Feature:1. [High Performance] Sound amplification function, gain 20dB (10x), drive a variety of sound amplifiers and high resistance, low resistance headphone without pressure. Dual op amp NE5532, high frequency electrolytic capacitors, noise reduction circuit design, no background noise, effective gain sound, improve sound quality.2. [Long Distance] Sound preamplifier with HiFi Bluetooth chip, external antenna to achieve long distance Bluetooth reception, measured up to 50m or 164ft or more, with volume adjustment knob, you can freely adjust the volume.3. [Sound Distribution And Mixing] Sound distribution function, three sets of interfaces can be output at the same time, two sets of RCA interfaces, a 3.5mm headphone interface sound mixing function, 3.5mm interface input and Bluetooth sound can work, mix and output at the same time.4. [Power Supply Specifications] DC5V12V power supply, 5v220ma, 12v85ma working current, stereo sound preamplifier can be powered by 12V power adapter, mobile power or cell phone charging head. Please use premium power adapter or charging head to avoid AC noise (without plug).5. [Compatible Devices] Input: DVD, CD, set top box, MP3, TV, cell phone, computer, tablet, microphone, phono turntable, sound card, guitar, bass, electronic musical instruments, game consoles and more. Output: Speakers, subwoofer, reverb, AV receiver, post amplifier, headphone, etc.Specification:Item Type: BT Sound PreamplifierMaterial: Aluminum AlloySize: Approx. 12 x 5.3 x 4.5cm or 4.7 x 2.1 x 1.8inColor: BlackPower Supply: DC 5-12VChip: Dual Op Amp NE5532BT: BT5.0Working Current: 5v 220mA, 12v 85mASound Amplification Gain: 20dBInput Interface: 3.5mm Dual Channel, Impedance 10kOutput Interface: RCA Interface Dual Channel, Impedance 600, 3.5mm Headphone Port, Impedance 16-600Working Frequency: 20HZ-20KHZ.Package List:1 xBT Sound Preamplifier1 x USB Cable1 x Antenna Note:Manual measurement, please allow some errors.