Capacitors in a passive circuit - Interesting Read!

[Stratman76]

Folks,

I just got some information that should generate some interest. I don't want to go on record as to who this is from, just let me say the quote below is from a guitar-circuit-savvy vendor who sells ceramic caps. So, there is an agenda behind the quote, however, what I ask of you EE types is whether or not this information is true as it applies to a passive circuit?

Here's the quote:

"For the purpose of passive tone control, ceramic caps are preferred above more advanced dielectric materials such as tantalum, polypropylene, metal films, etc, or even obsolete technologies such as wax paper + foil. Since the final signal does not pass through the cap, but rather is diverted AROUND the cap, the "sound" of a tone cap is actually never heard. The frequency that do pass through the tone cap are removed from the signal via shunting to the ground. This application stands in contrast to filter caps in active circuits such as amps, were the sound heard has passed through the cap, not around it, and thus, the construction quality and dielectric materials may affect the EQ curve in different ways. The point being - what sounds good in an amp has nothing to do with what sounds good in a tone pot."



In essence, what is being said here is that, in a passive circuit, cap TYPES/Materials will have no effect on tone. That assessment is very contrary to much of what I've read here as well as what Dirk Wacker has written for Premier Guitar. Are caps types/materials performance snake oil as they apply to a passive guitar circuit or is this quote inaccurate?

[Kingbeegtrs]

as I've said before "once you understand what a cap does in a guitar circuit you will realize that a ceramic cap from radio shack does the same thing as any boutique cap"

I could be wrong, but my ears tell me I'm right.

with that said, I use Orange Drop Sprague's in all of my guitars...they're boutique guitars that require boutique parts.

[andrekp]

The tone caps in a guitar circuit, as opposed to those in the signal path inside an amp, do not stand between the pups and the jack. The signal going OUT of the guitar does not pass through them. The caps are part of a shunt-to-ground circuit - they simply bleed off a portion of the treble in your pup's signal (making the tone more "bassy"). So, in theory, they shouldn't have any affect on tone.

HOWEVER, it is possible that caps of different composition might leave behind some artifacts, or shunt the treble slightly differently, and might sound slightly different. Seems like a read an article about that once. I would suspect that 99.9% of people would never hear any difference.

Personaly, I just use whatever's handy.

[Kingbeegtrs]

right. In layman's terms, the cap on a gutar circuit sends treble to the ground....this is why the treble bleed mod is so important (100K resistor + .02 cap) on the volume pot.

[uOpt]

That assumption that the sound "doesn't pass through the capacitor" is BS. Sorry. This man applies physics he made up in his head.

I can tell my musicap from the other types blind. Not a big difference but it's there. But let's leave that aside.

The tone pot at "10" is a resistor with 500 or 250 Kohm, and it's in series with the capacitor. That's a first class low pass filter. Even at "10".

Different capacitors reading the same value on a given meter react differently on different frequencies passed in (how steep the flank is), and that means that a complex signal like that from the pickup is influenced differently by the tone pot capacitor, even if the pot is at "10".

There is nothing magic about it. It's just that a 22nF capacitor is not a perfect black box that has a perfect capacitance of exactly 22 nF in every situation and no other physical properties whatsoever.

[jcoloccia]

Whether or not it "goes through" the cap is pretty irrelevant. Different caps have different characteristics, and will impart different characteristics on the resulting signal. To say it another way, the resulting signal is essentially:

signal = pickup - capacitor

so if the characteristics of the cap changes, the resulting signal will certainly change. If this wasn't the case, how would the tone knob ever work in the first place? Of course you "hear" the cap, whatever that means.

What he means to say is that because a large portion of the signal's spectrum is not filtered, different capacitors mostly roll off the higher frequencies in different ways and will impart minimal unwanted distortion to the rest of the signal.

If the cap is being used to AC couple a signal, i.e. all the signal goes through the cap, then the differences between caps is more apparent as the entire spectrum of the signal now has much greater potential for unwanted distortion.

I tend to think the choice of cap on the tone knob is not very important, although you can probably tell the difference. There won't be a better or worse, likely....just different. That would be my guess. Don't use electrolytic since they'll eventually drift with time. So will ceramic, by the way. Most will, in fact. If you don't mind paying $1.00 for a cap, mica is the Cadillac of small capacitors. Should be very stable for a very long time.

