Garbage in, garbage out!

It's always important to feed your soundcard the highest quality signal you can get. If your source sound is bad,
it won't be magically improved by the computer. Sound quality in general can only get worse.

Here are some useful tips to get good audio signals.

* Use good-quality, well-shielded cables. They don't have to be ripoff "audiophile" cables, they just have to be good.

* Keep all jacks and plugs clean. Corrosion and gunk can degrade the high frequencies, and in severe cases can cause noticeable intermodulation distortion (which can sound really, really bad). Gold-plated connectors may conduct better and be less prone to corrosion (but only if you connect a gold plug to a gold jack!).

*   It's annoying connecting the rest of your gear to those dumb little stereo 1/8-inch jacks, but try to avoid using lots of adapters. When they're clean and well-seated, there should be no problem. But adapters can work loose, get dirty and corroded, thus  degrading your signal before it even gets into the computer. If you know how to solder your own connectors (it's a good skill to  acquire), try buying some shielded cable and plugs and making cables that connect your gear directly without a bunch of adapters.

*    When recording microphone signals, an external mic preamp (even a cheap one like you find in a consumer tape deck or a
    cheap 4-track) is likely to sound better (less hiss and distortion, better frequency response) than the mic input on your soundcard. Try anything you have handy and see what sounds best. Connect the preamp to the "line" input on your soundcard. Obviously, use the best microphone and the best preamp you can find (probably in that order, though some well-known engineers disagree about the relative importance).

*    Chingson Chen points out that, if you DO use the soundcard's mic input, make sure to use the correct type of microphone:
<blockquote>
       "Today, most soundcard support Electret microphones only, because they are small and convenient. But some older or
       special cards support Dynamic microphones." 
</blockquote>

* Read about GainStructure, a very important topic.