Cap info?

[guitarrob]

Hey guys, I have been looking around and doing my homework but wen I look at many schematics around here is see two symbols for caps, either polarized or non-polarized.  Generally there are no notes on which to use for each type.  I have built many circuits in the past but the component list are usually very specific.

So, I guess you can just use electrolytics for polarized right?  Now what about the non-polarized circuit positions. 
Is this more of a preference or are there rules to use a certain type, say a film or a disc for certain signals..paths etc?
I am just trying to figure out what I should be using where so I know which to buy when I am sourcing parts for some projects.

I am running searches in the forums but please feel free to suggest some rules or ideas for which type to use where.

Thanks for any help you can give me.

[R.G.]

To an almost exclusive degree, all polarized capacitors are electrolytic. There are exceptions, but they are quite rare.

So when you see polarity markings, think "that's electrolytic".

You can replace any polarized capacitor with an otherwise equal non-polarized cap and the circuit will work correctly electronically.

In general, no one ever wants to use electrolytic; they are just forced to because electrolytics are much smaller for the capacitance and voltage rating than other types which are non-polarized, and also much cheaper for the equivalent capacitance/voltage. In many places it is not practical to find a non-polarized capacitor small enough and cheap enough to replace electrolytics in the 1uF and up range.

Film caps hold a reputation of being less "colored" than electros and ceramic caps. Ceramic caps have very good properties at high frequencies, so they're better for RF power bypassing.

There are a couple of posts in the FAQ on capacitor picking.

[guitarrob]

Thanks I appreciate the pointers.  When I am looking through component sources there are all these various types and I am not sure which to buy or try...so I am trying to figure out which types are for what.
For instance, if you look you can find, aside from just the ole' metal can electrolytic,
There are:
Ceramic
Tanatalum
Mylar
Film
Disc
Polyester
Metal Film
..etc
So, which to use for anyone position, is it just a matter of opinion or taste?
I appreciate any clarification you can offer.

[iccaros]

In most cases they do not matter, at least with guitar effects.  If you search for capacitors you will find lots of info

[guitarrob]

I mentioned I have been searching also but it helps when people fill in the blanks.

[amptramp]

Thanks I appreciate the pointers.  When I am looking through component sources there are all these various types and I am not sure which to buy or try...so I am trying to figure out which types are for what.For instance, if you look you can find, aside from just the ole' metal can electrolytic,There are:

Ceramic, disc

Ceramic has a very non-linear capacitance versus applied voltage characteristic, which is not what you necessarily want for audio coupling.  Add to that the piezoelectric properties which make them act like microphones and you can get some "interesting" results.  They are OK for things like bypass capacitors where the value is not critical or for small values to roll off op amp stages where the microphonic effect is minimal.  Disc is a ceramic capacitor in a circular disc format.  They are often used for RF coupling or decoupling.

Tanatalum

This is another type of electrolytic capacitor that uses tantalum pentoxide as the dielectric.  They are noted for low leakage but the pentoxide can turn to conductive tantalum dioxide if they ever short out.  This causes a fire in the capacitor, so never use dry-slug tantalum as a bypass capacitor where there is no series resistance.  It is best suited for timing applications where the low leakage is useful and series resistance prevents adding enough heat to convert the pentoxide to dioxide.

Mylar Film polyester Metal film

These are all film capacitors and are considered good for audio coupling.  You will see metallized film as a variant on these where the metal layer is sputtered onto the film and is so thin that local defects will self-heal, but by the same token, they cannot carry much current.

[guitarrob]

Thanks that help.  I am putting together some components for my parts bin for some projects so I am trying to figure out which cap
types I should purchase.  I have made a component list for some projects I would like to build but I think I may also buy some lots so I have an assortment of values and types.

[LucifersTrip]

Thanks that help.  I am putting together some components for my parts bin for some projects so I am trying to figure out which cap
types I should purchase.  I have made a component list for some projects I would like to build but I think I may also buy some lots so I have an assortment of values and types.

for stompboxes, especially as a beginner, honestly, just worry about the physical size and the value....or maybe price. ceramics are literally a penny each, but I've been using  mylar film polyester (3-4 pennies each) more since I have found that they have been much closer to the actual marked values.

this cap kit is a fun, inexpensive project:
http://www.amazon.com/JYE-Tech-Capacitance-meter-kit/dp/B0050ZKXHK/ref=sr_1_1?ie=UTF8&qid=1327959244&sr=8-1

[guitarrob]

I am just ordering a big assortment and I will add parts as I need them.

[DavenPaget]

I am just ordering a big assortment and I will add parts as I need them.

Caps ,
MKP or Metallized Poly Flim or Mylar if you really adore very sharp accuracies and less colouring of course , but for guitar applications ... It's alright to stay away .
Okay , ceramics aren't bad for guitar stuff .
Stay away from them if you are attempting high-end stuff clearly .