The Game Boy Classic only had a mono speaker. The games, however, were developed in stereo sound. Thus, the Game Boy did not do justice to the possible sound experience. The third party hardware  manufacturer and game developer Sunsoft took on this problem and brought out an attachable stereo speaker for the Game Boy. The speaker was plugged into the headphone socket, which supported the stereo signal nativly. A built-in amplifier turned the accessory into a little sound miracle for the Game Boy Classic.