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polar vs nonpolar capacitors

Discussion in 'Electronic Basics' started by Dave, Nov 28, 2005.

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  1. Dave

    Dave Guest

    I am interested in upgrading some audio components, and a lot of DIY tweak
    mention "replace the electrolytics in the signal path with Black Gate or
    other low-noise nonpolar capacitors." I know that polar capacitors cannot
    tolerate reversed polarity, and that bi-polars can as they are really two
    back-to-back capacitors. What is a non-polar? How is it different from a
    bipolar?

    Dave
     
  2. Well, it must be a non-polarized capacitor.

    Polarized capacitors exist not because of function but because of
    manufacturing process.

    There is no need for polarized capacitors.

    But, in order to have higher value capacitors in reasonable sized
    packages, the manufacturers have to switch to methods that result
    in a polarized capacitor. The capacitor itself objects if the
    wrong polarity is applied.

    For a lot of applications where higher value capacitors are required,
    that they are polarized doesn't matter, because they are mostly used
    where there is indeed a well defined DC voltage applied to one of
    the terminals. Thus, for filter capacitors in that power supply,
    a polarized capacitor doesn't matter because you connect the capacitor
    from a positive voltage to ground, so it's all very clear. A coupling
    capacitor on the output of an amplifier running off only a positive
    voltage has a positive voltage on that output, so again it's clear.

    In a few cases, the capacitor won't actually see a clearly polarized
    voltage source. Crossover capacitors in speakers are a prime example,
    because the DC component has already been removed, either because
    the amplifier feeding the speaker has a DC coupling capacitor on
    the output, or has a transformer on the output (not likely in recent
    decades). Here, there is no longer an AC voltage riding on a DC voltage,
    so no matter what the AC voltage one side of the capacitor is clearly more
    positive than the other; there is an AC voltage coming into that capacitor,
    moving from positive to negative and back, in reference to the other
    side of the capacitor. You need a non-polarized capacitor there, but
    the issue of size and capacitance comes into play, and most capacitors
    of the values needed will be electrolytic. A common trick is to put
    two polarized capacitors in series, and sometimes they are manufactured
    that way, so the capacitor is not polarized.

    But there are issues with that sort of scheme. For someone fussing
    with types of coupling capacitors in audio circuitry, they want non-polarized
    capacitors. Thus the capacitors need to be manufacturered using some scheme
    that will not inherently result in a polarized capacitor. If the values
    are low enough, this is not an issue. If the values of capacitance are
    higher, then one has to hunt around capacitors of mylar or polystyrene or
    some other scheme that does not result in a polarized capacitor, and
    the result may be a larger capacitor because those other formulations
    can't be so compact.

    Michael
     
  3. John  Larkin

    John Larkin Guest

    Ignore this silliness. A non-broken electrolytic capacitor is not
    noisy.

    John
     
  4. PeteS

    PeteS Guest

    More audiophools?

    Cheers

    PeteS
     
  5. Pooh Bear

    Pooh Bear Guest

    Non-polar electrolytics are 2 polar elctrotytics back to back in a single
    case.

    The validity of the benefit of black gate caps may be judged by the fact that
    they are no longer in production.

    Many circuits will benefit simply by fitting a larger value electrolytic
    coupling cap when operated 'zero-biased'. The reason is sufficiently
    complicated for me to leave it out of here for now.

    Caps don't make noise - so there's no such thing as a low noise capacitor.

    Most audio nuts are simply blowing out of their arseholes.

    Graham
     
  6. Pooh Bear

    Pooh Bear Guest

    Most pro-audio equipment uses large value coupling electrolytics in zero-bias
    conditions !

    Ever wondered why ?


    Graham
     
  7. Jasen Betts

    Jasen Betts Guest

    no different, In this case 2=0

    Bye.
    Jasen
     
  8. Noway2

    Noway2 Guest

    Most audio nuts are simply blowing out of their arseholes.

    You mean to tell me that you can't hear the missing music on aCD from
    the digitization process?? I am crushed!
     
  9. Not sure about "gold tabbed" but certainly if your laser isn't
    'silvered' with sputtered gold, your listening pleasure will be marred
    by quantisation noise, as any audiophallic will tell you.
     
  10. PeteS

    PeteS Guest

    Shhhhhh

    Next thing you know, they'll be complaining that the EFM encoding
    introduces noise unless read by a gold tabbed laser - only that would
    be good enough for audiophools.

    Cheers

    PeteS
     
  11. John  Larkin

    John Larkin Guest

    Yup. You can send in your old Heathkit or Macintosh whatever tube amp
    to folks who will replace all the caps with Black Beauties or silver
    foil or whatevers, at huge expense.

    John
     
  12. John Larkin () writes:

    About a decade ago, I got a catalog from a place here in Canada
    that did that sort of upgrade, and sold parts to do it yourself. I
    must have sent for the catalog thinking it might be a source of parts.

    The catalog arrives, and the prices on the components were outrageous.
    I think the capacitors were going for a couple of dollars each.

    Obviously, not a source for parts in Canada. And I still don't know
    if the parts they sold actually were expensive, or they just did
    a massive markup on them.

    Michael
     
  13. Guest

    Pooh Bear wrote
    In this context, I think they mean non-electrolytic non-polar
    capacitors.

    Bob Pease of National Semiconductor and Electronic Design magazine has
    asserted that tantalum electrolytic capacitors may introduce audible
    distortion due to dielectric absorption effects (and he regularly mocks
    the Golden Ear crowd). He refers to this in his article "What's all
    this soakage stuff, anyhow?" which can be found at
    http://www.elecdesign.com/Articles/ArticleID/6096/6096.html

    I seem to recall an earlier article by him from the 1970s where he
    found that an amplifier with tantalum coupling capacitors sounded
    terrible, but it was fine after he replaced them with aluminum
    electrolytics. I can't find that article on the internet, and I am
    sure that I have thrown away that issue of the magazine.

    If this argument is correct, then it might also apply to ceramic
    capacitors with high-k dielectrics.
     
  14. John Larkin () writes
    that did that sort of upgrade, and sold parts to do it yourself.
    must have sent for the catalog thinking it might be a source of parts

    The catalog arrives, and the prices on the components were outrageous
    I think the capacitors were going for a couple of dollars each

    Obviously, not a source for parts in Canada. And I still don't kno
    if the parts they sold actually were expensive, or they just di
    a massive markup on them

    Michae
     
  15. John Fields

    John Fields Guest

     
  16. Pooh Bear

    Pooh Bear Guest

    Probably so.

    Before even considereing DA, hi-K and also medium-K ceramic caps produce
    measurable distortion and so shouldn't be used for signal coupling or feedback
    networks.

    Graham
     
  17. Dave

    Dave Guest

    Large value coupling electrolytics where? In what type of audio equipment?
    Output stages? If there's no dc bias then they'd have to be nonpolars, no?
    I have read that larger-value coupling caps result in increased bass
    response... why is that? How are output coupling caps sized, I am guessing
    lowest-cost for "acceptable" performance. Can any coupling cap be replaced
    with one of a higher value?

    Dave
     
  18. Fermi

    Fermi Guest

    It's easy to overcome this with careful use of the "belt pen" and "quantum
    clip."
    http://www.positive-feedback.com/Issue1/beltpen.htm
    http://www.musicweb-international.com/classrev/2005/Sep05/Snark.htm
    http://www.belt.demon.co.uk/product/quantum/quantum.html


    "...capable of manipulating certain inanimate material into a condition
    that mimics the quantum state of our living senses."

    Don't forget to buy some quantum rainbow foil.
     
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