problem
A chain is only predictable when every processor receives a level it can handle.
A processor sounds better, but it is also louder. The next plugin reacts harder, the limiter works sooner, and the final comparison is no longer fair. That is gain staging drifting through the chain.
When level handoff is uncontrolled, you start approving volume changes instead of tone changes.
EQ boosts, saturation, widening, compression make-up gain, and clipper output can all raise level before you notice. Small increases add up fast across a mix bus.
Some plugins also have internal sweet spots. Feeding them too hot can change distortion and detector behavior before the output meter looks alarming.
Compare processed and bypassed signals at similar loudness. Watch input and output meters at every major stage, especially before compression, saturation, clipping, and limiting.
Meter Core gives the chain a fixed reference point so you can see whether a plugin improved the mix or only made it louder.