Unofficial Mackie User Forums > DL1608/DL806/DL32R/ProDX Mixers

Grounding Hum from FOH

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Harpman:
This issue doesn't happen all the time, but still annoying.  I get an occasional hum coming from the FOH.  I know it's a grounding issue. Maybe even a "ground lift" issue.  A buddy of mine Jeff (also a DL1608 user and member of this forum) suggested lifting the ground by using a 3-to-2 AC adapter to remove the ground. I'm using a GC LiveWire Power Conditioner (PC1100) to plug all the components into, including the DL1608.  I've thought of isolating the DL1608 on it's own power conditioner or removing the ground from the DL1608 using the adapter.  Any suggestions would be very welcomed here.  We have a gig tonight and it may not be an issue at this venue, but I don't want any surprises either ;).

Wynnd:
I like all my amps and mixer on the same circuit.  (Not always a possibility.)  I've noticed that most of the time when getting a hum, it's frequently on a single channel from a mic or instrument.  Bear in mind that plugs in the same outlet, can come from different circuits.  I bought a tester to keep the lights away from the sound equipment and now with LEDs, we don't need that anymore.  I'm not a fan of dropping the ground from the circuit.  It's there to protect you from electrocution.  (And you need it for surge suppressors.)  You should have a circuit tester to verify that the circuit is wired correctly.  They only cost a couple of bucks and don't take up much space.  Two of my power strips have nag lights on them when the circuit is bad.  (Bad or non-existant ground, incorrect hot and neutral.)   I've found bad circuits in Casino buildings that were less than 10 years old, so new isn't a guarantee that it was done correctly.  (And in spite of my better judgement, incorrectly wired circuits usually work anyway.)

WK154:
Based on your description of 1 AC source you should not encounter hum issues unless you are using unbalanced input or output devices or worst unbalanced cable to balanced devices. I would pack a few DI boxes. I'm enjoying Cyberhippie's Sonoma and Russian River Wine samples. One of these days I'll get down to your neck of the woods.

Harpman:
In this case the hum happens when all instruments and vocal mics are muted. I do have and carry a voltmeter for my IT business and work a lot with AC.  Ground-to-Neutral should be under .5 VAC, but I have seen it creep.  They certainly have "Ground Lift" on certain devices for a reason.  The issue I'm definitely getting is the 60Hz hum.  I will check it out.  It wouldn't matter if I moved the mixer to another receptacle anyway since in all likelihood, they are probably on the same 20A circuit breaker.  Thanks for you input.

Wynnd:
Balanced connections should help a lot!  Also, your gain structure can be used to minimize this issue.  Hopefully this is only something that you notice. 

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