Will hookig up only 2 channels on a 3 amp hurt the

Hi every one, another rookie question from yours truly, I have a dbx BX-3 power amp which can be ran in 2, 3, or 4 channel configurations. I'm using the amp for my main speakers, and have the inputs connected to my Yamaha receiver. I've attempted to place the amp in a 2 channel configuration for more power as the manual show's,
but I get a slit buzzing sound from the left speaker when I do this. To get rid of the buzzing sound, I've used the 3 channel configuration, but without a center channel. That's still running through my receiver. I hope I'm making myself clear. So, to my quesion. Could it hurt my main speakers by using the 3 channel configuration with out the bridged 3rd channel? Remeber, I'm a rookie
so please be nice.:)