Amazon.com: HiBy FC1 Portable dac Headphone Amplifier USB c dac amp hi-res Audio decoder with High Audio Quality Low Power Consumption for iOS Android Smartphones Computers-Black : Electronics
Sound Blaster X3 - Hi-Res 7.1 Discrete External USB DAC and Amp Sound Card with Super X-Fi for PC and Mac - Creative Labs (United States)
USB digital audio | Android Open Source Project
How to Record Audio with your Phone - Moody College of Communication - UT Austin Wikis