Review on Enhanced Bluetooth 5.0 Stereo Audio Amplifier: Fosi Audio BT10A (2021 Upgraded) by Jason Whitaker

Amplifier works and sounds good at all volume settings as long as you use the AUX jack. I tried a bluetooth connection and as others have noticed the sound turns on and off at about 1/2 the volume setting higher. BT is quite easy to connect and works great at low volume. But as soon as the volume gets too loud, the sound turns on and then off again after a 0.5 second pause. Rather annoying. The AUX input works fine so I just removed the BT antenna and just used AUX. Pretty and small, sounds good and is loud enough for general listening. Maybe one day I'll take it apart to see if I can fix the on and off problem. Being a Class D amp I suspect a shielding issue between the Class D and BT amp sections. After disassembling the amp, I found that the negative speaker output jumper (from the circuit board to the terminal pin) was routed right through the bluetooth section. The very close location of the speaker output seemed to interfere with low-level Bluetooth circuitry. I just bent the wire a bit and voila! Problem solved! The only tools needed are a 2.5mm hex wrench for the rear screws and needle nose pliers for the three volume controls (remove the knobs first).