[Steve Fernino]

Sometimes, certain gear has more hiss than others....Different combinations of gear can make it worse. There are setting to help minimize the hiss (as Drax mentioned), however, if you find that one piece of gear is contributing more than another of the same type....I would upgrade when you can, to something with a higher noise floor.

For example... The powered EV 100 has lots of hiss even with the power turned all the way down...No matter what system I use it with.

The Mackie 1530 has practically nothing....
The hiss with the 1530s is totally system dependant.

Maybe the Numark mixer has alot of hiss?
I don't know alot about that particular mixer, however, my experience with multiple CDMix1 and CDMix2 units has basically given me the conclusion that they are noisy units. Lots of hiss...and even some digital "whine" on the mic channels. The 2 is better than the 1, but it is still there. We were using these for ceremony work...we have since retired most of them and are going the route of a Mackie board for ceremonies.

Also, if the hiss is at a minimum, but it is just a personal annoyance to you... You can purchase a noise gate. When set properly -
all signals pass through without hesitation ....however, during moments of silence, the hiss is blocked as the gate is closed. I wouldn't use this piece as a bandaid...however, it can give you that extra little bit of peace if even the slightest hiss irks you.