SI Expression 3, stereo channel on mono mix

Audiocarlo

Hello, in my SI Expression 3 I want to send a stereo channel (ST 1) to two mono mixes (MIX 13 and MIX 14) at the same time. It works, but I have both Left and Right channels summed on both outs. Is that a chance to choose sending only one channel (Left or Right) to each out? I would like listen Left on MIX 13 and Right on MIX 14. Obviously Pan become Balance on stereo channels, so if I turn balance left I have Left channel on both outs, the same if I turn right. Am I forced to use two mono channels instead of ST 1 or is there a possible solution? Thank you.