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Old 19th April 2004, 05:58 PM   #1
hkoetz is offline hkoetz  Netherlands
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Default Film cap's

Can anyone tell me what is meant by film capacitors? They are suggested for audio applications.
Are any of the following types film caps and are they suitable for audio applications?
Orange Drops - Polypropyle
Silver Mica
Mallory (non-inductive)

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Henk Koetzier
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Old 19th April 2004, 08:45 PM   #2
EC8010 is offline EC8010  United Kingdom
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Film capacitors use a plastic film as the dielectric (insulator) between the (conductive) plates of a capacitor. Plastics used are; polytetrafluorethylene, polystyrene, polypropylene, polycarbonate, and polyteraphylate (polyester).

Silvered mica uses naturally occurring cleaved sheets of mica as the dielectric. Because mica is a natural material, it is variable quality. In general, silvered mica is not quite as good as polystyrene.

Those Mallorys are probably electrolytic. Some audio uses require electrolytics.

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Old 19th April 2004, 09:00 PM   #3
SY is offline SY  United States
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You caused great pain to my Inner Polymer Chemist. It's "polyethyleneterphthalate" or "PET" or "polyester." Trade name "Mylar" when it's sourced from DuPont.

Another popular dielectric these days is polyphenylene sulfide (PPS), which has excellent performance at high temperatures.
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Old 19th April 2004, 09:44 PM   #4
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Default The quick brown fox...

Quote:
Originally posted by SY
You caused great pain to my Inner Polymer Chemist. It's "polyethyleneterphthalate" or "PET" or "polyester."
My apologies. You will have to admit, though, that "polyethyleneterphthalate" doesn't roll easily off the tongue (or keyboard). I've just checked in my 1986 Mullard quick reference guide, and it splits them into two words, "polyethylene terephthalate". Which is still a tongue twister.
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Old 19th April 2004, 10:17 PM   #5
SY is offline SY  United States
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That's why we say, "PET," a much more euphonious appellation. The naming of copolymers is fraught with peril; today I placed an order for poly(styrene-isobutylene-butadiene-styrene), which is difficult to say ten times quickly.
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Old 20th April 2004, 02:41 AM   #6
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Quote:
Originally posted by SY
poly(styrene-isobutylene-butadiene-styrene)

... and what exactly is this used for?
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Old 20th April 2004, 04:18 AM   #7
SY is offline SY  United States
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Quote:
Originally posted by breguetphile



... and what exactly is this used for?
Nothing electronic. Wine corks.
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