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[bushwick]

Hi folks. Lookin for a source for the following values with normal prices.

Thanks Mucho!!!!!!!

22pf
33pf
47pf

The usual suspects have, none, some, or don't carry them. Web searches yield the same. Anyone have a good place for these?

Best,
josh

[bruno putzeys]

Polystyrene foil is no longer made. The mfgs that still make ps caps have simply bought a large stock of the stuff. No applications I know of call for ps that won't work equally nicely with polypropylene or even NP0 ceramic.

[Bogic Petrovic]

bushwick wrote on Thu, 09 December 2010 17:59

Hi folks. Lookin for a source for the following values with normal prices. Thanks Mucho!!!!!!! 22pf 33pf 47pf The usual suspects have, none, some, or don't carry them. Web searches yield the same. Anyone have a good place for these? Best, josh

I don't know if this will be "normal prices" for you but I can try  
22pF      http://uk.farnell.com/lcr-components/fsc-160v-22pf-1pf/capac itor-22pf-1pf-160v/dp/9519971
33pF      http://uk.farnell.com/lcr-components/fsc-160v-33pf-1pf/capac itor-33pf-1pf-160v/dp/9519980
47pF      http://uk.farnell.com/lcr-components/fsc-160v-47pf-2-5/capac itor-47pf-160v/dp/9519998

All others are here.

Hope this helps


Boggy

p.s. BTW, Bruno is right!

[John Roberts {JR}]

I don't know if this is any help, I have some 24 pF and 43 pF polystyrene caps laying around in my back lab (left over from the '70/80's)  if you only need a handful.

Sorry no 33pF or your exact values.

I'll also vote NPO for production quantities at those small values.


JR

[Geoff_T]

bushwick wrote on Thu, 09 December 2010 08:59

Hi folks. Lookin for a source for the following values with normal prices. Thanks Mucho!!!!!!! 22pf 33pf 47pf The usual suspects have, none, some, or don't carry them. Web searches yield the same. Anyone have a good place for these? Best, josh

Hi

I know this is bordering heresy, but the frequencies affected by those capacitors are so high you might consider ceramic type.

These are a no no at audio frequencies but I doubt that you would hear the difference around 22pF

[John Roberts {JR}]

Geoff_T wrote on Fri, 10 December 2010 11:21

Hi I know this is bordering heresy, but the frequencies affected by those capacitors are so high you might consider ceramic type. These are a no no at audio frequencies but I doubt that you would hear the difference around 22pF

Without knowing the application I would be reluctant to offer such advice.

I used similar values to terminate phone cartridges and make audio frequency filters back when I still did hifi poop..

While those values may be executing LP poles at the top of the audio band, if they suffer from nonlinearity (like voltage coefficient) they could generate audible IM distortion products down in the passband, from the wrong stimulus.

NPOs are ceramic, small and cheap so not the worst choice if he can't source polystyrene.

FWIW I loved polystyrene and used them whenever I could back in the day, but they were not very robust for large scale production.  I even have some old .1uF polystyrene caps back in my lab, about as fat as my thumb.  

JR

[bruno putzeys]

FWIW, having measured many caps in filters, NP0's appear to be perfectly linear. I've seen film caps distort as much as -90dB but never measured any distortion at all from NP0.

[John Roberts {JR}]

Good data. Better than 90 dB down should be good enough for government work.

Just for chuckles what kind of film caps did you measure? I hope there was some difference between film types, or we wasted some money over the years.

JR

[sodderboy]

I will still hoard my stash of polysty's for vintage Neve refurbs.  Is it just that other alternatives did not exist at the time?  I cannot use what RND is using now as an answer. . .
Mike

[Dan Kennedy]

I don't think there were any good ceramics way back.

RF bypass yep, audio no, too many dielectric effects.

Silver mica's were available with pretty good performance but at many times the price.

I imagine the low cost of the polystyrene's and good performance were the reason they were the choice for small value parts.

[Bogic Petrovic]

bruno putzeys wrote on Fri, 10 December 2010 19:58

FWIW, having measured many caps in filters, NP0's appear to be perfectly linear. I've seen film caps distort as much as -90dB but never measured any distortion at all from NP0.

I really appreciate this information! Thank you!

[bushwick]

Thank you all(!!!!!!) for the excellent info. Ceramic it is!

Super best,
josh

[maarvold]

This might be a dead end, or there might be some detective work involved.  Evidently a company called Electrocube acquired the company below a few years back.  But at one point in the late 90's I spoke to a guy named John there (owner?) who told me that they made very high quality polystyrene capacitors and, when they stopped manufacturing the polystyrene film he bought up something like 65% or the remaining supply.  He also felt that polystyrenes were among the best types of capacitors available, as long as you could deal with the physical size.  

SOUTHERN ELECTRONICS CO., INC.
726 South Flower Street Burbank, CA 91502 (818) 845-2458

[Jim Williams]

I was told by Bas Lim at Reliable capacitors (MIT MultiCaps, AudioCaps, etc,)that there is one source for polystyrene film left. They were out of production for a couple of years but it's now available.

The excellent Rel Cap RTX polystyrene film series is still available, some of the finest ever made. The MIT 10 section versions are also available to 1nf.

They don't make these caps below 100 pf. Besides mono ceramic NPO caps, silver micas are an excellent choice for these smaller values.

[johnR]

On the subject of capacitor distortion, Cyril Bateman's articles on "Capacitor Sounds" are an interesting read:
http://main.diycore.com/index.php?categories=Passive%20Compo nents