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November 22, 2014, 06:48:04 PM
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DIYstompboxes.com  |  DIY Stompboxes  |  Building your own stompbox  |  Polyester Film Foil vs. Metalized Polyester Capacitors 0 Members and 1 Guest are viewing this topic. « previous next »
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Author Topic: Polyester Film Foil vs. Metalized Polyester Capacitors  (Read 5447 times)
JRM
Posts: 151


Polyester Film Foil vs. Metalized Polyester Capacitors
« on: December 17, 2010, 05:35:49 AM »

Hi,

Metalized polyester film caps are much more readily available than film foil polyester caps (at least at my accessible suplliers) but they do have different construction types as can be checked at these links:
http://www.wima.com/EN/filmfoil.htm
http://www.wima.com/EN/metallized.htm

More than care about the technical advantages and disadvantages of each techonology, is there any influence in the tone between this two (as there is between film caps and electrolytics and ceramics)?
The question becomes relevant in trying to recreate (clone) some vintage effect pedals, like a 1973 Ram's Head BMP, that I believe uses the foil type ones (at least it's marked like that on the scheme).

Thanks,

Joćo
« Last Edit: December 17, 2010, 05:51:57 AM by JRM » Logged
defaced
Posts: 1178


Super Evil Genius


Re: Polyester Film Foil vs. Metalized Polyester Capacitors
« Reply #1 on: December 17, 2010, 07:52:55 AM »

I don't usually say this, but do a search.  This is easily one of the hottest topics in the audio world and has been hashed out many, many, many times.  I'll shorten it for you though: no one can agree so you'll have to do your own listening tests and judge for yourself. 
Logged

-Mike
JRM
Posts: 151


Re: Polyester Film Foil vs. Metalized Polyester Capacitors
« Reply #2 on: December 17, 2010, 08:36:22 AM »

I did searched but haven't found nothing. I might have done something wrong, so I'll try again.
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Electron Tornado
Posts: 688


Re: Polyester Film Foil vs. Metalized Polyester Capacitors
« Reply #3 on: December 17, 2010, 09:35:53 AM »

Capacitors are another source of myth in audio. I think most of what you'll find in audio circles will be anecdotal at best, and pure BS and hype at worst.

These may be the best questions to start with - why do manufacturers make capacitors out of different materials, or use different construction styles? What makes one 0.1uf, 250V capacitor different from another 0.1uf, 250V capacitor (micro Farads are micro Farads arent' they)?

If you find anything interesting on the subject, post a link.  


*** Actually, that site has some interesting info on caps. Click on the "Technical Info" button.
« Last Edit: December 17, 2010, 09:43:37 AM by Electron Tornado » Logged

OK, where's the data?

"Top hole. Bally Jerry pranged his kite right in the how's your father. Hairy blighter, dicky-birdied, feathered back on his Sammy, took a waspy, flipped over his Betty Harper's and caught his can in the Bertie."
R.G.
more
Posts: 16294


WWW
Re: Polyester Film Foil vs. Metalized Polyester Capacitors
« Reply #4 on: December 17, 2010, 09:42:53 AM »

These may be the best questions to start with - why do manufacturers make capacitors out of different materials, or use different construction styles? What makes one 0.1uf, 250V capacitor different from another 0.1uf, 250V capacitor (micro Farads are micro Farads arent' they)?
The difference between metallized and film-and-foil is pretty simple. The metal is much thicker on the film and foil, much thinner on the metallized.

This does the following:
- the metalized caps are smaller (thinner layers)
- the metalized caps are self healing - punch throughs burn off the metal at the hole and "cure" the short
- the foil caps have a much lower spreading resistance than metalized, which makes them better suited to high current and pulse applications.

I can concoct situations where you could hear a difference between the two (I think... you have to use high audio currents) but in low signal applications, I strongly doubt that even "golden ears" listeners could do better than random chance guessing between the two in a fair test.
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R.G.

Every single NASA manned mission starting with the Gemini series has carried a roll of duck tape.
Yes, really. Look it up.
therecordingart
Posts: 822


Re: Polyester Film Foil vs. Metalized Polyester Capacitors
« Reply #5 on: December 17, 2010, 10:16:52 AM »

I'm just rambling, but in my opinion if you pick two same value caps made of different materials that are both stable within the conditions they are being used....you probably won't hear a difference and if you do it is most likely expectation bias.




