Quick Overview The Dayton Audio HTA20BT combines the efficiency and power of solid state class AB amplifier topology with the warmth and character of a vacuum tube preamp section. The results are a delightfully articulate and natural sound that is sure to please even the most refined ears. Product Highlights Tube warmth, class AB efficiency Bluetooth 4.2, Aux, and USB inputs Subwoofer output for adding an active subwoofer High quality headphone amplifier built in Extremely low THD 80 dB • Signal-to-noise ratio: >80 dB • Preamplifier tube: 6F1 x 2 • Headphone amp output: 3.5mm, 15 mW @ 600 ohms; 11 mW @ 300 ohms; 7.8 mW @ 32 ohms; 5.6 mW @ 16 ohms (maximum @ 1 kHz,