How a counterweight controls stylus pressure
A turntable tonearm pivots like a small seesaw. The cartridge and stylus sit at its front end; an adjustable weight sits behind the pivot. Moving that weight changes the turning force, or torque, on each side. With the arm balanced, neither end strongly tips up or down. Set for playback, the balance leaves the stylus pressing into the record groove with a carefully chosen force—typically just a few grams.
That force is called tracking force. It is not simply the weight of the arm: the rear counterweight offsets much of the arm’s leverage, and its position determines how much downward force remains at the stylus. Many arms have a numbered dial that lets the listener set this force after balancing the arm, though the dial is an adjustment guide rather than a sensor measuring pressure directly.
Why “just a few grams” matters
The stylus must stay in contact with the groove as its walls move rapidly beneath it. Too little tracking force can let it bounce or lose contact, especially during demanding passages; that can distort the sound and make the stylus strike the groove unevenly. Too much force can increase wear on both the stylus and record. The correct setting depends on the cartridge, whose tiny suspension—the flexible part supporting the stylus—is designed to work within a particular range.
The counterweight therefore does more than keep the arm from drooping. It makes a delicate mechanical compromise possible: enough pressure for the stylus to follow the groove, but not so much that the record is unnecessarily burdened. A small adjustment at the back of the arm can change how a needle only millimeters long behaves in the groove.
