Hi croalex,
The first diagram is correct. You do not need to split the guitar signal and go into the H90 in dual mono. Just connect the guitar directly to input 1. If you require a stereo signal to your amp, just connect outputs 1&2 to the amp. However, if your amp does not have stereo inputs, you just need to connect Out 1 from the H90 to the input of your Triaxis. If your preamp has a stereo output connect them to Inputs 3&4 of the H90.
