Changed circ.breaker-vocals became shouty:why?

Hi
I live in pre-war apt.building.The circuit breaker that was feeding my system was an old 15 amp gadget that was long ago discontinued.When i noticed that it was 15 amp i went and bought a $25 30 amp replacement for it.After installing it in the box i noticed that vocals and solo guitars became shouty and flat even though the rest of the spectrum became more dynamic,especially bass.After i put back the old breaker,the sound became 3-D and warm again,even though the system was straining at high volumes.Is it a circuit breaker burn in factor or something else at play here?My power amp is Pass X 250,5 driving 86db/4ohm Snell type B speaker (6 drivers per side,3 of which are 10 inches).
Outlets by PS Audio.Any ideas?Thanks a lot.