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 through the Aux Outs 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 speakers. 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= 120Ω
Aux Out= 120Ω

Will I need to buy an amp of some type to put in between the mackie and the Sp 303? Like mackie aux out -> amp in -> amp out -> sp 303?

https://www.google.com/#q=mackie+u420