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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
holmz's avatar
holmz
2,328 posts
 

Off-topic, but do you use your turntable immediately adjacent to your speaker? If so, then I would anticipate experiencing problems much more significant than this finding.

If it was magnetic field I would agree, but I suspect that this is either voltage field, or noise coming in on the ground or neutral side.

It could take an O-Scope to figure it out.

Since the foil wrapping ameliorated the effect, then we can probably rule out the ground (and any added capacitance added in when it was touched.)

which leaver us with whether the tonearm tube is metal, plastic, wood, etc.?
I do not think that foil wrapping metal should affect it.
If it did it could be the ground of the tone arm, if there is any.

What is the tonearm made out of?

And if the arm is not conductive, then maybe the wires inside are not twisted at all. But I am not sure if is any concern.

 

While it is pretty interesting, I am not sure if it is a problem that begs a solution?

vinylandtubes
44 posts
 

@durte30 Yes, vibrations first came to mind.  Glad that you’re not experiencing any such issues.

edisoncarter's avatar
edisoncarter
27 posts
 

The metal light fixture is grounded. Your body is another path to ground. Touching it creates ground loop hum. Very low in level. But phono stage is very high gain. One might even say Max.

durte30 OP
17 posts
 

@holmz The tonearm is carbon fiber, the clearaudio ‘Satisfy Carbon’. I wasn’t really looking for a solution with this thread I just thought it was something interesting to share here. Although after a handful of people recommended ditching the dimmer for a regular switch, I’ll likely do that soon because now if I ever listen to a record with the lights on I’m going to think I hear the buzz.

@vinylandtubes Before purchasing the turntable I’d read some reviews of people having a lot of skipping issues just from foot falls. I had a local countertop company cut and polish a piece of scrap granite to the dimensions of the tabletop under the TT. I’m not sure if the granite is the reason I’ve had zero skipping/vibration issues but it certainly doesn’t seem to hurt. 
 

@edisoncarter Interesting, thanks!

holmz's avatar
holmz
2,328 posts
 

holmz The tonearm is carbon fiber, the clearaudio ‘Satisfy Carbon’. I wasn’t really looking for a solution with this thread I just thought it was something interesting to share here. Although after a handful of people recommended ditching the dimmer for a regular switch, I’ll likely do that soon because now if I ever listen to a record with the lights on I’m going to think I hear the buzz

For sure it is interesting.
That is why is would be nice to know the mechanism that causing it.

 

I agree on replacing the dimmer, the other option would be to replace the lights if incandescent or halogen are available, and probably the dimmer.
Whether it helps or not I also like the orange colour more, even not around halloween.

The last house had incandescent lights, and the new one has LEDs.

If you change the dimmer and keep the LEDs, then it would be interesting to know if touching the frame results in the same deal happening.

I am assuming that the frame is tied to the safety ground, which means that there is likely some difference in ground potential.
But if that were the case then it make little sense that hum is 60/120 Hz, I would think you would need a lot more voltage.

It would also be interesting to just get an extension cord near the tone arm to see if that also induces the hum.

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