[David Collins]

That assumption that the sound "doesn't pass through the capacitor" is BS. Sorry. This man applies physics he made up in his head.

This is of course is an issue many seem passionate about, but I think describing the argument in discussion as "BS" is a bit strong. In fact, his reasoning is correct in that the sound we are hearing does not pass through the cap - anything that passed through the cap is shorted to ground. That said, if different types of caps have differing frequency/impedance curves (even for the same ㎌ value), then there will indeed be a difference in what is left behind, or not run off to ground. So saying that there is absolutely no difference may be a bit strong. A change in capacitor type in a passive tone circuit will certainly not create the degree of difference as it would in something like a filter cap circuit. In this case much of the change in tone can be result of how the capacitor changes the shape of the wave, and not just the frequencies it transmits. That difference does not come through in a passive guitar tone circuit.

For those that want to really know what difference it makes, here's what you do. Pull the cap from a tone control, and wire it to a 3 or 4 position switch for changing the caps in real time. Make sure it can be switched while playing (by the player or an assistant) and make sure it cannot be seen which cap is in the circuit at any given time. If you have a 4 position switch, wire 2 identical ceramics, one mylar, and one Hovland or bumblebee (all identical values) to it. Invite a friend over to check it out. Tell them there are only two different types of caps in the switch, and see if they can determine by listening which positions are paired up with the same caps. Have them make their best guess with the tone at 10, then they can try again with the tone rolled off.

The important part is including the placebo test in here, which is why you have to lie to the tester. A person's expectations can certainly effect their perception, and this is a big part of the test here. You could use four different caps and tell them there are 2, or just 2 different types and tell them there are 4, whatever. No need for them to name which cap is which, just to be able to identify an existence similarities and differences. The point is, if there is a noticeable difference and the tester has good ears, they should be able to pick it out. If you told them there were 2 types of caps and they had to pick which positions matched, but actually used 3 types with only one repeated, they should be able to pick out the two positions that match but perhaps say there's something weird between the others - something doesn't quite match there. Of course if they say positions 1 and 3 are the same (which turn out to be a Hovland and a ceramic) and positions 2 and 4 are the same (which happened to be a ceramic and a mylar), then you can say pretty safely that they couldn't detect a difference. The more people you can repeat this test with, the more trustworthy your results will be.

Main point, if you really want to know what the difference is, you should set up to switch in real time, and blind. Even switching out with alligator clips is not good enough in my opinion - tonal memory fades pretty quick when you're looking at the subtlest of changes, and you should be able to listen for changes while playing. Expectations can also seriously effect one's perception, so the listener should also have no idea what cap is currently in the circuit.

I'll be listening if anyone feels like taking the time to do that. Until then, I won't go so far as to say it has no effect on the tone, but I still hold it is often credited with a bit more change than it actually affects.

[Kingbeegtrs]

Caps in an amp are a huge factor. caps in a guitar are not. With that said, I wouldn't go spending a fortune on caps for a guitar....but I would with an amp.

trust your ears.

[uOpt]

First of all, I have a pickup test harness that I hook up pickups to before soldering them into the guitar's circuit. I posted photos over at seymourduncanforum.

That harness has selector switches with 7-8 different capacitors, 4 of them 47nF. I can directly A/B with a simple flip of a switch.

This is of course is an issue many seem passionate about, but I think describing the argument in discussion as "BS" is a bit strong. In fact, his reasoning is correct in that the sound we are hearing does not pass through the cap - anything that passed through the cap is shorted to ground. That said, if different types of caps have differing frequency/impedance curves (even for the same ㎌ value), then there will indeed be a difference in what is left behind, or not run off to ground. So saying that there is absolutely no difference may be a bit strong. A change in capacitor type in a passive tone circuit will certainly not create the degree of difference as it would in something like a filter cap circuit. In this case much of the change in tone can be result of how the capacitor changes the shape of the wave, and not just the frequencies it transmits. That difference does not come through in a passive guitar tone circuit.



Uh. How in the world is reshaping the wave different from affecting the frequencies you omit?

You realize that the wave is just the addition of the different frequencies?

There's no such difference.



