Ceramc cap & noise

Discussion in 'General Electronics Chat' started by junlokk, Jul 10, 2014.

  1. junlokk

    Thread Starter New Member

    Jul 6, 2014
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    Hi,
    Does higher rated voltage ceramic cap is less noisy (on an audio amplifier).
    I have read 2 versions :
    - lower voltage is less noisy because it is smaller (less piezo)
    - higher voltage is less noisy because it is rated for higher voltage and thus is not pushed as much to the limits

    Between two SL(u) 1kv (9mm) and 2kv (11mm) ceramic which one will be quieter at 530vdc.

    They are the same price, and i don't know which one to use.
    Thanks.
     
    Last edited: Jul 10, 2014
  2. crutschow

    Expert

    Mar 14, 2008
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    Both versions of what you read make no sense. Capacitors don't create noise (resistors do) so there should be no difference between the two.
     
  3. junlokk

    Thread Starter New Member

    Jul 6, 2014
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    Hi thank you,
    I know about resistors, I know also that there is no electrical noise produced by a capacitor. I though ceramic where different, too much reading from unconfirmed sources lol.

    Thanks
     
  4. crutschow

    Expert

    Mar 14, 2008
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    Well some ceramics can produce microphonic (piezoelectric) noise from vibration. Perhaps that is what they were referring to. In that case less ceramic (lower voltage devices) could possibly be less noisy.
     
  5. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    Something that is more true for electrolytics because they just generally have poorer performance, but still is true for ceramics and all other capacitor types to varying degrees - lower voltage usually means thinner dielectric, and that means lower ESR, lower ESL, lower dissipation, and lower just about everything else - including reliability.

    ak
     
  6. takao21203

    Distinguished Member

    Apr 28, 2012
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    I would question that- a 6.3v cap will be totally relieable at 5 volts, and where do you see 2000v in an amplifier?

    It wont cut the mustard at all if you ask me.

    If you put cheap earplugs to your laptop it well, will sound cheap.
    If you plug 200 dollar headphones, the bass perception reasonably will be better.

    If the wires copper is oxygen free or not, gold plated or not- nobody ever will be able to tell just from listening. And 10sq mm cables for small 50W speakers also will cause the same sound emissions, no matter how thick the insulation.

    you could use simple bell wire probably.
     
  7. crutschow

    Expert

    Mar 14, 2008
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    The subject of this thread is capacitor noise. On did we get onto reliability and wire characteristics? :confused:
     
  8. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    I would question the logic of that. The high voltage caps have a much thicker ceramic disc, so will flex much less when exposed to vibration. They also have a much thicker external epoxy coating, which provides more stiffness, and being softer and more plastic than the ceramic also likely absorbs flex energy.

    I would think if the problem is flex induced voltage that HV caps would be far surperior. Some 2kV caps used in TVs are almost as thick as they are in diameter;

    [​IMG]
    .
     
  9. crutschow

    Expert

    Mar 14, 2008
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    That makes a certain sense also. Probably the only way to settle the question would be to do some microphonic tests with various ceramic caps.
     
  10. alfacliff

    Well-Known Member

    Dec 13, 2013
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    the microphonics related to ceramic caaps is probably due to vibrations of the cap if the leads are too long. ceramic for caps are not chosen for piezoelectric effect. it would be very rare to have the ceramic crystalise enough for generating piezoelectric voltae.
     
  11. junlokk

    Thread Starter New Member

    Jul 6, 2014
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    Well, first thank you all

    There is some food for though here, I must say I am still undecided between HV an LV ceramic cap. But I must say that thicker dielectric will flex less is a very good reasoning, but still the only way to make sure is to test.
     
  12. Veracohr

    Well-Known Member

    Jan 3, 2011
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    Do you have to use ceramic caps? How about film?
     
  13. to3metalcan

    Member

    Jul 20, 2014
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    I agree with Veracohr...ceramic and tantalum are both best kept out of audio signal paths unless there's a specific reason to use 'em (ie, size constraints.)
     
  14. ian field

    Distinguished Member

    Oct 27, 2012
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    Years ago I built an electret mic booster with a TL431 - the secret of huge gain is to AC shunt the stavilising DC nfb with a big capacitor.

    Among the experiments, I peeled open an electret mic and tried various piezo elements on the JFET inside - then, just for fun various capacitors.

    Most disc ceramic capacitors were pretty microphonic, but so were a lot of tubular foil types.

    But at least it makes possible comparing various types.
    If you don't want to mess with the TL431, there are other options for high gain amplifiers. Many off the shelf JFETS will work (after a fashion) - but none as sensitive as found inside an electret capsule.
     
    THE_RB likes this.
  15. junlokk

    Thread Starter New Member

    Jul 6, 2014
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    Thank you I use film all over the audio amplifier, but some places needs ceramic, because it's not an hifi amplifier (and I need the "coloration" of the ceramic caps = harmonic distortion that only ceramic produce. But I want to avoid piezzoelectric noise and microphony as much as I can :)
    Very nice idea !
    I may get back to you when I buy an electret microphone ;)

    So the definitive answer is to test them :confused:
    But thank you all it was fun trying to find a logic behind it.
     
    Last edited: Jul 29, 2014
  16. Veracohr

    Well-Known Member

    Jan 3, 2011
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    I dare say you'll get much more distortion ('coloration') from active elements than capacitors, regardless of the type.
     
  17. junlokk

    Thread Starter New Member

    Jul 6, 2014
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    Yeah I know but I try to replicate the sound of a very old 1970 amplifier, and I want to replicate as close as possible with the closest components.

    But it's not distortion like the 'saturation' of a 12ax7 tube. It's harmonic distortion, which color the signal witout adding noticeable distortion (every type of capacitor adds it's own harmonic distortion characteristics to the signal) but I may be wrong :)
     
  18. ian field

    Distinguished Member

    Oct 27, 2012
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    Scrounge or buy an old basic landline phone, most nowadays use an electret capsule in the handset, my usual source of salvage sometimes turns up mobile phones and occasionally handsfree earbuds & mic sets - but the capsules in those are tiny and very fiddly to do anything with.

    Some sound activated toys also contain an electret capsule.
     
  19. to3metalcan

    Member

    Jul 20, 2014
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    It's theoretically true that capacitors color tone, but most of these effects are insanely minor, especially across the audio spectrum. Theoretically, I'm told ceramics have "peaks" in their response which subtly alter the spectrum of treble coming through them, and electrolytics have series inductance that attenuates highs, etc. And certain dielectrics (such as tantalum) CAN supposedly create noise with sufficient voltage across them (though the better reason not to use tantalum in a signal path, imho, is that merest moments of reverse voltage can send them to a speedy death.)

    However, the only time I've ever personally been able to tell the darn difference is in highly sensitive, start-of-the-signal-chain applications like the capacitors in the internal driver circuits of condenser mics, and this seems to make sense...any effects, however small, the components in a microphone have would be multiplied by every successive stage of gain (and mics require quite a bit.) By the time you get to the amp, I'm skeptical that the cap type has a lot of effect, though I suppose if it's in the feedback loop of a hot gain stage, or something, it might...!

    Anyway, follow your bliss! I, for one, would be interested to hear how it goes. :)

    But
     
  20. Veracohr

    Well-Known Member

    Jan 3, 2011
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    You might find it revealing (or more precisely, NOT revealing) to set up a simple comparison where you run an audio signal through two opamp circuits with the same gain. One, capacitively couple it to the opamp so the capacitor is in the audio path; the other, leave out the capacitor. I'd bet you don't hear a difference.
     
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