Counterweight

The counterweight is the adjustable weight fitted to the back end of the tonearm, opposite the cartridge, used to balance the arm and then dial in the correct tracking force once balance is achieved.

Setting it up starts with zeroing the arm, sliding or rotating the counterweight until the tonearm floats level with no downward or upward pressure at all, before then applying the specific tracking force the cartridge manufacturer recommends, usually by rotating a separate calibrated dial on the counterweight itself. Because these dials can drift slightly out of accuracy, many enthusiasts double check the actual force with a separate digital or mechanical gauge.

When adjusting a counterweight, move slowly and support the tonearm by hand rather than letting it drop, since an unbalanced arm can let the stylus strike the platter or record. Recheck the setting whenever a cartridge is changed or the headshell is removed and reinstalled, since even small shifts affect tracking force. A common mistake is trusting the counterweight's numbered dial blindly without ever verifying it against a proper gauge, especially on turntables that have been used or serviced by more than one person.