In 1985, Sony corrected structural issues related to battery consumption and casing size. A design that prioritizes power efficiency and ease of operation has been incorporated.
D-50MkII
The D-50MkII is an improved model based on the original D-50, with a revised power supply system and internal design. It features a structure that tightly integrates the dedicated rechargeable battery into the main unit, enhancing the overall unity of the power supply. While the internal transport and digital circuits have also been updated, the playback system itself maintains the same configuration. It lacks vibration damping mechanisms, and its basic operating characteristics are the same as the original model. Although designed for portable use, it is intended for use in a stable installation environment. This model streamlines the configuration of early portable CD players.
D-55T
The D-55T is a portable CD player with a built-in AM/FM tuner. It features a tuner that supports television audio frequencies and utilizes the headphone cable as an antenna. It also supports mono/stereo switching and local/long-distance reception settings. The CD playback section inherits the configuration of the early Discman series and does not have a vibration-resistant mechanism. It is intended for use as a multi-function device, including the tuner, and is configured to support multiple audio sources for portable use.
By 1985, portable CD players had developed a structure that made them functional as practical devices. However, limitations regarding reliability and portability remained.
