Specifications: Type: 6J1 tube (substitution model 6AK5, 6AU6, 5654 etc.) Channel Types: 2.0 / stereo Voltage & Current: AC12V 0.8A or above Power Interface: 5.5 * 2.5 plug Circuit Board Size: 77 x 75mm / 3.03 x 2.95"" Instruction: 1, AC 12V Input: using DC 5.5*2.1 socket and AC 12V transformer, you can also use AC 12V transformer without plug, just need to weld the power cord onto the circuit board. DC power input can not be used, or it will not work. 2, Sound Channel Input: Connected to mobile phone, computer, MP3, MP4 and many other music players. 3, Sound Channel Output: Connected to the audio signal input of power amplifier. 4, Power Switch/Volume Knob: Rotate the knob anticlockwise to turn down volume, and continue rotating until you hear the sound ""tick"" to power off. Rotate the knob clockwise until you hear the sound ""tick"" to power on and continue rotating to turn up volume. Package Includes: 1 x Board 1 x 2W 2.2Ω Metal Film Resistor 6 x 1N4007 Large Current Diodes 6 x 4.7K Resistors 2 x 1K Resistors 4 x 47Ω Resistors 2 x 2.2K Resistors 2 x 470K Resistors 2 x 100K Resistors 2 x 200Ω Resistors 9 x 50V 470UF Capacitors 4 x 50V 1UF Monolithic Ceramic Capacitors 2 x D667 Transistors 2 x B647 Transistors 1 x 50K Potentiometer 2 x 3mm Blue LED 1 x DC005 Power Connector 2 x Tube Base 2 x 6J1 Tubes 2 x Base 1 set x Standoff and Screws 1 x Potentiometer