Studio lighting (LEDs) causing noise

[Guitarist]

Here and at the drummers rehearsal space are LED lights. They're causing havoc with my guitar fidelity. They don't use a step-down transformer rather the switching circuit. This results with some frizzy hash noise bleeding in. In the studio, I just turn them off and, ah, the silence!
I do have a small dual-coil pack (ala 5VR1 - TE CONNECTIVITY / CORCOM - RFI POWER LINE FILTER, 5A, 700UA | Newark element14) that I may insert prior to the power bar for the lights. But, like Johnny Be Goode, I'm in a cabin with one AC line for everything.
Also, if I add a ground wire going outside and bolt that to a buried rod/plate closeby, would that be a good idea making everything quieter? I realize that may introduce a ground loop. The wiring is olde but high quality. But the issue is mainly here in the studio anyways.

thanks so much.

[Mick Bailey]

Are you already on a three-wire supply?

Also, does the noise disappear if your guitar volume is turned down?

Those RFI line filters have limited ability to filter noise creeping into the audio spectrum. You may need something more sophisticated, such as a Samson Powerstrip that has a few more stages of filtering.

[tedmich]

here is the filter behavior of a rather expensive unit marketed to audiophiles

the $325 AS-AC15A from Array Solutions
Almost all the attenuation is above 100 kHz which may or may not clean up the AC noise going from the cheapo LED supply back onto the line. A Faraday cage around the PS may help too if its RF emission on the DC side of the PS that you're hearing. Al foil usually works well for the initial experiment

[Usable Thought]

I built what looks to be the exact same RFI filter that you have, as described at the end of this article. I don't know its merits - I made it while searching out a noise problem that proved to have an entirely different cause.

As for "power conditioners" I once tried a mid-level Furman. It seemed mostly built of marketing BS & so I sent it back for a refund. Don't know of others but the reading I did left me skeptical about more than just the Furman brand.

[Guitarist]

Yes, full three-prong wiring. The guitar is the main culprit an turning off blacks out the noise mostly.
I read that article too. I had such a RFI filter receiving the power to my rack. It did little and I never grounded it and took it out. It may work to isolate the lighting for the audio gear. Maybe I can wrap the LED controller plastic boxes in tin foil I have a Belkin Isolator (replete with MOVs, coils, etc.) for the gear but my guitars tend to be sensitive to radiative noise (though shielded) and one is about to get active pickups. Maybe I'll make a "balanced/mic cable" guitar cord with neutral tied to the shield at the send-end. But that would just cancel noise between guitar and interface. I had at one point, a couple guitars that were wired balanced.
A thorn to the blessings I suppose.
Thanks for the advise!

[tedmich]

I suspect its the radiated emissions from the cheapo LED SMPS going through air to your guitar, is it effected by their positions relative to each other?
Guitars can almost always be better shielded!
see: GuitarNuts.com - Shielding a Strat(tm)
(I'd recommend the 3M copper tape be used exclusively)
also: http://www.stewmac.com/How-To/Online...hielding_.html
I especially like their trick of shielding the coils

on the bright side active PUs are usually well shielded from the factory and may actually help your situation.
A nice linear supply for the LEDs might make everyone happier too.

[Guitarist]

OK thanks gents and Ted. I may wrap the humbuckers in copper tape (and ground it) but that's a job! I have done the GuitarNuts thing...

[olddawg]

Maybe I'm being simplistic. But I would just bring in an incandescent lamp or two and plug them into the AC mains. Then turn the LED stuff off. You already said it goes away if it's off. If you want low light use a lower wattage bulbs. Cheap and easy. Or you could build a conventional power supply for the LED lighting for little investment.

[Tom Phillips]

Agree with olddawg.
Additionally, I've been looking into LED lighting for my workbench. The goal is to have some small, bright but wide beam light on goose necks that I can position as needed. I want to avoid any lights that use an "electronic" transformer wall wart or that employ a pulsing circuit. Those are the "features" that cause the radiated noise problem. For dimming a variable transformer or rheostat would need to be used for the ultimate low noise dimmer. That's expensive / inefficient but gets the job done. I'm in the early stages of the LED lighting investigation. Maybe I'll start a dedicated thread on that when I have some detailed information.

