Buzz/ humm

Trying to utilize a 20w acoustic amp for a floor monitor by utilizing the Aux. output on the back panel of my LI compact and the line input on the acoustic but can’t get away from the buzz/humming sound coming out of the acoustic amp. Suggestions?

How old are your instrument cables?  Are they also good quality cables?  I had cheaper cables that caused humming and buzzing.  I bought better cables and that fixed it.