Polystyrene or polypropylene, given the choice? - Page 3 - diyAudio
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Old 3rd January 2007, 02:02 PM   #21
pjpoes is offline pjpoes  United States
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I noticed that RS International carries a line of Polystyrene caps that look very similar to the Relcaps I like for a bit less money. Though not signifigantly less.

It seems that lots of companies still make good Polystyrenes, just not many are easily accessible. RTI Makes some nice looking ones, but they aren't readily available to the public.

On a different note, I noticed that Wima is one of the only readily available film and foil Polypropalene capacitor available, and its priced high enough as to be about the same as the Dayton Film and Foil capacitors, and only slightly less than the Solens. I'm still not sure what I want to use for my project, but the Wima's may be the hot ticket I'm looking for.

For alternative MKP caps, I noticed that Epcos makes some stuff carried by Mouser. However all they cary are the Y rated RFI supression caps.

So I just want to make sure, Polyester generally bad. I found a bunch of lower priced Polyester Film and Foil caps that are very readily available. I just can't find a lot of Polypropalene ones.
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Old 3rd January 2007, 02:16 PM   #22
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I don't agree that polyester/mylar = bad on an absolute basis. Now, ceramic = bad is more likely to be an absolute truth, but even then not always.

Finding good quality polypropylene capacitors in the right form factor and values tends to be rather more difficult, and I often have to compromise until I can get a better quality part. I will preferentially use polystyrene when it's practical with silver mica as a second choice, mostly for pF values. Both these parts often have steel leads too, but again I have to use what I've got or can get.

Teflon would be especially great, but it's almost impossible to get at any sane price, in the values and form factors I want to use.
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Old 3rd January 2007, 07:21 PM   #23
AMV8 is offline AMV8  United Kingdom
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Hi

Some polyester caps are fine - I like Phillips polyester caps over some types of metalised polypropylene. If you want to try polyester caps you could always add a low value polystyrene capacitor in parallel to it and see how that sounds.

Wherher I use polypropylene or ployester I usually find I prefer the sound if I add a parallel low value polystyrene capacitor.

Don
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Old 3rd January 2007, 10:51 PM   #24
pjpoes is offline pjpoes  United States
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Thanks for the help guys, you are giving me ideas. I'm starting to learn why designers don't always use the best quality capacitors they can. It just doesn't always make sense, it can be cost prohibitive. I'm trying to find a nice balance. I appreciate the input.
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Old 7th January 2007, 05:04 AM   #25
KBK is offline KBK  Canada
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I had the bad taste to grab and hog the last seen batch of russian 'polystyrol' caps on ebay. All 600 of them or so. 0.5uf to 0.3uf, 250V.

They are marked K71-XX. Green in color at 2% or 1%, or semi transparent tan, at 0.5%. They are a pair of stacked caps inside,and each stacked cap is internally a double (multi) cap. They are filled blocks, squarish in nature.

So, they are double coated metallized polypropylene film, coated on each side, then a polystyrene seperator. The metallized film is one of the most uniform and difficult to remove metalized depositions I have ever seen. (I cut every cap I buy apart to do a quality check. The cheap ones at least) They are then covered on each end like built like an extended foil cap, and then the two stacked.

Each cap, is like 4 paralelled polystyrene/polyproplyene cap. Measures like a teflon cap. They kick serious ***. I've used them in speaker crossovers, a brutal test. And they pass it with flying colors.

I believe if you do a search for polystyrol on the forum here, you will find my supplied images of the innards of the russian teflons and the polystyrol caps.
An interesting capacitor question

Excellent. Grab 'em if they are on fleabay.

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Old 2nd April 2013, 05:02 PM   #26
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Hi All, I know this thread is over 6 years old from the last posting. If anyone has any ideas where polystyrene caps in the 10nF range can be purchased these days, I'd be grateful.
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Old 2nd April 2013, 06:11 PM   #27
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Rifa PFE225 and an equivalent yellow Philips part, both in 4-pin 5mm x 5mm square pitch, have been available off-and-on on EBay. Both are 10nF, 2% or better.

I've also seen 8.2nF/63V ERO KP1834 on EBay.

Last edited by linuxguru; 2nd April 2013 at 06:14 PM. Reason: addendum
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Old 2nd April 2013, 06:14 PM   #28
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Hi I have those new/unused from LeClanche (swiss and very good) but I will have to check. Since I will be checking parts inventory this evening I can give a quick answer (I hope).
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Old 2nd April 2013, 07:30 PM   #29
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Film Capacitors | Plastic, Polyester, Polystyrene, Polypropylene | Farnell United Kingdom | Results

polystyrene Capacitors | Mouser

http://www.newark.com/jsp/search/bro...3D422%2B202089
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Old 3rd April 2013, 03:57 PM   #30
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Many thanks. I missed them somehow when I first looked at Newark.
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