View Full Version : Cheap polystyrenes???
10-27-2003, 11:00 AM
Has anybody used PartsConnexion's $1 polystyrenes http://www.partsconnexion.com/catalog/capacitors.html ?
10-27-2003, 11:39 AM
My view is that a person is ( by a long shot ) far better to use any polystyrenes you can find vs going with no polystyrenes ( assuming they are not blown or "punched"). I use surplus Mallory types and like them immensely.
FWIW; All the anecdotal evidence I've seen, indicates that making a quality / consistent dielectric film from this type of plastic is quite difficult . As a result, it seems that QC is a real issue . Also, I've never seen this type of dielectric offered in a "metallized" form ( but maybe I'm not looking hard enough ) .
regards <> Earl K :)
10-27-2003, 12:35 PM
I don't recall ever seeing metallized polystyrene either. I've used Electro-Cap 0.01 uF polystyrene and foils since 1982.
I want to get a batch of AudioCap (RelCap) polystyrene and foil capacitors to compare against since my supply of Electro-Caps is finally running out.
10-29-2003, 05:51 AM
Are the " Electro-Cap 0.01 uF polystyrene and foils " that you use still available as a JBL part ( albiet with a different label ) ?
If so, how much ?
regards <. Earl K
11-02-2003, 04:23 AM
I have used mainly Mallory 630 VDC polystyrene caps, purchased from Newark Electronics, a huge electronics vendor. I purchased an "Engineering Kit", which is a selection of common values, 22pF through 0.1 uF, with drawered storage cabinets, so I could evaluate the caps. In the lab, I tested them for ESR & Da with a General Radio (GENRAD) Digibridge. Those results were consistently excellent, as were (IMHO) the audible results of using them in-circuit.
I also keep an eye on the current inventory of components at All Electronics Corp.
who buy & sell surplus inventories. you never know what they have at a given time, but the prices are always great and often there are excellent parts available for audio (and most any electronic uses).
BTW, I think Newark Electronics used to be Allied Electronics, a name I'm sure many here will remember! Good Luck!
11-02-2003, 12:50 PM
( I do love that moniker )
Thanks for the insight into the Mallory SX caps you've used. :yes:
I'm wondering if you might know why some speaker manufacturers use 100 volt bypass caps while others recommend the higher/highest voltage one can obtain.
For instance, JBL schematics are full of 100 volt caps - including all those acting in the bypass capacity. I understand the use of 100 volt types should offer better transfer/speed characteristics across a more permeable barrier ( ie 100 volt vs a thicker 250 volt foil ). I don't understand the advice to use the higher voltages for the smaller wavelengths - especially when these film/foil type caps are supposed to be "self-healing" .
I'm trying to reconcile these divergent approaches.
Can you offer any enlightenment here ? :)
regards <> Earl K :cheers:
11-03-2003, 02:13 AM
The 100 VDC caps are of course less expensive to make, and according to J. Meter Pontiff of Absolute Sound & wonder cap fame, the higher rated ones sounded less "constrained". But then again, we (I hope) all know here at LansingForms that subjective evaluations are a mindF*** at best, so who really knows. Anyone game for a double-blind test ?
I also use the 630 V polystyrenes so that I can put them in tube amp projects. Mostly guitar & oddball PA stuff, but they do seem (SEEM) (!!!), hehe, to help out in tone control stages.
BTW, in around 1984 I was ginning up, for an enginner at work, a prototype audio stage used just before the A/D in a weather data acquisition system. We were having a lot of problems with Q, jitter, and bandpass ripple inconsistencies using common film caps, silver mica, etc. We found some "monoliythic ceramic" caps that closely resembled 1N914 diodes. I was so impressed with these caps in that circuit that I ran them through my stringent GENRAD Digibride bench tests, and some in-audio circuit listening. Very good. But then again a just bit pricey for price-point margining in large production numbers. But for DIY & high end/botique gear, why not? You could call them PolyRazzMatazz-dielectric caps, and I know SOMEONE will hear something great or bad, based on their buzzword / alphabet-soup descriptions.
. I am surprised to never hear mention of these in audio/audiophile circles. Could be the stigma of cermaics in general?
I shoud revisit experimenting again whit them.
11-03-2003, 02:32 AM
Yeah, the rest of the audio nerds seem to think that the higher voltage caps sound better. Of course they are costlier to make and therefore they do cost more. Kind of funny how the more expensive components are always deemed the better ones by so many out there.
I haven't done any comparisons between different caps of the same design but with different voltage ratings. I usually buy the less expensive ones that will work. For a speaker crossover 100V is usually perfectly acceptable.
Has anyone done this sort of comparison?
