Well … several things …
I removed the H9 from the effects loop and back in front of the amp and it was apparent that was brought the issue to my attention. Cool … but I have a few observations: The effects loop was running much hotter than my instrument signal. When I raised the input level of the H9 to try to match the amp's hotter loop level … the effects fade. (And they become louder and more resonant starting about 10 Db below peak inputs.) Leads me to believe that my amp loop line level does not agree with these algorithms in particular. Check it out and see if you find the same. Thanks.
