We are continuing our big tonearm experiment
, and today I will talk about armtubes.
Theoretically, the job of armtube is an easy one. Together with a headshell, it has to firmly hold the pickup assembly in place, and deal with whatever mechanical energy the pickup cartridge transmits through its mount. This suggests that the best armtube is a shortest armtube made of the stiffest material with a highest damping capacity η
(ability to dissipate energy during vibration). By the way, here is an excellent article
for a variety of materials.
As magnesium alloys are quite strong and have the damping capacity at least an order of magnitude higher than other comparable materials, a tonearm with a short magnesium armtube should be by far the best. Unfortunately, it isn't quite so simple.
Experience tells us that there is no direct linear relation between stiffness or damping capacity one one side and the quality of the tonearm on the other. Such theoretically unsuitable materials as steel, titanium, ceramics and wood were often used with great effect.