I try to set up my H90 with the RJM pbc10 so I can use one patch before my drives and one at the end of my chain.
For this I recommend using the H90 in Dual Routing Mode where Path 1 (I/O 1&2) can be used for Pre effects and Path 2 (I/O 3&4) can be used for post effects.
I also want to send the ‘out 1-4’ straight to the H90, so I bypass my drives for one amp that has natural overdrive. Is it possible to have 3 mono inputs?
In Dual Mode, the H90 can only have two mono inputs, I/O 1 and I/O 3.
I recommend you study this video to get the best grasp of what is possible with dual routing modes. If you go to 12:35, I talk about how to connect the H90 to a loop switcher: https://youtu.be/0G_WtfUatSc?si=jUnDnDUf5UbRfZdI