Cassette to Computer
First I feel I have to say that your set-up probably is not the recommended "safe" way to go (going from a headphone jack to the line-in of your computer). There is possiblity that you could do harm to the computer by not going from a "line-out" source, but having said this, I admit to having done the same thing. I suggest if you are going to continue this set-up to try to keep your cassettes volume very low initially and gradually increase the volume when appropriate.
I would not think that you need a pre-amp...Maybe the setting for record within your computers settings is not set high enough...(according to what operating system you have this can be found in different areas withing your computer, but you could start by clicking on "control panel", you might find sound controls in various places, so do a thourough search) you should be able to find settings for things like "sound","play" volume, and "record" volume...By turning up your record volume this might solve your problem and allow enough signal through to get a proper recording.
I have been using (for the last 8 years) a 4-track cassette multitrack recorder and mixing down to a conventional cassette for my final song. A year ago I decided to try to put my cassette music onto CD...I came accross a program from RipEditBurn.com which had a great tutorial on connections and settings to use when you transfer records and cassettes to computer). You might want to check out this tutorial. They also had a 30 day trial which I took advantage of. I never could get the hang of the EQ in the RipEditBurn. Ultimately I choose to use a program from Cakewalk called Pyro 2004 (which costs around $30-$40). It has a very useful 5-band EQ control and you can even add effects (like reverb) to the song. There is controls to limit the "hiss" in a song (though it must be used very sparingly or you lose part of the music) and a way to boost the volume of songs that where originally recorded at low volume. It even has something called a "maximizer" which sort of acts like a compressor, making the overall volume of a song more consistent (which again, if your not careful with it, you can do more harm than good). In Pyro 2004 you get to see a visual representation of the sound (a "wave" that sort of looks like a picture of a heartbeat) which helps get an idea of the volume (especially in comparison to other songs) and helps you get more uniformity (of volume) amongst a group of songs...
Anyway, try finding and turning up your record setting on your computer.
