Also check the sound levels of the music 1st when you have it set up & ready to record. Play the loudest tune thru & set the recording level so that it doesn't go into the red or whatever the limit says on the sound app you use. You should read the manual of your sound app 1st about this. You don't want to record something & find that it has been 'clipped' (the highest points in the sound wave have exceeded allowable levels.) Clipping will cause distortion & other side effects such as clicking fx when played back on your stereo. Remember each song may have a different level so set it to the loudest tune on the album. Also each album******* etc. will have different levels so you'll need to reset them for each one. Clipping cannot be properly repaired so get it right in the recording stage. You can always safely maximize the volumes later by using Normalise for the entire album. Audacity has this ability. And don't convert to mp3 until you've finished editing & fx, etc. Record & save as wav/aiff initially. aiff & wav are lossless formats but mp3 is a 'lossy' format where it throws away info everytime you save to it.

Another point I forgot to mention is it's best to have some type of volume adjustor between the amp & the computer. Otherwise your outputs from your amp will be at line-out levels.