This small 15 mm x 24 mm x 2 mm shield features a class D audio amplifer and is capable of delivering up to 2.5 W into 4-8_ impedance speakers. The onboard amplifier runs at better than 90 percent efficiency when driving an 8_ amplifier at over half a Watt, making it well suited for portable and battery-powered projects. The board has a fixed 24 dB gain, but includes an onboard trim potentiometer for adjusting input volume.