Creating MP3 Files
Cassettes to Digital
Unfortunately, converting cassettes to digital is time consuming. It is prohibitively expensive to have someone else do it for you as it must be done at actual speed. It is not difficult to convert with a computer. The general procedure is:
1) Use the best tape deck you can get your hands on.
2) Use a computer with a good quality, low noise, sound card with stereo line inputs.
3) While playing the tape, capture the audio to .wav files using the highest possible output volume, without clipping. I have used Audiograbber, which is free. http://www.audiograbber.com-us.net/
4) After capturing the .wav files, apply any noise reduction filters you may need.
In my experience, filters distort the signal and don't help very much. I also tried a clean-up filter from Algorithmix: http://www.algorithmix.com/ My filtering experiments concluded that the best results came by leaving the tape artifacts in the recording, without applying any filtering.
5) Edit/split/merge the .wav files as necessary. There are many freeware programs for doing this.
6) Burn .wav files to a CD using most any CD burning software.
7) The final step is to convert the CD, or .wav files, directly to MP3 format. I have used audiograbber for this.
8) After the MP3 files are created, you will probably want to edit the MP3 tags (e.g. title, correct speaker, date) show up in the MP3 player.
I recommend MP3 Tag Tools, which is free: http://massid3lib.sourceforge.net/
A very good alternative is to run the output of the tape deck into a CD recorder instead of the computer. The recorder will have a low noise front end and can even adjust volume automatically and can add a new track every 3 minutes if you like. The resulting CD files can be edited on the computer. I personally would use a CD or DVD recorder instead of a computer to digitally capture the audio. They are no longer very expensive. Computers can be notoriously noisy unless you have a really good sound capture card (not on the motherboard).
You can directly record to CD or DVD instead of having to later transcribe analog tape to digital media.