Product Specifications:nbsp; Power Supply: DC 12V/1A Frequency Response: 20HZ -20KHZ((3dB) SNR: 100DB THD: 0.1% Control?Potentiometer knob and toggle switch Treble adjustment range: 6dB Bass adjustment range: 10dB Audio Inputs/Audio Outputs: Gold-plated RCA Machine Size: 100*95*32mm Adapter ?US plug Package Include: 1 x Tube Preamplifier 2 x 6K4 Tube 1 x Power Adapternbsp; 1.?NOTICE ?- This is a preamplifier but NOT a power amplifier, can't be used for turntables or passive speakers. The main purpose of this machine is to act as a "buffer" to sweet the sound. 2.?Sound quality ?- Vacuum tube preamp will give you a different acoustic enjoyment with dynamic, sweet tube sound enjoyment. You can feel improve of sound quality in your home theater, HIFI system and any streaming media. 3.?TUBES REPLACEABLE ?- The 3D sound quality of a good tube implementation is simply divine Tubes detachable design, you can swaps the tube to tweaking the sound, 6j1,6j2,6J4,GE5654,6AK5nbsp; tubes are fit for this preamp. 4.? RCA INPUT amp; OUTPUT? - Connect your computer, CD, phone, iPod and other player with RCA cables input and output to the digital amplifiers, active multimedia audio devices for lossless audio(The RCA cables not included). 5.?Good choice?- Features in volume, treble and bass control knobs for more delicate adjustment of the sound, much fun and high playability with this function, the best choice for either beginner or audiophile.