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Old 3rd February 2013, 07:54 PM   #1701
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Quote:
Originally Posted by davada View Post
Hi Scott,

I,m not clear about your meaning here.

You don't agree in-harmonic distortion in capacitors?
Non-harmonicly related distortion products can not exist, that is for two input frequencies the distortion products are only at A*F1 +- B*F2 where A and B are integers. I am speaking here of amplifiers and preamps, where this behavior is not observed, if you can present even one bona fide observation of this in capacitors hats off to you.
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Last edited by scott wurcer; 3rd February 2013 at 08:04 PM.
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Old 3rd February 2013, 08:22 PM   #1702
JensH is offline JensH  Denmark
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Regarding COG versus Polypropylene and Polystyrene this gives a lot of good information:

http://www.waynekirkwood.com/Images/...ap_Sound_4.pdf

It also shows that it is not just the material used that counts. Also the physical implementation is important. And the DC bias applied!

And I think all the notes from 1 to 6 are worth reading.

This also seems to support the thought that COG are excellent capacitors, but Polystyrene are slightly better:
Low distortion oscillator tests measurement circuits | TMW
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Old 3rd February 2013, 08:22 PM   #1703
davada is offline davada  Canada
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Quote:
Originally Posted by scott wurcer View Post
Non-harmonicly related distortion products can not exist, that is for two input frequencies the distortion products are only at A*F1 +- B*F2 where A and B are integers. I am speaking here of amplifiers and preamps, where this behavior is not observed, if you can present even one bona fide observation of this in capacitors hats off to you.
Well that really is just kind of the nature of things.
The same holds true for musical instruments.
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Old 4th February 2013, 02:48 PM   #1704
RNMarsh is offline RNMarsh  United States
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Notice what happens with DC added to the ac thd..... increases of 20-30dB are common.... worse in electrolytics. Note too that asymetrical waveforms have a DC component.
I have measured thd with asymetrical waveforms and find with FFT that it was primarily 2H. Thx-RNMarsh
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Old 4th February 2013, 04:34 PM   #1705
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Dick,

Doug Self maintains (and backs it up with measurements) that if you can keep the ac levels across an electronlytic below 70mV or so, the distortion is negligeable. That means that sometimes you need to use a much larger cap value that you would for the circuit time constants.
What's your take on that?

jan
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Old 4th February 2013, 06:03 PM   #1706
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I am confused.
According to http://www.janascard.cz/PDF/An%20ult...0-140%20dB.pdf they are able to get -150db.
But according to Bateman the capacitors have a distortion closer to -130db.
Any one got ideas?

Btw I have looked and can't find Bateman's website.
His articles were around 2003 in electronic world
I do have them in pdf format that I can share if anyone wants them.
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Old 4th February 2013, 06:21 PM   #1707
EssB is offline EssB  United Kingdom
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Some of the Cyril Bateman pdf's can be downloaded from here:
Capacitor Sounds, Speaker Cables and Crossover Inductors.

I have one of his CDROMs if anybody needs anything else.

Last edited by EssB; 4th February 2013 at 06:31 PM. Reason: 'some' not 'most'
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Old 4th February 2013, 07:18 PM   #1708
richiem is offline richiem  United States
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RE I am confused -- me too, but some of the issues here are the uncertainties of the measuring gear. These results are all near the residuals of the oscillators and analyzers. As such, the water is cloudy and not assuredly safe to drink.
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Old 4th February 2013, 09:04 PM   #1709
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Quote:
According to Chyba 404 - Stránka nenalezena they are able to get -150 dB. But according to Bateman the capacitors have a distortion closer to -130 dB. Any one got ideas?
Quote:
Me too, but some of the issues here are the uncertainties of the measuring gear.
This is likely all just measurement limitations. The Bateman setup is accurate to probably about -120 dB (it's some time since I've read his articles, so with reservations), so any comparison for lower distortion capacitors is meaningless. The Janásek article is, as pointed out several times already, pretty naive with quoting results at the -150 dB level. It could as well have been that the Polystyrene cap has higher distortion than the C0G, and that the higher distortion just happend to better cancel the contribution of the notch filter.

Samuel
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Old 4th February 2013, 10:49 PM   #1710
RNMarsh is offline RNMarsh  United States
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Quote:
Originally Posted by Samuel Groner View Post
This is likely all just measurement limitations. The Bateman setup is accurate to probably about -120 dB (it's some time since I've read his articles, so with reservations), so any comparison for lower distortion capacitors is meaningless. The Janásek article is, as pointed out several times already, pretty naive with quoting results at the -150 dB level. It could as well have been that the Polystyrene cap has higher distortion than the C0G, and that the higher distortion just happend to better cancel the contribution of the notch filter.

Samuel
I certaily would agree from the tests i have done recently.

Regarding ac level across caps as they were tested... Yes, keep the voltage drop across them as low as possible. This is easy to do in coupling cap apps. But in tone controls, EQ and filters, it doesnt work out quit so well. -Thx-RNMarsh
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