Distorted Aux Out Recording

by Alex
(USA)

I am trying to record to a Boss BR-800 digital multitrack recorder from my CVP 609 GP. I'm using the L and R aux outputs to corresponding inputs on the Boss. During gain adjustment I'm careful to keep max level to peak at about -6 db. However the resulting recording has terrible distortion. I've used exactly the same setup previously with very good results. What could I be doing incorrectly?