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After years of
research, this tonearm was published for the first time on the
italian review “Costruire hi-fi”, starting from the N°15 (july
1995). The main features are: unipivot bearing and a new magnetic
antiskating with 4 Alnico Magnets, published for the first time on
“Costruire hi-fi”N° 18 jan 96(copyright owned by the
author).
BEARING
In the unipivot bearing
the arm has only one bearing point for all planes, in the cardanic
bearings the arm has separated bearings, for the horizontal plane
and for the vertical plane. In the cardanic bearings some
clearance is required to have a low friction, in the unipivot
bearing the mass of the arm stands on the pivot, closing the
clearance to zero. In the cardanic the clearance is increased by
the wear, in the unipivot the clearance is self adjusted to zero
by the arm weight, and it is not increased by the wear. Why is the
clearance so important? The stylus, following the groove
countours, is a vibrations source, these waves see the clearance
as a boundary reflecting the waves back. The zero clearance
unipivot bearing is a pathway though which the waves are
discharged away from the arm, making the sound cleaner. The pivot
has a key role, in some arms very hard matters are employed, as
tungsten, wolframium, ruby, diamond or ceramic, but harmonic
steel, just a grammophone needle, is the best sounding pivot. A
true unipivot arm can roll around the stlus-pivot axis, in some
unipivot arms this is avoided adding friction surfaces, my reserch
demonstrated to me that all these devices reduce the sound
quality, the best way to make the arm stable is to lower the
barycenter, without adding mechanical linkages. In some unipivot
arms silicon dampers are employed to stabilize the sytlus
pressure, because unipivot arms can be only statically balanced
and not dynamically balanced, as some cardanic arms. In these a
spring is employed to make the stlus pressure stable, but the
spring works like a dynamic compressor. In the unipivot arm a
spring can not be employed, and the silicon dampers acts like a
mechanical linkage reducing the dynamic energy of the reproduced
sound.
ANTISKATING
The skating force pulls
the arm toward the disc center, this force is is not constant, but
it decreases toward the disc center. Standard antiskating produce
a constant force only, the pressure of the stylus on the two
groove walls can be balanced only in one point of the disc, this
means that in all other points the pressure is not balanced, the
antiskating force is not correct, and mistraking occurs, causing
noticeable distortion. My magnet displacement (copyrighted) is
shown in the drawing, there are 4 Alnico magnets. This is the
first antiskating in which the magnets can be adjusted to reduce
the antiskating correction with the same ratio as the skate force
is decreasing, the stylus pressure on the two groove walls can be
balanced from the beginning to the end of the disc. The stereo
image is focused and stable and the distortion low as never
previously experienced. In the past the only example of unipivot
tonearm with magnetic antiskating was the Decca International arm,
but the magnetic antiskating was not ajustable as in in my
tonearm. Some time after my tonearm presentation, other
manufacturers introduced unipivot tonearms with magnetic
antiskating, but to avoid law prosecution they do not copy exactly
my magnet displacement, and they do not claim their antiskating
with a decrasing force to the disc center. My pirates change
something, employing other displacements not so fuctional and
adjustable like my original arm.. Sorry: it is the previlege of
Originals to be plagiarized. To adjust the antiskating
an”antiskating test disc” is supplied with the tonearm. The
instruction manual is exhaustive with many
drawings.
CONSTRUCTION CM 1
CM 1
Carbon tube -graphite headshell. The arm
tube is made of carbon-fiber with inside wool damping. Two
lenghts aivable: 9 and 12 inches.
The
headshell is made of electrographite, ( not removable). The
graphite properties are explained in the following turntable
section . The 12’arm has less tangential error but an higher
inertia, it is advisable for medium-low compliance cartridges, (12
compliance units, traking pressure not less than 1, 8 grams). In
these cases the resonance frequency is not below 8 hz. For higher
compliance cartridges the 9’ arm is recommended, to keep the
resonance above 8 Hz. With the 12’ arm the resonance may be below
8 hz. In this case the subsonic frequencies are too much and the
elastomeric joint of the cartridge is weared more quickly.
Cm 1 "Low mass"carbon
tube -alluminium headshell.To match very high compliance
cartridge, the” CM 1 Low mass” is recommended, its headshell, made
of anticorodal, is lighter than the graphite headshell, reducing
the inertia to minimum. This arm can track well at 1 gram the
highest compliance cartridges aivable.
CM 1 Wood. This is
made of one wood piece . This arm is recommended only for low
compliace cartridges. The adjustments of the weight and lateral
balance are micrometric with endless threads.
WIRING. Ofc copper
silk coated). Van den Hul golden cartridge pins. The only
connectors are the cartridge pins and the RCA connectors for the
transformers or the preamplifier. On request other wirings and
connectors can be supplied.
Supplied accessories:
Computer made aligment
gauge is supplied with the arm.
Replacement pivots.
A stylus pressure gauge
is required to adjust the arm. The stylus pressure gauge is not
supplied with the arm, and it can be ordered as accessory.
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