different type caps sound different?

[Groover]

There seems to be general agreement that different type caps (ceramic vs polypropelene vs polystyrene vs paper-in-oil etc.) sound different.

What is the physics of this? (In advanced layman terms, not Feynman terms )

[R.G.]

There seems to be general agreement that different type caps (ceramic vs polypropelene vs polystyrene vs paper-in-oil etc.) sound different.

What is the physics of this? (In advanced layman terms, not Feynman terms )

Capacitors (and all other components, for that matter) are not pure. A "capacitor" is something that acts predominantly capacitor-like over a certain range of conditions. Every real capacitor has internal series resistance, leakage resistance around it, parasitic inductance and perhaps some effect of the electric field's effect on the insulator.

Whether these can be heard or not is subject to debate. Probably, if you set up a carefully controlled test to try it out. Absolutely certainly if you simply listen for a while to one cap, then stop, unsolder that one and solder in another type of cap with the same nominal value printed on it.

Capacitors have a tolerance, a variation in capacitance around the printed value. For capacitors this tends to be worse than resistors, sometimes much worse. Electro caps, for instance, have only recently gotten better than +/- 20%. They used to be +80%/-10%. Can you hear differences between +/-10% film caps and +80-10 electros? Oh, you betcha, given only that the cap sits in a position in the circuit where the edge effects matter.

Another thing is heavily in play. Humans are almost certain to fool themselves about what they hear. It's a basic rule of human sensory testing that you have to fool the person being tested to make them not know what is being tested to get valid results. If you tell a human to tell you what sounds better, this or that, they will. Sometimes even if it's the same thing both times. And it's even more likely if they have to do some amount of effort to do each test, like replacing their own parts. And it's even worse if they have a predefined or suggested "better" to listen for.

Another issue is that humans will invariably think something that's microscopically louder, even a fraction of a db, is "clearer". Well researched issue with human hearing testers. That alone means that you have to do exhausting matching of one trial versus the next to avoid presenting the listener with a fait accompli.

So yes, there are some differences, which could be heard perhaps, by carefully set up conditions. That's the physics.

The psychology of testing, plus the innate tendency of humans to insist that they can hear (or taste, feel, smell, do, think...) something different and better makes it a real bear to find any of the real physical differences. There may be real differences there, but they are trivial and negligible compared to the innate opinion bias of a listener.

[Groover]

Wow, excellent answer R.G. Just the level of descriptives I was hoping for. Thank you!

[daz]

As an example of just how much different they CAN sound, consider what happened to me this week. I had my home brew sounding just like i wanted with a nice smooth high end and i wanted to leave it like that. But because i had experimented with it so much the amp was a horrible slop fest. So i cleaned up every solder joint and other things and when i put it all back together and fired it up that wonderful tone was now a ear piercing treble fest. Turns out i used a different brand of 470pf in one place. when i put the one that HAD been there before back in the amp once again sounded smooth and beautiful. Both caps were the same value but different brands. I checked thier tru values with a cap checking meter and they were close. I had a few of each and tried others to make sure it wasn't due to one of the caps being defective. Nope....it was indeed the brand of cap, not even the type because they were both mica, that made that huge difference ! So if you consider that two of the same value and type could be so different, imagine how different types could be ! thats not to say they always will, or even *usually* will. But they can.

[R.G.]

Daz, please don't be offended by what I'm about to say. I'm not trying to argue with you, but there is more than one way to get the results you found.

As an example of just how much different they CAN sound, ...when i put it all back together and fired it up that wonderful tone was now a ear piercing treble fest. Turns out i used a different brand of 470pf in one place. when i put the one that HAD been there before back in the amp once again sounded smooth and beautiful. Both caps were the same value but different brands. I checked thier tru values with a cap checking meter and they were close.

Which is to say - by the measurement, they were NOT the same.

Nope....it was indeed the brand of cap, not even the type because they were both mica, that made that huge difference !

