I used two storey perfboard to assemble together following components

1) Onion Omega node

2) micro usb power connector 

3) 5v to 3.3v linear power convertor to power onion node

4) Conexant usb sound card (just what i had laying around). Originally i was planning to use I2S DAC but i found issues firing it up with onion node and downgraded to this simple usb card. One day i might fix it up and get back to DAc that i have prepared for that

5) Small schematic to power relay switch

This sandwich assembled on the back panel of my amp, which is hidden inside my couch and have no direct access. Relay module controlled by Omega replaces power switch inside my amp. This allows me to have it off when i don't need it and save some considerable amount of electricity.

Relay module is taken from pretty standart arduino relay module. I changed schematics with the one proven to work more reliable from 3.3v level line.

Whole Omega sandwich eats around 300mA of usb power.