Modular jack is right. The input is optimized for a condenser mic. Many mic. inputs with phantom also allow a dynamic mic. to be amplified, but my guess is that Korg didn't go to those lengths and assumed that most people would simply use the supplied free condenser microphone. The phantom power won't hurt the 57, but just don't plug in a ribbon mic. You will probably need to use a mic. pre into the input in order to achieve the gain you need. I have never heard the condenser mic. with that unit. Is it really that bad? It would certainly be low cost given the overall package. Can't go wrong with the eq curve inherently with the 57. it's not a hypercard, but you do need to pay attention to the polar pattern and stay on axis.