Hello Nick – that sounds a bit contradictory.  

If this is the setup:  H9(pre) > distortion pedal > H9(post) …  then the signal IS digitized twice.  

Once on the i/o for the pre and then a second time for the i/o on the post – regardless of where we place the effect (in the pre or post mode).    So it sounds like there’s an internal mixer that will now “hard pan” the effect based on the pre (side A) or post (side B) setting. But the signal will always be going through the convertors when the pedal is engaged.  Is that a correct assesment?