Perform V Ground Hum

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I just bought a Perform V about a week ago.  After hooking it up, there is a ground hum (about 80 hertz) coming out of it that I can't get rid of.   Here are a few notes about the setup:


 


Shure ULXD24/KSM9 > Perform V > Mixer (input>onboard compressor>onboard EQ).


 


1.  The input is all the way down and distorts if I turn up the gain at all.  I've trimmed down the gain coming out of the wireless receiver and it is working ok as far as input/distortion.


2.  I've swapped out the mic cables and checked wiring to make sure it isn't a problem with the cables.  Same result with all cables.


3.  It seems to be slightly less prevalent after a reset of the unit.  As soon any presets are loaded, it gets worse.  This is the case even without the preset being selected or HIT being on.  


4.  In order to get the mic up to an acceptable level on our sound system, we have to turn up the gain/fader which in turn amplifies the hum.  


5.  The firmware is updated to the most current version.  


 


Can anyone help?  Could this be a line/mic level signal problem?  It's a pretty neat little unit and I want to use it, but the hum makes it useless.