Hmm. Different manufacturers, different construction inside, perhaps. So all they *shared* was that they were both mica, and both the same nominal brand. Yes? Plus that you had to work on the amp, possibly with side effects, to change them out each time, right?

This is an example of the problems I mentioned. With you replacing the cap yourself, it's basically impossible for you to give a fair evaluation. Not because you're biased, not because you want to pre-pick the results, but because you're human, and humans have preconceptions that they're not only not aware of but cannot correct for even when they know they are doing it.

Yes, I understand how you can (and probably do) feel that I'm spouting nonsense, because you heard it with your own ears. It's been fairly proven that we cannot believe our ears. There is a HUGE amount of processing happening in the brain between the ears and the conscious sensation of hearing. As an example, some sounds which would be clearly audible become completely inaudible when other sounds are present. This is "auditory masking" and it's a well researched phenomena. There is also the well researched tendency of people to hear (and see!) what they're told they will hear and see. It's kept magicians earning a living for millenia.

There is a large body of psychological testing that says that you can't be objective when you know what you're testing and try to express a preference. Our minds don't work like meters. In fact, I suspect that me saying this makes you more determined than ever that you heard a real difference. Even if you're trying to be fair. Humans are like that. It's one reason we invented meters - to get the real stuff, unfiltered by what we think ought to be there.

[daz]

You're talking to a 56 year old who's known about placebo effect for decades and have fought it and been very very aware of it for decades. Trust me....when i say there is a huge difference between those caps there is zero doubt. If you choose to disbelieve me, head on brother. But i can tell you this much.....they are both silver mica or at least both look like it and were advertised as such, and the measurements with the meter showed a value difference no where near enough to begin to account for a noticeable difference let alone the HUGE difference i heard. trust me on this.....the amp went from smooth and mellow w/o a trace of treble harshness and a crapload LESS high end to harsh and bright to the point i couldn't turn the treble more than 1/2 way and couldn't used the presence at all. again, if you choose to believe i'm suffering from a horrible case of placebo, thats your right, but you're very wrong. It shocked me just as much as it apparently would you had you believed me.

[R.G.]

You're talking to a 56 year old who's known about placebo effect for decades and have fought it and been very very aware of it for decades. Trust me....when i say there is a huge difference between those caps there is zero doubt. If you choose to disbelieve me, head on brother. But i can tell you this much.....they are both silver mica or at least both look like it and were advertised as such, and the measurements with the meter showed a value difference no where near enough to begin to account for a noticeable difference let alone the HUGE difference i heard. trust me on this.....the amp went from smooth and mellow w/o a trace of treble harshness and a crapload LESS high end to harsh and bright to the point i couldn't turn the treble more than 1/2 way and couldn't used the presence at all. again, if you choose to believe i'm suffering from a horrible case of placebo, thats your right, but you're very wrong. It shocked me just as much as it apparently would you had you believed me.

I was afraid of that. I was trying to be respectful in my disagreement. I did not mean that you're confused, mistaken, inexperienced, or hoodwinked by placebo effect - which, by the way, is completely real, ask any doctor. It's just not what it appears to be.

Let's be clear here - there is no way to prove that you did NOT hear what you say you heard. First, it's your ears and brain, and second it's logically impossible to prove a negative. I'm not saying that you didn't hear what you say. I'm saying that there is more to the issue than the brand of cap. Reliably excluding everything except capacitor brand takes a fair amount of work, and that work has not been done by simply swapping a cap and listening for a while.

However, I'd be very interested in seeing if that simple change is reproducible. It could be you're onto something that would be a great advantage to all amp users.

If it really was the cap making that massive difference between butter-smooth and wood-rasp harsh, then the difference should be plain as day on a meter or oscilloscope or distortion analyzer, right? It can't be magic and simply not show up on instruments if it's a really big difference, now can it? I don't know of any haunted amps to account for things that can't even possibly be measured.

