Good source for assorted polystyrene caps?

elmegil

I'm particularly looking for 470pF ones, which I managed to forget to order in all the other stuff I got for my Analog Synth in the 21st Century project. I just tried to order them from PLCCenter/Radwell international only to find that they apparently think it's OK to inform me that the prices on some of the other items have gone up tenfold, sorry about that, and oh we're still checking the prices of the other items on the list.

The places i got the other poly caps for the project didn't have the 470's, and it seemed I had to piecemeal them from what I could find with google...

So any recommendations?

marvkaye · Joined: Mar 14, 2011 Posts: 225 Location: Fla

They've got them at Mouser, a quarter apiece in small quantities.

<marv>

elmegil · Posted: Thu Apr 19, 2012 8:23 pm Post subject:

Danke...

L-1 · Posted: Fri Apr 20, 2012 12:00 am Post subject:

I like to use polystyrenes in my builds and order them here:
https://www.rush-on-line.co.uk/cap_forums.html
They have wide assortment values which very hard to find.

marvkaye · Joined: Mar 14, 2011 Posts: 225 Location: Fla

inlifeindeath · Joined: Apr 02, 2010 Posts: 316 Location: Albuquerque, NM

mouser also has two different polystyrene assortments. one with the lower values and another with the larger values

frijitz

You don't need polystyrene any more. C0G or NP0 ceramics work just as well, if not better.

Ian

elmegil · Posted: Sun Apr 22, 2012 6:44 pm Post subject:

You know, I have downloaded the "how to choose capacitors" article from the resources, but haven't really been up to digesting the whole thing yet.

I'm woefully under informed about why I'd pick one dialectric over another. Are there any "quick" references? And something more current, apparently, since the article in question is several years old from the look of it.

I know that the Analog Synth for the 21st Century book is very specific about some polystyrene, some mylar, etc, so....

frijitz · Posted: Sun Apr 22, 2012 9:07 pm Post subject:

elmegil · Posted: Sun Apr 22, 2012 9:25 pm Post subject:

I'm not saying you or TH are one better than the other, I'm trying to point out that since I have little experience to guide me, I am going to go by the advice of those I'm trying to follow. I'm using ASft21C as a primary source of what I'm building right now, so of course I'm going to follow it carefully!

If you can point me at a reference to learn for myself, then I will gain that experience and be able to make good judgements on when I need to follow the book exactly and when I can adjust. I already have enough circuits experience to do that in other areas (e.g. subbing a different counter and zener diode into the MFOS calibration tool), but caps...I have very little idea what's a good sub and what's not. Google has been remarkably unhelpful in this quest for me so far, or I wouldn't bother asking people.

I think your advice is sound. But before starting all this I was unaware that there were anything but ceramic and aluminum electrolytics, and I don't know for certain whether there are other reasons beyond precision why you'd use one particular dielectric over another. Or if it would be a problem to mix them up...after all I already have the specified cap types for the project for all the other values; am I going to end up with a problem because I mixed dielectric types in key locations of the circuit? It's not like I can just pop over to the local store and get the other type if it doesn't work right....

inlifeindeath · Joined: Apr 02, 2010 Posts: 316 Location: Albuquerque, NM

inlifeindeath · Joined: Apr 02, 2010 Posts: 316 Location: Albuquerque, NM

excellent site for capacitor reference http://my.execpc.com/~endlr/

elmegil · Posted: Sun Apr 22, 2012 10:27 pm Post subject:

Awesome, thank you!

frijitz · Posted: Mon Apr 23, 2012 5:45 am Post subject:

elmegil · Posted: Mon Apr 23, 2012 5:49 am Post subject:

I'm sorry, I didn't think I was contradicting you.

What I meant was that I was using it as a source, it said "do it this way", and I didn't have any other reference until you made your statement (which I accepted, did not intend to contradict), so could you please help me find somewhere to learn where else I might be able to adjust or do better, and btw, can you give me more detail on this particular item....is it just the precision or are there other factors involved?

I have great respect for *everyone* here who has almost infinitely more experience than I do (divide by zero and all that), and I would not dream of contradicting you at the level you took offense to.

