Get Rid of Dimmer Buzz and Hum

Do you have a buzz or hum? Here’s how to track it down and get rid of it.

I want control over my light levels and I love dimmers. I have them all over the house. But one problem with dimmers can be buzz. Even if the buzz doesn’t sound like it comes from the dimmer, the dimmer most likely is the culprit.

Turn off the dimmer completely, not just dimmed down. If the buzz goes away, you can just replace the dimmer with a switch.

Not all dimmers are the same. A better dimmer might help.

If you can’t tell where the hum or buzz is coming from, try unplugging things until the noise goes away. You might be able to plug things in somewhere else.

How Dimmers Work

Solid-state light dimmers do not change the amount of electricity going into a light. They change the amount of time the full power line voltage goes to the light. They turn the power to the light off and on which makes the light look dimmer.

Solid-state dimmers operate by turning the current on and off 120 times per second to achieve the dimming effect.

Lutron: For Your Information…
Minimizing Radio Frequency Interference
www.lutron.com/europe/ResourceLibrary/360484.pdf

RFI: Radio Frequency Interference

The power that comes out of the outlet is a pure sine wave, with no harmonics. But the dimmer switching the power on and off makes high frequency harmonics, sometimes an audible hum.

Sometimes this goes through the air or through the wiring and creates a hum from nearby audio equipment.

This rapid current switching may cause radio frequency interference (RFI) — an audible buzzing noise — with sensitive audio and radio equipment.

Lutron: For Your Information…
Minimizing Radio Frequency Interference
www.lutron.com/europe/ResourceLibrary/360484.pdf

How Can You Get Rid of Buzz?

A better quality dimmer might help. Every Lutron dimmer contains a filter to suppress RFI, radio frequency interference.

If you can, move things. Sometimes just plugging it into a different outlet gets rid of enough buzz. Or move things to a different room. RFI goes through the air.

If the buzz is the bulb, try a different bulb. Try a different size, wattage, or shape bulb. Sometimes sturdier rough service bulbs reduce buzz.

Debuzzing Coils

A debuzzing coil can filter RFI, radio frequency interference.

Lamp Debuzzing Coils (LDCs)

The most effective way to reduce RFI is to install a lamp debuzzing coil (LDC) into the lighting circuit. Lamp debuzzing coils reduce RFI by slowing down the inrush of current during the rapid switching cycle of the dimmer. As the current inrush is slowed down, the effect is that RFI on sensitive equipment is reduced.

The type of LDC required depends on the total wattage of the dimmer’s lighting load. Lutron has two LDC models available to help reduce lamp buzzing. Listed below are the model numbers of the Lutron LDC models and their respective capacities.

Lutron: For Your Information…
Minimizing Radio Frequency Interference
www.lutron.com/europe/ResourceLibrary/360484.pdf

Lutron makes two models, LDC-10-TCP is for 600 to 1200 watts. LDC-16-TCP  is for over 1200 watts  up to 1920 watts. Lutron makes debuzzing coils for higher voltage, too.

UPDATE: Lutron now has four debuzzing coils.

Lamp Debuzzing Coils (LDCs)

If all other solutions are ineffective or impractical, an LDC can be used to reduce lamp buzz. When an LDC is wired in series with the dimmer, it slows down the inrush of current during the rapid switching cycle of the dimmer. As the current inrush is slowed down, the lamp filament vibration and lamp buzz are reduced.

Lutron has four LDC models available to help reduce lamp buzz. The type of LDC required depends on the total wattage of the lighting load. Listed below are the model numbers and their respective capacities.

Lamp Buzz with Solid State Incandescent / Halogen Dimmers
www.lutron.com/TechnicalDocumentLibrary/Lamp_Buzz_With_Solid_State_Incandescent_Dimmers.pdf

• CPW0035 (formerly LDC-17-TCP) for 100 to 200 watts
• CPW0036 (formerly LDC-33-TCP) for 200 to 400 watts
• CPW0037 (formerly LDC-67-TCP) for 400 to 800 watts
• CPW1346-OCP (replaces LDC-10-TCP) for 600 to 1200 watts

The same LDCs work for higher voltage, too. Just divide the watts in half. They fit into a standard size electric box, just like any switch or outlet.

The best prices I have seen are on eBay.

Find Lamp Debuzzing Coils on Amazon >
Find Lamp Debuzzing Coils on eBay >

Get Rid of Transformer Buzz

Magnetic transformers are often the source of the hum. Magnetic transformers usually cost less than electronic transformers and are often for much higher wattage. But, if they are dimmed, they buzz. The lights can buzz, too. This happens with Monorail and Cable Light.

If it’s just the transformer, can you move it? Low voltage wire is pretty cheap. Try moving the transformer into the attic or somewhere else far enough away that the buzz doesn’t bother you.

If the transformer can’t be moved or if the lights buzz, you can add a debuzzing coil.

Tech Lighting makes debuzzing coils for 150 and 300 watt tranformers that fit inside the transformer housing. The two models are 700DIM150 for 150 watt transformers and 700DIM300 for 300 watt transformers.

They call it a Debuzzing Dimming Coil, but it doesn’t dim. It just debuzzes the buzz from dimming.

Other manufacturers make them, too. WAC Lighting and Satco used to make them, although I don’t see them in their current catalogs. Edge or PureEdge Lighting makes them. The models are TDB for Transformer Dimming Debuzzing Coil, followed by the wattage they are rated for, TDB150 up to 150 watts, TDB150LED for LED drivers, TDB300 for up to 300 watts and TDB600 for up to 600 watts.

Find Debuzzing Dimming Coils on Amazon >
Find Debuzzing Dimming Coils on eBay >

Or convert to LED. LED uses much less power. In my experience, an electronic transformer or driver doesn’t make noise when it is dimmed. It really shouldn’t.

The photo at the top of the page is public domain from Popular Science magazine of a 1940 public relations demonstration of RFI frequency modulation improvements in FM radio. A lightning-like arc from a million volt three phase-transformer as a source of interference behind the radio. The prototype radio, center, had both an AM and FM receiver to demonstrate that RFI interference is less in FM.