Running a typical MC cart. with a load of 47K is kind of like driving your car without shock absorbers. The inductance of the cart. in combination with the load capacitance forms a resonance circuit. With a 47K load and typical values for inductance and capacitance the peak is usually well past the audio band. The audio band may still be flat, but he response above the audio band will be rising. This will make the system more sensitive to surface noise and pops and other ultrasonic disturbances. If rise intrudes into the upper audio band any excitation of the resonance (ultrasonic surface noise and pops) will be made more audible.
Load the cart. down with a too small value resistor and the frequency response starts to drop in the audio band. Get it right and the response will be maximally flat. Load it with a high value resistor and get an ultrasonic peak in the response.
Load the cart. down with a too small value resistor and the frequency response starts to drop in the audio band. Get it right and the response will be maximally flat. Load it with a high value resistor and get an ultrasonic peak in the response.