H90, amp, and Strymon Iridium

Ideally, what you want to do with PRE/POST effects is more easily done using Dual Routing mode. But because you want to split the output of the H90 this can only be accomplished using Insert Routing Mode.

Connect your Iridium to Insert 1. Place Algorithm A before Insert 1 for the “pre” effect. Place algorithm B after Insert 1 for your “post” effect. Place Insert 2 after algorithm B but turn the Insert Mix down to zero. The level to your amp is controlled by the Send level of the insert and the stereo mix from the H90 will go on to your interface.

Yes, however, the H90 only allows either two mono inserts or one stereo insert. So, as it pertains to this setup, you will not be able to do everything you want to do with a stereo insert. Regardless, there is no reason to need a stereo signal from the Iridium if even the Iridium doesn’t allow you to have disparity between left and right, that is, unless you’re using different IRs for left and right.

Pressing the Routing button, we can add inserts by turning the 2nd and 3rd quick knobs, which correspond to Insert 1 and Insert 2, respectively. If you take the 3rd Quick knob and turn it fully clockwise, then the H90 creates a stereo insert. The 2nd Quick Knob is used to position it in the signal chain.