The MP 4 is a professional 6-channel. USB sound card with a mixer wrapped. The MP 4 allows the user to simultane ously. Play analog sources. Play digital files. Record a stereo source and cue. Another source (digital or analog). Using the built-in headphone cueing. The MP 4 is a two-bus mixer with two. Stereo Line/Phono inputs, two stereo. USB digital audio inputs and one stereo. Digital audio output to USB. A-bus, B bus, Master Mix or Microphone may be. Assigned to the USB record channel. The MP 4 allows easy digital record ing of analog inputs not a.