The best cap material for tone pot

[Clint 55]

Re: The best cap material for tone pot

I haven't ponied up and got a mutimeter that measures capacitance yet. I guess I might.

[WDeeGee]

Re: The best cap material for tone pot

About the "placebo effect": on a discussion about capacitor types on an electronics forum a guy joined in who said he was an engineer for a big capacitor company, and he addressed some of the issues that exist with signal transmission in capacitors, mainly:

1) Variations in amplitude (volume) across the frequeny spectrum. No material on earth has a perfectly even resistance across the frequency spectrum, so there will be signal coloring.
For example, one of two common orange drops types (715 or 716), clearly accentuates the highs more than the other (I forget which is the brighter one). They are the exact same type, but one is rolled up into a cilincer and the other is a slightly squashed cilinder, which means the thickness of the dielectric varies across the shape of the cap, as well as inner pressure on the dielectric, causing a difference in signal transmission between the two types. One of the two is brighter and it's quite noticeable when used as a coupler or a cathode cap in an overdriven guitar amp gain stage.

2) Uneven variations in phase shifts across the frequeny spectrum.
Our brains are experts at detecting phase shifts in sounds, as it is how we perceive whether a sound is distant or near (regardless the volume), and whether a sound is approaching or moving away from us. So if you think one cap sounds more "open" and the other more "focused", that's likely not your imagination.

The factors that cause these distortions include but are not limited to:
The inherent frequency characteristics of the used dielectric, anode, cathode materials.
Microscopic vibrations that originate from electrons moving back and forth in the dielectric medium affecting certain frequencies within the signal.
Uneven resistance, inductance, stray currents etc. across the frequeny spectrum.
Uneven thickness of the dielectric across the capacitor.
Pressure cause by tightly rolling up the capacitor, etc.

These things all color the sound but aren't considered destructive because (within audio range) the effect is just that: a coloring. However, these imperfections do play a significant, deleterious role in high-frequency ultrasonic applications and so it's a topic of much technological and scientific research.

Oh, I forgot, transients was also mentioned. The speed with which a dielectric is able to pick up fast signal changes (the so called "attack").
I've always felt Orange Drops (or polyprops in general) have a bit of a spongy, bouncy attack, whereas ceramics produce a rather hard attack.

All of this is very noticeable when using these caps as couplers or snubbers in tube amps. In tone pots, the effect is less, naturally, but it exists, of course.

Which reminds me, I used to have these small elco's that sounded really spacial as cathode caps. Really made the sound very "wide", something akin to "stereo". I also used these yellow mylar caps from China, that had the opposite effect, making things sound very focused, or "mono". Those that do mixing in DAW's know what I mean. But how can a single guitar speaker sound "stereo" with one kind of cap in the preamp and "mono" with another? Simple: slight phase shifts caused by the cap's imperfections trick the mind into hearing "spaciousness" in the guitar sound. I remember those Svetlana EL34's producing a similar effect: they made the guitar sound appear to come from all directions, probably for the same reason: inadvertent phase shifts of certain frequencie bands.

Maybe if we had perfect materials all amps would sound somewhat the same?

[WDeeGee]

Re: The best cap material for tone pot

saying that someone can't differentiate between different tone colors because the values might be slightly different is like saying you can't hear the effect of A2 in 2 of the same pickups if 1 is 8.25k and the other is 8.5k. Also the argument that it can't make a difference because the top end is going to ground is not a valid argument. Different materials could (and do) filter differently and send different frequencies to ground.

That is a good analogy right there.

Also, some people may have 20/20 vision but then there's one or two colors they can't see, so let's not be too judgemental. People do imagine things, but I can tell you that when a guitar amp has orange drops in them, I recognize 'm from a mile away. Or at least, I used to be able to tell, as I have since stopped building amps.

[GuitarDoc]

Re: The best cap material for tone pot

That is a good analogy right there.

Also, some people may have 20/20 vision but then there's one or two colors they can't see, so let's not be too judgemental. People do imagine things, but I can tell you that when a guitar amp has orange drops in them, I recognize 'm from a mile away. Or at least, I used to be able to tell, as I have since stopped building amps.

No. Actually that was a very BAD analogy.

A better analogy would be: You have 2 identical planes. One can fly at 385 mph and the other at 386 mph and you're telling me that you can feel the difference in speed while flying in them; or that you can see the difference in speed while watching them from the ground. Sure the instruments can detect a difference, but YOU cannot...not with any of your 5 natural senses (nor even your 6th sense if you have one).

Instruments (oscilloscope) can detect differences in caps of different materials, but your ears can't. Assuming, of course, that their VALUES are exactly the same.

[ItsaBass]

Re: The best cap material for tone pot

I haven't ponied up and got a mutimeter that measures capacitance yet.

Yet you’re fine with proclaiming that we’re all challenged in the senses because we can’t hear differences between cap materials in onboard tone controls like you can with your golden ears.

