SA-20 HiFi Vacuum Tube Audio Sound Processor Preamp Pre Amplifier USB or Bluetooth Features: Tube preamp and Audio Switcher and Headphone Amp Mysterious built-in tube design Independent tone knob and input selector Exquisite appearance and perfect design Specification: Product size :145x85x85mm Frequency response :20HZ-20KHZ Input sensitivity :0.775V High and low adjustment range: 6db Operating voltage :12V Harmonic distortion :0.04 percent typically Output signal :XLR balanced output, RCA Headphone output load negative resistance :32-300Ω Analog output, 3.5 headphone output Headphone Max power :160mW or 32Q SNR :>100DB(20HZ-20KHZ) Input signal: Bluetooth, U disk, RCA Package Includes: 1xTube Preamp 1xPower Adapter Note: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement.