FE-6J1-2 fever tube pre-amp board is the circuit schematic design imitation crew Music fax X-10D,to be rational optimization,more stable performance than the machine,tube play 10% increase. This board uses a single 12V AC input,the circuit processing provides 6J1 tube needed positive and negative voltage and filament power supply voltage. Power works: an open power tube filament heating is started,when the boost from the zero-voltage start boosting hot filament tube,etc.,also happens to boost boosting finish,so this is the same with the rectification,8*470UF the capacitor filter very clean,good power supply system not have a ,the filament is 12V DC power supply,need two filament tube is connected in series with a DC filament also in order to reduce the noise. 6J1 Tube Buffer 0.85 times magnification, connected between and before or after class, can effectively filter digital flavor. AC 12V input: The DC3.5 / 5.5 x 2.1 socket, 12V AC power adapter, if you use non-plug AC 12V transformer, power cord need to solder on the circuit board. Remember: You can not use a DC power input, otherwise it does not work! the left-channel input / right channel input: audio signal input, can be connected to mobile phones, computers, M3, the MP4, and other music players. the left channel output / right channel output: an audio signal output terminal can be connected to the audio signal input amplifier, power amplifier board. the power switch / volume knob: turn the knob counter-clockwise to decrease the volume beginning, when the volume down to the minimum, if it continues to rotate until the "ticking" sound, then the power off, the light goes off; in the closed state, Turn the knob clockwise to hear "tick" sound, light is on, the power is turned on, then the volume is minimal, then continue clockwise rotation is to increase thevolume. Type: 6j1 tube Power input : AC 12V 1A, 5.5x2.5 plug Channel :2.0 / stereo Potentiometer Role: Volume adjustment + Power Switch Size: 77 x 75 x 52mm Colour:As shown Material:PC+Metal Package Contents: 1 x 6J1 preamp amplifier board diy kits Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.