For those that want to really know what difference it makes, here's what you do. Pull the cap from a tone control, and wire it to a 3 or 4 position switch for changing the caps in real time. Make sure it can be switched while playing (by the player or an assistant) and make sure it cannot be seen which cap is in the circuit at any given time. If you have a 4 position switch, wire 2 identical ceramics, one mylar, and one Hovland or bumblebee (all identical values) to it. Invite a friend over to check it out. Tell them there are only two different types of caps in the switch, and see if they can determine by listening which positions are paired up with the same caps. Have them make their best guess with the tone at 10, then they can try again with the tone rolled off.



As I said, I have not only done that in the past, it is my standard mode of testing for all pickups I try.

There's no question that I can tell, at least in recordings, the musicap from the other caps if you'd flip the switch without me seeing it.

It's tougher when it comes to the paper-in-oil versus ceramic since they have the same character (to my ears).



Main point, if you really want to know what the difference is, you should set up to switch in real time, and blind. Even switching out with alligator clips is not good enough in my opinion - tonal memory fades pretty quick when you're looking at the subtlest of changes, and you should be able to listen for changes while playing. Expectations can also seriously effect one's perception, so the listener should also have no idea what cap is currently in the circuit.



I'm not the only one who did this.

You have a point. Somebody who just exchanges the whole wiring harness without being able to get back, and not comparing recordings, will most likely suffer from selective memory and/or mis-identify which of the three things he just exchanged actually caused a certain difference.



I'll be listening if anyone feels like taking the time to do that. Until then, I won't go so far as to say it has no effect on the tone, but I still hold it is often credited with a bit more change than it actually affects.

Well...

Now, as I said, the difference is very small. I find it easier to identify different caps in recordings than during live play (reason unknowns, you'd think it's the other way round).

Also, before I did these tests I was running around telling people it's not possible that different capacitors sound differently. I was wrong, plain and simple, and it's not voodoo, it the very physics of the capacitor. Even if they read the same base capacitance on one given capacitance meter then they still react differently on how steep a flank comes in. In music terms that means the frequency response under varying play inputs is different.

And it doesn't matter at all whether the signal "passes through" or just goes "around it". Now that is something that BS is not a too strong word for. It's all filters, either way and they filter different frequencies differently.

That ongoing battle between misguided physics people who fail to identify the finer actual physical parameters and the voodoo people who think that physics are nonsense is really not helping.

The only thing that helps is trying to use physics as far as you can but keeping in mind that there are (are, not only might be) more physical parameters looming that you don't have on the horizon yet.

[David Collins]

uOpt,

If not clear before, I should make the point that I am not one who argues that cap type has no effect at all, only that I believe many make it out to be a much more dramatic an effect than it actually is.

It sounds like you've done a good share of reliable A/B comparisons, and I don't doubt that you've heard some differences. I actually don't disagree with you on any points you made other than one. When I refer to "changing the shape of a wave", I'm not talking about omitting certain frequencies to effect the end shape of the sum wave. I'm referring to the capacitor's ability to actually affect changes in the form of the waves passing through it, as in softening a square or sawtooth wave, or compressing or squaring off a sine wave. Of course a simple cap is not going to make such a drastic change as to totally square off or smooth out a wave, but just like tubes (to a lesser extent though), different capacitors can play a roll in changing the shape of waves in more ways than simply allowing through or filtering out a range of frequencies.

This is the basis of the argument for caps directly in the signal path having greater influence than those parallel to the signal path. When you hear the signal that actually passed through the cap, these effects will be heard. When the signal passing through the cap is drained to ground, you can't hear whether the wave may have been squared off, smoothed out, or shifted phase by the time it comes out the other end.

So I will agree that the differing impedance curves of different types of capacitors will have an effect on the way a guitar's passive tone circuit sounds. It's just not as much as something like a filter cap, as a capacitor anywhere directly in line between the input and the speaker will have even greater influence depending on other changes it can have on the wave.

[Kingbeegtrs]

uOpt,

When the signal passing through the cap is drained to ground, you can't hear whether the wave may have been squared off, smoothed out, or shifted phase by the time it comes out the other end.

what he said.:)

[jawjatek]

I trust my EE education, my experience, and my ears. I don't believe anything any layman says, especially a vendor, "savvy" or not. Lots of BS, no basis in physics. Laughable, IMO.

[Kingbeegtrs]

I trust my EE education, my experience, and my ears. I don't believe anything any layman says, especially a vendor, "savvy" or not. Lots of BS, no basis in physics. Laughable, IMO.

Well, I don't have an electrical engineering degree, but I do have a pretty good ear. If there is a difference it is only noticed on a graph. YOur insults were totally uncalled for.

