Silmic II (RFS Series) Electrolytic Capacitors
High-grade Silk fiber capacitors for Audio.
The SILMIC II series are Elna's highest grade audio
capacitors that exhibit superior acoustic characteristics.
An entirely new type of electrolytic separating paper
is used, containing silk fibers. The extreme softness
of silk can mitigate vibrational energy (generated by
the electrodes, by external vibrations and by electromagnetic
Due to it's new electrolytic and foil design the signal
propagation speed has increased (the ESR is reduced)
and a more powerful, yet-mellow, sound is possible than
before. When these capacitors 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
Features of the SILMIC series
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 seriesexhibits a superior acoustic
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
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
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.
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
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
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