Equalisation for PC mic input/line input

Discussion in 'DIY Computers' started by David Peters (UK), Mar 12, 2006.

  1. The great beauty of the analogue PPM is that it gives a good indication of
    perceived loudness as well as the electrical value. It's the Holy Grail to
    find something which does this better - but it hasn't happened yet.
    Dave Plowman (News), Mar 19, 2006
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  2. It's relatively trivial to make a PPM with an LED analogue scale, arranged
    in an arc if that's what's more familiar. The PPM's software can be set for
    BBC dynamics, both rise and fall, or true-peak rise and conventional fall,
    (or any other dynamics that you may care to think of). When we supplied
    digital desks to various radio stations, we started with the PPMs indicating
    true-peak rise, but within a week or two, the user always reset them to
    mimic conventional mechanical pointer rise and fall. It seems that nobody's
    actually interested in what the real levels are, just what it looks like -
    as you say, they have a mental map of perceived loudness, and that's more
    important than the actual level - after all, isn't 10dB headroom enough to
    catch any nasties?

    Serge Auckland, Mar 19, 2006
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  3. David Peters  (UK)

    Jim Lesurf Guest

    Alas, this is another one of the areas where it is easy for statements to
    be ambiguous. Partly due to the confusions between instantaneous peak
    levels versus rms, partly due to unspoken assumptions at times that you are
    dealing with a sinewave.

    To make things even more confusing wrt terminology I am currently doing
    measurements and statistics of how the 'short term' peak level varies with
    time with some audio waveforms. Thus I'm using peak levels, and then having
    to say what the 'peak' peak level is, and how often a given 'peak' level
    occurs... There are times when normal English can become hard to use to
    deal with such things. :)


    Jim Lesurf, Mar 19, 2006
  4. David Peters  (UK)

    Jim Lesurf Guest

    Also for 'random noise' ... Although all being well, this isn't a
    worry in terms of FS clipping. If it is, statisics may be the least
    of your concerns. :)


    Jim Lesurf, Mar 19, 2006
  5. David Peters  (UK)

    Jim Lesurf Guest

    FWIW My impression is that R3 at least are generally well clear of
    clipping. For example, from DAB I've not yet seen a single sample that got
    to the clipping level, or even within a dB or two of it! However unless
    they are clipping earlier in the chain, I guess it must happen
    occasionally, simply due to the statistics of the real world, and the Laws
    of Murphy. ;->

    So I guess the answer to your question is similar to that for, "Will I
    survive one pull of the trigger when playing Russian Roulette?"... i.e.
    "Probably!" Alas, there is a distinction between trying this once, and
    repeating it on a regular basis... 8-]


    Jim Lesurf, Mar 19, 2006
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