Bluetooth uses the QCC3034 Bluetooth module, which supports HD lossless transmission, and Bluetooth decoding uses PCM5102, which makes the sound quality of Bluetooth comparable to wired transmission. Plus U disk playback function, support MP3, WMA, AAC, WAV, FLAC format. The op amp uses the NE5532, pluggable design, which can be upgraded to a more advanced op amp by itself. The large heat sink ensures long-term stability, and the large capacity filter capacitor makes the power supply more stable and the ripple is lower. RCA seats are gold-plated for greater durability. Product model: D21U Output channel: 2.1 channel Input : RCA, Bluetooth BLUE, U disk U disk file format: MP3, WMA, FLAC, WAV 16BIT, 44.1KHZ-48KHZ Power amplifier chip: TPA3116 x 2 Bluetooth version: Bluetooth 5.1 Frequency response range: 20-20KHZ Power supply: 19V-24V, the higher the voltage, the greater the power Output power: 50W x 2+100W/4 Adaptive horn: 10W~300W 4 8 6 Bluetooth transmission distance: 10 meters Protection mechanism: power reverse protection, short circuit protection, self-recovery overheating protection Size: 116 x 150 x 38MM DC power socket specifications: 5.5 x 2.5 color:Grey Material: aluminum Package Contents: 1 x amplifier 1 x English instruction manual Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.