Used Fosi Audio BT30D 2.1ch power amplifier. This product has been tested and is in working order. Sound output via RCA terminals and wireless sound output via Bluetooth are both confirmed to be working without issue. The product is generally in good condition, but: The power adapter has slight scratches (see photos). The box has scratches and dents (see photos). Included: BT30D amplifier unit Bluetooth antenna Power adapter English manual Original box The following is quoted from the product introduction HP: Equipped with Bluetooth 5.0, compared to Bluetooth 4.2, it increases the efficiency of wireless music playback transmission and extends the transmission distance. The 2.1-channel power amplifier can connect two passive speakers and one passive subwoofer. There are bass and treble adjustment knobs for sound quality adjustment, allowing you to adjust the sound quality to your liking. The volume and frequency of the subwoofer can also be adjusted individually. Speaker outputs include + - speaker cables, and the subwoofer output is equipped with RCA active and passive output terminals. It can also be used as a 2-channel power amplifier. DC input range: 12-24V Maximum output: 50W x 2 + 100W Total Harmonic Distortion (THD): ≤0.04% Signal-to-Noise Ratio (SNR): ≥98dB Frequency Response: 20Hz-20kHz (±1dB) Input sensitivity: ≤280mV Termination impedance: 2-8Ω Input modes: Bluetooth and RCA Outputs: Active subwoofer, passive subwoofer, passive speakers For those interested in this product, we assume you have experience with used items. Please refer to the photos and understand that returns are not accepted before considering a purchase. Ships from Tochigi Prefecture No smoking environment There are pets in the household, so please refrain from purchasing if you are sensitive to this.