I just got my used EBS BassIQ pedal today

I hooked it up through my Eden rig with my Modulus Q5 and it sounds awesome! But... when the filter is engaged and I'm not playing, there is a loud hissy/buzzy sound. I tried moving the 1/4" cables and the power supply cable, which helped a little, but didn't solve the problem at all. From what I've read these are supposed to be "noiseless" pedals, which this one is far from. Any help on how to fix this would be appreciated! Thanks!