« Last Edit: December 17, 2010, 10:38:11 AM by therecordingart » Logged
Maudibe
Posts: 45


Re: Polyester Film Foil vs. Metalized Polyester Capacitors
« Reply #6 on: December 17, 2010, 10:58:22 AM »

All caps being equal... erm

rise time, dissipation factor, voltage versus frequency... impedance versus frequency... tollerance, stability....  Cool

food for thought  Kiss
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JRM
Posts: 151


Re: Polyester Film Foil vs. Metalized Polyester Capacitors
« Reply #7 on: December 17, 2010, 11:00:07 AM »

Thank you guys. From the additional search I did, I've found nothing more conclusive than:

"You can't tell the difference in low signal aplications"

And by the way, there's no "golden years" around here, just regular human tissue ones. And they work fine. I'll relax and enjoy the build first and the fuzz afterwards...
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Mark Hammer
Posts: 22226


WWW
Re: Polyester Film Foil vs. Metalized Polyester Capacitors
« Reply #8 on: December 17, 2010, 12:45:13 PM »

What I keep reminding people of is that any capacitor type will likely have some sort of property that makes it ideal for a certain context, but not necessarily "better" in any context.  the question to ask is whether film vs foil vs tantalum vs whatever makes a difference in our context (which is not the same as, say, studio quality music reproduction) and in the specific context one is interested in.
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chi_boy
Posts: 576


George


Re: Polyester Film Foil vs. Metalized Polyester Capacitors
« Reply #9 on: December 17, 2010, 02:03:32 PM »

In my little world the biggest difference in those good quality caps, excluding ceramics for now, is avialability.  Panasonic and AVX were my goto brands. Now they are drying up. Wima is a little pricy and Epcos seems to be having production problems.  I built a project recently that looks like a Christmas tree with all the different colored box caps. 
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"Great minds discuss ideas, average minds discuss events, small minds discuss people." — Admiral Hyman G. Rickover - 1900-1986

The Leftover PCB Page
ddpawel
Posts: 70


Re: Polyester Film Foil vs. Metalized Polyester Capacitors
« Reply #10 on: December 17, 2010, 06:17:23 PM »

Don't listen to guys saying "there is no difference".
Bulls*** and other s*its together.
There's a major differences in impedancy, capacitance is changing different with temperature and frequency, noise level & ...

Maybe this can help:

http://www.elportal.pl/pdf/k01/06_07.pdf

This pdf is in polish language, but you can read some properties from figures.
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Electron Tornado
Posts: 688


Re: Polyester Film Foil vs. Metalized Polyester Capacitors
« Reply #11 on: December 18, 2010, 12:48:51 AM »

Don't listen to guys saying "there is no difference".
Bulls*** and other s*its together.
There's a major differences in impedancy, capacitance is changing different with temperature and frequency, noise level & ...

Maybe this can help:

http://www.elportal.pl/pdf/k01/06_07.pdf

This pdf is in polish language, but you can read some properties from figures.

icon_question

Don't take this the wrong way, but unless someone is fluent enough in Polish, that article isn't useful. It's easy enough to see what they are saying, but it would be much better to be able to know what the author is saying.  I can see that some of the graphs cover the audio frequency range, or part of it, but there's still nothing to show whether that has any audible effect on how they will perform in a stompbox.

Can you translate the article?
Logged

OK, where's the data?

"Top hole. Bally Jerry pranged his kite right in the how's your father. Hairy blighter, dicky-birdied, feathered back on his Sammy, took a waspy, flipped over his Betty Harper's and caught his can in the Bertie."
phector2004
Posts: 984


Phil T.


Re: Polyester Film Foil vs. Metalized Polyester Capacitors
« Reply #12 on: December 18, 2010, 01:25:26 AM »

Knowing how the ear works, hearing is a very complex, dynamic system, but we're just not tuned to notice these kinds of differences.

I've swapped in half-cent cheapo ceramics for mylars for WIMAs and haven't noticed any change whatsoever. Mind you it wasn't a blind test, but if its obvious enough to NOTICE in the same circuit, it exists IMO. I've seen some sites with graphs and oscilloscope readings and other VISUAL representations, but the only variable that matters is how the ear picks it up.

