2. (For MG20XU/MG16XU/MG12XU) Press the [ST] switch for the stereo channel that you set to USB and channels connected to mics.
For MG10XU, set the [TO MON/TO ST] switch on the stereo channel to [TO ST].
3. Turn on all channels to be used (except for the MG10XU), and adjust the levels as necessary.
For the MG10XU, simply adjust the level as necessary.