Audio Research CA50 is a high definition, vacuum tube stereo integrated amplifier with a variety of features and possible use cases. It has five single-ended input sources: tuner, video, CD, Phono, and Aux. It has a 2-Way volume control switch with a spring-loaded center return position that electronically adjusts volume level either a step at a time or continuously. It also has an operate/mute circuit LED that flashes for approximately 60 seconds after start-up until the automatic muting cycle is completed.