Not sure I follow. But if you’re using 4CM, I’m assuming you’re using Dual routing mode. One thing is for sure. If you’re connected to input 1, you can only come out of Output 1 for mono or Output 1&2 for stereo; this is considered Path 1 when running the H90 in Dual Mode. Path 2 uses Input 3 (and/or 4) and Output 3 for mono and 3&4 for stereo. In dual routing mode you can use Path 1 for electric and Path 2 for acoustic. With an A/B switch, you can connect either guitar to H90 in both Dual and Insert mode. You’ll have to arrange your Playlist in such a way that you can access the electric effects and the acoustic effects at any given moment – example, Program 1-10 electric, Programs 11-20 acoustic, or something to that effect.
