Earth loops are tricky things, as removing safety earths can cure hum, but could kill you if there's a fault.

For example, you're holding your guitar and your lips touch a microphone. One is plugged into faulty equipment which isn't earthed, the other is plugged into equipment whish is correctly earthed... you become a capacitor between the two. Death can be instant. No joke.

Simple answer? Leave earth loop tracking to those who know what they are doing, or learn about it. An earth loop hum is caused by a current flowing in the earth wire - maybe only a few millivolts, maybe more - and you need to know how it is getting there.

Your best protection is a good DI box with transformer isolation. If used properly, the current then has nowhere to flow.

I'm a professional P.A. engineer, BTW.