DAC/AMP Fosi Audio K7 used for sale, clean, only three months old Device specifications - High sound quality - Ease of use, it has Bluetooth and wired connection via USB-C or regular USB - It runs most professional headphones without problems - It has a 4.4mm balanced port, a 3.5mm single-ended port, and a 3.5mm mic port - It has an EQ for Bass and Treble