[jcoloccia]

Really, for the benefit of getting this right, this whole business of passing through the cap vs "draining" to ground is totally irrelavent.

To put this another way, when you AC couple through the cap you end up with (excuse the loose notation):

signal = (idealFreqResponse*signal) + noise = filteredSignal + noise


when you "drain to ground" you end up with

signal = signal - ((idealFreqResponse*signal) + noise) = filteredSignal - noise

Either way, you end up with a noisy signal.

[Stratman76]

Well, I don't have an electrical engineering degree, but I do have a pretty good ear. If there is a difference it is only noticed on a graph. YOur insults were totally uncalled for.

Actually, King, I think he was dissin' the original quote source who I described as "guitar-circuit-savvy." As for me, I just appreciate your posts. Thank you!

[Kingbeegtrs]

Actually, King, I think he was dissin' the original quote source who I described as "guitar-circuit-savvy." As for me, I just appreciate your posts. Thank you!


I won't lose any sleep over it.

[AndrewSimon]

My ears tell me that there is a difference between ceramic and PIO caps.
(I didn't try any others)
How much of a difference and how important is it it's up to interpretation
but bottom line is that there is a difference.

:)

[Old Tele man]

...if the tests weren't done as "double-blind" tests, they're all just "opinions" and as such are merely subjective and not scientific and thus not proven!

[Tonefish]

I trust my EE education, my experience, and my ears. I don't believe anything any layman says, especially a vendor, "savvy" or not. Lots of BS, no basis in physics. Laughable, IMO.

...and what does this tell you about the OP's question? IS there a difference?

[Curly]

I usually say we spend more time arguing about this than it's worth -- a good quality cap is about $1

here are some comments from one of the most respected tone gurus (now deceased):


... I said, "Never use a ceramic disc as a tone cap in a guitar". Of course the question became what I should use? I don't know!!! O.K., I do know! (You guys, and gals are sharp)
First capacitors come in multitude of types, values, and voltages. The Sprague Black Beauty, also known as "bumble bee caps", are really great. Of course they don't make them any more.
If you have a 50's Gibson, the .02 (really .022) Black Beauty was used. I used an old Fender value, Black Beauty in my Tele. It is a .047, (Fender calls for .05, which is for our purpose, the same thing). These caps were nicknamed Bumble Bee because they had color code bands around a black body. They look sort of like a giant Bumble bee.

Let's get to the important points of choosing a modern cap. First you want the correct value. Of course, feel free to try other values than traditional ones, if you are after something different. Most humbuckers use .022 (.020), and most single coils .05 (.047). You want separate film foil, not metallized types. Mylar and polyester film works better then polypropylene film.
Since pickups put out very low voltage, the voltage rating should not matter, but it does seem to have an affect. Traditional voltage values are commonly, but not always, 200 or 400 volt ratings.
The Black Beauty caps used in old guitars were typically the 400 volt type. Another interesting point is that, if you reverse the cap end to end, it will sound different in use. I jump mine in with test clips, run the tone control through its range, and use directions my ear choose. Also, if you have many of the same type, try a bunch of them. They will vary slightly from cap to cap. It's worth the time to choose one you really like with your gear.

[Kingbeegtrs]

Behold the black beauty: http://www.allparts.com/store/electronics-capacitors-etc-ep-4056-000,Product.asp

is it worth $60? I dunno...

[Curly]

is it worth $60? I dunno...
I don't know either ... I just use orange drops, like you ... they cost $1, and I think they sound better than a ceramic cap.

"Not to get too technical, a capacitor creates a phase angle shift. In a circuit with a resistor (pot) in series with a capacitor, this angle lags or leads, depending on the order of hook up. A personal note, never use a disc type cap in a guitar. They do not resonate right in a guitar circuit. A proper tone control should also add resonant tone as it is used, not simply flatten the high end.

Well, this voodoo is all beyond my personal understanding, so until next time, All the best, Ken Fischer (http://www.ultimateguitargear.com/ken_fischer_chapter2_1.htm) "

[Jim85IROC]

Even in my speaker crossovers, I use cheap caps. I don't hear capacitors and resistors. They filter the signal based on frequency and nothing more. In a situation where the signal doesn't pass through the cap (like a shunt cap) it's even less of an issue.

