This is a Class A portable amplifier from XRK Audio. I had the completed product of a DIY kit using an Altoids tin made by the circuit designer. Despite being unbalanced with a 3.5mm jack, it runs on two 9V batteries, which is quite luxurious, but the sound is simply amazing. A search reveals that it's highly rated in reviews on overseas sites. https://www.etsy.com/shop/XRKAudio A 2.5mm to 3.5mm conversion cable and a Cypher Labs mini-mini cable are also included. Thank you.