74NK 
http://www.iqaudio.co.uk/home/9-pi-digiamp-0712411999650.html image: http://74nk.xyz/gpio.php - 74nk.xyz/pi-digiamp.jpg I want to is this worth a purchase as an amplifier extension for my Nano-Pi2. Do you think this might work? What packages should i download for the GPIO be able to able to turn on off, and other connections with GPIO headers? for example it says "AMP can be enabled / disabled via Raspberry Pi’s GPIO22" what pin would that correspond to on NanoPi-2? In friendlyarm wiki it says 22 pin is for "PWM0/GPIOD1".