Capacitors.. which ones for which applications?

[kepeb]

i think the test mentioned earlier would be pretty interesting (changing out caps of the same rating/value in a blind test)

i was confused at first when i was doing little guitar pedal circuits, there were, as some of you have said already, lots of opinions and statements which were misleading and seemed to have no real basis for the claims.
i just used what i had, and have come to the conclusion that the cheapest is usually what goes in with many manufacturers.

i have often also questioned the tests and comparisons i listen to online.
i think they very rarely give an accurate example of whats going on with the sound because they all have far too many unaccounted variables.

if anyone does ever get round to doing a test like this i think you should have all of that removed to make it fair.

one of the main points people seem to miss is the performance aspect.
the signal should be a re-amped unaffected guitar with the speaker/cab, mic and all the settings untouched inbetween.
i have seen and heard many rave reviews based on 5 second youtube clips of amps pedals, guitars etc.
you need a fair comparison.

the cap one would be very interesting tho.

who's volunteering?

[Phostenix]

Rod Elliot's take on this can be found here:
Cables, Interconnects and Other Stuff - The Truth

[kepeb]

thats some good stuff. if only i could write like that
i'm gonna read the rest probably maybe clear up an issue i have over instrument cable capacitance too.

i still wouldn't even say there is a 'definitive' answer after reading that
i would definitely say those who are on the 'it makes a big difference' side are either:
capable of super hearing
already convinced mentally, and therefore believe what ever they want (or dont want )
or
are in marketing


there is still room for debate tho.
theres always last straw theory... so although the affect of one cap is practically immeasurable, or completely invisible to our standards. thats not to say that the combination of 50+ caps in one circuit wouldn't amount to a register-able difference in how we hear it.

regardless, the whole debate comes from a question about what the audible difference is at the end.
i think everyone can agree that some things sound better than others, whatever you use, somebody's gonna be there to tell you different.

but its also nice to think you have put the best available ingredients into whatever your making. if its better or not is ALWAYS opinion.

i like cheap stuff personally.
i also know electrolytic's have a shorter lifespan.
but those ones on ebay for guitar tone controls, that look like bumble bees are cool. without doubt!

think i'll just stay confused

[Enzo]

LAst straw?

Yes accumulated small differences can add up to a much larger one. However, over the course of an entire circuit, they tend to cancel out, unless oddly ALL of them lean to the same end of their scale.

COnsider that the old Fenders were made with 20% parts. 20% resistors were not uncommon in those days, though they did have the 10% and 5% readily available. But Leo Fender was into "good enough" and didn;t spend the extra money for more precision in the parts.

Of course a 100k resistor could measure from 80k to 120k and be within its specs. Electrolytics were worse. A common tolerance spec was -20/+80%. Seriously. Many Fender schematics say right on them, readings are for reference only and my vary by 20%. The net effect was one amp didn;t sound like the next, depending upon how all the tolerances added up. You could seriously have a discussion about how Joe's new Fender was a "better one" than Fred's new Fender.

[Steve Conner]

What Rod Elliot and Douglas Self said. If you still have any unanswered questions after reading their work on capacitor sound, then propose some experiments and we can see about getting them done. Here are some random thoughts:

1: Actually using live guitar playing in a test complicates things hugely, for two reasons. It varies between tests, and the guitarist is subject to experimenter expectancy. (If he knows his favourite capacitors are in the signal chain, he might play better.) Cancelling this expectancy effect would mean the extra hassle of a blind test, and we still have the random variations.

So the thing to do is put recorded music through a capacitor, or test amps with a 24-bit recording of DI'd electric guitar into the input. (Not sure if this is what a previous poster meant by re-amping.)

2: Micing up an amp is fraught with difficulty, too. If you even stand in a different place in the room, or don't quite close the door properly, it can affect the frequency response. Only by a tiny amount, but tiny differences are what we're looking for here. So another vote for just sticking canned music through a capacitor.

3: The S-shaped curves generated by ceramic caps in Steve Bench's experiment look like some pretty significant harmonic distortion that would very probably be audible in a test. At least as much mojo there as carbon comp resistors. If anyone wants to try an experiment, I suggest we do an ABX test between a silver mica and a ceramic to start.

4: Douglas Self argued that a capacitor can only affect tone in proportion to the AC voltage across it. He backed this up with distortion analysis experiments. A DC blocking capacitor theoretically doesn't have any AC voltage across it, except at very low frequencies. So DC blocking capacitors should not affect tone. However, bright caps, tone stack caps, presence circuit caps, all have significant signal voltage across them in the midrange and treble, that's their purpose. If I were doing tests with amps, I'd concentrate on these capacitors. Probably the bright caps and tone stack treble caps are the most important.

