Film capacitors are NOT microphonic?

[Ittaku]

There is a long-standing wikipedia article https://en.wikipedia.org/wiki/Microphonics that has been quoted over and over again on the internet which states the following:

Quote

^"[2] Film capacitors using soft (mechanically compliant) dielectric materials can also be microphonic due to vibrational energy physically moving the plates of the capacitor. Likewise, variable capacitors using air as a dielectric are vulnerable to vibrations moving the plates. Capacitors using glass as the dielectric, while quite expensive, can be made to be essentially nonmicrophonic.^[3]"

 

It's been bugging me for a while since increasingly expensive mechanisms for reducing vibration in capacitors are being employed leading to capacitors costing thousands of dollars even (CAST Duelund, copper or silver). Now I'm not writing this post to ask people what they've heard and what they believe about microphonics, I'm posting this purely to say there is no science that supports this theory.

 

The first issue is that there are 2 references cited in that article. The first is called "Capacitors for reduced sound emissions." and has been universally accepted as the reference article that states this is the case. Except it is NOT. The article is about ceramic capacitors and their microphonics and the ONLY reference to film capacitors actually says the opposite!

 

Direct quote from the article for the section that mentions films:

Quote

Noise may be reduced or eliminated via several approaches such as use of non ferroelectric dielectric MLCC (class 1 COG or the like), use of low distortion dielectric class 2 dielectrics (anti-ferroelectrics, reduced field sensitivity ferroelectrics, increased dielectric thickness or the like), use of film dielectric multilayer capacitors, etc.

 

It appears that whoever wrote this part of the wikipedia article was a "film vibrating is microphonic" believer and wrote it as fact when the actual cited reference says nothing of the sort. I've seen dozens of pages across the internet quote this wikipedia article as fact in the meantime, without actually looking at the reference itself.

 

Next is the next claim of "Capacitors using glass as the dielectric, while quite expensive, can be made to be essentially nonmicrophonic.^[3]"

 

This one's easy to debunk. The #3 reference cited is actually SPAM for a site that advertises "The Most Expensive Headphones Ever Made that you never know".

 

Looking at the wikipedia article there has been an edit war going on for years on that page, but mostly trying to fix the spam reference.

 

Now I'm not saying definitely whether film capacitors are microphonic or not by writing this post, but I AM trying to point out that there is, in fact, no scientific paper quoted on wikipedia that supports the theory.

 

Edited August 5, 2018 by Ittaku

[MLXXX]

1 hour ago, Ittaku said:

Now I'm not saying definitely whether film capacitors are microphonic or not by writing this post, but I AM trying to point out that there is, in fact, no scientific paper quoted on wikipedia that supports the theory.

I see that the version of the  article (as accessed a moment ago), indicates there is no citation to support the claim. The current wording is:

 

Film capacitors using soft (mechanically compliant) dielectric materials can also be microphonic due to vibrational energy physically moving the plates of the capacitor^{[citation needed]}.

 

1 hour ago, Ittaku said:

It's been bugging me for a while since increasingly expensive mechanisms for reducing vibration in capacitors are being employed leading to capacitors costing thousands of dollars even (CAST Duelund, copper or silver). Now I'm not writing this post to ask people what they've heard and what they believe about microphonics, I'm posting this purely to say there is no science that supports this theory.

This in my opinion is an example of misdirected activity in a segment of the audiophile industry, characterised by dubious or no scientific evidence to back the manufacture of a very expensive specialised part, and an obsession by a small percentage of audiophiles to pursue possible very minor audible improvements through acquiring very expensive specialised parts.

Edited August 6, 2018 by MLXXX

[Ittaku]

3 minutes ago, MLXXX said:

I see that the version of the  article (as accessed a moment ago), indicates there is no citation to support the claim. The current wording is:

 

Film capacitors using soft (mechanically compliant) dielectric materials can also be microphonic due to vibrational energy physically moving the plates of the capacitor^{[citation needed]}.

Yes that's because I had a friend who's a regular wikipedia editor look into the claim and address what I see as a longstanding issue I'm trying to see this claim that's been considered fact converted back into the realms of opinion only.

Edited August 5, 2018 by Ittaku

[rocky500]

I did read something on the Jantzen capicitors once a while back when looking at them.

Did find a quote searching just now.

