1.The filament is powered by 3.15V-0-3.15V AC power supply, with all ground wires grounded at one point. The bottom noise is extremely low, and if a coil is used, the bottom noise is basically inaudible. 2.The finished board uses 4 electronic tubes (1 5Z3P rectifier tube, 2 6P3P/6L6/EL34 power tubes, and 1 6N1 push tube), which are not included and need to be purchased separately by the buyer. 3.Model: 6N1+6P3P (replaceable with 6L6/KT66/EL34) 6W x 2 stereo power amplifier board (excluding electronic tubes, which need to be purchased separately) 4.Suitable for 5H 200mA coil Color: Material: PCB Package Contents: 1 x Vacuum Tube Amplifier Board Only the above package content, other products are not included. Note: Light reflection 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.