Question: When to use a box cap over a film cap

[Chris60601]

Hey everyone -

I would love to have something somewhat cleared up or at least, get some ideas as to why we use certain items over others.  While  I understand the whole pf are ceramics, nf are box/film and uf are electros my issues (and Im using that term very loosely cuz its not really an issue, more like an educational lacking on my part). My wish is to know why some of us use box caps for nf and others will opt to use film.

I understand the thoughts of Beavis (he uses box because they are sexy), I get it. There s a certain neat aesthetic look to use them and only them (I prefer to use box caps).  But is it really just a matter of preference as to what you might want to use? I can also see the use of film simply because it has a wider footprint to accommodate the need to span several rows.

So  I guess what I'm asking (because I certainly don't know) is there a "code" to use when mixing both box and film caps and if so, what is it? Or does it really boil down to what a person wants to use.

I'll apologize for asking if this was covered sometime ago and I guess I really don't know if it warrants being called an intelligent question - but it's been something that has been eating at me for a few months now.

Cheers and Thanks!
Chris

[Silver Blues]

Most of the reason that pF are ceramic, nF are film/box and uF are electrolytic is because of form factor. It is a lot easier to get relatively large capacitance in a small space with the electrolytic design, hence why they use it. if you've ever seen uF box caps, they can get pretty big. I'm not actually entirely sure why pF caps and other small values are ceramic, but they do stand up to some abuse so that may be part of it. I've seen pF caps in other materials (I've recently used polystyrene 47pF caps). Honestly it shouldn't really make much of a difference in applications like ours. The box caps are usually also film. Have a read of some of this and see if it helps.

I mix box caps and regular film caps in circuits all the time. Use what's the right value and fits the space.

[rocket88]

internally there is not much difference between box caps and typical film caps, its the external that;s different. the box caps all are uniform in size, shape, and pitch is all the same. if you look at the typical poly caps, like the greenies there is a huge difference in size, shape, and pitch depending on the the value (higher value larger cap). even the panasonic poly caps, which are smaller, the pitch, and size to vary, especially the widths. also, the cost for box caps is usually more then poly.

you can mix and match as much as you want. i typically use the panasonic poly caps, and when i need something in a tight space i use multilayer ceramics, which mark turned me onto. they work great for small builds too, especially 1590a builds, cause they are not only very narrow, but they are super short, and take up like no space.

silver, my understanding for the use of ceramic for small values, pF, is because they are super cheap to manufacture, and can withstand high heat. but, not sure why you would need small values in high heat applications.

[IvIark]

A box cap is a film cap.  Depending on whether I want a common look for all the caps in a build, I tend to use the common short legged box caps when the caps required have a 5mm pitch, although you can get away with a 2.5mm and 7.5mm pitch as well by bending the legs in or out slightly.  I do have quite a lot of box caps now that were originally on a reel and so have the long leads which makes them useful in wider spans where previously I may have used Panasonics or Greenies.

So basically I just use what I'm in the mood for.  Box caps do look cool I think (but only when all the caps in a build are the same colour ), but so does an all Panasonic cap build so it just depends what I'm in the mood for aesthetically.  I don't think there are any audible advantages in any of the different form poly caps which could sway your decision, so just use what you like.

[Frank_NH]

I started out by getting one of those capacitors assortments, which had all "greenies" for the nF range.  I used those in my first build (a Univox Superfuzz clone) and they sound fine.  These days I have standardized on box caps because they fit better especially in crowded layouts, as shown here (a Crunch Box clone).  Plus I like the way they look, especially different color caps!



As IvIark said, I don't think there is a sonic difference between the box and "greenie" types*.  However, when you buy caps, try to get 5% or 10% (5% are common enough) tolerance.  That can be a factor if you're trying to dial in a filter with a specific frequency response.

*There is a LONG thread at FSB where the sonic merits of different caps are debated...if you're interested in that sort of thing.

[benjammin]

Where do y'all source your box caps at? Just individually from tayda? I bought a kit of the greenies off ebay, but I'm running dry on some values. A lot of times when I google for a box cap collection it just matches box with a plastic box filled with greenies..

[rocket88]

just to add about thread over at FSB. i've read through that thread a lot, and one about resistors and other mojo parts, and i have to agree with R.G. Keen, who has explained using electrical engineering and physics, that really there is no tonal difference based on the material of passive components as long as the value is the same, except if it induces microphonics. there is no experimental data to show one material sounds different then another if they are the same value. i've even had people A&B two pedals one with mojo parts and one with the normal panasonics and metal resistors, and 1 out of 15 people guessed right. this hasn't stopped me from doing mojo builds, as it's just neat to have, but i don't think sonically it makes s difference. but, use whatever parts make you happy, as long as the tone is what you want it will be awesome.

what could make a difference is the tolerance of that component. so if you have a 100nF cap that has a 10% tolerance it could be anywhere between 110nF and 90nF, where as if there's a 1% tolerance it could be anywhere between 101nF and 99nF. the greater variation could alter how the effect sounds.

even though i don't use box caps super often, what i do like is when you see a circuit that uses them exclusively it looks like a little city inside the enclosure. so i can just imagine little people moving the signal through the city altering the signal.

[rocket88]

benjammin wrote

Where do y'all source your box caps at? Just individually from tayda? I bought a kit of the greenies off ebay, but I'm running dry on some values. A lot of times when I google for a box cap collection it just matches box with a plastic box filled with greenies..

i've gotten most of my from tayda i know that smallbear has a small kit of box caps that is something like $15 the last time i saw them, so they should also have a large stock of individual values. i've seen them on ebay but i forget how i found them.