Best "value" cap to build with???

[cdoggy81]

I'm building a 3 way & have some pretty high # uF caps to use. Using a single high quality cap is very $$$ so I plan to use a few "value" caps in combination with a high quality cap (40uF value cap + 1uF quality cap to get my needed 41uF for the x-over). My question is which brand of value cap should I use from the following list? I have already put them in order from lowest cost to the highest:

Dayton DMPC-10 10uF 250V Polypropylene Capacitor (5%)
Jantzen 10uF 400V Crosscap Polypropylene Capacitor (5%)
Solen 10uF 400V Polypropylene Capacitor (5%)
Jantzen 10uF 400V Z-Standard Polypropylene Capacitor (5%)
Dayton PMPC-10 10uF 250V Precision Audio Polypropylene Capacitor (1%)
ClarityCap PX range Polypropylene Capacitor (5%)

[Helmuth]

About the best dielectric for caps.

auricap
Een non inductive polypropyleen condesator auricap specificeerd dielectrical absorbsion shell not exceed 0.1% (een wima FKP 0.05%)

On Capacitor Dielectric Materials - A Chemist's View
Karl A. Weber, Ph.D.

The fundamental function of a capacitor is to store opposite polarity electrostatic charges on a pair of electrically isolated (insulated) conductive surfaces. The quantity of charge stored on each of these surfaces is ideally directly proportional to their surface areas and inversely proportional to the distance between the surfaces. Such a simple understanding needs to be refined to take into account the effect of the electric field set up between the charged plates on the insulating material. In theory this concern could be avoided by constructing capacitors without any material between: a vacuum.

Unfortunately, such high vacuum devices would be impractical. The next best insulating material is air since it provides limited interacting material and a very high resistance. Air is only practical for the lowest capacitances. Other insulating materials have included: paper/oil, minerals, ceramics, glasses, ceramic corrosion layers on metals and plastic films. Any insulating material used in capacitors of identical dimensions will increase the capacitance with respect to that of a vacuum.

The proportionality constant relating each material's capacitance enhancement over that of a vacuum is known as its "dielectric constant." The dielectric constant is a measure of the extent to which the insulating material's surface interacts with the electric field set up between the charged plates. The constant is dependent on two molecular level properties: the permanent "dipole moment" and the "polarizability" or the induced change in dipole moment due to the presence of an electric field. The permanent dipole moment is the average over the various dipole moments given rise to by structural charge density differences over intramolecular distances. The charge density differences result from the electronegativity differences between the various atoms which comprise the molecular structure of the insulator. Polarizability is the property which arises from changes in the molecular electron distribution induced by the applied electric field. Both of these properties contribute to a net field, of opposite orientation to the inducing electric field between the charged plates. The larger the dielectric constant, the greater the induced field on the surface of the insulating material or "dielectric."

In A.C. applications, where signal handling is involved, factors which affect the rates of both charging/discharging become key issues. Even though dielectrics with larger constants allow smaller size/capacitance devices, the properties of such dielectrics contribute deleteriously to audio signal processing. Where dielectrics with larger constants are employed, their larger dipole moments/polarizabilities interact more strongly with the inter-plate field, resulting in a stronger induced opposing field on the dielectric. When a capacitor is discharged across a load the polarized dipoles thermally relax in a statistical manner, exhibiting a time decay, observed as a tailing decay of residual current as complete discharge is approached. If the capacitor is suddenly discharged, allowed time to set and then shunted across a load it will discharge a residual current (of the same polarity as the initial charge). Upon dissipation of the bulk of the charge, the polarized dipoles on the dielectric thermally relax, which results in a residual charge on the plates. The residual charge from dielectric relaxation is known as the "dielectric absorption." When an audio signal is passed through a capacitor the dielectric absorption prevents full charging and discharging of the capacitor at the frequency of the alternating current signal. When the signal reverses the charging on the plates the dielectric absorption presents a lagging current of the former polarity, a hysteresis effect results. This effect becomes more acute with increasing frequency.

