Can't get rid of hum/buzz!

[ggunn]

thanks for the reply ggun.. yea ground loop seems to be the culprit, unanimously..

but you say "all but one of the components".... i have found that the buzz only disappears when i remove the ground of ALL of the components (the entire power bar)
with the ground lifted, the "grounded" light on the power bar comes back on soon as anything with 3 prongs is plugged into it. either one of the keyboards make it come on clear & bright, less bright with the mixer & even less with my keyboard amp.. but they all (each) cause it to light back up, to a greater or lesser extent, thus proving the existence of the ground loop.

Well, the third prongs are still connected to each other through the power strip even though they are separated from ground, so the loop is still there. Are you sure you have nothing else interconnected with cables that is grounded?

if i have an electrician friend come over, would it be a complicated job to check/reinforce the connection to ground for my house? isn't it as simple as tying a wire to a water pipe or something?

No, it is not that simple; the articles on grounding in the National Electric Code go on for about 70 pages. A visit from an electrician friend, if you have one, might indeed be helpful. A six pack of beer ought to pay for a short consultation.