A:Answer After your turntable's built in preamp properly equalizes and boosts the signal level coming from the tonearm's cartridge, then it is considered a 'Line Level" signal. At this point you can connect to any one of the LINE 1 through LINE 3 input RCA Jacks. They are all electrically identical, but offer the possibility of connecting up to three external playback devices (i.e. amplifier turntable, CD changer, headphone output of an MP3 player or smartphone, etc.).