with
    Dolby B, and I ought to play them back with Dolby B, too?

    Or does that indicate some other, record-only Dolby format?

    - Tim

    Guest, Oct 22, 2004
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  2. If they were Dolby you need to play them back with Dolby on or you could get
    some nasty peaks that are almost impossible to remove later.
    Ricky W. Hunt, Oct 22, 2004
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  3. Guest

    David Satz Guest


    The simple Dolby symbol on prerecorded cassettes means that the product
    can be played back with Dolby "B"-type noise reduction. Any other Dolby
    noise reduction system has its own, different logo. Dolby "A"-type noise
    reduction was never used for mass-produced consumer recordings.

    If you have Dolby "C"-type decoding equipment, you might want to try it
    out to see whether it sounds more natural than "B" when playing back a
    particular cassette. I have a vague memory that when "C"-type noise
    reduction came out in about 1980, some cassette duplicators moved to
    that system without changing their logo, and claimed that the tapes
    were still "compatible with" "B"-type playback, but gave "even better"
    fidelity when played back through "C"-type circuitry. I never came
    across any definite case of this myself and am not certain whether it
    really happened or not--but you may want to check this for yourself.

    Dolby HX ("headroom extension"), which has been mentioned in other
    replies, is a system for controlling the record bias as as function
    of the high-frequency content of the signal being recorded, and doesn't
    require any particular playback compensation. It isn't noise reduction
    as such.

    --best regards
    David Satz, Oct 22, 2004
  4. Guest

    Mike Rivers Guest

    If they're commercially released prerecorded cassettes, you can be
    certain that if it says "Dolby" and has the logo, it will be Dolby B.
    No cassette recorders or players were ever built with Dolby A or SR
    (the professional systems) though many had Dolby C and a small handful
    offered Dolby S, but other than very early ones or special purpose
    cassette recorders, they all have a Dolby B setting.

    You should use it, or at least try it. Since the playback operation of
    Dolby noise reduction is dependent on the level of the signal reaching
    the electronics, while prerecorded tapes are usually recorded at the
    correct level, cassette decks are notorious for not being accurately
    calibrated more than an hour after they leave the factory. So it's
    rare that a randomly selected cassette on a randomly selected deck
    will play back accurately (with or without Dolby decoding engaged).

    SO, listen and decide if it sounds better with or without Dolby
    engaged. Understand that one of the things that Dolby B decoding does
    is roll off the high frequencies (they're boosted when recording) so
    flipping the Dolby switch to the OFF position will always make the
    playback sound duller. Don't be misled by this and think that brighter
    is always better. Transfer your cassettes however they sound best.
    Clean the heads often, and if you feel brave and your deck is
    accessable, try adjusting the head azimuth to peak up the high
    frequency response.

    I'm really Mike Rivers ()
    However, until the spam goes away or Hell freezes over,
    lots of IP addresses are blocked from this system. If
    you e-mail me and it bounces, use your secret decoder ring
    and reach me here: double-m-eleven-double-zero at yahoo
    Mike Rivers, Oct 22, 2004
  5. Guest

    Scott Dorsey Guest

    Right. If they were made with Dolby C, they wouldn't be very old. And
    if they were made with Dolby A, they wouldn't be cassettes.
    No, the only record-only dolby process that I know of is HX-Pro, which is
    pretty much always used along with Dolby B.

    As always, use an outboard Dolby converter if you can, so you can set your
    levels properly to keep it from pumping.
    Scott Dorsey, Oct 22, 2004
  6. When you compare the two the novice will usually think it sounds better with
    the NR off because it's brighter but as Mike said that's not always a good
    thing. If it does need brightening (IMO) you are better off capturing it
    with the NR on (unless it sounds horrid with it on) and using software to
    brighten it later because if not there could be some very nasty peaks that
    not only can you not remove (should you choose) but any brightening you do
    will only make them worse.
    Ricky W. Hunt, Oct 22, 2004
  7. Unless you have entirely too much time on your hands do an Amazon search for
    the recordings.... $15 for a better transfer is a bargain unless they are
    out of print....

    I find it amazing how much time people are willing to spend for an inferior
    product... just to save 2 hours wages at minimum wage....

    Eric K. Weber, Oct 22, 2004
  8. Guest

    Mike Rivers Guest

    Right. Flipping the Dolby switch OFF will make it sound BRIGHTER.
    When I used to play cassettes in my car, I'd often play Dolby
    cassettes with the decoding switched off. It made up for the loss of
    high end in the car (by exaggerating what was there) and since Dolby
    noise reduction involves dynamic range compression, that helps in a
    high-noise environment. Then I got a quieter car and it had a CD

    I'm really Mike Rivers ()
    However, until the spam goes away or Hell freezes over,
    lots of IP addresses are blocked from this system. If
    you e-mail me and it bounces, use your secret decoder ring
    and reach me here: double-m-eleven-double-zero at yahoo
    Mike Rivers, Oct 23, 2004
  9. Guest

    Scott Dorsey Guest

    You should. You should adjust the azimuth until they -are- audible.
    Scott Dorsey, Oct 23, 2004
  10. Guest

    Guest Guest

    Thanks, Mike, for all your suggestions!

    If I could afford it and wanted to deal with all the hassel, I'd get
    a Nak Dragon and adjust it for each tape (or use the auto adjustment
    I think it has), but I'm not SO tied to perfect reproduction of my tapes
    that I'll do that.

    So I'll just leave the Dolby B on (unless it seems like it really
    reduces the quality) for all tapes that say "Dolby" on them. I've
    got a few Dolby C tapes, too, so I know what to do with those. :)

    - Tim

    Guest, Oct 25, 2004
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