The way I see it, you'll hear more "tone" blowing your nose than you would changing cap types
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Electron Tornado
Posts: 688


Re: Polyester Film Foil vs. Metalized Polyester Capacitors
« Reply #13 on: December 18, 2010, 09:47:06 AM »

It's easy enough to see what they are saying, but it would be much better to be able to know what the author is saying. 

Sorry, that should read, "It's easy enough to see what some of the graphs are saying......"
Logged

OK, where's the data?

"Top hole. Bally Jerry pranged his kite right in the how's your father. Hairy blighter, dicky-birdied, feathered back on his Sammy, took a waspy, flipped over his Betty Harper's and caught his can in the Bertie."
merlinb
Posts: 1221


Merlin, Lancashire UK


WWW
Re: Polyester Film Foil vs. Metalized Polyester Capacitors
« Reply #14 on: December 18, 2010, 11:50:00 AM »


Self's new book has a wonderfully concise chapter on component distortion. See page 53 onwards for plastic caps:
http://books.google.co.uk/books?id=PvKPEFu2PVkC&lpg=PP1&dq=small%20signal%20audio&pg=PA53#v=onepage&q&f=false

In short, although they do produce measurable distortion, it is far too small to be audible even at 20Vrms signal levels. At the <3Vrms levels we use in pedals, it probably wouldn't even be measurable.
Compared with the distortion that your amp / other effects will inevitable add, plus unavoidable noise, it is a non issue. You won't hear the difference between plastic caps (unless it's because they have different capacitances!  Wink)
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JRM
Posts: 151


Re: Polyester Film Foil vs. Metalized Polyester Capacitors
« Reply #15 on: December 19, 2010, 04:26:34 PM »

When I've started this thread, I was more interested in understanding if and why there was any difference in tone between this two types of cap than which one is best. The question becomes relevant when one is trying to recreate (clone) some vintage effect pedals. All the guys that tried to answer that question pointed out that the differences are very, very small for the signal levels we usually have on guitar effects.
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ddpawel
Posts: 70


Re: Polyester Film Foil vs. Metalized Polyester Capacitors
« Reply #16 on: December 19, 2010, 05:30:15 PM »

Metallized capacitors have a slightly better performance because the aluminum foil used has a lower resistance (lower dielectric loss) than thinner sputtered metallization on the dielectric. In addition, depending on the type and the metallization (or not) capacitors have a different capacity depending on the frequency, voltage, etc. Sometimes these differences are even a few percent!

So when you are at least several capacitors of the same type of difference will be slightly audible, but it will be. In some effects changes are even quite good hear.
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phector2004
Posts: 984


Phil T.


Re: Polyester Film Foil vs. Metalized Polyester Capacitors
« Reply #17 on: December 19, 2010, 05:36:25 PM »

Don't forget to gold plate your circuit board, though... copper sucks tone like a dyson
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Electron Tornado
Posts: 688


Re: Polyester Film Foil vs. Metalized Polyester Capacitors
« Reply #18 on: December 19, 2010, 07:16:23 PM »


Self's new book has a wonderfully concise chapter on component distortion. See page 53 onwards for plastic caps:
http://books.google.co.uk/books?id=PvKPEFu2PVkC&lpg=PP1&dq=small%20signal%20audio&pg=PA53#v=onepage&q&f=false

In short, although they do produce measurable distortion, it is far too small to be audible even at 20Vrms signal levels. At the <3Vrms levels we use in pedals, it probably wouldn't even be measurable.
Compared with the distortion that your amp / other effects will inevitable add, plus unavoidable noise, it is a non issue. You won't hear the difference between plastic caps (unless it's because they have different capacitances!  Wink)

Thanks for the reference, merlinb. I found a copy of the book. Yeah, even any measureable difference is still too low to be a factor in pedals.  But just to be on the safe side I'm going to start using unobtainium.
Logged

OK, where's the data?

"Top hole. Bally Jerry pranged his kite right in the how's your father. Hairy blighter, dicky-birdied, feathered back on his Sammy, took a waspy, flipped over his Betty Harper's and caught his can in the Bertie."
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