Sounds like there’s a signal mismatch. Most amp effects loops function at line level, not instrument level. Go into the H90 system menu > I/O > and set “In 1/2” to Line. On the second page set “Out 1/2” to line as well. These parameters can serve to match the signal going through the amp’s effects loops.
For me, the best way to ensure the H90 is setup properly, I like to use an INIT Program, which you find on the User 2 Playlist. They are just programs that consist of two THRU utility algorithms. They are set for unity gain, so it’s the perfect way to ensure that whenever the pedal is bypassed or activated the signal should not change. Set your input and output operating levels (instrument or line) so that you don’t hear any change at all. Then you’ll start with the optimal foundation to start making adjustments to factory programs.
