The new amp add-on board for NanoSound DAC, NanoSound Amp^2 (Pronounced as "Amp Square"), include both a headphone amplifier as well as a very efficient 5W speaker amplifier!
It runs very cool due to its up to 90% efficiency allowing the whole unit (Raspberry Pi + NanoSound DAC + NanoSound Amp^2) to be powered by one single microUSB power supply (individually if you choose to). It's surprisingly loud, and is enough to power a large room or a small lounge.
Switch On/Off via onboard bottons on the NanoSound DAC
Onboard relay rated up to 2A
Powered by single microusb or individually
Input Voltage: 5V
Output Power: 24mW @20Ω, 22mw @32Ω
Signal-To-Noise Ratio (SNR): 100db @20mW
Total Harmonic Distortion + Noise (THD+N): 0.01% @25mW