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The "SILMIC" series of aluminum electrolytic capacitors for acoustic applications uses an entirely new type of electrolytic paper. The primary constituent of the newly developed electrolytic paper is silk fiber. This paper was believed unfathomable as an aluminum electrolytic capacitor. The new product beats the silk fiber and mixes it with Manila hemp fiber to provide an aluminum electrolytic capacitor used for high-grade music. Therefore, the series exhibits a superior acoustic characteristics.

Silk Fiber

It is well known that silk is spun by silk worms. Since silk is an animal product, the primary constituent of the fiber is protein. Normally, the vegetable fiber (Manila hemp or craft pulp) used in normal aluminum electrolyte capacitors has a cellulose base material. Simultaneously, this gives different shape and different characteristics of the fibers.

For example, normally when paper is wrinkled, it produces an exciting sharp crisp sound. Manila hemp paper is quieter than craft paper, but still makes a fairly loud rustling sound. These sounds are mainly the result of hardness of the cellulose fiber. In contrast, paper made from 100% silk fiber is extremely flexible and there is absolutely no hint of any rustling sound.

When we look at these types of physical properties, the limit of elongation is between 1.9 and 3.9% for cellulose, with a tensile strength between 4.9 and 6.4 gram weight per denier. In contrast, the limit elongation ratio of silk is 7 times as high at 20 to 23% while, conversely, the tensile strength is weaker at 3.6 to 4.1 gram weight per denier.

In silk, the fiber-like protein called fibroin is enclosed in a protein surface layer known as sericin. Because these proteins are primarily from glycine, alanine, and serine amino acids, they have extremely simple structures when compared to other natural fibers. Moreover, the fiber surfaces are smooth and in the axial direction. Also, the fibers have long and well-defined crystalloid polypeptide chains.

As described above, silk is extremely soft when compared to cellulose and is remarkably better when it comes to resistance to physical shock -- in a word, silk fiber can be described as "supple."

The Sound-improving Effect of Incorporating Silk Fibers

At Elna, we have moved forward with development activities based on the perspective that this "softness" of silk can mitigate vibrational energy, which is generated from the electrodes in the capacitor. Also, this silk softness will mitigate the vibrational energy of the music propagating through the air and striking the capacitor. Ultimately, the softness will mitigate the mechanical vibrational energy that comes from transformers or rotating systems within the final product.

As described above, silk is not mechanically strong. Therefore, we arrived at a feasible product through mixing the silk fiber with the Manila hemp fiber. In this mixed paper, the fibroin is extracted alone in the silk fiber beating process. Although it is broken down into fine fibers during the process, the silk fiber becomes far finer and softer than even the individual silk fibers. Thereby, splitting into long thin protein chains.

The raw fibers have diameters between about 10 and 15µm for both the silk and the Manila hemp. The diameters are reduced to about 0.2 to 2.0µm in the beating process because the mixing is allows paper to blend with the silk fibers by filling in the gaps (between about 20 and 50µm) between the Manila hemp fibers. (See the photographs below.)

From the vibration absorption perspective, this structure is entirely ideal.

Due to the increase in surface area at the interface between the electrolytic paper fibers and the electrolytic solution used for driving the device, we also discovered an increase signal propagation speed (the ESR is reduced). For example, the ESR at 1kHz in the GBL electrolytic fluid for a given thickness and density ended up approximately 20% less than for the separator paper made from Manila hemp alone.

Except for the electrolytic paper, we used the exact same materials and conditions to produce a 63V 15000µF block-type capacitor and a 50V 1000µF radial lead-type small-footprint capacitor. When these were subjected to aural evaluations, the high range peak and midrange roughness were reduced substantially. Also, the low range richness and power were increased in the obtained high-quality sound.

In the "SILMIC" series, we also use anode growth foil with more unetched parts and a 55µm low multiplier high-purity cathode foil in order to improve the signal propagation. Through a synergistic effect with the characteristics of the silk, we have made it possible to produce a powerful, yet-mellow, sound that was not possible in the past by using aluminum electrolytic capacitors.

Photograph

Manila hemp: 100% x 1000

Silk: 70%, Manila hemp: 30% x 1000