Abstract: An adapter for a phonographic tone arm for interchangeable mounting of a plug-in cartridge of a linear tracking arm to a head shell of an offset tone arm. The plug-in cartridge has a predetermined mass and center of gravity and has a plurality of small diameter contact pins projecting from the cartridge. The cartridge housing is secured to the head shell by the adapter which has a housing with a recess for accepting the cartridge. The adapter also includes a plurality of hollow terminal pins for receiving the contact pins of the plug-in cartridge. The predetermined mass and center of gravity for the plug-in cartridge enables attaining a predetermined tone arm balance without balance adjustment being necessary. The adapter housing also includes at least one groove for attenuating undesirable acoustic vibrations present in the tone arm.