Help with Marantz NR1510


Trying to help a friend with New AV unit.  He ran his rega TT strait in to the phono stage fine.  Then he wanted to compare that to the external phono stage he has.  I told him to go into the audio in assignable 1 , 2 or 3 but when he tried that no sound.  Does he have to activate those inputs in the "audio in" section of the NR1510?

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