Hi Toril, what KeyboardED refers to, is that the XLR connector is better because you can use a condenser microphone, obviously this configuration will need phantom power available on the keyboard. Summing up the subject, the microphone connector of the SX900 is for dynamic microphones, which only need a jack, for domestic recordings, while the XLR combo can be used to connect dynamic microphones, (for domestic use) and also for condenser (for recording in the studio) for the latter it is required that the keyboard in addition to having the XLR connection (Jack + three holes) have the option of the phantom power button. I hope this helps a little to clarify the differences between a dynamic microphone and a condenser microphone. regards. Hans