Inductors are the only component that I'll spend more on if it's in the signal path, and that's simply because smaller chokes have a higher R value which can have an audible effect on the driver.

The issue of the "sound" of items such as caps and resistors will wage forever. There will always be the camp who trusts their ears, and there will be the camp that understands the scientific principals that govern the flow of electrons through the components.

Might one cap sound different than another? Absolutely. But, the reason is simply that the two caps in question won't ever be exactly the same value. There will be some difference no matter how minute, that may or may not be significant enough to be audible.

Then there's always the psychoacoustic effect which it becomes impossible to differentiate between actual audible differences and percieved audible differences, which is why double-blind testing is really the only way to be sure, though that method has its critics as well.

[909one]

I find it hard to believe that the filtering agent... the cap... would have no effect on tone, even if its just shunting it to ground. The remaining signal that is passing out to the amp has to be affected by the thing that it filtering it, no matter how small of an effect it has. Its seems logical to me. You can't inflect change on something without leaving some trace of thing that's inflecting the change.

How big of effect a cap has is another story. Those differences are negligable playing with loud rock band in a crowded bar.

[Kingbeegtrs]

I find it hard to believe that the filtering agent... the cap... would have no effect on tone, even if its just shunting it to ground. The remaining signal that is passing out to the amp has to be affected by the thing that it filtering it, no matter how small of an effect it has. Its seems logical to me. You can't inflect change on something without leaving some trace of thing that's inflecting the change.

How big of effect a cap has is another story. Those differences are negligable playing with loud rock band in a crowded bar.

pot - cap - ground

[Stratman76]

Might one cap sound different than another? Absolutely. But, the reason is simply that the two caps in question won't ever be exactly the same value. There will be some difference no matter how minute, that may or may not be significant enough to be audible.

This, friends, may well constitute a significant factor in a tonal difference observed between caps. I need a capometer! :love:

[Slick51]

Here's a thread/poll we "spent some quality time" with back in 2002.
:horse

Great discourse, everyone had opinions and often the supporting facts. I enjoyed it then; so I repost it here, not to hijack the thread, but thought some of the newer members would like to help :horse!

If not, there are several others around to flog the room temp glue-to-be.

http://www.thegearpage.net/board/showthread.php?t=122507



:horse


Same as it ever was; same as it ever was.

[Rick51]

The standard manufactuing tolerance for capacitors is plus or minus 20%. So that .05 uF cap might actually be .04 uF or .06 uF. I'll bet we could all hear the difference between those two. If they were different types of caps, we would all be saying we could distinguish different types by ear.

BTW, mention has been made by other posters to the effect that different types of filter caps in an amp have a much more audible impact on tone than different types in the guitar. I have to question that. In any amp I've ever seen, the filter caps are part of the power supply - nowhere near the signal. Can anyone explain this to me?

[shane88]

this thread justifies why i don't use no stinkin tone pots :)

[Kingbeegtrs]

this thread justifies why i don't use no stinkin tone pots :)

all of my telecasters are wired with two volumes...no tone.

[Quarter]

I've heard great sounding guitars using all kinds of caps, from cheep to boutique.
That said, I like and use Orange Drops, not expensive, fun to say, and brings back fond memories of days done by ...

[Kingbeegtrs]

Orange Drops are great and they're only about $1 each if you shop around. That's what I use just because they're pretty consistent.

[Stratman76]

Here's a thread/poll we "spent some quality time" with back in 2002.
:horse

Great discourse, everyone had opinions and often the supporting facts. I enjoyed it then; so I repost it here, not to hijack the thread, but thought some of the newer members would like to help :horse!

If not, there are several others around to flog the room temp glue-to-be.

http://www.thegearpage.net/board/showthread.php?t=122507



:horse


Same as it ever was; same as it ever was.

Interesting disclosure but I just realized that thread was in the Amp Tech forum and it seems many of the posts applied to active circuits in amps and effects; not so much passive circuits in guitars. That said, it's 11 pages long and I haven't traversed the entire landscape.

[Kingbeegtrs]

you are correct. Caps are very important on an amp...not so much on a guitar (passive).

[Tone_Terrific]

I have a guitar with a no-load tone pot, probably lots of the readers do, too.

I can hear a little difference in top end rolloff when the pot/cap is then bypassed.

It's a Strat, the difference is insignificant above the microscopic tgp level of analysis.