Such a comparison starts, at the most basic level, with caps of identical capacitance. Until you get that, your experiment is totally useless.

[zionstrat]

Re: The best cap material for tone pot

I'm not in a good place to look it up right now, but there's a double-blind study out there that shows that when the values are the same people cannot statistically hear any differences between capacitor types.

It's all placebo effect and companies taking advantage of people who want it to be true.

Sent from my SM-G960U1 using Tapatalk

[GuitarStv]

Re: The best cap material for tone pot

You can see full frequency responses for 90 different capacitors in a tone circuit application graphed out here: http://zerocapcable.com/?page_id=224

[Clint 55]

Re: The best cap material for tone pot

I only see a comparison of caps of different measured values. Although their frequency plot does show them to be different. I'm not sure how they can conclude that there's no difference.

I'm not saying you guys are deaf. I'm saying you're relying on scientific conjecture rather than analyzing real world observations. I know what I can and can't hear. I'm not sure why you're telling me I can't.

[GuitarStv]

Re: The best cap material for tone pot

I only see a comparison of caps of different measured values.

Please, read the web page a little more closely. They list all 90 of the capacitors tested, and include both the type of capacitor, it's stated value, and it's measured value. Even a picture of the capacitor tested.

Although their frequency plot does show them to be different.

The frequency plot is not "different". It's shifted. Again, if you read carefully you'll see that the response is shifted corresponding to the measured value of the capacitor tested . . . which is given in the legend for each graph.




This information is all summarized in their conclusions section:

The data and sound clips above show clearly that for tone capacitors of close measured capacitance value there is no difference in tone. For example, compare the clips and plots for the “Monolithic X7R 0.022uF – 0.0204” and the “Vishay 225P Orange Drop 0.022uF – 0.0204”. (You can click on the colored box in the legend and the line will be highlighed briefly.) These two capacitors, of the same measured value (0.0204uF) but different dielectrics have indistinguishable plot lines, differing in frequency at the 0dB crossing by about 0.3%. This difference is below the rated accuracy of our measurement equipment and is statistically insignificant.

The capacitor values in the 0.022uF graph vary from the 0.022uF nominal value -15.5% to +12.7%. (The obvious outlier, the ceramic disc, was a junk drawer special from a Radio Shack grab bag.) The range of frequencies where the curves cross 0dB headed down on the right is about 728Hz (-11%) to 906Hz (+11%), using linear interpolation. The actual dependency is nonlinear, but we used linear interpolation as an approximation to compute these percentages. Going further and plotting a frequency vs. capacitance curve in a spreadsheet and fitting a quadratic polynomial, the correlation coefficient is better than 0.97.

We found only moderate statistical corrleation between the voltage rating of a capacitor and the frequency response (0.45). However, the correlation between the value and voltage rating of all 90 capacitors was 0.40, explaining the former correlation and eliminating voltage rating as a tone determining factor.

It appears that the variation in frequency response is due to the values of the capacitors and not any other factor. From the sound clips, you will notice that you can hear NO difference between the capacitors, except for the most extreme tolerance variations.

There is no advantage to using large, high voltage capacitors. The smaller, lower voltage units work as well.

[Clint 55]

Re: The best cap material for tone pot

I don't see why they didn't group some caps with the same measured value and test and compare those. Their conclusion isn't congruent with their findings lol.

[GuitarStv]

Re: The best cap material for tone pot

I don't see why they didn't group some caps with the same measured value and test and compare those.

They did.

If you read the legends of the graphs provided, you will see the exact measured values of the caps tested . . . many of which are identical, or less than 1% different from others in the same graph.

Their conclusion isn't congruent with their findings lol.

Can you reference the data points you're drawing that from? From what I am seeing, their findings show no difference between material type when taking into account the actual value of the capacitor. Which is what they concluded.

[Clint 55]

Re: The best cap material for tone pot

They compared caps of different measured values, posted the results on a very imprecise graph, which yielded different frequency responses, then loosely claimed that there's no difference between caps of different materials but the same measured value... When they didn't even compare caps of the same measured value in the first place!! Lol!!

[GuitarStv]

Re: The best cap material for tone pot

They compared caps of different measured values, posted the results on a very imprecise graph, which yielded different frequency responses, then loosely claimed that there's no difference between caps of different materials but the same measured value... When they didn't even compare caps of the same measured value in the first place!! Lol!!

The second graph shows nine caps of different materials with the same measured value (between 0.0219 and 0.0218), compared.

[Clint 55]

Re: The best cap material for tone pot

I see values as low as 18.6nf and as high as 24.8nf.

[Jacew]

Re: The best cap material for tone pot

I see values as low as 18.6nf and as high as 24.8nf.

Here for your convinience:



All labeled 22nf caps, there are caps of same real value and caps of different real value. That's not important: Notice how the lines exactly line up based on only the real value of each cap.

No difference in different caps otherwise.

I'm out.