should be able to directly connect the tape to your
soundcard,
 provided is has line-level inputs (most cards do). Personally I just
 connected my computer to the monitoring Tape2 input/output of my hifi
 amplifier, so I can also record from a vinyl record player if I want
 to.  (You cannot directly connect a record player to most soundcards
 because of RIAA distortion, you need a real phono input.) 
 Actually, to use a phono level signal into regular line inputs you can
 use a matching transformer or a preamp 
 
 The problem with records is not levels, but the RIAA distortion. You
 need a device which can adapt to this. There are special preamps for
 this, some cards like the Terratec Phase26 USB has them built in,
 normaly hifi amps have them (the input labeled "PHONO" most of the
 time), but most soundcards do not have them. 
 
 Jan Depner has made a JAMin config file that undoes the RIAA curve, its
 shipped with the latest tarball IIRC.