nad left channel goes out


i have a nad 2400 w/ 1600 monitor series...it will be playing just fine, and all of a sudden left channel goes. if i crank the volume up on pre-amp it comes back (i know you shouldn't do this), my question is, how do i tell if it is amp or pre-amp problem.. i do not want to disasmble entire system, if i can just remove one for repair.
jean
inletwolf
Jean,

It certainly sounds like you did the right thing and, yes, the balance control should control the sound in reverse. Just to confirm - you did only switch the cables in one place - the inputs to the amp?

Dick
that is what has me totally confused..the balance control..DOES NOT control in reverse?????????? i thought that was what was supposed to happen..but it still controls left and rt in the same way. the 2400 has the speakers attached to it.. the outputs are plugged into normal(as opposed to lab) on rear i wonder if that is why the balance doesnt change. the a side controls the front speakers and the b the rear..neither one will change from left to right balance..so i am not crazy!! i dont think>>>
just terribly confused..is there an input i am missing on the pre-amp??
jean
i really do not want to be the dumbest one here...but could you be more specific??? swap them from where to where... the speakers on the A channel go diectly out of the power amp to the speakers. the B chanel goes into a speaker switching box.
thanks
jean