Why turn off cab sim/IR for power train?

[Billc]

Hello. First time post and apologies if this is old stuff but why is it recommended that one turn off IRs etc in a preamp - in my case, Two Notes Le Clean - from the feed into my Power Stage 170? Thanks.

 

[Mincer]

Welcome to the forum!
My guess is that you would be going from the PS170 into an actual cab, which you would then actually mic up...so no need for an IR. If you were going from the Two Notes directly to a PA or recording console, you would use the IR.