new amp vs old amp


i bought a acurus a150,i also have a dynaco st120,very different amps!one circa 1970 the other 1990'ish.ive done brief a/b testing,swapping them back and forth.my problem,i hear very little difference.why?do i need to listen longer?ive always though i had a good ear,i can here light notes and quiet backround instruments in music that most people cant!!!whats wrong
ampzilla747

Showing 1 response by bob_bundus

Ampzilla: your "brief A/B testing" makes it seem as though neither piece was warmed up thoroughly. By "thoroughly warming up" I mean powered on for at least 30 hours.
In solid state equipment it takes that long a time for the power supply regulators to attain thermal stabilization; any comparisons prior to that may be preliminary at best.