[kepeb]

COnsider that the old Fenders were made with 20% parts. 20% resistors were not uncommon in those days, though they did have the 10% and 5% readily available. But Leo Fender was into "good enough" and didn;t spend the extra money for more precision in the parts.

definitely. your right.
and with the possible drifting of any of those components since as well.
i think its too easy for me to go off topic with this one. but it seems that was the way with the guitars too, i know they are all still cherished and continually copied, replicated and reproduced. but the FACT is, they were jammed together with the least expensive parts and shipped out fast for maximum turnover.

its only possible to measure something to within the boundaries of our understanding or even equipment on a lesser scale.
but to the original question imho is
i think caps are chosen through efficiency/reliability vs. cost and lastly, personal choice.

it would be nice to have a reliable reference set of test results to base that 'choice' on tho. instead of just marketing and bad mojo.

also i was thinking specifically of guitar amps when i mentioned 're-amping' that was to avoid differences in playing, the exact same guitar part played from a digital source is the only way to measure accurately.
reamping is like the reverse of a DI tho. puts the impedence and signal level back to what the guitar preamp would expect from a signal.

[Gollum]

What Rod Elliot and Douglas Self said. If you still have any unanswered questions after reading their work on capacitor sound, then propose some experiments and we can see about getting them done. Here are some random thoughts:

1: Actually using live guitar playing in a test complicates things hugely, for two reasons. It varies between tests, and the guitarist is subject to experimenter expectancy. (If he knows his favourite capacitors are in the signal chain, he might play better.) Cancelling this expectancy effect would mean the extra hassle of a blind test, and we still have the random variations.

So the thing to do is put recorded music through a capacitor, or test amps with a 24-bit recording of DI'd electric guitar into the input. (Not sure if this is what a previous poster meant by re-amping.)

2: Micing up an amp is fraught with difficulty, too. If you even stand in a different place in the room, or don't quite close the door properly, it can affect the frequency response. Only by a tiny amount, but tiny differences are what we're looking for here. So another vote for just sticking canned music through a capacitor.

3: The S-shaped curves generated by ceramic caps in Steve Bench's experiment look like some pretty significant harmonic distortion that would very probably be audible in a test. At least as much mojo there as carbon comp resistors. If anyone wants to try an experiment, I suggest we do an ABX test between a silver mica and a ceramic to start.

4: Douglas Self argued that a capacitor can only affect tone in proportion to the AC voltage across it. He backed this up with distortion analysis experiments. A DC blocking capacitor theoretically doesn't have any AC voltage across it, except at very low frequencies. So DC blocking capacitors should not affect tone. However, bright caps, tone stack caps, presence circuit caps, all have significant signal voltage across them in the midrange and treble, that's their purpose. If I were doing tests with amps, I'd concentrate on these capacitors. Probably the bright caps and tone stack treble caps are the most important.

WORD!!! (again, I'm a self proclaimed newbie, so don't over analize my posts m'kay?)

I'd read that article previously and it truly made sense in my mind, though Rod Elliott is obviously focuse on Hi-Fi amplification, which can be apples to oranges sometimes for us guitarists. But it really made me wonder how much things like filter caps could truly make a difference, as long as it does it's job within spec of course...

It wouldn't be hard to rig up some ON/ON/ON switches to some various caps and see how different they sound. Personally I'd like the test subjects to actually be put through some tests to see how close to spec they are from the get go though.

I think personally though, I'll not worry too much about my caps, and focus more on buying the right type of resistors, which seem to have a more proven tonal difference.

[Howlin' Mad Mac]

Good info here

Found this to be a very good thread folks. I've always had my own thoughts & ideas on this subject & found a lot of wisdom from some of the posts from people who seem to be more in the know & was glad to not see a lot of the usual posts like "if you don't use "xyz" you ain't got sh*t kinda stuff. As for my two cents from somewhat limited but educated experience use polys whenever possible/practical with a prefrence for a quality-made cap (which does not necessarilly mean the most expensive) as their values tend to be more consistent & don't deteriorate over time the way many of the older "more botique" types, especially beeswax & many paper foil & oil types tend to. Second use electolytics only where you have to due to cost or size & here is where you definitely don't want to "skimp" & use the cheapies. The longer life of the better electrolytics always pays in the long run needing to replace them much less often & less tube/transformer failure usually due to caps going bad. That said while "Sprague Atoms" are well made quality caps there are many other caps as well made yet much smaller in size with better temperature ratings & tolerances. Most newer types of Sprague, Illinois & Nichicon electrolytics are IMHO superior to Atoms though I will be the first to admit I can't hear any sonic difference myself though I won't judge those that say they can. When I use Atoms it's because who I'm doing the work for tends to prefer them or in my own builds to be more historically acurate or because using them will help sell the finished product. Now for the very tiny values I prefer silver mica types to ceramic discs as they tend to have tighter tolerances & in my opinion a nicer "look" though again I'll admit not because I find them to sound different. Now to go against everything I've just said... when it comes to coupling caps I've used both Orange Drops & Mallory 150's seeing little if any real sonic difference between them but I will sometimes use foil & oil caps here only because they sound more "round" or less "edgey" (how do you like those descriptive terms) or what I guess you would call "smoother". Again I've come across others that prefer the tone of a good poly cap here. If you decide you would like to try an old school foil & oil cap here, my recommendation would be to use the Mojo Vitamin Q caps only because they're a quality built cap selling for much, much less than any other foil & oil types I've come across & again personally can't hear any difference from other types selling for 2, 3, 4 or more times as much. In conclusion always use quality caps while keeping in mind sometimes (& more often than you might think) more expensive doesn't mean better... just more "snob" appeal. Please feel free to clarify/debate/argue any "valid" points you should care to offer but as stated these are only "my" opinions not etched in stone & handed down to me from the guitar amps gods on high so no need for "name calling" or "finger pointing". We all share a love & passion for great guitar tone & life's to short & precious to be nasty to others... & I promise to treat everyone else with the same respect. Peace.

