Record Player, Tonearms

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Solutions vary, but all modern tonearms are at least relatively lightweight and stiff constructions with precision, very low friction pivot bearings in both vertical and horizontal axes. Most arms are made from some kind of alloy (the cheapest being aluminum), but some manufacturers use balsa wood, others use carbon fibers. The latter materials favour a straight arm design, while alloy is easier for producing S-type arms.

Through to the crystal pickup, this was required to create sufficient tracking force to follow the grooves adequately with relatively stiff styli. Record wear was high. With better technologies (magnetic cartridge), far-smaller tracking forces became possible, and the balanced arm came into use. Most use a counterweight to offset the weight of the arm, cartridge included. A separate spring or small weight provided for finetuning in tracking force. Often, a calibrated dial on the weight provides quick adjustment of stylus force. Stylus forces of 10 to 20 mN (1 to 2 "grams-force", frequently mis-labeled by manufacturers as simply "grams") are typical for modern high-fidelity turntables, while forces of up to 50 mN (5 "grams-force") are common for DJ use. Stanton cartridges of the 681EE(E) series had a small brush attached to it, the weight of which required compensation of both stylus force (1 gram-force extra needed) and anti-skating adjustement values (see next paragraph for its description).Tonearms are prone to two types of tracking errors that affect the sound. As the tonearm tracks the groove, the stylus exerts a frictional force tangent to the arc of the groove and since this force does not intersect the tone arm pivot, a clockwise rotational force (moment) occurs and a reaction skating force is exerted on the stylus by the record groove wall away from center of the disc. Modern arms provide an anti-skating mechanism, using springs, hanging weights, or magnets to produce an offsetting counter-clockwise force at the pivot, making the net horizontal force on the groove walls near zero. The second error occurs as the arm sweeps in an arc across the disc, causing the angle between the cartridge head and groove to change slightly.

The quality of the available record players, tonearms, and cartridges has continued to improve, despite a diminishing market, allowing turntables to remain competitive on the high end audio systems market.

Source: Wikipedia > Phonograph