"I am testing the Superior Z-Cap which, like the Silver Z-Cap, has been wound using a “special machine…so that the capasitors become a very tight reel.  This minimizes the inner vibration and keeps microphonic effects as low as possible.”  The ends appear sealed with some sort of resin to keep out moisture, a nice touch, and the overall look and feel are definitely a notch or two above the common polypropylene types.  "

 

Not sure if they were the only one to mention vibration and microphonic and there way of dealing with it is in tight windings.

Maybe this is not the case, but might be a factor that some have picked up on?

 

Edited August 6, 2018 by rocky500

[Ittaku]

1 minute ago, rocky500 said:

I did read something on the Jantzen capicitors once a while back when looking at them.

Did find a quote searching just now.

"I am testing the Superior Z-Cap which, like the Silver Z-Cap, has been wound using a “special machine…so that the capasitors become a very tight reel.  This minimizes the inner vibration and keeps microphonic effects as low as possible.”  The ends appear sealed with some sort of resin to keep out moisture, a nice touch, and the overall look and feel are definitely a notch or two above the common polypropylene types.  "

 

Not sure if they were the only one to mention vibration and microphonic and there way of dealing with it is in tight windings.

Maybe this is not the case, but has might be a factor that some have picked up on?

 

Well see this is the issue - every manufacturer is now quoting the effort they go to to reduce microphonics... except there is no citation to support that there are microphonics there in the first place! I'm not saying I've done the most thorough literature search on earth to see if there is a citation, but the one that is always quoted does not say anything about there being microphonics. Manufacturers can say whatever they want - and in this audio world we often cross the line between demonstrable evidence and none. I'm trying to get to the bottom of whether there is any demonstrable evidence at all here.

[rocky500]

And another manufacturer mentioning microphonics in their literature.

http://www.claritycap.co.uk/products/cmr.php

 

Edited August 6, 2018 by rocky500

[Ittaku]

18 minutes ago, rocky500 said:

And another manufacturer mentioning microphonics in their literature.

http://www.claritycap.co.uk/products/cmr.php

Yep, every single high end audio capacitor manufacturer mentions them. You don't need to look hard.

[Guest Muon N']

58 minutes ago, MLXXX said:

This in my opinion is an example of misdirected activity in a segment of the audiophile industry, characterised by dubious or no scientific evidence to back the manufacture of a very expensive specialised part, and an obsession by a small percentage of audiophiles to pursue possible very minor audible improvements through acquiring very expensive specialised parts.

If you are talking about Duelund Capacitors with this statement? then it appears you have not used them.

[rocky500]

Here are some tests

http://ns2.partsconnexion.com/t/claritycap/Reseach_Summary.pdf

[Ittaku]

1 minute ago, Muon N' said:

If you are talking about Duelund Capacitors with this statement? then it appears you have not used them.

The Duelunds sound great indeed, but please let's just stick to whether there's evidence for microphonics specifically for this thread only.

[Ittaku]

1 minute ago, rocky500 said:

Here are some tests

http://ns2.partsconnexion.com/t/claritycap/Reseach_Summary.pdf

Thanks, that's the sort of thing I'm looking for. Reading now.

Edited August 6, 2018 by Ittaku

[Zaphod Beeblebrox]

How curious that people concentrate on irrelevant aspects of the performance of components. SS equipment, for the most part, is unaffected by microphonic capacitors. Largely because they are not used as coupling components. In valve equipment coupling capacitors are common. In that sense, microphonic aspects of valves are well documented and significant efforts are used to reduce those effects. The microphonic aspects of valves are also several orders of magnitude greater than any capacitor. 

[Ittaku]

3 minutes ago, Zaphod Beeblebrox said:

How curious that people concentrate on irrelevant aspects of the performance of components. SS equipment, for the most part, is unaffected by microphonic capacitors. Largely because they are not used as coupling components. In valve equipment coupling capacitors are common. In that sense, microphonic aspects of valves are well documented and significant efforts are used to reduce those effects. The microphonic aspects of valves are also several orders of magnitude greater than any capacitor. 

I'm actually looking specifically into whether it's of relevance to speaker crossovers by the way.

 

12 minutes ago, rocky500 said:

http://ns2.partsconnexion.com/t/claritycap/Reseach_Summary.pdf

What's interesting about this paper is it's testing mechanical resonances related to the waveform that is being input into the capacitor due to the charge attraction and repulsion moving the dielectric. That's not the same thing as being microphonic!

