Can you help to choose capacytors for crossfeed?
I built that crossfeed > http://www.meier-audio.homepage.t-on...sivefilter.htm
Its said there that "The capacitors are all high-quality polypropylen versions." but I used cheap capacitors and sound is not what it should be.
What is important? high voltage? metallized construction or film/foil construction?plastic film capacitors?Mixed Dielectric,Polypropylene or Polyester / PET?
Local store can sell me these polypropylen caps: http://www.tevalo.ee/cgi-bin/web_sto...=15a3b&lng=est
http://www.yeint.ee/index.php?&PID=p...D=223&LANG=est
Prices are in Estonian currency. 15 eek = about 1$ or 1eur
There's so big choice and I dont know what is best ..not over 10$ each please
Thank you

Polypropylene caps are generally considered the best, though some swear by electrolytics and other more exotic varieties. Voltage level is not critical, as long as it is higher than anything you anticipate experienceing in your circuit. I'm not sure of the differences between metallized and film and foil, but I have used both and was happy with the results in both cases.

What capacitors did you choose ?

Did you make your own PCB layout for this crossfeed ? Don't use electrolyticshere since 1) it's coupling/in signal path 2) The high capacity is not needed.

I used what Jan Meier used, the blue Vishay caps, along with the green Wima FKP2 series at the back of the switch.

All but the Axial polypropylene capacitor on top of the page you linked to will be fine, as long you select the right pin spacing/size.

From the page you linked to, either the SCR or the Wimas would be a good choice. Both are reasonably high quality caps.


Quote:



Film and foil have a layer of film alternated with a layer of foil. Metallized polyprops have a metallic layer sprayed onto the film. Film and foils are generally of higher quality, however they are also larger and quite a bit more expensive for a given value.

Quote:



No PCB, just soldered together all the stuff as short path as I could.. What means coupling? I didn't use electrolitcs at all, used small ceramic things
Quote:



I don't have them here
Quote:



Why these Axial are bad?

Quote:



Larger is no problem as if it sounds better. Should I prefer Film+foil?

Quote:



Depends. If the values are the ones in the parts list you linked to (1.5, 47, and 100nF) these are really small caps and I would go with silver mica or polystyrene caps (people say that silver mica's are the most detailed, but can also be a bit bright). These are both generally higher quality than even film and foil, but are only available in very small values. If, however, your values are higher, then film and foil is a good choice. Keep in mind that while there are inexpensive film and foil caps (Dayton brand from partsexpress in the US or wima FKP) you should expect to pay anything from $20 to $200 per cap or even more for very high quality. Another good option is to look on ebay for vintage caps -- things like "Vitamin Q" oil caps or the like. In small values these are quite afffordable. Last, metalized polyprops are fine caps. Unless your equipment is very high end (i.e., sources and amps in the $1000+ range) you probably won't notice much difference. (I don't know why daroid doesn't like axial polyprops. My guess is that those particular caps are made by Solen, and they should be fine too.)

Quote:



Price, size, and the fact that these type of capacitors (also the like from Mundorf, Jensen just to mention some) are mostly and often used for speaker crossovers. They will work fine, but is a true overkill for this application.
Tola555, what is wrong with the sound of your crossfeed as it is now ? What is the dielectric (polyester, polypropylene, polycarbonate etc.) of the capacitors you used ?

Coupling: basically in signal path.

Quote:



dielectric? I don't know how much they are di but from there > http://www.tevalo.ee/cgi-bin/web_sto...&on=&oe=1&oo=1
its ceramic.
they didn't have others in stock.

Quote:



Ceramics are considered terrible for audio. Look for silver mica caps instead.

Quote:




Silver-mica caps are currently available in up to 22nf aka .022uf aka 22000pf.

A bit on the huge side, almost an inch on a side and about a third of an inch thick. Won't fit in a mint tin standing up.

I used a pair on the high side of a modified linkwitz crossfeed and it sounds pretty good but i don't have another high-z crossfeed to compare it with. As soon as my .022uf polycarbonates arrive I'll make a micro-sized high-z linkwitz with all-polycarbonate caps and compare them side by side.

