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Why Mylar in AN silver foil caps?
Why Mylar in AN silver foil caps?
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Old 10th September 2019, 01:58 PM   #1
Francois G is offline Francois G  United States
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Default Why Mylar in AN silver foil caps?

I was looking at Partsconnexion’s sale of the Audio Note silver foil capacitors with Mylar dielectric. At $640 (before discount) per for the 1 mF/630v specimen these are expensive. Made me wonder why they used Mylar, rather than polypropylene, polystyrene or PTFE, in that order of reported improvement, which are widely manufactured.

The text on Partsconnexion talks about the balance between performance and reliabilty, but since many caps are successfully manufactured with these “better” dielectrics I am left puzzled.

Audio Note Capacitor 1uF 600Vdc Silver Foil
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Old 10th September 2019, 02:30 PM   #2
Osvaldo de Banfield is offline Osvaldo de Banfield  Argentina
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This cap are only foolery. As any other "audio grade" product in the Earth.
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Old 10th September 2019, 02:30 PM   #3
DF96 is offline DF96  England
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Normal engineering considerations do not apply to capacitors in this segment of the market.

Be aware that "1mF" has a perfectly well-defined meaning, but it is not one microfarad.
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Old 10th September 2019, 02:33 PM   #4
Osvaldo de Banfield is offline Osvaldo de Banfield  Argentina
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For me is 1 millifarad or 1000µF.
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Old 10th September 2019, 03:08 PM   #5
analog_sa is offline analog_sa  Europe
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Why Mylar in AN silver foil caps?
IMHO AN UK have always been after a specific non-neutral sound signature. Apparently the fans just love it. No direct experience with the caps, only with products using those.

And anyway, too many aspects of cap design affect sound, zeroing on the dielectric is an extreme simplification.
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Old 10th September 2019, 06:38 PM   #6
Bare is offline Bare  Canada
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Been MY experiences that Parts Connexion Over hypes ALL their products.
Often far above that of the maker.
Justifying their too high pricings perhaps ?
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Old 10th September 2019, 08:30 PM   #7
Mark Tillotson is offline Mark Tillotson
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Quote:
Originally Posted by Francois G View Post
but since many caps are successfully manufactured with these “better” dielectrics I am left puzzled.
Even more markup to rip off the snake oil victims, surely? After all they use vegetable oil, how cheapskate is that - the stuff is not stable.

BTW how come a plastic film capacitor has oil in it at all?

How come an audio capacitor needs litz wire leads?

Nothing to do with audio engineering, everything to do with ruthlessly exploiting the gullible, and wasting valuable metals, come to that.
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Old 11th September 2019, 10:43 AM   #8
DF96 is offline DF96  England
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Paper in oil was used as a dielectric before plastics were invented; they used what they had. Paper is an awful dielectric on its own, but oil improved it. The resulting caps were leaky and mostly unreliable, but that was the state of the art 70 years ago.

Modern plastic dielectrics are much better so going backwards is plain daft. No need to add oil; that is just an efficient way of extracting money from certain audiophiles.

No need for silver or litz wire; again this is economics not physics.
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Old 11th September 2019, 11:00 AM   #9
cumbb is offline cumbb
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1 uF = 1 µF;-)

Use a small electrolyt; may be, it sounds better.
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Old 11th September 2019, 10:57 PM   #10
PRR is offline PRR  United States
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Originally Posted by DF96 View Post
Paper in oil was used as a dielectric before plastics were invented; they used what they had. Paper is an awful dielectric on its own, but oil improved it. The resulting caps were leaky and ...
Arguably: the oil is the dielectric, the paper is just a mechanical separator. Obviously they are so commingled that they have to be considered together.

An advantage of oil is that after a breakdown, fresh oil seeps in and the gross damage is "repaired". But the zap releases gas and metallic byproducts, and eventually the cap is kaput.

A real problem with oil is that it is best when DRY. This is a wet planet and oil gets moisture in it. This reduces its breakdown voltage. Also increases breakdown of the paper.

MEGA-watt transformers, before they are put in service, or after long running, they wire reduced voltage into a short and let them heat-up for days to boil the moisture out of the oil, until oil tests show good results. (There are other methods, particularly to dry oil without taking the tranny out of service.)
https://www.vaisala.com/sites/defaul...%20Webinar.pdf

House-size utility transformers are fairly well sealed and over-spaced so they do not need the DRYest oil, but this is one reason why pole-pigs overheat and burn after 20-30 years.

Radio-size capacitors can't even try to be sealed. Humidity never sleeps, seals weep, and the high surface/volume ratio means a lot of seepage for the oil inside. Also the narrow separation of 400V caps means hardly any "repair" after a breakdown, and no place for metallic zap-crap to fall out.
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