Edited August 6, 2018 by Ittaku

[MLXXX]

The question to be more precise is not whether film capacitors can be microphonic at all, but whether the effect of their microphony could be significant (having an audible effect) in an audiophile application.

 

In the exacting task of providing a very stable capacitance for an oscillator, a particular film capacitor was reported* as exhibiting variation when tapped with a plastic rod. I note that that was an extreme form of stimulation! There would be less stimulation if the circuit board in which a capacitor was mounted were placed directly on top of a speaker enclosure, and even less if the circuit board were merely in the same room as a loudspeaker.

It might be helpful in discussing microphony in capacitors to refer to test conditions (e.g. direct mechanical stimulation, or exposure to a sound wave in air at a distance of 1 metre), and the extent (e.g. the number of parts per million) by which the capacitance varied (at different stimulation frequencies).

 

________

 

* From https://www.electronicspoint.com/threads/microphonic-film-capacitor.157441/ :-

 

Microphonic film capacitor

Discussion in 'Electronic Design' started by Andrew Holme, May 28, 2009.

 

1. 

   Andrew HolmeGuest

   I'm developing a frequency synthesizer.
   
   I was worried about ceramic capacitor microphonics, so I used these film
   capacitors in my loop filter:
   
   Panasonic ECPU1C105MA5 1uF, 16V, 1210, PPS (Farnell 969-4315)
   AVX CB017D0223JBA 22 NF, 50V, 1206, PEN (Farnell 165-7961)
   
   The 1uF is microphonic. Tapping it with a plastic rod produces FM on the
   VCO equivalent to ~ 20uV amplitude on the control voltage.

   ...

Edited August 6, 2018 by MLXXX

[Zaphod Beeblebrox]

5 minutes ago, Ittaku said:

I'm actually looking specifically into whether it's of relevance to speaker crossovers by the way.

 

None whatsoever. Any microphonic effects will be way too small to be of any significance. Microphonic effects of capacitors are only of interest at very low signal levels. 

5 minutes ago, Ittaku said:

 

What's interesting about this paper is it's testing mechanical resonances related to the waveform that is being input into the capacitor due to the charge attraction and repulsion moving the dielectric. That's not the same thing as being microphonic!

Correct. And in the case of speakers, the differences will be completely swamped by a range of other issues. Driver changes, ambient temperature and humidity, along with other things are far more influential on speaker performance.

[Ittaku]

17 minutes ago, MLXXX said:

In the exacting task of providing a very stable capacitance for an oscillator, a particular film capacitor was reported* as exhibiting variation when tapped with a plastic rod. I note that that was an extreme form of stimulation! There would be less stimulation if the circuit board in which a capacitor was mounted were placed directly on top of a speaker enclosure, and even less if the circuit board were merely in the same room as a loudspeaker.

Very interesting anecdote and certainly big enough to not need measuring. It is an electrolytic cap with different film and metallisation than what we use in crossovers so it's hard to know how much - if at all - it apples to polypropylene/mylar/polyester/WPIO metallised or metal foil capacitors we use.

[davewantsmoore]

All of the statements on the wikipiedia article are technically true.

 

Film capacitors can be microphonic

Mechanical compliance is a factor in microphonics

Using multilayer films can reduce microphonics

Using glass can reduce microphonics

 

... but the wikpiedia articles are poorly written / referenced, and this is in part because most of the literature focuses on ceramic, because these are widely discussed due to specific / problematic microphonics.

 

2 hours ago, Ittaku said:

Now I'm not saying definitely whether film capacitors are microphonic or not by writing this post, but I AM trying to point out that there is, in fact, no scientific paper quoted on wikipedia that supports the theory.

Indeed.

They should cite something...  They could just cite theory/empiricism which shows that all capacitors are "microphonic" (at some level).

 

 

 

 

 

[Zaphod Beeblebrox]

In respect to loudspeakers, I have stated that the movement of the plates in a crossover capacitor is, essentially, so minuscule, that it can be ignored. I would posit that a far more influential part of the speaker, is the connecting cable. When current flows through a conductor, an electromagetic field is set up. With two parallel conductors (which is common in 'figure 8' style speaker cables), then the AC current will cause the two conductors to be attracted to each other. The movement of the conductors will affect the inductance and capacitance of the cable. Is it significant? Very possibly, when dealing with particularly "current hungry" speakers and at high power levels. The effect is totally eliminated when using high power coax, like RG213/U cables and if very stiff insulation (like polyethylene - PE) is used. RG213/U uses PE insulation. 