[Usable Thought]

Additionally, I've been looking into LED lighting for my workbench.

I was totally ignorant of all this back in March when we had our detached garage redone into two rooms, a workshop for me & an art studio for her. She got track lighting with dimmers (which she always keeps on high) and I got four big LED panels on the advice of the electrician who did our rewiring & lighting. He just went & got the lights from Home Depot so I assume they are lowest common denominator.

And somehow I lucked out - I have been doing a lot of work on a tube amp & no EM noise. But I admit that prior to that, I had completely shielded my guitar. Even so I have the impression from checking the background EM with a spectrogram hooked to a signal tracer that it is probably less now that it had been with the old-fashioned ballast fluorescents that got ripped out and replaced.

[tedmich]

For dimming a variable transformer or rheostat would need to be used for the ultimate low noise dimmer.

Most LEDs do not respond linearly to source voltage and cannot be dimmed effectively this way, which is part of the reason PWM circuits are almost always used. They tend to have a relatively narrow voltage band where they light. One possibility is to run parallel LEDs and switch them on individually to change brightness.

Conveniently this is what most common big bright 50w LED modules from SEAsia look like:


You can see how the 7x7 1w LED array is arranged to have 4 parallel arrays each taking 30-36VDC at about 12.5w. Its not too hard to cut either contact to have individual cathodes or anodes, and then wire them individually. Newbs complain but they aren't SMD small

Typical prices for these are $5,
add a 19" mic gooseneck
http://www.amazon.com/Stage-Micropho...B00080KNG8#Ask
$10
and this base
Amazon.com: On Stage TMO8B Threaded Table Microphone Mount: Musical Instruments
$6
and this smaller one on the LED end
Amazon.com: On Stage Microphone Table Mount, Black: Musical Instruments

Put LED on nice thick Al plate, run small leads through gooseneck (i'd use teflon stranded, ~20AWG) and have a PS with a 50VA 24V transformer
AS-0524 - 50VA 24V Transformer - AnTek Products Corp
FWB rectified with decent caps,

LED modules are 120-140 degree emitters, so you may want a ~90 degree lens like this
http://www.amazon.com/Wit-Lighting-R...=44mm+led+lens

You could probably have a very bright (last forever) work light with 4 brightness levels for under $50

[Tom Phillips]

Red,
Thanks for all that great information and the links. They will be a great start for me to research the lighting. This project is on my list but the list is long.
Cheers,
Tom

[olddawg]

Most LEDs do not respond linearly to source voltage and cannot be dimmed effectively this way, which is part of the reason PWM circuits are almost always used. They tend to have a relatively narrow voltage band where they light. One possibility is to run parallel LEDs and switch them on individually to change brightness.

Conveniently this is what most common big bright 50w LED modules from SEAsia look like:


You can see how the 7x7 1w LED array is arranged to have 4 parallel arrays each taking 30-36VDC at about 12.5w. Its not too hard to cut either contact to have individual cathodes or anodes, and then wire them individually. Newbs complain but they aren't SMD small

Typical prices for these are $5,
add a 19" mic gooseneck
Amazon.com: On Stage Microphone 19-inch Gooseneck, Black: Musical Instruments
$10
and this base
Amazon.com: On Stage TMO8B Threaded Table Microphone Mount: Musical Instruments
$6
and this smaller one on the LED end
Amazon.com: On Stage Microphone Table Mount, Black: Musical Instruments

Put LED on nice thick Al plate, run small leads through gooseneck (i'd use teflon stranded, ~20AWG) and have a PS with a 50VA 24V transformer
AS-0524 - 50VA 24V Transformer - AnTek Products Corp
FWB rectified with decent caps,

LED modules are 120-140 degree emitters, so you may want a ~90 degree lens like this
http://www.amazon.com/Wit-Lighting-R...=44mm+led+lens

You could probably have a very bright (last forever) work light with 4 brightness levels for under $50

That's basically how modern stage lighting works. With a clean DC supply you get away from Triac phase conduction dimmers and such that gets into everything. I used to play this old building called "The House of the Future" that was built in 1928. The stage lighting had these giant rheostats with a huge lever handle to dim the lights!