And if it's that different, then it should improve any amp, not just your particular one, or only to your hearing.

My issue is this - you say you heard a massive difference. OK, fine. You did. My position is that the brand of the cap is not all there is to it. For instance - if it's really mica, fine. But if somehow the "harsh cap" managed to be ceramic, many ceramic caps are piezoelectric and microphonic. They pick up and get back into the signal chain *mechanical* vibrations from their mounting place and that can be resonant in the upper audio register, nonlinear and yes, harshly treble.

I'm not saying that's what's going on, but it is one that I've run into fixing an amp that had suddenly become harsh and nasty sounding. It had a film cap replaced with ceramic of similar value. Damping the vibration with a drop of goo on the cap stopped it, as did replacing it with a film cap.

You're telling me that you hear a massive difference between your amp's sound with one cap over another which differ only trivially in capacitance and in the brand of cap. Good, I agree. You hear it. Now what's causing it? Because I promise you that it's not just the brand of cap. There's something that accounts for it other than two different sources of mica and different manufacturing prep. Otherwise, let's go find the source for the magic mica and make everybody's amp better.

With respect, I believe there is more going on there that simply changing the brand of cap.

[daz]

Fact: the meter showed them to be very close. If i recall i believe it was around 25pf

Fact: there WAS a huge difference.

Fact: i have 3 or 4 of each and they all show the same results

Maybe your ears aren't as sensitive as mine, but to my ears, and NOT due to placebo effect, it was huge. Did i mention the amp literally went from a brightness that made the treble and presence controls like ice pick controls to a tone that allowed me to turn the presence most of the way up and the treble up 30% higher at the same time?! If you still feel i wasn't hearing that please tell me in no uncertain terms and i will end my side of the discussion right now because i won't argue facts any longer.

That said, you should consider other possibilities that don't include me being deaf or oblivious to placebo effect and having zero ability to understand these things. Maybe a manufacturer that produced and sold some defective caps or some such thing. I am NOT saying some such fluke is not possible. But the facts and i mean FACTS are that i did get a huge tonal difference between them, and the meter showed them to be much too close to be the reason for the difference in tone. Past that you can come up with all the possible scenarios you want and i'm happy to listen. But if you refuse to believe what i'm telling you where those two facts are concerned, i'm done discussing this. You probably know well enough from my posts on this forum that i'm not a tech and i'm pretty pathetic when it comes to tube circuits. But i'm not stupid and i'm not young and unwise, and i really hate being told that i'm an idiot, which basically is what i see it as when someone says i'm oblivious to some things like this which i don't need to be a tech to know. My ears are not the ears of a tech, but they've spent decades evaluating guitar tone both as a gigging guitar player and tweaking gear.

Also, try reading my initial post again. If you recall, i didn't just swap caps and think wow, this one sure sounds different. I had the softer sounding one in the amp and at this point i was so thrilled with the tone, mainly because for the first time the high end was so in balance i could jack up all the highs as much as i wanted, that i decided to tear it apart and clean up all the sloppy joints and such. Upon completion i used a different cap in that spot and when i fired it up I HAD ZERO KNOWLEDGE OF HAVING A DIFFERENT CAP IN THAT POSITION! I couldn't figure out why the amp now sounded horrible. Thats HORRIBLE as opposed to THE BEST ITS EVER BEEN. So much for placebo effect. Think about it.

[R.G.]

Fact: the meter showed them to be very close. If i recall i believe it was around 25pf

Fact: there WAS a huge difference.

Fact: i have 3 or 4 of each and they all show the same results

Maybe your ears aren't as sensitive as mine, but to my ears, and NOT due to placebo effect, it was huge. Did i mention the amp literally went from a brightness that made the treble and presence controls like ice pick controls to a tone that allowed me to turn the presence most of the way up and the treble up 30% higher at the same time?! If you still feel i wasn't hearing that please tell me in no uncertain terms and i will end my side of the discussion right now because i won't argue facts any longer.

