The Rocktron Buzz Kill AC HUM Exterminator Audio Isolation Transofrmer is designed to kill 60Hz/120Hz ground hum (BUZZ) by cutting the ground loop that can exist between audio products such as guitar rack systems, pro audio products, mixers, etc. Two channel inputs and outputs make it ideal to use in rack systems to KILL that constant ground hum. This is done automatically inside the Buzz Kill without affecting your tone or degrading your signal. 
Once you have detected a ground loop issue with your system, in order to exterminate it you must first find the connection causing the issue. Begin with one unit at a time until you have found the unit(s) causing the ground loop. Insert the Buzz Kill using the inputs and outputs between the offending units to eliminate the ground hum. NOTE: you should not use the Buzz Kill after a power amplifier.