If you don't use the tone control much, the cap thing is near, but not quite, meaningless, if the tone control is a big part of your style finding one that responds over the range in which you use it is probably important but you need to investigate value as well as type.
Changing the cap value on your treble bypass, that makes a difference and we haven't even discussed the type for that, yet.:drink

[Kingbeegtrs]

I have a guitar with a no-load tone pot, probably lots of the readers do, too.

I can hear a little difference in top end rolloff when the pot/cap is then bypassed.

It's a Strat, the difference is insignificant above the microscopic tgp level of analysis.

If you don't use the tone control much, the cap thing is near, but not quite, meaningless, if the tone control is a big part of your style finding one that responds over the range in which you use it is probably important but you need to investigate value as well as type.
Changing the cap value on your treble bypass, that makes a difference and we haven't even discussed the type for that, yet.:drink

agreed.

[walterw]

Changing the cap value on your treble bypass, that makes a difference and we haven't even discussed the type for that, yet.:drink
hadn't thought of that, but i guess that's one cap that the sound you hear does go through, doesn't it?

[jcoloccia]

You guys are really hung up on this "goes through" vs "doesn't go through", and passive vs. active.

All passive means is that there's no gain components like transistors, i.e. what you put in is always less than what you get out. This eliminates fun possibilities like uncontrolled oscillations and makes the filter design stupid simple. There are passive filters in amplifiers too. In fact, I'm pretty sure the filter caps everyone is talking about are passive filters also, though I'd have to look closely and see what's there.

What's the logic that it should be important that the signal either "passes through" or "doesn't pass through" a components? Either way, the signal is filtered and the characteristics of the things doing to filtering are imprinted on the signal.

I really don't think we should be teaching the next generation a bunch of voodoo and mumbo jumbo. Debate the sound qualities all you want, but get the engineering right.

[ChickenLover]

You guys are really hung up on this "goes through" vs "doesn't go through", and passive vs. active.
Are you saying there is no merit to the idea that different types of caps might excel more/less than another type depending on whether they are 'pass' caps and 'shunt' caps?

Just to give a really simple example (sort of dumbed-down...work with me here ;))...suppose that you've compared ceramic disk to silver mica in a particlar 'pass' cap application. Suppose you thought the SM sounded a little dry and dull in comparison. So does that mean that the SM will sopund dry and dull in comparison when used as a 'shunt' cap? If the SM sounds 'dry and dull' as a pass cap then you might figure that it's not 'passing' as much high end. But if you then use it as a shunt cap...now it doesn't 'shunt' as much high end to ground and the resultant tone should be brighter. Are you saying there is 100% no merit to any of this?

[jcoloccia]

Are you saying there is no merit to the idea that different types of caps might excel more/less than another type depending on whether they are 'pass' caps and 'shunt' caps?

Just to give a really simple example (sort of dumbed-down...work with me here ;))...suppose that you've compared ceramic disk to silver mica in a particlar 'pass' cap application. Suppose you thought the SM sounded a little dry and dull in comparison. So does that mean that the SM will sopund dry and dull in comparison when used as a 'shunt' cap? If the SM sounds 'dry and dull' as a pass cap then you might figure that it's not 'passing' as much high end. But if you then use it as a shunt cap...now it doesn't 'shunt' as much high end to ground and the resultant tone should be brighter. Are you saying there is 100% no merit to any of this?

Of course it matters where you place the cap in the circuit. You can make a low pass filter, or a high pass filter. You can AC couple the signal. You can even make band pass filters (sort of like a graphic EQ).

The sticky point here is this notion that the characteristics of the capacitor don't matter because the signal's not "passing through" the cap. I say that's 100% false. The type of cap may well not matter, but it's for a completely different reason! We can argue that most people can't tell a difference, and that's fine, but this whole business that it matters if it "passes through" and doesn't if it doesn't pass through is setting up another generation of myths, black magic and voodoo.

[David Collins]

You guys are really hung up on this "goes through" vs "doesn't go through", and passive vs. active.


To recap -

1: A capacitor not only selectively transmits different frequencies at different impedances, but can alter the shape of the waves as they pass through as well (i.e., smooth them out, shift the phase).

2: If the signal passing through the cap eventually comes through the speaker, these alterations to the wave may have some effect on the tone. If the signal passing through the cap does not come through the speaker (like being grounded out in a conventional passive tone control), then any changes created in the parts of the signal that pass through the cap will not be heard.

