Advantage:  1. Wide range of applications.  2. APP has a timer shutdown function.  3. Supports custom 10-segment sound effects to be adjusted arbitrarily to make up for the deficiencies, so that different speakers can achieve better sound effects.  4. The mechanical switch can be turned off with one turn, no need to wait for a long time, which is convenient and fast.  5. Support Wuzhi Audio APP. Modify and change for Bluetooth name, password setting, prompt volume adjustment, on/off prompt tone, sleep aid, sound effect selection + custom sound effect, U disk playlist.     Note:  It is recommended to use an 8?? speaker and power supply of 9-24VDC without overvoltage.  If driving a 4ohm speaker, the power supply cannot exceed 12V.     Feature:  Adapter power supply: 9-24V/2A (can not be connected to AC).  Bluetooth version: 5.1.  Audio input: BT+AUX+USB+USB sound card.  Audio output: Left channel 15W + right channel 15W.  Volume adjustment: classic mechanical knob (with volume scale), stepless adjustment.  Switch machine: classic mechanical switch to turn ON and OFF,  no need to wait for a long time.  Adapter speaker: 5-30W 4-8ohm.  Protection mechanism: overheating, overcurrent, short circuit, anti-static protection.  Product weight: net weight 40g, including packaging 76g.  Special Feature:  Support Wuzhi Audio APP. Modify and change the Bluetooth name, password setting, volume adjustment of prompt sound, on/off prompt sound, sleep aid, sound effect selection + custom sound effect, U disk playlist.  Dimensions: 71*50*20mm.     Package includes:  1 x Audio Digital Power Amplifier Board