might have been Stereophile from the early 70's or a book I got on HiFi from the same time period: minimizing ground plane potential
need a VOM meter set for 120 VAC
plug the gear in, turn it on
measure the V between the equip chassis or ground lug and the power receptacle ground pin or cover screw...if a symetric plug (not with a larger blade for N) reverse the plug (after power down, etc., lol) and re-measure...orient for the lowest V...do this for all components...
the differences can be significant at times