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[Jason R. Callahan - CSS]

I've recently installed a system in a new construction church. The challenge is, as we fired up the new system this week, it appears the church lighting system w/dimmers is causing a buzz in the system.

After some troubleshooting, there is no question it's the dimmers. Turning the lights off totally resolves the problem. As the dimmers are turned up, so is the level of the buzz in the system.

I've explained to the electrician the challenge, which he then shared with me he wasn't sure how to fix? Nice!

I specified in the proposal that the audio/video would need to be totally isolated. Didn't happen. Although I'm no electrician, I explained that the dimmers were causing the challenge and they needed to be isolated from the audio circuits in the panel.

I'm meeting with the electrician this week. From talking to a buddy of mine that's just starting out in the electrical field, he suggested...

1. Moving the audio circuits to the other leg
2. Creating an isolated ground for the audio circuit.

I'm not for sure what the fix is, but ANY suggestions that I can share with the electrician to resolve this are much appreciated!!!

Kind Regards,
Jason

[BigEarsVA]

Ahhh.. yes, electricians.  

What you are getting is mostly from a grounding problem.  The best option is to move the audio circuits to another panel with an isolated ground.  It should be a real ground not something tied to a neutral.  I've seen that done more times than I can count.  

If you cant move to another panel, then you still need to isolate those grounds as much as possible.  You may still have some issues as lighting dimmers can feedback and cause all kinds of odd power flucuations.  Grab a meter and check the outlets for you audio system as you power the lights up and down.  See if there is considerable drain.  There is no easy solution really.  Continue to work with the electrician to get things separated as much as possilbe and make sure you have REAL grounds.  Make sure ALL your audio, mixer, processors, eq's, amps, EVERYTHING is on the same ground.

Hope it helps.

[Jason R. Callahan - CSS]

Awesome Info!  Thanks! - J

[Jeremy Short]

The most common thing I have seen over the years is the wiring up of the XLR jacks on the hardwire from the sound board to the stage. Pin 1 is the Ground/Drain (Bare Wire/Shielding). Pin 2 is the positive (Red, White or Clear Wire. Pin 3 is the negative (Black Wire). Do not connect the Shield wire to the casing I have found that this causes ground loop which can cause the hum from dimmer switches. The other problem I have found with dimmer switches is that if the sound wiring is next to the dimmer switches or the wires run over or next to lights that are on the dimmer switchs will cause this problem. Is there any movement of the sound system wires (ie. in an atic) I would move them a bit. The other thing I have found is that if the system is using unbalanced cables in the rack (ie. from mixer to eq to power amp) could also cause problems if posible I would switch to balanced cables at the rack.

[ProSoundWeb Community]