capacitor types?

[bsmcc2010]

So i posted about building a dynacomp style compressor a few days ago, and now i'm wondering about capacitors for the circuit.

On the schematic i found it gives capacitor values but not the type for each one (film, ceramic etc)

What should i use? i've heard that the more film capacitors than ceramic, the better-but what about electrolytic or other types? is what i think even right?

thanks

[.Mike]

The general notion seems to be...

> 1uF = Electrolytic.
< 1uF = Film, Ceramic, Mica.

Now, when it comes to electrolytic, there has been much discussion about whether to use the aluminum variety, or the tantalum variety. Off the top of my head: Aluminum is cheaper, bigger, has a shorter lifespan, has a wider tolerance range, and is more forgiving to mistakes. Tantalum is more expensive, smaller, lasts longer, and has a tighter tolerance, but if you apply incorrect polarity or too much voltage, they die. Also, when you buy tantalum capacitors, there is a chance you are supporting the oppression, enslavement, murder, torture, and mutilation of the people who are forced to mine tantalum in the Congo.

The same amount of discussion has been had over the Film/Ceramic debate. Film capacitors are generally bigger, more expensive, and are accompanied by mojo. Ceramic capacitors are smaller and cheaper, and in some circumstances that you will likely never encounter or observe, they can distort or become microphonic. They are available in smaller values than film capacitors. Mica capacitors are expensive, and generally used when people have convinced themselves that they can differentiate between the distortion created by their amplifiers, and the distortion created by ceramic capacitors.

And last, hit that search button and type in "capacitor type." What I typed is the quick-and-dirty rundown as I understand it. This has been discussed in depth many times before.

Mike

[digi2t]

< 1uF = Film, Ceramic, Mica.

Just be careful here. I've recently seen a circuit spec a polarized cap with less than a 1uF rating. No voltage rating, but definately polarized. It surprised me, but it was there. Looking at pictures of the original circuit, it turned out to be a resin tantalum looking cap. Probably because tantalum caps are more readily available in < 1uF denominations than aluminium caps.
I'm no EE, but I tend to believe that if that's what was called for in the original circuit, there's a damn good reason for it.

Apart from that, I have to agree 100mph with Mike insofar as sound is concerned. Unless I have other stuff kicking around the shop, for non-polar, I use ceramic caps almost exclusively in all my builds. They're dirt cheap, don't require much space on the board, and easily obtainable. 

[bsmcc2010]

So i'm going to build a compressor pedal, taking a schematic of a dynacomp style compressor and adding some extra stuff, and there are capacitor values ranging from very low to very high.

> 1uF = Electrolytic.
< 1uF = Film, Ceramic, Mica.

would this rule achieve best sound quality?

[digi2t]

As I mentioned before, I'm no EE, but this is what I've learned to date; The bigger (polarized) caps are generally for DC blocking / power filtering, and the smaller (non-polar) ones are for filtering frequencies in the audio path. The most important thing here is to observe where a polar, or non-polar cap is required in the circuit. It has nothing to do with sound quality per se, but EVERYTHING to do with whether your circuit will function properly.... or not.

And before anyone jumps all over me for over simplifing... I know... I'm over simplifing. Just trying to stick to the KISS principle here.

As for sound, as I mentioned before, I stick with ceramics where non-polars are called for, for the aforementioned reasons. Besides, I've tried, and failed to hear any acoustic differences between ceramic, mica, polyester, etc. caps. But then again, years of "crankin' it" may have had an impact here  .

For polar caps, your standard aluminum can will do just fine, unless you run into an application where a REALLY small value polar is called for. Then you might need something a bit more exotic.

Again, sound-wise, highly doubt you'll notice any difference using anything else for a stompbox. Just my 2 bits.

[bsmcc2010]

OK, so you can probably tell i'm new to all this...

how do i know if the cap is polor or not?

[petemoore]

  Yes...
 Plenty of mojo in the capacitor choicings.
 When does it matter ?
 depends on the priorities list...and where the capacitor is/what it will be expected to do.
 RG stated it simply: Reliability...anything else.
 It's the anything that brings up the question 'What?'.
  In this case it is answered: Compressor.
 The input is sensative becuase of what it is [turns up the gain when input 'value' goes low..sustaining a note as opposed to whapping on a full low chord], if choosing to obsess beyond the excellent film types, the input would be...the most sensative.
  It seems to actually matter when designing say a high-spec-mic-preamp or medical measurement device, and since the values are 'tight' and the Uf tolerance requirements are basically 'loose' [to change the voicing requires a substantial Uf adjustment, way more than the tolerance difference between say a .1uf film cap and a .1uf film cap... if a voicing change is needed, moving to .22uf might not even do it, .33uf might be enough to make a percievable voicing alteration.
  I've tried metal film caps before and they seemed to work quite well too [not that much lab-test analysis was performed on them here, only a teeny fraction as much experimentation, testing and usage compared to film caps].
  Perhaps I'm just accostumed to the sound of film caps, I've listened to countless thousands of them in a huge variety of devices....stereos, TV's, monitors, amps...I've seen them and heard 'em ..everywhere.

