sonic difference between Mylar and Poly caps?

I've been trying to do some research on the sonic differences between mylar and poly caps. Some articles I've read said that mylar is OK to use in Power supplies, but not in an audio path... some sites claim that there is no sonic difference between the two. I havent set up an A/B test yet... wondering what you guys think? is there a difference?

uh Mylar IS a poly cap..

Mylar is the trademarked name for polyester.

so I suppose you mean polyester VS. Polypropylene?

Polyester is "warmer" since it introduces a small amount of distortion, fine for power supplies, OK for audio if you don't mind some distortion.

Polypropylene is much better.

Polycarbonate is better yet.

Polystyrene is even better..

Polytetrafluoroethylene(Teflon) is the best.

Polyphenylene Sulfide Film is supposed to be really good but is still expensive and hard to get in certain values.

again caps are cheap try them out. Get a cap tester and match the value between them to reduce some of the variables

poly can be PET(Mylar) I seem to remember ETK posted over 900 types of PET film. OR polypropylene OR poly............

Then there is film and foil or metalized film.

I use different polys for different parts or sounds sometimes even a cheap microphonic ceramic.

Don't trust what you read test it if possable

I use PETs over polypro sometimes

What are you reading? Remember this stuff is sometimes wanted as a producer of sound (adds something like different transfomer alloy and winding) not a clean reproducer.

What you might want for a preamp etc you might want for your home stereo

Google the Jung Marsh stuff
or look in the meta I believe there are some good links in there

I posted my list in order of distortion byproducts only, from testing RF sample-hold/averaging circuits.

As for audio, the less distortion, the more sterile they sound OTOH. good for some things, bad for others.

As Gus mentions, try some caps out, 8 times out of 10 you won't hear the difference anyway.

Oh sure, I believe it. Sometimes a cap with higher distortion can work magic on a rather sterile circuit, giving a little life where there would be an otherwise boring sound.

I just wouldn't use a whole lot of them in the circuit where it would color the sound *too* much going through stage after stage.

[quote author="Svart"]I posted my list in order of distortion byproducts only, from testing RF sample-hold/averaging circuits.
[/quote]

I've found that absorption not necessary means distortions, though sometimes indicates it (in metalized caps).

[quote author="dustbro"]I've been trying to do some research on the sonic differences between mylar and poly caps. Some articles I've read said that mylar is OK to use in Power supplies, but not in an audio path... some sites claim that there is no sonic difference between the two. I havent set up an A/B test yet... wondering what you guys think? is there a difference?[/quote]

There are maybe a half dozen important performance parameters that differentiate capacitor types from each other. Which metrics are important often depends on how they are being used in a circuit. For example a DC blocking cap with almost no working terminal voltage change in use will be quite a bit different than a small film cap in an EQ circuit, or worst case IMO for capacitors is in passive speaker crossovers where they are working pretty hard, passing high current with large terminal voltage changes with signal frequency.

For active EQ circuits I would read up on voltage coefficient (actual value changes with terminal voltage, a direct source of distortion), and perhaps to a lesser extent DF (dissipation factor). In heavier lifting application equivalent series inductance and resistance can cause errors. It all comes down to how does Cap XYZ deviate from a perfect or theoretical capacitor in your circuit.

Some applications, like sample and holds, are very sensitive to DA (dielectric absorption) but this is not as much of an issue in light duty blocking applications.

Years ago I liked polystyrene as a really nice dielectric that was also quite inexpensive. Unfortunately polystyrene was not very robust for commercial manufacturing and has fallen out of favor.

While I am not a huge fan of listening tests, it might be interesting if you have multiple identical audio paths to load alternate channels with different test components and null two channels from each other to reveal differences "in circuit" and with real music test signals. Of course be careful as a value difference can diminish depth of null in some circuits. Listen to the null, and if nasty, one or both of your test devices is nasty. I'm not quite sure how to identify which one is which.


JR

[quote author="JohnRoberts"]Years ago I liked polystyrene as a really nice dielectric that was also quite inexpensive. Unfortunately polystyrene was not very robust for commercial manufacturing and has fallen out of favor.[/quote]
What is/was the problem with polystyrene? Heat sensitivity?

They are still made BTW - I bought some last month.

Best regards,

Mikkel C. Simonsen

Polystyrene will not take the heat of wave soldering processes.

The Polystyrene caps used thin wire gauge to keep too much heat from wicking up the lead and melting the body of the cap. I also encountered some parts destroyed by cleaning (actually high pressure air blew moisture inside caps?).

But they are a sweet dielectric for hand builds and DIY. I did have a few customers back in my old kit company days trash them hand soldering.

JR

[quote author="JohnRoberts"]
While I am not a huge fan of listening tests, it might be interesting if you have multiple identical audio paths to load alternate channels with different test components and null two channels from each other to reveal differences "in circuit" and with real music test signals. Of course be careful as a value difference can diminish depth of null in some circuits. Listen to the null, and if nasty, one or both of your test devices is nasty. I'm not quite sure how to identify which one is which.
[/quote]

Hmmm... If both are equally nasty what should we hear?

