A non-compressed format would be best. Considering the general quality of cassette tapes you may have some degradation and add to that any lossy format is asking for disaster. I would suggest that you read them into the computer first as data NOT audio. As I recall they are written to the tape as square waves in Intel Hex Checksum format which can help identify lost bits (Not great but better than some.) Square waves in an audio can generate distortion. (One of the early copy protection schemes?) I can remember lots of loads aborting due to checksum errors and the standard response was to back up the tape and restart. If you have problems let me know; I think I have the old source code for the monitor (BIOS) in a closet somewhere. Be careful though if you copy the BASIC. The MSA BASIC that was released for the SOL carries a copyright notice of the MICROSOFT CORPORATION and Big Bad Bill might come and get you. Seriously, this is some of the software B.G. wrote about in his open letter to hobbyists. Good Luck, Wayne -- Wayne Talbot <awt(a)io.com>