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So I was changing a lightbulb last night…

I had just finished listening to a record and decided to change a lightbulb that had gone out directly above my turntable. When I started unscrewing the bulb I noticed a faint buzz coming from my speaker. I then turned the volume way up on my amp and tried again. Turns out the buzzing was happening when my hand touched the metal light fixture, not the lightbulb. 

At first I thought the tubes in my phono stage were picking up an EM field from the light fixture and out of curiosity I grabbed a piece of foil and covered the phono stage and then tried tapping the fixture again, same buzzing. Then I switched the input on my amp to my DAC and tried the tapping, no buzzing. Switched the input back to the phono stage and tapped the fixture, buzzing continued. Then I covered the tonearm with the foil and the buzzing went away almost completely. 

So it appears my tonearm is picking up some sort of signal from the light fixture but only when I touch the fixture. If I turn the lights off there is no buzzing when I tap the fixture. The setup is in the basement and I use LED lights that are recessed in the ceiling and wired to an “LED” dimmer switch. The audio gear is on a dedicated circuit.

Any of the knowledgeable folk on here have an explanation for what’s going on? Doesn’t effect SQ AFAIK since the buzzing only occurs when I touch the metal fixture. Seems odd but I thought it was interesting and maybe a chance for me to learn something from the members. 

I uploaded a video of this happening to Imgur that I’ll try pasting here:   
 

 

Cheers

durte30
durte30 OP
17 posts
 

@jonwolfpell you’re right, the buzzing was worse with the dimmer all the way down.  Maybe I’ll get a regular switch after all.

@musicfan2349 any advice on how to make sure the fixtures are grounded?

This has reminded me that I used to have a musician roommate in the room directly above this and he would always turn the lights off in the basement when he was recording music. I’m guessing he heard something similar with his recording gear as I’ve heard with my stereo gear. 

On another note, I pulled all of the LED’s to see if another bulb would make a difference but then realized I didn’t have any incandescents laying around but I did have a fluorescent so I plugged that into one of the sockets. For the first 5 seconds or so the light was like pulsating on and off and each time it came on the buzz would come from my speakers. Also the little light on the dimmer switch was going up and down with the light. It sounded like a light saber going back and forth. My dog was looking at me like surely this is Armageddon haha. I’m guessing the bulb just needed to warm up because it stopped flashing after a bit and stayed on. The buzzing wasn’t any better with the fluorescent vs LED. 

durte30 OP
17 posts
 

@harpo75 maybe for the sake of experimentation I’ll try some ferrite rings on the switch wiring and see if that does anything. 

harpo75
128 posts
 

dirte30 - That would probably help with RFI. Different sizes affect different frequencies. It can get pretty technical trying to examine the line noise for the frequency or frequencies that are causing the problem. But if you have some lying around it would be worth the experiment.

designsfx
803 posts
 

@durte30 

Did you just say that you plugged in a fluorescent bulb? Are you light fixtures meant for CFL lighting? Some LED’s will work with this type of lighting if they are compatible with the fixtures ballast. My guess again- the dimmer. I’d check to see if your dimmer is meant to work with CFL fixtures.

musicfan2349's avatar
musicfan2349
317 posts
 

@durte30 DISCLAIMER: I'm  NOT an electrician. Read on at your own risk.

Please don't put a fluorescent bulb in a dimmable fixture. From what I understand fluorescent bulbs are designed to work in a fairly narrow voltage range. You can damage the bulb and perhaps your dimmer.

Through a surfeit of caution I've installed several dimmers and LED bulbs in my home and managed to not kill myself or burn down my home. I like Lutron products as their website has some handy on-line tools for the do-it-yourselfer.

Phono sections tend to be very sensitive to EMI so I'm not too surprised by your experiment. You might talk to an electrician about checking your home's wiring.

OTOH, I'm of the opinion that unless you stand on a ladder touching the fixture while you're listening to music, you might be able to just leave well enough alone. Remember the old "Hee Haw" skit?

Patient: Doc it hurts when I do this. *waves arm around*

Doctor: Well, don't do that! *smacks patient with rubber chicken*

Happy listening. 😉

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