I need some fairly specific capacitors types, like polyester or silva mica. - diyAudio
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Old 25th August 2011, 12:36 PM   #1
bigwill is offline bigwill  United Kingdom
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Default I need some fairly specific capacitors types, like polyester or silva mica.

Normally this wouldn't be a problem, but I have some PCBs that dictate that I use axial capacitors in certain positions calling for a low value, the values being:

270pF (220 should do)
340pF (330 should do)
500pF (470 or 510 should do)
1000pF
4700pF

The 4700pF and 500pF need a voltage rating of 400v or more, whereas the rest can be rated at 125v or more.

I'm having great difficulty finding suitable parts that aren't ceramic or insanely expensive (1 per cap?)

Does anyone know where/if you can get these types at a reasonable price? NOS should be fine if I can buy a fairly large quantity.
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Old 25th August 2011, 02:17 PM   #2
Cassiel is offline Cassiel  Libya
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I'm also looking for 330pf/500V and 100pf/500V 1% silver mica caps for a phono preamp. Don't care if they're expensive - I only need four.
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Old 25th August 2011, 02:44 PM   #3
TheGimp is offline TheGimp  United States
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Check fleabay. I got several batches of former Soviet Union Silver Mica caps at reasonable cost.

Like these 4700pF at 500V:

4700pF/500v./10% SGM-4 Silver Mica CAPACITORS (6pcx.) | eBay

No affiliation, blah, blah, blah....
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Old 25th August 2011, 02:47 PM   #4
jcx is offline jcx  United States
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if you're looking at NP0/C0G ceramic then they are superior on all measures to polyester, and if dielectric absorption is taken as a "audio quality" indicator they overlap with Silver Mica depending on manufacturer

polyproplylene is common and good, polystyrene would be most people's choice for RIAA filter
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Old 25th August 2011, 03:49 PM   #5
bigwill is offline bigwill  United Kingdom
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I have no audiophool neurosis with using ceramic as long as they don't introduce measurable distortion

As long as they're axial and fit, I'm not too bothered :P
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Old 25th August 2011, 04:27 PM   #6
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Ive successfully used ceramic 4.7 uf coupler caps instead of grainy sounding (from the distributor that way) tantalum electrolytic caps. The caveat is I had a 1.6 V signal, and I used 50V caps. They are non-linear, but less so over only 1/25th of the curve.
That said, mica caps are available, I think from tubesandmore.com AZ, although it might have been triodeelectronics.com IL. Antique radio parts houses specialize in these. There is another radio parts house in Canada, I haven't bought from them so I don't remember the url.
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Old 25th August 2011, 04:28 PM   #7
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Silver mica capacitors/Dipped silver mica

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Old 25th August 2011, 04:28 PM   #8
TheGimp is offline TheGimp  United States
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Avoid X7R and Z5U, they are microphonic due to the use of type 2 High-K dielectrics which are piezoelectric.

Why don't people use polystyrene for coupling?
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Old 25th August 2011, 04:51 PM   #9
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Quote:
Originally Posted by TheGimp View Post
...

Why don't people use polystyrene for coupling?
Maybe because of their somewhat higher inductance and heat sensitivity? Not sure though...
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Old 25th August 2011, 08:41 PM   #10
Cassiel is offline Cassiel  Libya
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Quote:
Originally Posted by Rodeodave View Post
Thanks for the link.
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