i recently purchased the yamaha hs80's and i'm getting used to them, when i've noticed that after several minutes use, i'm getting an oscillating hum (low, like a grounding issue hum) from the right side. i can turn the monitor off, and back on and it disappears; however after a few moments it's back. it also seems to distort the output from that side considerably as well as the cut the volume in more than half. i'm running them into a mackie 16 track mixer (used primarily for output only), but i do have another set of unpowered monitors being used by a power amp into a separate pair of main outs from the mixer. the hs80's are using balanced cables via the xlr main outs. i've moved the AC from one power strip to another with no results; the power strips are your average home depot types. i want to trouble shoot by unplugging the amp from the mixer, but since the amp isn't providing anything to the speakers, and this seems like an AC issue, i'm just shooting in the dark.
are there any suggestions to this annoying issue?