50 v ac on inputs tssub

I noticed some buzzing coming through amp. I used a ground loop isolator and it got worse. . I i measured several voltages all around my setup by systematically connecting things one at a time. It lead me to check a multimeter between earth and each pin on the input. every single pin had 50v ac (not sure how much current)..
I have not been game to connect anything back into it . In fear that the 50 volt will blow the sub up or worse blow my mixer and other equipment up..

Is this normal and what can I do to get rid of this voltage or at least protect sub and any equipment i connect to it..
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