They vary from unit to unit in internal resistance. Therefore, a 47K ohm load would be good for some and not for others. Mine has a relatively high internal resistance. (Cannot recall the number.) vdH recommends "200 ohms to 47K ohms" for the load resistance. JimJoyce, any MC or MM cartridge will have an internal resistance or impedance way below 47K, so I was not sure exactly what you were getting at.