[digi2t]

OK, so you can probably tell i'm new to all this...

how do i know if the cap is polor or not?

A good starter; http://www.kpsec.freeuk.com/components/capac.htm . Google is your friend.

Thanks for chirping in Pete. Eloquence and simplicity. Both, admirable traits.

[.Mike]

OK, so you can probably tell i'm new to all this...

how do i know if the cap is polor or not?

If you are looking at a physical capacitor, polarized capacitors are usually marked. On aluminum electrolytic capacitors, the negative side is marked with a black band that is usually littered with minus signs. The tantalum capacitors I have seen usually have a little plus or minus size by one of the legs. Film caps and ceramic caps, I believe, are always bipolar.

If you're looking at a schematic, there are a couple of ways. Bipolar capacitors usually appear as two parallel lines: -||- Polarized capacitors will usually have the negative side curved: -|(- Polarized capacitors will almost always have a plus or minus indication next to the appropriate side. If there is no indication, I generally assume it is not polarized, but...

If you are looking at a circuit in front of you, and trying to find out if you need a bipolar capacitor or if a polarized one will do the job, put in the closest bipolar cap you have to the correct value. Measure the voltage from either side of the capacitor to ground. If one side is always higher, a polarized capacitor will work. If each side is sometimes higher than the other, and sometimes lower, you need a bipolar.

All according to my understanding, and all generalizations.

Mike

[bsmcc2010]

So how would i know from this diagram which caps need to be polarised?

[digi2t]

The round pink ones, like C1 are polarized. If you look carefully, one side has a black (more gray actually) band, this is the negative lead of the capacitor. The green ovals, like C2, are non-polarized (or bipolar) capacitors. There is no particular orientation.

[bsmcc2010]

oh ok, awesome

so i need electrolytic caps for the polar ones and ceramic or film for the bipolar ones?

[waltk]

so i need electrolytic caps for the polar ones and ceramic or film for the bipolar ones?

yep.

It's unusual to find electrolytic caps under 1uf, and unusual to find ceramic or film caps over 1 uF.  Caps that are exactly 1uF are readily available in either eletrolytic or film, but the films ones are a lot pricier, and usually bigger too. 

[bsmcc2010]

amazing, thanks

this is a bit unrelated to the topic, but how would i wire C6 and C6a on that diagram?

[.Mike]

C6/C6a are soldered across the lugs of a DPDT toggle switch.

Mike

[bsmcc2010]

ok, so this is for the jangle box...anyway to just bypass that, eg: soldering the wires together with no switch?

[george]

< 1uF = Film, Ceramic, Mica.

Just be careful here. I've recently seen a circuit spec a polarized cap with less than a 1uF rating. No voltage rating, but definately polarized. It surprised me, but it was there. Looking at pictures of the original circuit, it turned out to be a resin tantalum looking cap. Probably because tantalum caps are more readily available in < 1uF denominations than aluminium caps.

Hi, I'm not sure I understand you here.   Why can't a non-polarised cap can be used in place of a polarised cap, provided it can physically fit in the space???   

With a non-polarised cap it doesn't matter which side is more positive than the other?

[iccaros]

< 1uF = Film, Ceramic, Mica.

Just be careful here. I've recently seen a circuit spec a polarized cap with less than a 1uF rating. No voltage rating, but definately polarized. It surprised me, but it was there. Looking at pictures of the original circuit, it turned out to be a resin tantalum looking cap. Probably because tantalum caps are more readily available in < 1uF denominations than aluminium caps.

Hi, I'm not sure I understand you here.   Why can't a non-polarised cap can be used in place of a polarised cap, provided it can physically fit in the space???  

With a non-polarised cap it doesn't matter which side is more positive than the other?

you are correct, but may not exist, or be too big..  As a person with a EE (it is 20 years old and I have been doing digital and computer stuff with it), there is no, not one, circuity that requires polarized caps, but there are some that will blow if you do use them, and some that when design for  audio work with polarized caps, but should not have them as they are not as efficient as non polarized in the same design, c3 in the valvecaster could reverse polarity, not likely to exceed the threshold of the cap, but could, and would block AC  or signal at that instance, when its purpose is to block DC from the output, so a non polarized would be a better design. IF this was for a digital design, it would be fine.  

Just because someone specifies in a design, polarized caps, does not mean it is required, and in the digital world, all this arguing about what they are made of is crazy talk. ESR and Breakdown voltage ratings is what we care about, but in audio when we have the ear aa a  judge, people make all kinds of claims, like some capacitors block dc (note all capacitors up to breakdown voltage only pass AC),

so you can replace any polarized cap with a non polarized with zero issues.. zero..  but you may not do the reverse, as if the polarity of voltage changes on a polarized cap and exceeds tolerance, you will blow the cap.