John,

I think  headphone out to mic in  on the pc is the worst of both worlds.
Headphone jacks usually have  lower  output than  the speaker output so  you
don't blow out your ears.   It might be possible to increase the  level on
the mic input  to get more into the soundcard, but  I think you would be
much better off  using a  line in.   The headphone jack may  work much
better going into a line in.    I think most guys use speaker out or get
audio  from an accesory jack that offers a line level audio output.

Have fun, Steve KW3A