3: This should not be taken to say that changing a capacitor type in a guitar circuit will have no influence on tone however. Different types of capacitors will have different frequency/impedance curves, even if their measured capacitance is the same. Different caps of the same rating (even of the same type), can of course have very different actual capacitance, which can of course account for a difference in tone as well.

I really don't think we should be teaching the next generation a bunch of voodoo and mumbo jumbo. Debate the sound qualities all you want, but get the engineering right.

I believe separating the snake oil from the legitimate claims about effects of capacitors in passive tone circuits has been the goal of many in this thread.

Mainly that -

A: Capacitors can have a larger effect on tone if the signal passes through them on it's way to the speaker, hence the justification for better caps in Hi-Fi audio circuits and amplifiers. Many of the qualities engineered in to certain caps to control or limit things like phase shift in the wave (or often just designs to handle high power and current) are wasted on a guitar, where the most effected portion of the signal is just grounded out.

B: Claims that different capacitor types make no difference at all fall short as well (see 3 above).

C: Different capacitors can make a difference when using your tone control, but it is a subject to personal interpretation and very few people have done blind, controlled comparisons.

There is a great deal of placebo effect that the sale prices of certain boutique capacitors rely heavily upon. This is reinforced by people who put a new tone cap on to their 500kΩ pot which they never move from 10, and swear that their tone has suddenly come to life. In general people hear what they want to hear.

Just trying to give an honest appraisal of how a capacitor change can potentially effect tone. I'm a firm believer in separating the voodoo from the reasonable explanations. John, it sounds as though you have a more thorough understanding of electronics than most here, and I'm certainly open to review if you find flaws in any points I made above.

[jcoloccia]

Just trying to give an honest appraisal of how a capacitor change can potentially effect tone. I'm a firm believer in separating the voodoo from the reasonable explanations. John, it sounds as though you have a more thorough understanding of electronics than most here, and I'm certainly open to review if you find flaws in any points I made above.

The only point that's being lost is that electricity is very much a zero sum game. In other words, if you start with X, when you add everything up (stuff going to the amp, stuff going to ground, etc), you have to end up with X. If there's something going on in the cap, you're going to see it on the signal that's left, i.e. the stuff that hasn't been shorted to ground. It doesn't just somehow get messed up in the cap and then dissapear. If it's messed up going through the cap to ground, then it will be messed up in the signal that's left.

Like most here, I believe tone caps are relatively insensitive to cap construction but not for the reason given. I think it's insensitive because a very small portion of the signal, namely the high end, is affected. Whatever the cap is doing is only going to be apparent on a very small portion of the signal.

Let's remember how a capacitor works. Essentially, it's two plates (wrapped in a cylinder, or whatever, depending on construction). For low frequencies, the plate has enough time to "charge up", coming up to the same voltage as the signal. The cap will not "pass" those frequencies because the signal sees the same voltage as itself...there's no potential so there's no where for the signal to go except down the wire (where there is a difference in potential).

For high frequencies, the plate does not have time to fully charge up so there is current flowing in and out of the plate with extrememly low impedence, and the higher the frequency goes the more it looks like the other side of the cap, in this case ground, so the high frequency signal goes *poof*.

So the proper way to think about a capacitor when used in this way is it's a variable resistor, where the value of the resistor is a function of the frequency. This function is determined by the capacitor's rating and construction.

So even through you're plucking off the signal on the low frequency side as opposed to the high frequency side, what you're left with is a function of the original signal minus the capacitor's response. As the capacitor's response changes, so does the signal that's left over.

I hope that makes sense. If you think about what the cap is really doing at the lowest levels, as opposed to what's passing through where, it should start to make more sense that no matter where you put that cap, it's an integral part of the circuit and it will make any of it's quirks known!

All that said, I typically use mica for no other reason other than their values are very stable with time. Electrolytics and ceramics drift quite a bit. I want my guitars to be as good as the day I built them, 20 years from now.

Amps are a completely different animal. Now you're talking high gains, active components with their own frequency responses, resonances, transformers, power filtering, AC Coupling, high voltages with significant EMF, etc etc. That's totally different and things always become much more critical when you're amplifying them 100,000 to 1 (or whatever it is...that's just a WAG).

