Nobsound&reg; Audio Receiver Bluetooth Transparent Chassis valve 6J1 tube headphone amplifier HIFI AMP For Phone / PC / Sound system Main amplfiier board is solder finished,when you get package. you just need assemble the panel case on PCB! This item is Pro version. with bluetooth function. you can connect to your cellphone by bluetooth. Pair bluetooth do not need enter password, the name is:"LITTLE BEAR". Immersion Gold PCB,perfect signal transmission; Input/output interface using Gold parts.(RCA adapter.tube socket all is gold) HiFi WIMA filter capacitor *6 units,be sure quiet back noise. you almost can no hear any noise whatever turn volume up to MAX. and good sound output. With warm sound for your headphone; Tube model: Peking 6J1(you can replace it to other tube. like:5654,6AK5,EF95 tube.)