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Wima  MKS4

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The best capacitor is

no capacitor!

What is a capacitor?

The capacitor is one of the oldest electronic components. Electrical conductors where discovered in 1729. In 1745 the Leyden jar, the first capacitor, was discovered by Ewald Georg von Kleist, a German inventor. A Dutch physicist, Peter van Musschenbroek of the University of Leyden also discovered the Leyden jar independently in 1746.

Currently, the Leyden jar is a glass jar with a metal foil coating on the inside and outside.

The capacitor serves as a means of storing electricity, and the greater its capacity the more electricity will it store. The capacity depends on the size of the plates opposite to each other, the distance between the plates and the nature of the insulator between them.

Capacitors as used in audio amplifiers

There are several types of capacitors (caps), such as the conventional capacitor with metal foils for both plates and impregnated paper between them. Even today there are Metallized Paper (MP) capacitors, also called paper/oil capacitors available.

Later Mylar (Polyester) and other synthetic dilectrics (isolators) became more common. In the sixties, the metallized Mylar cap became very popular. The two strongest points of those caps are there smaller size and the fact that they are self-healing. Today they are used in almost every electronic device. Because of the huge quantities that are manufactured of this kind of cap, they are rather cheap.

An other kind of capacitor is the electrolytic capacitor. This is a very special cap with mostly high to very high values, starting by around 1F to several ten thousands of F. In tube amps are values from 4 to 220 F most common. They are mainly used for decoupling or for filtering in the power supply. Electrolytic capacitors will not be used as coupling caps in tube amps, also not in good Quality transistor amps.

The most common coupling caps in middle of the road amps are metallized Mylar or Polyester caps (MKT). In higher Quality amps mostly metallized Polypropylene will be used (MKP).

A mostly forgotten type of capacitor is the metallized Polycarbonate type (MKC). Especially the MKC types from ERO are very famous. Particular because they have a very balanced, musical sound with very little coloration. However MKP types have a brighter sound, they have mostly more coloration too.

An other rather unknown type is the MKV capacitor, this is a metallized Polypropylene capacitor in oil. It has better specifications than metallized Paper (in oil).

Even by the today commonly used MKP capacitors, there are differences between different brands. Of course there are very exotic capacitors with very little coloration, but they have also very exotic prices.

Except the common metallized types there are also not metallized types, a good example is the Styroflex or Polystyrene capacitor. Mostly they are limited to values of about 0.1 F, because they are much larger as metallized types.

A many times forgotten aspect of a decoupling capacitor is, that it is in the signal way! A perfect capacitor should have an impedance of zero Ohms from DC to light-frequency. But there exists no perfect capacitor ...!

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The intention of this article will be that every (de-) coupling capacitor in an audio amplifier has its own particular "sound". It is also possible to use transformers as a coupling element instead of capacitors, such as interstage and balanced input or line output transformers. If you use a good Quality, you will be surprised by the audible results!

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"Tubes are for Music, transistors are for TV and electronics in general"