JimS888
Member
- Location
- California
- Occupation
- Electrical Contractor
I have a problem that I've spent months trying to diagnose. Our church recently moved to another building and installed a new audio system. The problem is that there is noise coming out of the audio system. It sounds to me like A/C hum. I seems to be related to the electric guitar and bass. When the system is powered up, the sanctuary lights are on and the guitar is plugged in with the gain turned up, there is an irritating buzz/noise/hum coming out of the speakers.
The setup is a multi amplifier rack powering speakers and subwoofers. There is LED and fluorescent house and stage lighting powered through a large Leviton dimmer rack. The dimmer is powered from an underground line that comes from a distribution panel (Panel "S") with a 230 amp 3 phase breaker. Panel S is fed from the main service located in a metal cabinet outside the building. That main service is fed from a transformer owned by the electrical utility.
The noise is at its worst when the lights in the sanctuary are at full brightness. When I shut the lights off, the noise is gone. The noise increases as the electrical load increases. When the guitar player faces forward or he turns 180 degrees, facing backward, the noise is somewhat reduced but when he turns to either side the noise gets worse.
Tests I've tried:
Bypass the dimmer panel by wiring the lights directly into the feed coming from Panel "S" - No improvement in the problem
Tried Furman power conditioners on each phase in line with the lights. - No improvement in the problem
Installed a Furman Power conditioner in the line feeding one of the amps. - No improvement in the problem
Temporarily disconnecting the ground going to the guitar foot controls. - No improvement in the problem
Tried a dual pickup guitar (Humbucker) - Slight improvement in the problem
Temporarily fed the dimmer panel from an isolation transformer that feeds another panel. - No improvement in the problem
I've tried several other tests with no success and am stymied, so I am reaching out to this forum for help
I talked with the installers who put in the new audio equipment and they seem very knowledgeable and professional. Several of them quickly said the problem isn't a ground loop but didn't explain their reasoning but it seemed to be based on the fluctuation in the noise when the guitar player turns from side to side. They offered no other explanation.
The in house audio tech bought a small device that plugs into an outlet that buzzes and displays line noise and the readings correlate with the noise coming out of the audio system.
I also set up a small portable 110 volt generator outside and wired several of the light channels into it, bypassing the dimmer rack. - the noise was gone! This test was just a small number of the lights but those same lights alone running through building power makes noise.
I also plugged one of the Furman power conditioners into a nearby 120 volt outlet and ran those same lights and that also seemed to cure the problem.
So I think I've eliminated the dimmer rack as a source of the noise and there also seems to be similar noise in other parts of the building when plugging a guitar into a small amp. My current theory is that the problem is emanating from somewhere upstream of Panel "S".
Has anyone ever run into anything like this? Any things you can suggest to test?
The setup is a multi amplifier rack powering speakers and subwoofers. There is LED and fluorescent house and stage lighting powered through a large Leviton dimmer rack. The dimmer is powered from an underground line that comes from a distribution panel (Panel "S") with a 230 amp 3 phase breaker. Panel S is fed from the main service located in a metal cabinet outside the building. That main service is fed from a transformer owned by the electrical utility.
The noise is at its worst when the lights in the sanctuary are at full brightness. When I shut the lights off, the noise is gone. The noise increases as the electrical load increases. When the guitar player faces forward or he turns 180 degrees, facing backward, the noise is somewhat reduced but when he turns to either side the noise gets worse.
Tests I've tried:
Bypass the dimmer panel by wiring the lights directly into the feed coming from Panel "S" - No improvement in the problem
Tried Furman power conditioners on each phase in line with the lights. - No improvement in the problem
Installed a Furman Power conditioner in the line feeding one of the amps. - No improvement in the problem
Temporarily disconnecting the ground going to the guitar foot controls. - No improvement in the problem
Tried a dual pickup guitar (Humbucker) - Slight improvement in the problem
Temporarily fed the dimmer panel from an isolation transformer that feeds another panel. - No improvement in the problem
I've tried several other tests with no success and am stymied, so I am reaching out to this forum for help
I talked with the installers who put in the new audio equipment and they seem very knowledgeable and professional. Several of them quickly said the problem isn't a ground loop but didn't explain their reasoning but it seemed to be based on the fluctuation in the noise when the guitar player turns from side to side. They offered no other explanation.
The in house audio tech bought a small device that plugs into an outlet that buzzes and displays line noise and the readings correlate with the noise coming out of the audio system.
I also set up a small portable 110 volt generator outside and wired several of the light channels into it, bypassing the dimmer rack. - the noise was gone! This test was just a small number of the lights but those same lights alone running through building power makes noise.
I also plugged one of the Furman power conditioners into a nearby 120 volt outlet and ran those same lights and that also seemed to cure the problem.
So I think I've eliminated the dimmer rack as a source of the noise and there also seems to be similar noise in other parts of the building when plugging a guitar into a small amp. My current theory is that the problem is emanating from somewhere upstream of Panel "S".
Has anyone ever run into anything like this? Any things you can suggest to test?
