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Old 15th October 2019, 05:02 PM   #1
RickTH is offline RickTH
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Default polypropylene capacitors

Looking around on various sites : Why is it so hard to find small (so low voltage) MKP (polypropylene) capacitors for audio ?
There are : AC/puls , DC link , motor run, power factor correction, RC snubber, RF and power , RF microwave, suppression film capacitors and... general use .
Which are for audio , in the 4,7 uF to 10 uF range ? ( for input of amps , not for speaker filters)
Sure I can find these Wima red ones and those grey Kemet, but often only for high voltages which makes them very bulky.
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Old 15th October 2019, 07:26 PM   #2
DF96 is offline DF96  England
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Maybe it is difficult to make or handle very thin polypropylene film? Audio is a small niche market. There are not many instances in circuits where you actually need a low voltage 10uF film capacitor, despite what many people think.
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Old 16th October 2019, 03:31 AM   #3
mchambin is offline mchambin  France
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Quote:
Originally Posted by DF96 View Post
Maybe it is difficult to make or handle very thin polypropylene film? Audio is a small niche market. There are not many instances in circuits where you actually need a low voltage 10uF film capacitor, despite what many people think.
Right.
It took me years to find out the reason for huge capacitors used on a microphone preamplifier.
450V 33μF where there is no need for more that 63V. The reason is simply price and availability.
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Old 16th October 2019, 03:50 AM   #4
gabdx is offline gabdx  Canada
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Erse makes lower voltage caps for audio, they are very good and cost is reasonable.

These other caps could be good too and over-specified for audio purposes.

Always think about the signal, the AC, the DC and the peeks, and RMS, it needs to match.
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Old 16th October 2019, 08:54 AM   #5
mchambin is offline mchambin  France
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Quote:
Originally Posted by gabdx View Post
Erse makes lower voltage caps for audio, they are very good and cost is reasonable.

These other caps could be good too and over-specified for audio purposes.

Always think about the signal, the AC, the DC and the peeks, and RMS, it needs to match.
A search for those film caps just gave me the usual very same caps but named "audio grade".
Where are the low voltage ?
Where is the reasonable cost ?
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Last edited by mchambin; 16th October 2019 at 09:04 AM.
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Old 16th October 2019, 09:33 AM   #6
dotneck335 is online now dotneck335  United States
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I have found that the Polyethylene Terephthalate (PET) capacitors from Wima are nearly as good as the polypropylene, and are a good compromise due to their small size. A 10 F 50 volt Wima MKS2B051001N00JO00 is only 7 x 11 mm. A little pricey @ $2.51 each, though.
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Old 16th October 2019, 09:46 AM   #7
mchambin is offline mchambin  France
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Very interesting.
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Old 16th October 2019, 12:50 PM   #8
RickTH is offline RickTH
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Quote:
Originally Posted by dotneck335 View Post
I have found that the Polyethylene Terephthalate (PET) capacitors from Wima are nearly as good as the polypropylene, and are a good compromise due to their small size. A 10 F 50 volt Wima MKS2B051001N00JO00 is only 7 x 11 mm. A little pricey @ $2.51 each, though.
PET is MKT or MKS , polyester then. A good compromise.
Elektor tested caps for audio back in the 90'ties: MKP the best.
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Old 16th October 2019, 02:13 PM   #9
DF96 is offline DF96  England
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Those tests appear to show that distortion was below the measurement threshold for all film caps, so in what sense is MKP the best - based on those tests? DA does not count because DA does not affect audio.
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Old 16th October 2019, 03:49 PM   #10
jackinnj is offline jackinnj  United States
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polypropylene capacitors
Kemet F461 have 15mm lead spacing

The article which Sam Groner and Scott Wurcer wrote for Linear Audio Volume 12 ("Quadrature Bridge Measures Harmonic Distortion in Capacitors") indicates that C0G have much more consistent distortion than polyester or polypropylene. While the hybrid metalized polypro can be much lower, it can also be much higher!
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