 The Sonnet features a built-in USB audio function for audio playback, recording and live streaming. With Blackstar's accompanying Rec Root software, you can adjust the routing of USB audio between two useful modes, as well as fine-tuning the USB output level. Simply download the Rec Root application for PC or Mac from the Blackstar website and install. Plug in your Sonnet amplifier via USB and launch the Rec Root program. Here you can choose between two modes. Split mode allows you to record channels one and two separately, but as dry, post-EQ signals. Stereo Mix mode allows you to record a stereo mix of both channels, this time as a wet signal.