This incredibly small stereo amplifier is surprisingly powerful, delivering 2 x 2.1W channels into 4 ohm impedance speakers (@ 10% THD). It features a class D controller that runs from 2.7V-5.5VDC, providing high efficiency (89% efficient at 1.5W into 8 speakers), making it ideal for portable and battery-powered projects.

The amplifier includes built-in thermal and over-current protection and remains cool in use. It offers fully differential inputs with 1.0uF capacitors, and the outputs are bridge-tied to drive speakers directly. The board comes fully assembled with 1.0uF input capacitors, a dual mini DIP switch for gain selection, 3.5mm screw-terminal blocks for easy speaker connections, and header pins for breadboard use. Speakers are not included, but any 4 or 8 impedance speakers will work.

• Output Power: 2.1W at 4, 10% THD; 1.4W at 8, 10% THD (5V supply)
• PSRR: 77 dB typical @ 217 Hz with 6 dB gain
• Designed for use without an output filter (wires under 2-4 inches long)
• Selectable gain: 6dB, 12dB, 18dB, 24dB via onboard switches or G0/G1 pins
• Excellent click-and-pop suppression
• Thermal shutdown protection
• Independent channel shutdown
• Low current draw: typical 6mA quiescent, 1.5A in shutdown

For more details, check the Adafruit tutorial. Note that the terminal blocks may be blue or black.