Damping
As mentioned above, damping of the cantilever is extremely critical. Too much and
the cartridge will sound dull, as a large amount of the critical energy from the record
will be absorbed in the damper instead of reaching the coils, reducing the efficiency
of the energy transfer from the record (as vibrational energy) to the cartridge (as
electrical energy).
Conversely, too little damping will make the cantilever prone to uncontrolled
excursions, resulting in unwanted distortions and poor tracking.
Much experimentation led to a precision Butyl rubber damper, offering a wide
operating temperature range and minimal hysteresis effects. The tension on the
damper is furthermore adjustable, allowing very accurate set-up of each cartridge
ʼ
s
individual suspension.
Stylus Choice
Finally the assembly is completed with the use of a solid diamond stylus. A heroic
degree of effort has been expended finding the best possible solution to this, the
most critical interface with the “plastic”. Having been ultimately unsatisfied with the
offerings from the various stylus manufacturers around the globe, in 1995 we
contracted a company to develop a process which would allow them to cut and polish
a perfect, natural octagon to a level of the best surgical instruments used for eye and
other fine surgery, on a diamond less than half the size of the closest, readily
available option at that time. This remains to the best of our knowledge the finest
diamond in use on any cartridge available today.
The improvements over any standard diamonds use in other cartridges can be briefly
described as better tracking of high frequencies, lower surface noise, lower record
wear, longer stylus life, smaller tip mass and lower tracking force.
The stylus is first
ʻ
pinched
ʼ
into place by the cantilever and then glued, using a single
component epoxy resin, which needs
ʻ
baking
ʼ
for about three hours to harden.
Test Procedure
After assembly, each cartridge is subjected to a series of tests, one of which involves
a fast dynamic frequency sweep, at high amplitude; this method shows up any
undesirable problems in the cartridge. Special test equipment and test records had to
be developed for this process, which is exclusive to Audio Note (UK).
IO LIMITED MOVING COIL CARTRIDGE
