Quoted from Pintopia:DMD Hum trough speakers SOLVED! Had the hum throughput my speakers in the display panel.
Removed the grounding straps from the two display speakers. No more noise. Problem solved.
Would you be able to take a pic and point out which components were moved or removed. If not, no problem at all. I'm going to try and experiment with it sometime this weekend.
Recently, I floated the sound board with nylon screws and washers, and I feel it made a slight difference for the better, but not enough to consider it a victory. Hoping the solution mentioned above is my golden ticket as well.
Thanks!