Sounds like you may have the recording level set too high(in your computer). The mic input cannot handle a line level signal. Once you have recorded onto analog tape(speaking of narrow format like cassette), there isn't much you can do to eliminate tape hiss. At the very least, you should look into a USB/audio interface that can handle line level. You would realize a major quality jump if you ditch the Tascam and start recording directly into your computer with a decent
audio interface(M-Audio with protools M-Powered, Cubase, Nuendo or regular protools). The cheaper units have a mix knob that can be a hassle but the firewire interfaces can run at a much lower latency so monitoring is much better so you can skip dealing with the mix knob. Watch some tutorial videos from the various manufacturer websites or even youtube.com.
