This is the Bluetooth stereo system that utilizes a vacuum tube amplifier to provide superior audio performance. Vacuum tube amplifiers are known to generate warmer, more dynamic tones than transistor-based models because they limit distortion when overloaded, providing better signal-to-noise ratio. Two 12AX7 vacuum tubes—the same used in guitar amplifiers—generate a distortion-free signal to the pair of included 12-watt speakers or to an iPhone, iPad, or other Bluetooth device. The tubes also provide robust bass response by ameliorating the natural acoustic qualities of second and third harmonics for richer sound coloration. A switch on the amplifier enables selection between a Bluetooth audio source or an RCA input, allowing play from a CD player or turntable (RCA cables included). With volume knob. Four binding posts in the rear connect to the included two-way high-fidelity speakers. Plugs into AC. Each speaker 8 1/4" H x 6" D x 5" W, amplifier 7" H x 9" D x 4 3/4" W. (13 1/2 lbs.)