NWZ-S639F

The NWZ-S639F is the highest-capacity 16 GB overseas model in the sixth-generation S Series Network Walkman lineup. It incorporated the full set of unified design and Omakase Channel features. The player provides 16 GB storage supporting MP3, WMA, AAC, and WAV files along with the 240x320 TFT display, FM radio with recording, WM-PORT, video and photo playback, Clear Audio, DSEE, and 40-hour lithium-ion battery life.

This Walkman model was the fullest version of that late-2000s settled S Series idea. By this point Sony had largely solved the line's identity problem. The player no longer felt like a side branch still looking for a job. The S639F came from the point when Sony finally made the S Series feel like a natural permanent part of the Walkman hierarchy instead of a category experiment.