Grado hum -
That can be a problem with their plastic bodies as well, not just the wooden ones Al mentions. Possibly other cartridges can have this problem too but Grados seem to be best known for this potential.
In my experience when hum occurs it is a function of the location of the motor. Tables with the motor under the platter mean it is in closer proximity to the cartridge than those outside the platter so more likely to induce hum.
That can be a problem with their plastic bodies as well, not just the wooden ones Al mentions. Possibly other cartridges can have this problem too but Grados seem to be best known for this potential.
In my experience when hum occurs it is a function of the location of the motor. Tables with the motor under the platter mean it is in closer proximity to the cartridge than those outside the platter so more likely to induce hum.