Volume from Aux Out is extremely low?

I'm using the Mackie U.420 Audio Interface. I'm trying to run Aux Outs into my external sampler, the Sp 303. When I do this, the volume is extremely low and I have to turn all my volume up (both inside Windows and on the U.420). I've tried different cables, same thing. The other outs work perfect. Headphone outs are working and so are the main outs, which are going to my KRK Rokits. I have all my volume up, the lights are even flashing to let me know they're peaking and still all I hear is barely anything.



Here is some info on the Mackie U.420, if it helps.



Maximum Output Impedance:

Main Out= +15dBu

Aux Out= +15dBu



Output Impedance:

Main Out= 120?

Aux Out= 120?















Mackie - U.420

Volume from Aux Out is extremely low?