Noisy digital out- defective MPC ?

There is noise making the digital out unusable. Only when in play mode or when pads are played. The noise continues some seconds after , clearly visible on the software /card mixer, crackling noise (spikes up to -3) . The cable is digital, no cheap sh..., it is Audiofire card,digital in/out works fine with everything else. Tried internal or Spdif clock source , same thing, also read here about setting the clock before starting MPC, same thing.
Could it be my MPC is f..d? I really want/need to use digital out, my MPC is new but I wouldnt like to loose my JJs OS in case of giving it back to the store.