WM-4

The WM-4 is a budget-oriented early Walkman built as a smaller and more efficient follow-up to the WM-1, while still relying on a robust transport architecture closer to Sony's dictation-derived designs than to the compact WM-2 family. Its upright plastic body over a metal frame kept the player physically simple and fairly durable, with dual headphone jacks, 2x30 mW output, DC input, and four-AA power covering the essentials. There was no radio or Dolby, and the relatively power-hungry amplifier limited battery life, but the machine remained straightforward and dependable.

At this point Sony was making the Walkman more ordinary on purpose. The WM-4 was not built to impress or define the future, but to keep personal stereo from remaining a premium novelty. It helped prepare the format for wider, less self-conscious adoption.