Cary Audio Design SLP-50 is a vacuum tube-based line stage preamplifier with 10 dB of gain. It features a class A triode design with a pair of 12AU7 tubes. The SLP-50 has three line level input jacks and one output jack. It also has a selector switch for choosing the input source, a mute/operate switch, and a master volume control. The SLP-50 is designed to be used with power amplifiers and can be used in a variety of audio systems. It is known for its excellent sound quality and is a popular choice for audiophiles.