WM-SX77

Sony continued refining its outdoor-oriented Walkman designs in 1990 with a cassette model built around impact resistance and moisture protection. The SX77 used thick resin, a reinforced cassette door with an aluminum plate, and a die-cast center lock that kept the housing sealed during movement.

The unit weighed about 245 grams without its battery, and both the bundled earphones and the remote were designed to resist moisture along with the player. Inside the enclosed body, the mechanism followed the quality of Sony's higher-tier cassette units.

An EX Amorphous head supported clear high-frequency response, Dolby B reduced hiss, and a system known as sound shaking guard helped the transport stay stable during running or uneven movement. The sealed layout limited how many features could fit, so the model centered on cassette playback with logic control, auto reverse, hold lock, and Extended DBB.

Power came from a gumstick cell that provided a little over three hours of operation, and longer outings could rely on the waterproof C-cell case. The clip-on remote attached securely to thicker jackets or bags, and the earphones were shaped to stay in place during active use.