Nobsound MS-10D MKII Hybird Tube Amplifier with Bluetooth/USB/Headphone for Hifi This tube amplifier is the best choice for Primary HIFI friends (it's the Nobsound MS-10D Upgrated version);The best-selling and most cost-effective tube amplifier in the World. Every ten people buy tube amplifier, eight people choose him Input Voltage: 110V-240V/50-60Hz .Output Power:25W+25W Power consumption:100W Input impedance:47 kohm SNR:80DB Frequency response:28HZ-20KHZ Output Impedance:4-16ohm Tube:Beijing 6N1*2+6P1*2.Weight:6KG Size(D*W*H)31.2CM*27CM*15CM. If there is sound dropout problem when using bluetooth function,please connect the amplifier with USB flash driver and play music with it.Then pull out the USB flash driver and connect with bluetooth again. Please Note:AS the USB and Bluetooth are connected through the same signal Channel,so if you want to connect with the bluetooth,firstly please pull out the usb,restart the bluetooth function and the machine,then connect.The USB supports only 5 formats:MP3/FLAC/WAV/APE/WMA,and the Bit Rate should not be higher than 16BIT/48KHz.Otherwise,there maybe noise.