There is probably more to this than you are telling us – bypass of DSP B is essentially the same as Thru' so is unlikely to cause a problem.
Your problem may be the equipment that follows the H8000 – try turning down the output gain and see if the distortion changes.
Also, make sure that your expensive 1/4 to XLR cable has all the XLR pins connected (typically 1 and 3 to sleeve, pin 2 to tip.
