whoa... be careful on your ears...
maybe your headphones impedance is too high so they sound not as loud as others. have you tried another pair of headphones?
here i tried it with a pair of semiopen beyerdynamic dt 880, with closed sony mdr v500 and with several random walkman headsets and i could have blewn my ears easily with all of them!
maybe your samples are at a low volume or you are not using full velocity or your mpc master level is too low (factory setting -12db)?
what headphones by the way?
peace jo