I'm very grateful for the capacitor reference inlifeindeath posted, and I will work on digesting it.

frijitz

inlifeindeath · Joined: Apr 02, 2010 Posts: 316 Location: Albuquerque, NM

ok then, maybe i will!

Tim Servo

Hi Everyone,

Ian, I don't think the OP meant any disrespect. He was simply going by what was (until recently), accepted practice for choosing critical timing caps in a circuit. Most of the literature out there still recommends using poly or film caps for VCO, VCF and S/H circuits, and it's only been fairly recently that C0G ceramics have been an acceptable substitute. I'm sure we'll be getting "where do I find xxpF polystyrene cap" questions for some time to come. I'm just glad we have SO many alternatives and great sources these days.

Tim (although sometimes the film caps are prettier) Servo

jumunius

Not to ruffle any feathers further, but does the same apply for VCFs and the like? People attribute mystical properties to certain components, and certainly to component choices in VCFs. Even without getting into silly boutique caps, people claim to hear differences between different makes, dielectrics, packages, etc. Does polystyrene have any special "mojo" that other caps lack, or is stability the only requirement for filter performance? Where a VCF calls for polystyrene, is it assumed that a C0G/NP0 would sound as good?

I'd like to add that from the perspective of a builder like myself (as opposed to a designer or EE expert) I would always defer to a BOM unless I am really confident about modifying any of the component specs. I have read Capacitors 101 by Harry Bissell and other docs, but since I don't always understand the circuits that I'm building, it is hard for me to know what dielectric features are important for C4 and C7 in my latest project, for example.

And for the record, I have read Ian's comments about C0G/NP0 several times, have even repeated them when others ask about polystyrenes. So generally now I'm sold, and am buying NP0s in many instances. I just don't have the knowledge to suppose that because NP0 works well for VCO timing, that it will work equally well for in place of some critical capacitor in a VCF.

Hope that makes sense and thanks to Ian and the rest for the wisdom.

L-1 · Posted: Thu Apr 26, 2012 11:00 am Post subject:

I agree, I hear foil in my polystyrenes. Wink

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Scott Stites · Posted: Tue May 01, 2012 6:11 pm Post subject:

Here are some really cute polystyrenes. I've bought from them before. I've heard their foil, too. A bit crisp, with a nuggety glassiness, exacerbated by a rubbery yet non-vulcanated warmth:

http://www.surplussales.com/Capacitors/Poly-Unelco.html

L-1 · Posted: Wed May 02, 2012 10:29 am Post subject:

Yes. I just seen these polystyrenes in Moog 907
http://m.matrixsynth.com/2012/01/moog-907-fixed-filter-bank.html

I liked them, and made minimoog filter clone (photo above). But in final version I used THAT300 transistor pairs. It sounds good, and I plan to make 907 clone with real inductors and polystyrenes. Already bought winding tool and ordered all parts.

Here are some samples of minimoog filter clone with polystyrenes. Just simplest basic patch, two oscillators: saws then triangles then squares, I play funny melody. Then the same but with delay.

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Scott Stites · Posted: Wed May 02, 2012 5:30 pm Post subject:

Sounds pretty good!

jumunius

Hi, so nobody from the pro-C0G/NP0 camp ever really answers this question when I ask it. In a couple instances I've seen it argued that C0G/NP0 are as good as polystyrene, but it seems like people are talking specifically about this with regards to VCO stability, and when I ask "does this pertain to filters too?" I get a chorus of crickets in response. I don't know if this is because my question is really stupid (very possible), but I'd really love an answer.

Ian, or anyone else, in terms of caps for analog filters, do believe that C0G/NP0 are going to sound just as good as polystyrene? Or do you agree that polystyrene imparts a different sound (a mojo even) when compared to C0G/NP0?

I ask because I am trying to figure out if I need to source any parts for my next project (Shruthi 4 Pole Mission) and as it stands I am pretty sure I can build the whole thing with what I already have, except for the 4 polystyrene caps. I have C0G/NP0 for that value but not polystyrene. My pocketbook wants to be convinced I already have what I need but my dedication to quality wants my to sure I am also doing the best for my new synth.

Thanks in advance!

frijitz