The Unseen Hand
It guides the stylus through its delicate dance. The tonearm is a component of supreme importance, a fusion of physics and material science dedicated to one goal: letting the cartridge read the groove perfectly.
The Geometry of Perfection
A pivoted tonearm naturally travels in an arc across the record, but the groove is cut in a straight line. This discrepancy creates tracking error. The goal of tonearm geometry is to minimize this error to an inaudible level.
Effective Length
The distance from the pivot point to the stylus tip. A longer arm results in a shallower arc and therefore less tracking error.
Overhang
The distance the stylus "hangs over" the center spindle. This is a crucial adjustment for aligning the cartridge.
Offset Angle
The angle of the headshell relative to the armtube. This angle positions the cartridge to be tangent to the groove at two key points on the record, minimizing distortion.
The Pivot: Freedom and Control
The bearing system is the heart of the tonearm, defining how it moves both horizontally and vertically. The ideal bearing has zero friction but is infinitely rigid—a true engineering challenge.
Gimbal Bearing
The most common and robust type. It uses two sets of bearings, one for horizontal and one for vertical movement, providing high stability and control. A well-made gimbal provides a stable, controlled, and focused soundstage, where instruments have a solid, unwavering placement.
Unipivot Bearing
A minimalist, high-performance design. The entire arm balances on a single, sharp point. This offers incredibly low friction but can be less stable and more challenging to set up. Proponents praise its lively and unconstrained sound—one that can feel incredibly fast and open, as if the music is breathing with greater freedom.
Materials and Resonance
The tonearm itself is subject to vibrations from the stylus, the motor, and the environment. The material and construction of the armtube are chosen to dissipate this resonant energy before it can color the sound or feed back to the stylus.
Common materials range from aluminum on entry-level arms to more exotic options like carbon fiber, magnesium, and even wood on high-end models. Each has a different resonant frequency and damping characteristic, contributing to the arm's overall sonic signature. A successful design allows the music to bloom from a silent background, free from the haze of unwanted vibration.