The first fully transistorized Japanese reel-to-reel recorder with a built-in amp. Developed to bring studio-class recording into the home. With buttons instead of levers for tape control, the design reinforces the impression of a precision instrument. This was the first Sony recorder made of die-cast aluminum. The professional three-motor, three-head open reel recorder was affectionately known as "Three Sevens" among the many audiophiles who admired it.