Be sure your recording levels are set high enough as stated in the previous question. If the levels are set properly, Be sure the Record Select M/G Line mix switch is set in the proper position. If should be to the left if you want to record the Mic/Line input, it should be in the center if you want to record the L/R line inputs on the back, or it should be to the right if you want to record the Mic/Guitar and line inputs simultaneously.