An improperly calibrated tonearm causes permanent groove wear and causes distortion known as inner-groove pinch effect. Achieving pure analog sound requires precision geometric calibration.
1. Cartridge Alignment with Alignment Protractors
Because a radial tonearm moves in an arc across the record rather than a straight linear path, the stylus is only perfectly tangential at two points on the record (null points).
- Download or purchase a Baerwald, Löfgren, or Stevenson alignment protractor.
- Place the protractor spindle hole over the turntable center spindle.
- Adjust the cartridge body within the headshell slots until the cantilever aligns parallel with the grid lines at both inner and outer null points.
2. Tracking Weight Calibration (VTF)
Vertical Tracking Force (VTF) determines the downward pressure placed on the stylus. Too light causes tracking slippage; too heavy damages vinyl grooves.
- Balance the tonearm into zero-gravity float mode with the stylus guard removed.
- Set the counterweight index ring to zero.
- Rotate the counterweight forward to the cartridge manufacturer's target specification (typically 1.8 to 2.2 grams). Verify with a digital stylus force gauge scale.
3. Anti-Skate Force Adjustment
As the record spins, centripetal friction pulls the tonearm toward the center of the disc. Anti-skating applies outwards horizontal tension to equalize contact pressure against both left and right groove walls. Match the anti-skate dial setting directly to your measured tracking force.