11-03-2003, 08:13 AM
Well, subjectively, the closest I've come to any double-blind type comparison is that a lot of the time I don't know what sort of dielectric I'm listening to. This is part of the peril of being a "junk-yard dog" and buying stuff at surplus shops . The upside is that all my sonic impressions are created by what I hear ( or not ) versus being driven by marketing . I've recently formed the opinion on this limited info base , that ; "Size Matters" . Ie; All the caps that I now prefer are generally larger than their comparable brethern. This is of course not very scientific and hardly worth considering as a guiding principle .
I've included a photo of one chnls' worth of RC charge-coupled network. The "grey" caps are 3uf . I've included for the sake of size comparisons, a 3.3 & 6.8uf Solen MPP type. Notice how massive two of the "greys" are compared to the one 6.8 Solen . Like I said , not very scientific . The Grey (RC) type sound like a "soft , well balanced ( timbrally ) Polypropylene sort. There are times when I feel they are just so smooth that they appear as almost "milky" - ie; a softer type of focus. ( These work very well for blending or voicing a large 4" metal diaphragm with papered cones in reflex style enclosures - no, in your face compresson driver ). Based on their size alone, these may be of film & foil construction. Won't know until I actually sacrifice one to the dissection table . They are 275 Volts AC which I'm sure contributes to their larger size.
The "silvered" barrell caps sitting on top of the network are .09uf polystyrenes ( H tolerance ). They are twinned with .088uf MPP types made by F-Dyne ( a PPA code ). I experiment a lot with different "Bypassing" ratios. They all effect the final sort of topend response one ends up with. It's pretty easy to go from "incisive and articulate to soft & airy by just changing these ratios . ( I hear this most in hihats and ride cymbals on jazz recordings ) The G.T., .01uf film & foil PP with .005 SX is really just one flavour - though - really the best place to start and maybe finish if one doesn't like playing around with these sort of things.
Mallory offers from their ancient line of caps a type that is of film & foil construction. This is their "Type PVC" . They are huge for their capacitance capabilities. Most of this PVC product line is Mylar Film & Foil but some higher voltage / smaller capacitance sorts are actually polypropylene. They aren't cheap at $1 to $5. for the sizes in this range - but - in my case, the supply depot is a short drive away. Here's a link into their database search engine for a .1uf PP film/foil type (http://www.e-sonic.com/electrosonic/productsearch/productAdditionalDescription.asp?CategoryName=AC+A nd+Pulse+Film&GroupName=CAPACITOR&GroupID=4091BFB4-E3C1-4343-96C7-24100B3B8450&CategoryID=1BBAF5FB-9650-4238-A35E-3B5597D8A8D4&SearchType=Items&QueryItem=PVC+601&Spacer=&manu=280&part=PVC601++++++++++++++++++++++++). Here's another link for the recommended .01uf PP film/foil (http://www.e-sonic.com/electrosonic/productsearch/productAdditionalDescription.asp?CategoryName=AC+A nd+Pulse+Film&GroupName=CAPACITOR&GroupID=4091BFB4-E3C1-4343-96C7-24100B3B8450&CategoryID=1BBAF5FB-9650-4238-A35E-3B5597D8A8D4&SearchType=Items&QueryItem=PVC611&Spacer=&manu=280&part=PVC611++++++++++++++++++++++++) . I plan on purchasing some of those .1uf film/foil PP and pair them up to "biased" electrolytics to see if they'll fix/tame the usual crunch from the electrolytics. Sometimes this search engine is "off" / other times it boots me off after 4 searches and no purchases - it seems "Cookies" must be enabled. This is a Canadian electronics supply house so it may be of limited use to those outside this country. Handily, the electronics industry strives to maintain these "part numbers" as being unique - ie; use these number on the electronics suppliers' search engine of your choice . NOTE; "Mylar" and film are now used as generic catch all phrases. NOTE: I find Polyester ( Mylar ), Polypropylene and even Polystyrene are usually lumped together under the the "Mylar" heading in most database search engines.
regards <> Earl K :)
11-03-2003, 11:34 AM
The comparison I was looking for was the same type and value of a cap from the same manufacturer but with different voltage ratings.
11-03-2003, 11:35 AM
The comparison I was wondering about was the same type and value of a cap from the same manufacturer but with different voltage ratings.
11-03-2003, 12:36 PM
Hi Mr Widget
Well I guess you got me.. :) I just took your "comparison" word as an opportunity to runoff at the mouth :blah: about something I have actually done.
No, I haven't done the voltage type comparisons and likely can't on my constrained "junk-yard" budget.
By asking the 100 volt question , I was hoping to get some insights myself. According to the color banding of my SX types, I'm using 63 volt and 160 volt polystyrenes.
regards <. Earl K :blah:
11-03-2003, 12:59 PM
Could be the stigma of cermaics in general? Yep, that's probably it.
This link to "The Sound of Capacitors" (http://members.aol.com/sbench102/caps.html) will only add the uphill battle the monolythic ceramic cap type will have to overcome.
regards < Earl K :)
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