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125.237.16.23
In my recent experiments with these caps (in combo with various R values)trying to create a shunt filter that actually improves rather than just changes the sound I discovered to my surprise that these caps are actually wound rather than stacked. They therefore have an inner and outer foil. This indicates that it may be best to orient the cap with its outer foil to the neutral terminal. I also noted that caps from different batches did not necessarily follow any convention in terms of the outer foil corresponding to the direction of any printing on the case...
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IMHO FWIW, Wima caps are best avoided from a sonic degradation point of view. They tend to introduce a harsh, nasal, metallic sheen to all circuits, even when not directly in the signal path. My ears are hyper-sensitive to the Wima "sound".
I've read several threads on German audio DIY forums, plus a couple in English, where just about all savvy German audio guys disavow any recommendation of that brand of capacitor. Won't so much as touch 'em. Several years ago one German DIY poster suggested the reason for Wima's poor sonics is the company's inadequate method of internally connecting leads to dialectric/film/foil. Maybe?
I also know of a roaring trade in "cheap Wima caps" out of Asia. The Asian-sourced Wima's I've seen/desoldered don't appear to be authentic, but I have no means to prove or disprove this (and little interest, to be sure).
Once again, YMMV, JMTCW, each to their own. Enjoy the music!
spindrifter
I've experimented with several types of AC-rated (both X and Y) capacitors for noise suppression. The Wima MP3 (metallized paper) give far superior results to any other type or manufacturer I've tested. Rifa makes metallized paper suppression caps, but these give a harsh sonic result. Synthetic dielectric films all have strong sonic flavors that are obvious when removed.
While there may be better caps for sonic results, it is absolutely necessary in my view to use only caps rated for AC line exposure. The risk of fire is too great to do otherwise.
What caps do you find superior for AC noise suppression, and how do you load them with resistors?
If that works best for you, stick with 'em, Al.
I haven't bothered going to great lengths regarding AC noise suppression options. Maybe I should, given your findings?
spindrifter
It only takes some time to see if you have non-audio appliances that affect your audio system through RF noise. My revelation on this whole business came when a power surge killed our satellite receiver/DVR. The sound was much improved as long as we did not have one.
The method is to listen carefully, turn off and unplug a candidate appliance, and listen again. Use a good recording, obviously, that will reveal treble and midrange problems.
one lives in medium-high density housing. It helps that we live way out in the country (tranquil village of about 40 homes.)After using a few AC filter devices over many years, I decided to experiment by going back to basics. That is, no active/passive filtering between mains wall socket(s) and AC cable entry into audio components. I assembled an ultra-thick-copper-rail mains distribution board and invested in Cardas and Zu Audio mains cables.
Inside some components I installed small-medium AC line chokes and improved RC networks on outputs. Also I modded components with optimal power rail and other filtering, but with minimal device count, plus shortest signal and DC path, allied to premium internal cabling. One theory is that RF/inductance is best squashed/quarantined nearest active devices.
Also I've found that chassis-lined internal shielding can be most beneficial, having tried ERS and adhesive pure copper tape.
What I've found where we live is that music dynamics, in particular, seem to have an unrestrained dimension which was not as pronounced with previous external active/passive mains filtering. I'll be sticking to this "unfettered" method now.
Nonetheless, Al, I certainly agree that mains and other forms of unwelcome electrical/telecomms/wireless/extra-terrestrial interference are best avoided. They can affect audio performance drastically. Enjoy the music!
spindrifter
Edits: 05/04/10
Almost all caps are wound....very few stacked foils. So, yes indeed, they sound best with the outer foil oriented to the lower potential. I mark all my Wimas/Rodersteins/Vishays/etc. this way. I also replace the steel leads on any caps with 6N copper leads.
Never verified this but I've always "assumed" the outer foil was located on the end/side closest to the the vertical black line. Apparently untrue.
Yes correct, the printing including the line is random. If you managed to buy all your caps from the same batch you may be fooled into thinking it is consistent.All my caps of one value were oriented the same way by reference to the printing, as soon as I measured some different values I found this was not consistent.
Here's a copy of a post from another forum by Jonathan Carr which might help those (including me) who don't happen to own an o-scope in determining the outer foil orientation. Haven't tried this but I will soon.
"As long as the film cap value is not too big, you can use a precision AC millivoltmeter to check the polarity. Ground yourself, hold the cap body in your bare hand, hook up the millivoltmeter input to the cap leads (first with plus to one lead, minus to the other, then flip the leads) and look at how much the needle swings (you may need to switch the range setting on the millivoltmeter). The polarity that gives the lower needle swing is the "right" one.
Mark the film cap, and use it thereafter in the same orientation that you would use an electrolytic cap. Most film caps sound smoother and a little darker when the outer foil is connected to ground, or the signal output side (the side at the lower voltage potential).
In practice, if I have unmarked film caps that I plan to use, I will test them all in one sitting. It doesn't take that long."
regards, jonathan carr
___
http://www.lyraconnoisseur.com/, http://www.lyraaudio.com
The Wima MP3 suppression caps are encapsulated in transparent epoxy. It is possible to see which lead connects to the outside of the core by inspecting with a good magnifying glass. There is some sort of bonding agent present around one of the leads, and I assume it is on the outside of the metallized paper winding.
These caps have the printing on a foil piece that covers, but does not connect to, the core. The AC voltmeter test gives identical results no matter how I hold and connect the leads, and I believe the foil piece acts as a shield.
They definitely measure differently depending on orientation.I do not use Jonathan Carr's technique though. I wind wire around the case and attach the caps to a variac, crank it to 50v and measure the voltage on the uninsulated wire for both orientations. It is a pain, but works.
Yes, I apologize any confusion I might have caused in this regard. I do not have any of the MP3's on hand and so assumed they "looked" like other Wima capacitors, having a vertical black line imprinted on the right hand side of the cap. I've always assumed this line indicated the outer foil. So...I don't know what to conclude regarding the correct orientation when using Wima caps.
FIW...Jonathan Carr's method is a relatively easy and consistent way to identify the outer foil and seems to work well on all other caps I've tried.
Bob
Jonathan Carr's method works (as I suspected). Just to clarify...in the orientation which produced the lowest meter reading, the outer foil is located on the side connected to the (-) lead of your VOM.
Bob
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