Anyhow, I'm glad there are others out there like myself that are interested "lifting the veil" and getting to the bottom of good tone, what really matters, and what really doesn't. Until recently, I honestly thought that cables DIDN'T matter all that much until I A/B some cables for my fiance. She heard an ENOURMOUS difference between cables. I thought it was all in my head. And then I thought I could tell the difference between batteries and wall warts. WRONG. Maybe someone can, but I certainly can't. I'm constantly learning about my own human limits, constantly expanding and contracting what I think I can do :)

[David Collins]

The only point that's being lost is that electricity is very much a zero sum game.

I simply cannot accept that theory, as it would just interfere with my perpetual motion free energy machine I'm trying to patent. :rolleyes:

Really though, your points are very good, but it's the subtleties that make it quite abstract and challenging to reason. It's not the zero sum game in terms of energy that I grapple with, but rather this - aside from slight energy lost to heat as it passes through a capacitor, can the form (but not the sum energy) of a signal be altered as it passes through a capacitor so as to have it's effect only observable on one side of the circuit? Say you made a small passive circuit in which you could maintain constant qualities other than shifting the phase - if you were to put that in place of the tone cap, could you detect a difference in the output of the guitar if the phase were shifted 20° one way or the other on it's way to being bled off to ground? Given that audio signals are a 2-way street, I'll have to consent to your explanation. Still, I have to let these thoughts ferment for a while and reason through a bit more before fully embracing them. Damn.

I think we do agree overall on the end effect anyway. And yes, these discussion do get silly.

[Kingbeegtrs]

http://i10.photobucket.com/albums/a144/lomis/beating_a_dead_horse.jpg

[Tone_Terrific]

Folks,


"For the purpose of passive tone control, ceramic caps are preferred above more advanced dielectric materials such as tantalum, polypropylene, metal films, etc, or even obsolete technologies such as wax paper + foil. Since the final signal does not pass through the cap, but rather is diverted AROUND the cap, the "sound" of a tone cap is actually never heard. The frequency that do pass through the tone cap are removed from the signal via shunting to the ground. This application stands in contrast to filter caps in active circuits such as amps, were the sound heard has passed through the cap, not around it, and thus, the construction quality and dielectric materials may affect the EQ curve in different ways. The point being - what sounds good in an amp has nothing to do with what sounds good in a tone pot."


Close enough for all 'non-intensive' purposes.:D

If we can beat it some more-
Run a square wave into a 'scope, attach a small cap to ground and you will see a slight rounding of the waveform edge. Can you hear that? Hardly, if at all.

Attach a bigger cap and you get more rounding, add a series resistor and less rounding in either case.
Run the wave through the cap and you will get far great variations with frequency and level and cap characteristics. I believe that is what the OP quote was addressing, most especially, with reference to amps that rely on caps to control tone in the tone stack (all of them, eh?) which is a far more complex filter arrangement and the guitar signal is far more complex than a square wave.

So, use what works best for you but keep expectations low with regard to type, as this is not the tonal biggie some sell it as, imo, per usual.

[uOpt]

The tolerance is not the factor that's accounting for all the difference.

I have measured all the capacitors I put into my pickup testing harness.

For 42 nF tests it holds four capacitors behind a switch:
a musicap
one of the paper-in-oil sold here
one randomly picked ceramic
and one ceramic hand-picked out of dozens to have the same actual capacitance as the musicap


I have the values somewhere in case anybody needs them.

The two different ceramics are still sounding the same, although their metered value is different. On the other hand, the musicap sounds different from either ceramic, the one with the same measured value and the other one.

The paper-in-oil is on the other side of the musicap, so an entirely different beast.

Those who say that there's no difference have, by their own admission in this thread not A/Bed different capacitors. What else is there to say?

(no, the difference isn't big enough to make a tralala about in the first place)

[fullerplast]

The tolerance is not the factor that's accounting for all the difference.

That's right.

The reason that caps sound different is because they are not purely capacitive. This is what the model looks like for a capacitor (and this is not even a complete model):

http://img.photobucket.com/albums/v83/fullerplast/cap_model_3.gif

It's the various elements besides the primary capacitance that give a cap it's unique characteristics relative to other capacitors with the same primary capacitance value.

Also, Jcoloccia is absolutely correct that the concept of a signal "passing through" (as in a coupling cap) vs shunting (as in a tone cap) is meaningless WRT evaluating whether you will hear a difference or not. Either configuration can (and will) affect tone and either can be influenced by choice of cap. Just plug in the model and you can see why that is.