The Akai GX 400 D is a reel-to-reel tape recorder/player. It was introduced in the 1970s and is notable for its high-quality audio playback and recording capabilities. The device features a three-head configuration, allowing for simultaneous recording and playback. It also includes various advanced features like adjustable tape tension, auto shut-off, and sound-on-sound recording. The Akai GX 400 D has become a sought-after vintage audio equipment among enthusiasts and collectors of reel-to-reel tape recorders.