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Topic: Building Noise |
Bob Brocius
From:
Lake Katrine, NY USA Don't blink, you'll miss it.!
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Posted 26 Oct 2001 8:44 am |
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I frequently play in a place that has many electronic dimmers on the lights. These dimmers play hell with all our equipment and the buzzing is terrible. I have heard that there are devices available that will suppress this. I've already considered using a motor-generator set out in the parking lot with a long heavy cable. Does anyone know of other, less drastic, devices? If so, please reply and tell me what they are and where I can get them, if you would know. Thanks.
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Bobby Brocius, ZumSteel D-10, 8x8, Blue, BL910 PUs
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Johan Jansen
From:
Europe
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Posted 26 Oct 2001 8:51 am
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Bob, I don't think this really helps..
If you are on the same powergroup as the dimmers, check the voltage delivered to your amps, when they are used.If it changes, shut the amps off, you will ruin your gear!
Try a different"free" group for your amps, if this doesn't help, it's the "radiation"from the lightshow , dimmers and maybe fridge etc.A big powersuply outside won't make any difference then, but it's worth the try..
JJ
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STEELDAYS 2002
my web-site
my bands CODand TSC
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Greg Cutshaw
From:
Corry, PA, USA
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Posted 26 Oct 2001 10:10 am
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Bob, I emailed you a fix that I have used in the past for cheap dimmers if that is your problem. Try this link for more info:
http://www.epanorama.net/documents/lights/lightdimmer.html#harmonics
or read the excerpt below:
Buzzing problems with dimmers
Each good dimmer has a filter choke inside. Those chokes help to filter out electrical noise that often causes hum to be picked up in sound system and musical instrument pick-ups. The slower the current rise is, the less noise is picked by sound system.
The chokes also help to eliminate 'lamp singing' that can cause audible noise to come from the lighting fixtures. Lamps with power rating of 300W or more tend to more or less acoustic noise when dimmed. If this acoustic noise is a problem can be removed by adding a series coil which limits the current rise time to around 1 millisecond.
In providing those filtering functions, the chokes themselves can generate a slight buzz. Fast current changes in the coil can make the coil wiring and core material easily vibrate which causes buzzing noise. A little bit of buzzing is normal with filtered dimmers. If the buzz from dimmer can be a problem it is recommended that the dimmer is placed in the area where this buzz will not be a problem.
As far as the 'bulb singing' concerned, a bulb consists of a series of supports and, essentially, fine coils of wire. When the amount of current flow abruptly changes the magnetism change can be much stronger than it is on a simple sine wave. Hence, the filaments of the bulb will tend to vibrate more with a dimmer chopping up the wave form, and when the filaments vibrate against their support posts, you will get a buzz. If you have buzzing, it's always worth trying to replace the bulb with a different brand. Some cheap bulb brands have inadequate filament support, and simply changing to a different brand may help.
Buzzing bulbs are usually a sign of a "cheap" dimmer. Dimmers are supposed to have filters in them. The filter's job is to "round off" the sharp corners in the chopped waveform, thereby reducing EMI, and the abrupt current jumps that can cause buzzing. In cheap dimmers, they've economized on the manufacturing costs by cost-reducing the filtering, making it less effective.
In very high power dimming systems the wiring going to lighting can also cause buzzing. The fast current makes the electrical wiring to vibrate a little bit and if the wire is installed so that the vibration can be transferred to some other material then the buzzing could be heard. The buzzing caused by the vibration of the wiring is only problem in very high power systems like theatrical lighting with few kW of lights connected to the same cable. Better filtered dimmers can reduce the problem because the filter makes the current changes slower so the wires make less noise.
Greg |
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Donny Hinson
From:
Glen Burnie, Md. U.S.A.
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Posted 26 Oct 2001 5:00 pm
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| There are devices called "notch filters" which take a very narrow frequency band (say from 56-64 cycles(hertz), and attenuate it by 30 or 35dB. These can prove very helpful when nothing else will do the trick. (Actually, I've often thought good amps should have this circuit built-in for both 60 and 120 cycles(hertz) noise problems...the two major offenders.) |
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