A&K first with flagship ESS DAC for portable hybrid audio system
Amazon.com: eSynic Professional 16-300Ω Headphone Amplifier Portable Headphone Volume Amplifier Rechargeble Headphone Amp Desktop Amp With 3.5mm Jack & A Two-stage Gain Switch for MP3 MP4 Phones and Computers etc : Electronics
Headphone Amp | Personal Practice Amplification - Electro-Harmonix