The method described in this article is really only good for mono cassettes,
i.e. spoken word, live recordings done with a boom box, etc. where the quality
of the tape already matches the lower quality of the recording method.
The only real way to do this right is to buy a) a high quality tape deck with
stereo RCA outputs, b) a nice PC soundcard with stereo inputs, and c) a
soundcard and/or audio recording program that includes noise reduction
(specifically those designed for transfers from LP or cassette to digital).