So this may be the same behavior in the "real world" but I don't have a way to check it.
I'm trying to go for a Smashing Pumpkins thing which, I'm pretty sure, is a JCM800 + Big Muff. I've got a Reampzone JCM800 2203 gained up (no pedal baked in) and trying to add a Big Muff to that. I've tried both the old Muffin distortion and also playing with the Kemper Fuzz. What's happening when I hit that fuzz is that the whole bottom end is falling out and also...probably because of that...it feels like it's actually dropping the volume which is not what I want. Is this how it happens with a real Big Muff? Even if an amp is gained out, a pedal normally just changes the tone and doesn't drop the volume per se. Maybe I need to be adding the Big Muff to more of a breakup amp.
I think I've seen some others counter this kind of thing with a post amp block EQ. Just looking for some tips and tricks here.