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Old 27th December 2006, 07:55 PM   #1
pjpoes is offline pjpoes  United States
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Default polystyrene or Polypropelene, given the choice

Hey guys, I'm working on a few of my phonostages and some mods, and I have a choice of those inexpensive polystyrene caps, which I understand are very good, or Wima poly caps. Which would you use. The polystryrene are much cheaper, but are they as good. The cost isn't great for either part, so let me know.
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Old 27th December 2006, 08:02 PM   #2
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same capacitor value: polystyrene
Especially for RIAA, polystyrene generally has beter accuracy, and sound is better with styrene.
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Old 27th December 2006, 09:29 PM   #3
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Default Re: polystyrene or Polypropelene, given the choice

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Originally posted by pjpoes
inexpensive polystyrene caps, which I understand are very good, or Wima poly caps.

I am not sure if Jacco's recommendation goes for the dirt cheap 'styroflex' caps. IME these are generally quite nasty. Reasonable, inexpensive Riaa-quality styrenes are per example REL RTE 2%.
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Old 27th December 2006, 10:30 PM   #4
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Got me there, A-SA.

I did not mean the really cheap axial styrenes, those go for $0.05 the piece overhere.
NOS Siemens are ok, the rest is garbage.
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Old 28th December 2006, 04:38 AM   #5
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So what's wrong with the cheap polystyrenes? I like to use them for values under 1 nF, else I use silver-mica. I've never tested any of them for leakage.

Any preferences on silver-mica, by the way? For values under 47 pF, they're easier to obtain.
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Old 28th December 2006, 06:09 AM   #6
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Default Re: polystyrene or Polypropelene, given the choice

Quote:
Originally posted by pjpoes
Hey guys, I'm working on a few of my phonostages and some mods, and I have a choice of those inexpensive polystyrene caps, which I understand are very good, or Wima poly caps. Which would you use. The polystryrene are much cheaper, but are they as good. The cost isn't great for either part, so let me know.
Try Russian Teflons. Tolerance is usually better than the spec.
K72p-6 are they called. (the p is written as a pi in Russian)
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Old 28th December 2006, 12:31 PM   #7
pjpoes is offline pjpoes  United States
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Ok these are the very inexpensive polystryrenes I believe. I will attack a picture of what I'm talking about, these are the ones from Parts Conextion, and look the same as what I have. They are 75 cents from them.

I have used the Rel cap polystyrene's before, they are quite nice. I would choose them over the wima, but no room on the board.

Click the image to open in full size.
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Old 28th December 2006, 01:59 PM   #8
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Polystyrenes are out of favor with manufacturers because they have to be soldered by hand, no reflow ovens. You can find high quality devices from TRW at hamfests. Polystyrenes were used in the RIAA networks of the Audio Research preamps (or so they are indicated on the schematic.)

I use WIMA polypropylene in a lot of tube stuff.

In the Marsh/Jung articles which I link below, they rank polystyrene #1 for all round quality/value, teflon #1 for quality, polycarbonate #2, metalyzed polypro #3. If you have to use a large value electrolytic, a shunt from one of these materials is helpful.

Articles to read:
http://www.national.com/rap/Applicat...570,28,00.html
http://waltjung.org/PDFs/Picking_Capacitors_1.pdf
http://waltjung.org/PDFs/Picking_Capacitors_2.pdf
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Old 28th December 2006, 02:58 PM   #9
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Unfortunately there seem to be substantial quality differences in those axial styroflex caps and quite opposing oppinions. I saw a Graaf GM70 phono pre with Styroflex bybass caps in a recent review and it was said to be very musical. A small company in Germany (Steinmusic) are promoting their NOS styroflex caps from NSF and claim that they are excellent bypass caps and are substantially better than comparable types. But Allen Wright, in his Preamp Cookbook, warns from using any axial Styroflex cap whatsoever, and he also refers to the RIAA networks of Audio Research preamps.

I am wondering what really makes the difference to the new “boxed” radial Styroflex caps? One explanation could be the way that the leads are connected. I notice that the leads can either go directly to the foil or alternatively a second flat piece of wire connects the leads to the foil. By comparison, KPs and MKP’s usually have the ends of the foils soldered together and the leads attached to this surface.

I have a number of different axial styroflex caps which I was going to use in an RIAA network, but now I am getting second thoughts and I might actually use other caps instead.
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Old 28th December 2006, 03:09 PM   #10
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I have a reasonable quantity of Suflex polystyrenes that I got in a bulk sale from ebay a couple of years ago. I would recommend them to anyone.
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