 

https://en.wikipedia.org/wiki/Electromagnetism

[davewantsmoore]

1 hour ago, Ittaku said:

except there is no citation to support that there are microphonics there in the first place!

The theory of how a capacitor works, tells us that all capacitors are microphonic on some level.

 

1 hour ago, Ittaku said:

and in this audio world we often cross the line between demonstrable evidence and none. I'm trying to get to the bottom of whether there is any demonstrable evidence at all here.

Indeed.

There are microphonics, this is a simple truth.

 

When, how, and how much, microphonics, is very situationally specific ..... then we get to "do those microphonics actually have any relevant effect on anything" .... and the complexity has jumped a lot.

[davewantsmoore]

2 minutes ago, Zaphod Beeblebrox said:

In respect to loudspeakers, I have stated that the movement of the plates in a crossover capacitor is, essentially, so minuscule, that it can be ignored.

Indeed, you would expect so.

 

This has now moved beyond the scope of the wikipedia whinge (which is a fair enough complaint) ... do you know of any data on this?   SPL and vibration inside a speaker can be high.

 

 

My totally unsupported hunch is that 50 million frenchmen surely all can't be wrong on 'capacitor sound' .... which leads me to be vary wary of using a capacitor to 'shape the speaker response'.

[Addicted to music]

If you think that a capacitor is microphonic.  Hook it up to a CRO and tap onto it.  As far as I’m concern it’s all a marketing. 

 

The only capacitor that i kmow and can confirmed that is microphonic are mainly ceramic caps.

 

someone here provided a link in these neck of the wood where someone on utube was demonstrating which type of capacitors are microphonic and shouldnt be used in audio.   Every film was silent and the only one that exhibit a piezo electric effect were  ceramics. 

[davewantsmoore]

52 minutes ago, Ittaku said:

What's interesting about this paper is it's testing mechanical resonances related to the waveform that is being input into the capacitor due to the charge attraction and repulsion moving the dielectric. That's not the same thing as being microphonic!

Is same, just has a different cause.

 

<something> causes the capacitor to move, which changes the capacitance.

[davewantsmoore]

1 minute ago, Addicted to music said:

If you think that a capacitor is microphonic.  Hook it up to a CRO and tap onto it.  As far as I’m concern it’s all a marketing. 

The only capacitor that i kmow and can confirmed that is microphonic are mainly ceramic caps.

We are starting to descend into specifics.... but what you have said should be clarified so people don't get confused.

 

If you are saying that capacitors are not microphonic.   You are plain wrong.   All capacitors are, it is the pure basics of how they work.   C=Q/V

 

If you are saying that most caps are not microphonic enough to be worried about .... then that's another thing.

 

 

Quote

Hook it up to a CRO and tap onto it

When I do that (Mcap Supreme) is see microphonics <shrug>.    I can't remember what the scale was, but it was reasonably small.   I wasn't surprised or concerned about it, but I have little idea whether I should really be (I'd think not).

[Addicted to music]

8 minutes ago, davewantsmoore said:

We are starting to descend into specifics.... but what you have said should be clarified so people don't get confused.

 

If you are saying that capacitors are not microphonic.   You are plain wrong.   All capacitors are, it is the pure basics of how they work.   C=Q/V

 

If you are saying that most caps are not microphonic enough to be worried about .... then that's another thing.

 

 

When I do that (Mcap Supreme) is see microphonics <shrug>.    I can't remember what the scale was, but it was reasonably small.   I wasn't surprised or concerned about it, but I have little idea whether I should really be (I'd think not).

As far as I know and have tested, only MLCC (multilayered ceramic capacitors ) or anything that’s ceramic is microphonic.  

As I have indicated b4 the rest is effective marketing.

 

https://product.tdk.com/en/contact/faq/31_singing_capacitors_piezoelectric_effect.pdf

[davewantsmoore]

3 minutes ago, Addicted to music said:

only ceramic is microphonic

It is well agreed that ceramic can be "badly" microphonic.

 

 

However, please be clear.   All capacitors are microphonic.    To state otherwise belies the basic theory of how a capacitor operates - and would be very confusing for someone trying to learn.