Obviously now, not all dielectrics are equal. In audio applications it is desirable to seek the insulating material with the lowest practical dielectric absorption; hence, lowest dielectric constant, barring size and economics. Dielectric materials can be classified based on their relative polarity/polarizability properties, which the dielectric constants and dielectric absorptivities parallel.

What follows is a qualitative categorization of dielectric materials in decreasing polarity/polarizability based on chemical structure considerations (Dielectric constant data "K" given when available):

I. Metal oxide corrosion layers (electrolytic capacitors):

1) Tantalum oxide (K = 11)
2) Aluminum oxide (K = 7)

Both consist of polar metal oxide bonds possessing large permanent dipole moments, polarizability factors are negligible.

II. Ceramics and Glasses:

1) Ceramics - typically alumina or aluminosilicates (K = 4.5 - thousands)
2) Glasses - typically borosilicate (K = 4-8.5)

Similarly, the polar inorganic oxide bonds in these materials have large permanent dipole moments.

III. Minerals:

1) Mica (most common) - an alkali metal aluminosilicate, hydrate (K = 6.5 - 8.7)

Same as II.

IV.

A. Polymer films - functionally linked - ranked in order of decreasing functional linkage polarity (brackets "[ ]" indicate guess based on functional group polarity):

1) Polyesters (ex. Mylar) - ester (K = 3.2 - 4.3)
2) [Kapton - ether and imide]
3) Polyamides (ex. Nylon) - amide (K = 3.14 -3.75)
4) Polycarbonate - carbonate (K = 2.9)
5) [PEEK - ether and ketone]
6) [Poly(phenylene oxide) - PPO - ether]
7) [Poly(phenylene sulfide) - PPS- thioether]

The members of the above list can essentially be ranked based on polarity considerations alone, though polarizability considerations are significant for the latter members of the list.

B. Polymer films - carbon chain backbone - ranked in order of decreasing attached-group polarity/polarizability:

1) Poly(vinyl chloride) - PVC - chloro-substituted (K = 3.3 - 4.55)
2) Poly(chlorotrifluoroethylene) - chloro- and fluoro-substituted (K = 2.48 - 2.76)
3) Poly(p-phenyleneethylene) - Parylene - exception to list phenyl ring in backbone (K = 2.65)
4) Polystyrene - phenyl-substituted (K = 2.54 - 2.56)
5) Polyethylene - essentially unsubstituted carbon chain (K = 2.3 - 2.37)
6) Polypropylene - methyl-substituted (K = 2.1)
7) Poly(tetrafluoroethylene) (ex. Teflon) - perfluoro-substituted (K = 2.0 - 2.1)

[Helmuth]

To rank the first two members of this list consideration must be given to both, polarity and polarizability considerations. Polymer 2) is adequately fluorinated to cancel C-F bond polarities, the C-Cl bonds are the prime contributors to its polarity. Since C-F bonds are not verypolarizable, polymer 1) has a higher polarizability than polymer 2) and a correspondingly higher dielectric constant. Polymers 3) and 4) can be ranked primarily on their polarizabilities, which are significantly higher due to the pi-electrons in their phenyl moieties. Polymers 5 and 6 differ mainly in that the methyl substituted chains are less prone to wrap against themselves due to steric methyl-methyl interactions. In Teflon the C-F bond polarities essentially cancel since it is completely fluorinated, and given that the C-F bonds are not very polarizable it exhibits overall less polarizability than its unsubstituted carbon chain analogue, 5), polyethylene.

Based on polarization/dielectric constant considerations for minimization of dielectric absorption, the best films for audio applications are teflon and polypropylene. Runners up would be polyethylene and polystyrene, based on these considerations alone. Throughout this discussion, I have assumed that dielectric absorption and the dielectric constant are directly correlated.

Apparently, when polarizability factors predominate, the time constant for relaxation of the field induced dipole is critical. Otherwise, one would expect polypropylene to have a lower dielectric absorption than polystyrene, which is not the observed result. This can be reasoned by re-examining what is being polarized by the field in each. In the case of the polystyrene, the pi-electrons in the aromatic rings (which have been modeled, in the past, as a "free electron gas") can orient electronically, with less mechanical change in the polymer structure. Hence, it can relax faster. In contrast, the polarization of polypropylene involves more mechanical change of the structure, and hence a slower relaxation rate.