I bought the only two big mica caps that my local electronics store had, old stock from the 70's. I forget what i paid. It wasn't the $16.99/ea Mouser wants, probably a few bucks each. catch as catch can.

They also had funny looking punk-rocker-mohawk-orange Mallory PVC caps in that size but i have no clue how linear their frequency response is supposed to be. They had nothing to offer me in mylar, polypro, etc, for .022uf, which i found a little odd.

I've seen some ebay sellers boosting their mica caps as "rare" and stating that they're hard to make because mica is a mineral found in limited quantity.

Silver-mica caps are made of the same mineral as pearlite and vermiculite sold by the truckload for high temperature flame retardant insulation at pennies per cubic foot. It's just that so many other capacitor technologies have advanced to the point where the size and cost of silver-mica caps often isn't justified vs. a good quality monolythic or film cap where they're out of critical signal paths, so demand is way down.

They're still the gold standard of temperature stability but a lot of recent ceramics aint far off.

Polystyrene were made up to at least .33uf aka 330nf and i know this because i have a few hundred .33uf 100v epoxy-dipped radial caps that i bought from some dude on eBay for about $0.03/ea.

They make very nice input couplers but only just barely fit in a mint tin standing up with the bottom of the pcb insulated and the cap touching the lid. I haven't actually found another use for them, and i have, you know, a couple pounds of 'em. Want some?

Polystyrene fell from favor not due to no availability of polystyrene films as some people propose, but because of the ban on fluoridated hydrocarbons - e.g. freon - in manufacturing.

Factories that use wave soldering systems print the board with solder paste, place the components, solder the whole board in one pass, and then wash the board. They used to use fluoridated hydrocarbons to wash the boards.

They mostly switched to toluene when the fluoridated solvents were taken off the market, and toluene turns polystyrene caps into little puddles of sticky goo.

These days the shift from rosin flux to water soluble organic flux in mass-manufacturing has obviated the whole issue and polystyrene is making a small comeback.

I don't have silver mica in our country and they are too small capacity as it seems

Quote:



It means the capacitor is in series with an AC signal, such as audio.

The alternative is "decoupling", which usually means the capacitor is across the signal of interest, such as bypass capacitors on IC power pins. A decoupling capacitor prevents some signal from "coupling" further into a circuit. This is why they are also called bypass capacitors: they force an unwanted signal -- such as power supply noise -- to go past some critical section of the circuit instead of through it.

Quote:



Unless you used C0G or NP0 dielectric ceramics, this explains your problem. Ignoring the two dielectric types I mentioned, ceramics are very nonlinear. This means that when you pass an AC signal through them, they will distort the signal. See the links at the end of this article for more information on why certain capacitors are better than others for audio.

iirc, polystyrene was phased out due to its rather low melting temperatures - it made it difficult to work with.

afaik, almost always, foil > film. for film, a film is 'sputtered' on (similar to how they make metal-film resistors), while with foil, a piece of metal foil is used.

afaik, for capacitor dielectrics, PTFE > polystyrene > polypropylene > polycarbonate > polyester. afaik PTFE is quite rare and expensive, and polystyrenes are usually large for their values, so polypropylene is next best alternative.

Quote:



They're a little more prone to melt from soldering heat than mylar but it's not much of a problem in practice. I'm not exceptionally talented with a soldering iron but I haven't managed to melt any of mine.

Mine are rated to perform at 85c just like most general purpose caps, and polystyrene caps are exceptionally temperature stable within their operating temperature range.

You can't hold a hot soldering iron on the legs for two minutes straight, but you shouldn't do that to polypros either.

The EEs I know - some of whom used to work QA on the production lines - tell me it's the way that toluene and other similar solvents reduce them to a sticky mass that made them unusable for wave soldering production lines in the post-freon pre-organic-flux manufacturing world.

Ever drip model airplane glue onto styrofoam?