Yes. In order to record the audio from a device connected to the MIX IN jack, a cable must be connected from the MIX OUT/PHONES jack to an audio interface that is connected to the computer. Use a cable with a stereo mini phone type plug.
**The audio signal from a device that is connected to the MIX IN jack will not be routed through the USB port to a computer. Only the internal sounds and audio of the S-1 will be routed through the USB port.