Feature: 1. Qualcomm BT version 5.0, support protocol: APTX-LL/APTX/AAC/SBC. 2. Support BT reception and one RCA audio input, automatic switching, BT priority. (The default is RCA input, automatically switched to BT mode after BT connection.) 3. Support high and low frequency adjustment, independent knob adjustment, increase or attenuate high and low frequency sense through knob adjustment to meet listening needs. 4. Use DC12V power supply, power adapter is included. 5. Tube hot plug design, easy to replace different styles of tube, common models are 6j1/6k4/5654, etc. Only tube with the same pin definition can be replaced. If the model is uncertain, do not replace it to avoid damaging the mainboard components. Specification: BT receiving sampling rate :16BIT/44.1KHZRCA input: 10K ohm impedance, ≤3VrmsRCA output: 10K ohm impedance, 3VrmsDistortion rate: 0.03%SNR: 100dBInput: DC 12VMaterial: Aluminum alloyColor: Black, Silver (Optional)Item Size: 15.5*9.5*3.0cm/6.10*3.74*1.18inWeight: 347g/12.24ozPackage Size: 27.8*21.2*6.7cm/10.94*8.34*2.63inPackage Weight: 635g/22.39oz Package List: 1 * BT Decoder2 * Vacuum Tube1 * BT Antenna1 * Power Adapter1 * User Manual