, Interfaces, MK-121, capacitors

Read more on Acoustat in our home audio section

Ronald Hicks2004-02-23 22:21

Hello Andy,any known source(s) for the 6KV coupling caps in the MK-121 interfaces. I know from the site they are a hard find and a check with Rockford Fosgate shows they have no more available. When my interfaces were upgraded in 1999, RF put in Sprague 430P\'s, but I haven\'t found a source that carries the Spragues in that high a voltage. I noticed one of my panels slightly distorting and upon opening the interface, discovered one of the caps had \'split open\' and the other feeling \'soft\', although it still works. Is there a possibility of damage to other components running it like this? What might have caused the damage since the other interface is fine? What about paralleling some 1K\'s or 1.6K\'s to get the required 6KV capacity?


Andy Szabo2004-02-23 22:21

If your 0.01-uF, 6000-volt capacitors are showing signs of physical failure, I would caution against using the speaker, particularly at high levels. Although the chances of symptomatic failure are low, a failed capacitor could damage an audio transformer or cause burning of adjacent components. When you replace these capacitors, I recommend that you replace all four (two per speaker). This will ensure consistency and balance between the two speakers. Capacitors cannot be paralleled for increased voltage rating: they must be connected in series (i.e. end-to-end) for the voltage ratings to add. In other words, you would need six 1000-volt capacitors in series to make a 6000-volt rating. Combining six capacitors could be a physical mounting problem, so a better solution would be to use four 1600-volt capacitors, which would yield a rating of 6400 volts.

When capacitors are connected in series, total capacitance CT is determined by the formula 1/CT = 1/C1 + 1/C2 + 1/C3 + 1/C4. . .where C1, C2, etc. are the values of the individual capacitors.

Using standard capacitor values, you can use two 0.047-uF and two 0.033-uF capacitors in series to achieve 0.01-uF. Digi-Key www.digikey.com has parts that should work okay (note that I have not personally evaluated these parts):

Panasonic Series ECWH, 1600-volt metallized polypropylene
ECW-H16333JV 0.033-uF digikey #P10513-ND
ECW-H16473JV 0.047-uF digikey #P10515-ND

These parts have radial lead cases and are 28 mm (1.1”) long, so you\'ll need to arrange them sideways across the board to fit in the available space. Connect them in series with short bits of buss wire, and glue them to the PC board with silicone glue. Cover any exposed connections with silicone.

So, one can combine capacitors to reach the desired value of 0.01-uF and 6000 volts, but there are space limitations and the concern of mounting the capacitors so that they cannot arc to other components. This all depends on the physical size of the capacitors you intend to use. In choosing an appropriate capacitor, one must consider more than capacitance and voltage ratings. Most important to sound quality is the type of dielectric. Metallized polypropylene or polypropylene-and-foil are the most desirable types for audio applications. Stay away from ceramic, polyester, paper or other types of dielectrics. These types have their advantages for some applications, but not for audio.

Case style is also important. High voltage capacitors come in many package styles, including screw mount, metal cans, etc, most of which are not suitable for this application. The original capacitors were epoxy wrap-and-fill, with axial wire leads. This case style, or the radial package like the Panasonics mentioned above, are probably the most cost-effective and easiest to mount.

I am conducting a web search for a source for 0.01-uF, 6000 -volt capacitors. If I get any positive results, I will post them under the ”Available Parts” section.

Dick Lanham2004-07-13 11:23

I know where 0.01 microfarad 6000 volt capacitors can be bought. Please see the answer to my own inquiry about these in Capacitors, again, in this Question and Answer portion of the site. Thanks

Patrice Clipez2007-10-15 14:51

Hello, Capacitors of 0,01 mF at 6000 volts are available under WIMA brand. The serial is FKP1 at +- 5%. It\'s a polypropylen capacitor,in a radial configuration. I have just replaced the used genuine capacitors by the WIMA capacitors and the result seems to be perfect. These capacitors are not easy to find in distribution. For European people you can find it on a german website eshop.euras.com which offers interfaces in different languages. One entry address of the site is http://www.eshop55.sup.fr/. The part number to write in the research engine is #3364624. To have access to your own language you have to do a simulation of buying and select directly your country, the web address will be automatically redirected.Capacitors tend to loose their original value, more that ten years is a long life for a capacitor. I suggest to check the value of your capacitors with a multimeter(don\'t forget to open the circuit). 3 of my capacitors where only 6 nF and not 10, the fourth was at 2nF. Don\'t forget to stick the radial capacitor whith silicone and to isolate the connection wires with silicon too. The risk of arcing with other component exists. Good Luck.

Bob Fountain2007-11-21 17:44

I just thought it might be helpful to know that the .01uF, 6kV capacitor is a part that my company, EFC/Wesco, can supply. We are a manufactrurer of film capacitors located in Waterbury, CT. I was recently contacted by an individual who purchased 8 caps from us to refurbish his Acoustat speakers. He directed me to this site. Anybody interested in these capacitors can contact me at fountain@filmcapacitors.com.

Post a reply

Your name will appear on the website next to your contribution. Your email address will only be used to contact you if something is wrong with your contribution. It will not be shared with others.