Thanks, Alex. I’ve destroyed enough power supplies to know that a G3 with minimal cooling doesn’t live very long when running OS X, so I’m afraid I need to stick with OS 9. I have tried, and failed with Audacity (locks up the machine), Audion (“plays” the timeline, but no sound is produced), and Cabrio (nothing happens at all).
PlayerPRO works as well as iTunes–it plays the high-res files too slowly. Both iTunes and PlayerPRO seem to be limited to 48 kHz/24-bit (but they both down-sample the 24 to 16-bit on import, so hi-res content is lost).
