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Q Should I use the quartz lock feature on my Audio-Technica AT-LP120 turntable? I don't see or hear any difference when I press the quartz lock button. Same thing when I press the +10 /+20 pitch control button. FYI, I usually play records with the +10 pitch option selected. —Josh Rosenthal

A Unless you’re a club DJ, yes. The quartz lock feature on direct-drive turntables like your AT-LP120 is there to maintain a stable speed for platter rotation (e.g., 33-1/3 or 45 RPM). It does this using a quartz phase-locked loop circuit that 1) compares motor rotation speed to a reference frequency generated by a quartz crystal oscillator, and 2) makes fine adjustments should the values drift.

When you press the Quartz button on your turntable, the LED next to the pitch slider on its right side turns green to indicate that quartz lock is active. You can also activate the feature by adjusting the pitch slider to its middle position. With quartz lock enabled, the turntable’s pitch control feature is disabled and won’t have an impact on motor speed — the reason you don’t hear any difference when pressing the pitch control button.

If you were to do the DJ thing and play with pitch, selecting between the +/-10 and +/-20 settings would let you extend the range of the turntable’s pitch control. In this case, you would switch quartz lock off and push the pitch slider up or down until you hit the desired speed (the green LED will turn red, indicating that quartz lock is disabled). One more FYI: You can always confirm motor speed accuracy on the AT-LP120 by checking the strobe dots on the platter’s edge to see if they line up.