This is the hybrid vacuum tube amplifier that pairs with any Bluetooth music device 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. The two 6N3 tubes in this amplifier generate 20 RMS watts per channel of distortion-free signal, adding punch and clarity to high bit-rate MP3s, Apple Lossless, or CD-quality audio played wirelessly from an iPhone, iPad, iPod touch, or Android phone. 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's top enables selection between a Bluetooth audio source, 1/8" stereo audio input, or a pair of RCA inputs, allowing play from multiple audio sources, such as a CD player or turntable (requires RCA cables). Four binding posts connect to your preferred pair of 4-8 Ohm speakers using speaker cable (not included). Plugs into AC. 10" H x 17 1/2" W x 10" D. (9 lbs.)