Full Upgraded Version of ST-01: 1. Supports U-disk input to play lossless formats music. 2. Add sensitivity adjustment of VU meter on its bottom, easy to set and match better with different input signals. 3. Add three decorative golden circles around tubes and VU meter, looks more exquisite and luxury.Unique and amazing combination: With VU meter into whole in such a mini size, the pointer dancing in the warm light with strong vintage feelings when enjoy HiFi music, dynamically decorates the audio system space.HiFi clear sound with tone control: resonable circuit and concise wiring, adopts vacuum tubes to soften the sound and filter out the digital feelings, sounds warm and sweet without noise. Also with treble and bass knobs to adjust one's own preferable sound styles, presents HiFi music with rousing highs and deep lows.Strong output power and special AUX output: use TI's classic power amp IC, each channel can output 100W(4Ω) and easily to drive all 3-8Ω passive speakers, adds 3.5mm AUX output easy to connect another amplifier or active speaker / subwoofer to build multiple channel system and enjoy wonderful home theater experience.With multiple digital audio inputs: Bluetooth 5.0 / USB / Coaxial / Optical / stereo RCA, compatible with most audio device such as phones, computers, tablets, TVs, TV, CD players etc. The perfect combination of DAC and amplifier, very suitale for audiophiles who have various audio devices. Product Description 1*ST-01 PRO Amplifier with Bluetooth Antenna1*DC 24V Power Adapter1*Remote Control1*USB Cable 1 Front 2 Back 3 Side 4 Top 5 Packing List Technical Specifications Audio input Bluetooth / USB (PC-USB) / Coaxial / Optical / RCA / U-disk (only ST-01 PRO supported) Audio output Banana speaker jacks / 3.5mm AUX Max output power 100W+100W (4Ω) Matched impedance 3-8Ω Sampling rate supported USB input: 96KHz/24Bit, Bluetooth input: 48KHz/24Bit, COAX/OPT inputs: 192KHz/24Bit Supported formats of U-disk MP3 / WAV / WMA / FLAC / APE Max capacity of U-disk 64G Treble / Bass adjustment range ±6dB System PC-USB supported XP/W7/W8/W10/MAC/ Linux Frequency response 20Hz-20kHz(±1dB) S/N ratio ≥98dB THD 0.07% Working voltage DC 18-30V Dimensions(W*D*H) 115*98*54mm / 4.53*3.86*2.13in Net weight 661g / 1.46lb