eXtream Software Development has written custom USB audio code from scratch because Android does not support USB audio. No rooting is required.
Your USB audio device must be class-compliant in order to work: USB 1.1 and USB 2.0 class-compliant devices are supported with either USB audio spec 1.0 or 2.0. Devices that require you to install specific drivers under Windows or OSX will usually not work.
Make sure to connect your audio device BEFORE starting the app. If you get a message on start-up saying that the device failed to initialize, your device will not work (for now). Reasons can be that your Android device does not meet the requirements, it does not supply enough power (try a powered hub), the USB audio device is not class-compliant or you are not using an OTG cable (if needed).
USB Audio Recorder PRO v1.4.1 Apk