Polystyrene or polypropylene, given the choice?

pjpoes · 27th December 2006, 06:55 PM

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.

jacco vermeulen · 27th December 2006, 07:02 PM

same capacitor value: polystyrene
Especially for RIAA, polystyrene generally has beter accuracy, and sound is better with styrene.

analog_sa · 27th December 2006, 08:29 PM

Quote:

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%.

jacco vermeulen · 27th December 2006, 09:30 PM

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.

Damon Hill · 28th December 2006, 03:38 AM

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.

QSerraTico_Tico · 28th December 2006, 05:09 AM

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)

pjpoes · 28th December 2006, 11:31 AM

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.

jackinnj · 28th December 2006, 12:59 PM

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

MRupp · 28th December 2006, 01:58 PM

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.

pinkmouse · 28th December 2006, 02:09 PM

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.

27th December 2006, 09:30 PM	#4
jacco vermeulen diyAudio Member Join Date: Oct 2004 Location: At the sea front, just under Rotterdam	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. __________________ Looks like Sponge Bob has killed another thread.

28th December 2006, 01:58 PM	#9
MRupp diyAudio Member Join Date: Dec 2003 Location: Frankfurt area	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. __________________ Martin Rupp

28th December 2006, 02:09 PM	#10
pinkmouse diyAudio Moderator Join Date: Apr 2002 Location: Chatham, England	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. __________________ Al I conceive of nothing, in religion, science or philosophy, that is more than the proper thing to wear, for a while. Charles Fort

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27th December 2006, 06:55 PM	#1
pjpoes diyAudio Member Join Date: Jan 2005 Location: New York	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.

27th December 2006, 07:02 PM	#2
jacco vermeulen diyAudio Member Join Date: Oct 2004 Location: At the sea front, just under Rotterdam	same capacitor value: polystyrene Especially for RIAA, polystyrene generally has beter accuracy, and sound is better with styrene. __________________ Looks like Sponge Bob has killed another thread.

28th December 2006, 03:38 AM	#5
Damon Hill diyAudio Member Join Date: Mar 2001 Location: Auburn, WA (somewhere between Seattle and Tacoma) Blog Entries: 1	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.

28th December 2006, 11:31 AM	#7
pjpoes diyAudio Member Join Date: Jan 2005 Location: New York	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.

28th December 2006, 12:59 PM	#8
jackinnj diyAudio Member Join Date: Apr 2002 Location: Llanddewi Brefi, NJ	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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