Turn on the unit and hold A/B on the remote for 5 seconds. If it shows 1.67 or higher , you are already up to date.
While Yamaha doesn’t release firmware updates for the CD-S303 as frequently as they do for their network receivers or streaming amps, occasional updates do appear. Knowing how to check for and apply them is key to keeping your player in top shape. Yamaha Cd S303 Firmware Update
: Maintains reliable playback for MP3, WMA, LPCM, AAC, and FLAC files. How to Perform the Update Turn on the unit and hold A/B on the remote for 5 seconds