for the third mic you would just run one channel in the 2nd v2. think of it this way, grace makes 3 main models for studio pre's. the 101 (1 channel) the 201 (2 channels) and the 801 (8 channels) you can run the 801 with 5 mics in it and still get the same effect. the v2 doesnt mix down to a stereo mix, it just preamps each channel individually.