Clarity SA Voor de clarity SA word een dielectrical absorbsion gespecificeerd van < 0,1% (wima FKP 0,05%)


The SA range of capacitors is now recognised as one of the best audiophile components currently available.

Specially developed to meet the needs of the professional audio engineer in both hi-fi and studio monitoring, these components are the result of extensive consultation between the audio industry and ClarityCap.
The capacitors are hand wound using a 10µm(630Vdc) rated polypropylene film. Following a special heat treatment cycle,insulated copper terminals are hand soldered to give the best possible connection.

The inherently low dissipation and dielectric absorption factors of polypropylene allied with an excellent mechanical stability results in an extremely detailed sonic performance. The construction also results in a low self-inductance and ESR and the devices are highly stable with regard to temperature and frequency.
Tape and resin colours are flexible with options shown in Custom products. Unless specified, capacitors would be supplied with black tape and black resin.




Wima polypropyleen MKP, FKP is
Dielectric:
Polypropylene (PP) film
Capacitor electrodes:
Aluminium foil and double-sided metallized plastic film
Self-healing
Internal construction:

Deze constructie lijkt me ook non inductief.
Dielectric absorption: 0.05%



My choice Mündorf Tinfoil polypropylene.

The tin as a conductor has a 10 times lower resistance than normal foil capasitors. Resulting in a extreme small tanges delta.
These caps are designed for loudspeaker XO.
But I use them also in my tube amp because off their excellent electrical behaviour.

And they are not extreme expensive.

http://www.mundorf.com/english%201.1/kondensatoren.htm

Over here the most common professional quality MKP is WIMA. And with the lowest price due its popularity.
wima

[dpuopolo]

Radio Shack has .01, .1 and 1.0 metallized film 250 V capacitors that are really cheap and sound great.

You'll be surprised how good these sound....

[Cloth Ears]

You might also want to look at the Mundorf "audiophile" M-Cap (white with red writing). We liked them due to their 'lack of' sound when we tried them, compared to some others (more expensive) that coloured the sound a little (or a lot).

Best thing is to find an application where you already have a small value cap - buy replacement values of all the caps you want to use - test them all and then resell the ones you don't want on eBay. You don't lose that much and you can satisfy yourself that you have the one you want...

[JohnL]

If you are in Orlando, you should know where Skycraft Surplus is. If you look in their cap section (the one in the back where all the oil caps and electrolytics are) there are some (or were the last time I checked) 40uf caps that are ~ 1.75" x 2.25" x 2.75" square with a couple mounting holes. Markings say EC MP9-11192 K, 40.0±10%,450VDC. Those sound very good and are a bargain at $4.

[JohnL]

This is what they look like.



Looks like Skycraft is cheaper than this place in Nebraska, but here's the info on those caps.
Capacitor

[Helmuth]

This is what they look like. Looks like Skycraft is cheaper than this place in Neraska, but here's the info on those caps. Capacitor

looks like very good tip.


mundorf up to 330uF mkp

[Cloth Ears]

Originally posted by Helmuth
looks like very good tip.


mundorf up to 330uF mkp

Seconded! Those look interesting - let us know your opinion if you get any...

And, yes, those were the ones I was talking about.

[cdoggy81]

A lot of good info here guys & I thank you all!

I'm in Gainesville now but still go to Orlando all the time. I know Skycraft well & will check it out next time I'm there. For the price it can't hurt right. I'll do the same with the Radio Shack caps too. What size do they go up to?

The Mundorf caps looks good but for the price I think the ClarityCap is a better buy... This based on best price I have seen to buy them here in the US is:
http://www.partsconnexion.com/catalo...itorsFilm.html

Tony G had some very good reviews about all these caps except for the Daytons which I assume can't be that much different than a Solen/Axon/Jantzen...

http://www.humblehomemadehifi.com/Cap.html

That being said I think I will go for the ClarityCap.

Again, thank you all for your time to post on this & help me out