That said, you should consider other possibilities that don't include me being deaf or oblivious to placebo effect and having zero ability to understand these things. Maybe a manufacturer that produced and sold some defective caps or some such thing. I am NOT saying some such fluke is not possible. But the facts and i mean FACTS are that i did get a huge tonal difference between them, and the meter showed them to be much too close to be the reason for the difference in tone. Past that you can come up with all the possible scenarios you want and i'm happy to listen. But if you refuse to believe what i'm telling you where those two facts are concerned, i'm done discussing this. You probably know well enough from my posts on this forum that i'm not a tech and i'm pretty pathetic when it comes to tube circuits. But i'm not stupid and i'm not young and unwise, and i really hate being told that i'm an idiot, which basically is what i see it as when someone says i'm oblivious to some things like this which i don't need to be a tech to know. My ears are not the ears of a tech, but they've spent decades evaluating guitar tone both as a gigging guitar player and tweaking gear.

Also, try reading my initial post again. If you recall, i didn't just swap caps and think wow, this one sure sounds different. I had the softer sounding one in the amp and at this point i was so thrilled with the tone, mainly because for the first time the high end was so in balance i could jack up all the highs as much as i wanted, that i decided to tear it apart and clean up all the sloppy joints and such. Upon completion i used a different cap in that spot and when i fired it up I HAD ZERO KNOWLEDGE OF HAVING A DIFFERENT CAP IN THAT POSITION! I couldn't figure out why the amp now sounded horrible. Thats HORRIBLE as opposed to THE BEST ITS EVER BEEN. So much for placebo effect. Think about it.

Would you read my last note again, please?
- I said, and I quote:

I did not mean that you're confused, mistaken, inexperienced, or hoodwinked by placebo effect

and

I'm not saying that you didn't hear what you say.

and

you say you heard a massive difference. OK, fine. You did.

and

You're telling me that you hear a massive difference between your amp's sound with one cap over another which differ only trivially in capacitance and in the brand of cap. Good, I agree. You hear it.

What exactly do I have to say to get you to think about it instead of just getting mad? You're reacting like I kicked you in the shins instead of trying to get some more detailed information about a report of mysterious capacitor action. And you won't discuss anything except "placebo effect" when I just made it clear that there are and should be other explanations as well, even coming up with an example from my experience.

I'm trying to find out why this event you reported flies in the face of logic. You're having a one-sided argument.

I have thought about this, for much longer than this issue has been up on this board, and for quite a while now that the discussion is here. That's why I said - and notice - with respect both implied and explicit:

With respect, I believe there is more going on there that simply changing the brand of cap.

That's not said satirically or sarcastically. I believe you hear a difference, and I can't really be clearer about that than rephrasing it *four* times, can I?

Wouldn't it be good to find out *why* you hear a difference if we can? Better than just saying "some caps are magic"?

[daz]

No, i'm not mad. But instead of trying to choose my words carefully so as to not sound like i am, which I usually do and is tedious, i decided to just say it the way i needed to to get the point across at the risk that you'd think i'm mad. I'm irritated to a dgree yes, because when what i know for a fact keeps being questioned it's very frusterating. I know what you said, but no matter what you said it comes across like you don't believe me. Just like you thinking i'm mad, i can read things into what tyou said that makes me believe that you really ARE saying you think i'm oblivious or exaggerating etc. It sounded as tho you're sure that if YOU had heard the amp both ways there would have not been near as much difference because as far as you know it's not possible for a non defective cap to cause that. I tired several of the same ones and i'm telling you it is, whether or not you personally have run across any like this. I just did ! And yes, for the 1st time ever. And to be honest i really believe that the manufacture of those caps is why they sound so different because the fact is they are both within a close tolerance and the only real difference is the manufacture, or BRAND. You apparently haven't seen this. Big foot may exist too, but you you can't assume it doesn't because you never saw one. Oh, and once when walking thru the woods i came across this...........ahhh, nevermind.