[Alf]

I have always wondered if you have got a good quality cap then imho the most important thing next would be : how much phase shift does it have ?
Especially when used within the nfb loop. It can cancel out certain frequencies ?
Unfortunately I don't have the time to test this laboriously but maybe somebody already has.

Is there a way of knowing the degree of phaseshift a cap has ?

Please comment on this thought.

Alf

[Steve Conner]

Quick answer: 90 degrees. That's the whole point of capacitors, the (assumed sinusoidal) current through one leads the applied voltage across it by 90 degrees.

More carefully thought out answer: 90 minus the inverse tangent of the dissipation factor (see your capacitor datasheet) so 89.99999 or something. The dissipation factor is a measure of the capacitor's quality, the smaller it is the lower the ESR and dielectric losses, and the closer the capacitor is to an ideal capacitor.

Even more in-depth answer: 90 degrees applies to a capacitor tested on its own. Most capacitors are in circuits with resistors and inductors. The phase shift of a RC or RLC circuit is a well-known function of frequency that you can look up in any electronics text book or Wikipedia.

You would struggle to find a capacitor whose ESR and dielectric losses were anything but negligible, compared to the other impedances in tube audio circuits.

[melvin]

I can't wait to look at data for the audible effects of lead free solder (does SAC305 sound better than SAC105)???

The Pb free solder sounds greener.

[Alf]

Thanks Steve for the explanation , I really thought there might be lots of inferior caps ( phasewise), I remember having seen an article about caps and fourier lines (?) which could be made visible with a scope.

[Rhodesplyr]

You may have a point being fair to ceramic caps, but when the cap in question is a .01, your fave NPOs don;t make it onto the playing field, and by elimination making all the remaining ceramic candidates "bad."

Quite true--and a friend of mine has a Supro/Montgomery Wards amp that's full of Z5U disc capacitors. He loves it.

I haven't been able to come up with a rule for replacing them. Sometimes it makes a noticeable difference; sometimes it makes none.

A Dean Markley amp I have from the 1980s had lots of the tiny cylindrical Z5U caps in it, up to .22uF, and replacing them with film or mica gave the subjective impression of greater clarity and transient response. These are not discs, so I guess they might be the "monolithic" type.

[Tom Phillips]

...A Dean Markley amp I have from the 1980s had lots of the tiny cylindrical Z5U caps in it, up to .22uF, and replacing them with film or mica gave the subjective impression of greater clarity and transient response. These are not discs, so I guess they might be the "monolithic" type.

The thing about replacing a batch of caps all at one time is that you don't really know why the sound changed. It's not a controlled experiment. It could be that the new caps were "better sounding". However, it could be that just one of the old caps was bad. Maybe there was one bad cap leaking DC through to the grid of the next stage and completely screwing up the bias of that circuit.

Some things are just physics that can't be changed. Such as the fact that you can't specify a cap that has 40% of phase shift. One thing that I subcribe to is to use parts that are of good quality so they 1) don't have a high infant failure rate, 2) are not adversely affected by environmental changes like temperature & humidity, 3) are built to have a nice long life and 4) I use ratings that are conservative to #3 can happen. Then the final circuit is tweaked to taste.

Cheers,
Tom
Cheers,
Tom

[imaradiostar]

Some amps I've seen used polystyrene film/foil caps in the tone stack positions where Fender would have used disc ceramics. These caps don't have any outer casing and look like tiny Swiss rolls.

Electrically they're probably no different to a silver mica cap, although they have more self-inductance that makes them a bit useless for RF. I prefer them to silver mica or ceramic for my own amp building, though I'm not exactly sure why

I have a bunch of these that I acquired when a local electronic parts supplier in Nashville went out of business. I've always wondered what the story was- they test "good" and seem to have pretty tight tolerances and say "630 volts" right on the side but I've never quite understood what they were. Sound fine- once again, doubt I can hear the difference in two equal value but different construction caps.

I wonder about a particularly demanding application- what about a big cap used in a conjunctive filter like the output section of some el84 amps? Could this separate one type from another because of the high power dissipated in the cap?

jamie