60 hz hum & Ebtech Hum Eliminator

[backbeat2000]

Anyone out there know anything about these:

www.ebtechaudio.com

We're running 2 & 3 way, JBL/Altec, crown, BGW, Rane x-over w/ 24Db slope, Rane MP 24 mixers, all balanced lines @ +4, sources are pro dj cd players w/unbalanced outs, low z mics.

All one nighters........one night no hum, next night hum's back

ground lift on crowns is no help, have isolated components from racks etc..

Any ideas will be much appreciated!!

Thanks,
Bill

[boputnam]

Originally posted by backbeat2000
We're running ... pro dj cd players w/unbalanced outs ...

This might be your (intermittent) source. Ground loops are tough.

One night you get set early (yea, right!), leaving everything on, start un-plugging from the source(s) toward the amps. Keep the gains low, and as you take the signal chain apart (working toward the amps) note the change in the ground-loop as you do it. Then work on that part of the chain that produces the GL.

My suggestion is to also try some custom cabling where you drop the shield/ground at the next component. Say, for instance with the unbalanced outs, as you wire those into the next component (say, the board), drop the shield (that's right, only use the tip/signal). In some racks, we've had to drop the shield/ground AT each next input (from CD player to board/pre-amp, board/pre-amp to crossover, crossover to amps) before we could lose the ground loop for good.

We had a 'round with this a while back:
Consumer and Pro gear - Connectivity (Link) You might also Search the Forum for "Ground Loops" - we've all had 'em...

Oh, and I WOULD NOT lift the ground on those Crowns...
Good luck!