[Steve Conner]

There seems to be general agreement that different type caps (ceramic vs polypropelene vs polystyrene vs paper-in-oil etc.) sound different.

As you can see, there isn't general agreement. I personally don't believe it, and I don't think RG does either. But many others do, and there are several threads worth of this kind of bunfight if you care to search the forum.

Silver mica vs. ceramic, and different grades of ceramic, are one of the cases where there may be an audible difference, because some ceramic grades (all of them except C0G, if I remember right) are known to generate a lot of distortion.

But two different silver mica caps should sound the same unless one of them is faulty. Maybe the "smooth and beautiful" ones are old duffers with 10k of ESR or something.

Or maybe the amp has a layout issue that makes the treble response unstable, enough that small changes in value, or even the lead dress and positioning of the cap affects it.

[Groover]

Maybe solder flow can be though of as a subset of lead dress which is going to be different after every component swap??
And/Or... Imagine a solder splash creates a tiny trace across parts of the circuit that goes away at the next tweaking event... or next big jostle of the amp.

These seem to me to be examples of things that might seem "indistinguishable from magic" to quote either Carl Sagan or Arthur C. Clarke, I think.

[Groover]

Regarding distortion generated by a ceramic cap as above described, if that were true, then in the setting of the familiar TBM passive tone stack we know and love, would the distortion be confined to the treble frequency band ?

[trem]

As an example of just how much different they CAN sound, consider what happened to me this week. I had my home brew sounding just like i wanted with a nice smooth high end and i wanted to leave it like that. But because i had experimented with it so much the amp was a horrible slop fest. So i cleaned up every solder joint and other things and when i put it all back together and fired it up that wonderful tone was now a ear piercing treble fest. Turns out i used a different brand of 470pf in one place. when i put the one that HAD been there before back in the amp once again sounded smooth and beautiful. Both caps were the same value but different brands. I checked thier tru values with a cap checking meter and they were close. I had a few of each and tried others to make sure it wasn't due to one of the caps being defective. Nope....it was indeed the brand of cap, not even the type because they were both mica, that made that huge difference ! So if you consider that two of the same value and type could be so different, imagine how different types could be ! thats not to say they always will, or even *usually* will. But they can.

If I can inquire..... So from this one cap change , your amp was a ear piercing, treble fest. Just that one cap and no other. Have you ever experienced this before.?
I am asking because I have changed a lot of parts in a lot of amps, and I have never experienced such a huge change from one component. I have removed "bright caps" from a circuit and experienced a change, and also from changing the value of that cap. But I have never swapped the same value component and heard such a big change. Have you.? Is this the first time in your amp building/tweaking experience that this has happened.?
Thank You

[Hardtailed]

Let's not completely write out the possibility that the "bad sounding" Silver Mica cap had failed...

I have a no-name Silver Mica 470pF go on me (in the tone stack), it became partially leaky and screwed up the top end of the amp and added ugly noises too. When testing it, it seemed perfectly normal, because the multimeter didn't put enough voltage across it to reveal the leakiness.
Turning down the treble pot almost made the problem go away because it added much more series resistance after the leaky cap. You did mention you couldn't put the treble pot more than halfway up...

I don't use the no-name SMs anymore, I stick to the "NOS" Cornell Dubilier parts I found at the surplus store or go ceramic (unless they're not blocking DC). But to be fair, they both sounded pretty much the same... until the no-name started leaking.

And again: it tested just fine
Silver Mica are notoriously unreliable, the silver starts migrating through the mica under the electromagnetic forces. After a while, it creates small paths where tiny little arcs form randomly under high DC. It will test just fine, and it's not a completely open circuit either, but it just doesn't work the same anymore.
I haven't had any problem since switching to the Cornell Dubilier ones