If the nastiness is well correlated perhaps nothing, if random 2x, but most nonlineaities are not random.

Here is another possible technique for (amplifying) revealing problems in an audio path. Visualize an arbitrarily linear wide band and wide dynamic range digital A/D, storage, and D/A path.

A given audio sample, say a few seconds long, could be looped through the audio path being tested, say a hundred times. One would need to compare this to the baseline reference of 100 similar loops through just the A/D-D/A path for comparison. A saved digital copy of the original sample could be subtracted from the final result for a hyper sensitive null. Of course after 100 loops even minor gain or frequency response errors would be amplified to significance.

While perhaps not trivial getting a A/D-D/A loop that clean could be the first project. :wink:

JR

Here is the copyrighter bragging about it:

http://heritage.dupont.com/touchpoints/tp_1952/overview.shtml

Here's more info than you probably need about it:

http://en.wikipedia.org/wiki/PET_film_(biaxially_oriented)

I personally have tried Sprague and EFC mylar caps in mic preamps, DC blocking duty, and they sound different from one another. Spend a few bucks at ApexJr and try them in your application:

http://apexjr.com/capacitorA.html

[quote author="JohnRoberts"]If the nastiness is well correlated perhaps nothing, if random 2x, but most nonlineaities are not random.

[/quote]

No doubt innocent phase shifts will be heard louder than non-linearities. I know that because back in 70'th I put an audio amp and a speaker in 2-ray oscilloscope hoping to hear nastiness, but unfortunately it did not help much so I gave up the idea. I was very disappointed because it took me long time to make it look nice both inside of the scope and outside on the panel.

Indeed, that was an early revelation about the unreliability of simple THD analysis for absolute playback accuracy. Fundamental components spit out at varying amounts of phase shift are routinely ignored. While perhaps a fair assumption for audibility when reproducing pure tones, complex music is not that accommodating.

I am not smart enough to declare absolutely what other people hear as nasty or nice (while I have spent decades studying to better prioritize my engineering efforts).

The conservative approach from my perspective is keeping all deviation to a minimum and only make tradeoffs when no other solution presents. The most "harmless" deviation, is still an error.

Getting back to my proposed "century loop" test, some specific test signals could be used to parse out minimum phase and non-minimum phase EQ/phase shift errors. While simple null tests present the conundrum of coming up with an accurate reference or "golden standard", the multiple loop often amplifies errors to the point of easy identification by simple listening.

I know of a world class speaker designer who uses this technique on loudspeakers. The typical loudspeaker is so flawed that it doesn't take many loops or an incredible storage medium to reveal errors. Applying the same technique to a high performance audio path is far from trivial, but never say never.

JR

I've found also such approach useful: many of stages in question, with adequate attenuation between them. However, it is again not fair since the same transfer function multiplied by itself results in higher order function, it is the simple math...
Speaking of conservative approach, I try to use as less of active elements in signal path as possible adding them only when it is absolutely necessary. For example, combine HPF and buffer instead of adding one more stage for HPF; bypass a mic pre for line level in instead of putting attenuator on it's input, and so on.

Rich May asserts that a great deal of the difference attributed to dielectrics has in fact more to do with the details of capacitor construction---for example the tensioning of a film/foil winding apparatus and the uniformity obtained.

He also mentioned once that the Panasonic stacked-film mylars did not sound as good as the somewhat bulkier radial wrapped mylars (not sure of the representative manufacturers of the latter; sometimes colloquially called Chiclet caps).

Peter Qvortrup of Audio Note asserts that the best sounding caps are his variety of paper/foil/oil, which are strongly damped mechanically so that piezoelectric effects are suppressed. I note that Pease (although he may not have evaluated Audio Note caps per se) finds paper-oil to be very poor.

Thats different I like the pan Vs and I am not a fan of the green/yellow Chiclets. Is your def of Chiclets the more long than wide wound mylar ones often green or translucent yellow?

FWIW Back when I raced RC electric cars I did some tests on different caps on the brushed motors used in the racing. Different caps reduced the arcing and burning of the brushes and comms. The chiclets and ceramics did not seem to work as well as the pan Vs. I built a simple pulse circuit at about the RPM and comm segments and did see differences in the waveforms across the caps. I will look for my notes and circuit but this was about 20 years ago so I don't know if I still have the notes and circuit.

I use pan Vs (sometimes M series in phasors)in most of my guitar and bass effect builds and they are the ones I liked in the mxl603 microphone at the .22uf coupling caps.

The article I learned about the pan Vs was the TAA Jung one for the mod of the DAC circuit used in the magnavox phillps CD players.

Yeah the green fairly tall ones are what I think he meant by Chiclets.

I would expect the stacked films to be lower inductance, which may contribute to their superiority in some apps.

[quote author="bcarso"]
I would expect the stacked films to be lower inductance, which may contribute to their superiority in some apps.[/quote]

If wound films are soldered through all layers on both sides they should have the same inductance, no?