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led lights hum- how best to deal with it?
Old 27th November 2016
  #31
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There is no set number of turns, just add more until the interference stops.
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led lights hum- how best to deal with it?-ferrite-chokes.jpg  
Old 27th November 2016
  #32
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Quote:
Originally Posted by eor View Post
ok, here's a verrrry rough acoustic guitar/vocal clip featuring two mics and the buzz. the levels are a little hot to make the point come across, but no other plugins or processing was done. it doesn't sound all that great but it was 7am

a couple of photos- one of the back of the power supply with the specs listed, and one of the supply with the chokes installed. you can see the smaller white ones leading to the light, and the larger black ones heading toward the power strip.

perhaps worth noting is that there is just under 10' of cable from the light to the power strip, including the line lump. so i couldn't wrap the cord around the chokes as in the photo way up the thread if i wanted to. is there a clever way around that? they are too short. and they do slide on the cable like an abacus, but they are on there. the chokes aren't wide enough to accommodate more than one pass, anyhow.

i'll check out the cat 5 cables, thanks.
take the bigger ones off the power cord, and use one of those Looks like you should get a few wraps with the bigger one. You need them on the secondary side of the PS anyway. and maybe put one on the cable going to the lights.

Last edited by Deleted User; 27th November 2016 at 05:26 PM.. Reason: added
Old 27th November 2016
  #33
Deleted User
Guest
Also,,,, you need the choke close to the controller, because if its the dimmer causing the EMI the closer the better to the controller, as the power supply cable is acting as an antenna.
Old 27th November 2016
  #34
Do what Stevie Wonder does.
Old 27th November 2016
  #35
Deleted User
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Quote:
Originally Posted by Jim Williams View Post
Do what Stevie Wonder does.
Whats that? Just leave the Lights off?
Old 27th November 2016
  #36
Deleted User
Guest
" Heres something. You mentioned. "i did note that my dynamic vocal mic (sm7) picked up the hum, but when i switched over to my phantom powered condenser (an sm81) it didn't pick up any of that hum. those are my best sounding mics for my current needs, so i'm not sure what to do with this info just yet. none of my other mics require phantom power, so i can't fully confirm this discovery."

The Pin 1 Problem you should read this.

Link Pin 1 Revisited

hers something else I found, you should be able to get the XLR cables already made up

http://www.fullcompass.com/prod/1388...k-NC3FXX-EMC-B
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led lights hum- how best to deal with it?-n165fig8.jpg  
Attached Images
led lights hum- how best to deal with it?-neutrik-nc3fxx-emc-b.jpg 

Last edited by Deleted User; 27th November 2016 at 07:25 PM.. Reason: added
Old 27th November 2016
  #37
Deleted User
Guest
Maybe you need to clean the inside connetion of the SM57? and the cable, or try a new/different cable and make sure you have a good tight connection. aslo try the other mic's its starting to head back in that direction, if you think about it, you never tried anything else that got EMI that I recall, other than the SM57. Could just be dirty connection.

Last edited by Deleted User; 27th November 2016 at 08:20 PM.. Reason: typo
Old 28th November 2016
  #38
Just a question...how close is your SM7 to your LED light? Get some of this DeoxIT® D-Series - Contact Cleaner & Rejuvenator and clean your contacts on the microphone and the XLRs on the cables. I once spent an entire afternoon trying to track down a hum in a friend's studio only to find that he had wired up his own XLR cables and had done them backwards so the shield was on pin 2 and the hot was on pin 1. Once I rewired the cables we were fine. FWIW
Old 28th November 2016
  #39
Gear Addict
 

Quote:
Originally Posted by 2MuchStuff View Post
Get a couple Shielded CAT5 Cable with Shielded RJ45 Connector... connect those to your Controller DMX in/outs, and on the other end put some tape over the pins just to isolate them and wrap/cover foil around those ends use a rubber band to make tight, this is to terminate those two in/outs on the controller, might use a couple of those bead on the CAT5. Also take an Ohm meter and check the ground prong on the power cord to the shield on the controller connector , if no continuity, check just the power cord grounds end to end, I seen bad ones. You might try wrapping the power supply with foil (if its not a vented PS) and put the foil ends of the CAT5 with/against that foil wrapped PS. If that works, you may need to make a an shielded inclosure for the PS if it seems to get hot being wrapped.Trying to create a EMI shield. Hope your following me?
so get two shielded cat 5s, let them dangle, wrap them in electrical tape and copper foil and slap a bead on them? and then maybe wrap the whole thing in foil? that's... elaborate. not sure if a have a ohm meter around, but i'll check.


Quote:
Originally Posted by 2MuchStuff View Post
There is no set number of turns, just add more until the interference stops.
i tried to get two turns around the larger one but it didn't make the cable happy. i barely got it to close and it bit into the cable a bit. may not be the best course of action with these particular ones. maybe i should seek out larger ones.


Quote:
Originally Posted by 2MuchStuff View Post
take the bigger ones off the power cord, and use one of those Looks like you should get a few wraps with the bigger one. You need them on the secondary side of the PS anyway. and maybe put one on the cable going to the lights.
so focus on putting on the side leading from the line lump to the power strip, and not from the dimmer to the line lump?


Quote:
Originally Posted by 2MuchStuff View Post
Also,,,, you need the choke close to the controller, because if its the dimmer causing the EMI the closer the better to the controller, as the power supply cable is acting as an antenna.
how close? the cables are pretty short, but i could maybe tape them so they stay near the dimmer. or should i but them between the light and the dimmer?


Quote:
Originally Posted by 2MuchStuff View Post
hers something else I found, you should be able to get the XLR cables already made up

Neutrik NC3FXX EMC B 3 pole Female EMC XLR Cable Connector with EMI Suppression Ferrite Bead Black | Full Compass
i hope its not cables because i just bought some from monoprice. i'd either have to find someone that makes cable using those specific connectors, or cut up the ones i have. and i'm not that great at soldering.


Quote:
Originally Posted by Thomas W. Bethe View Post
Just a question...how close is your SM7 to your LED light? Get some of this DeoxIT® D-Series - Contact Cleaner & Rejuvenator
now deoxit d5 i do have. i'll give that a shot. the cables are brand new but the mic has been around forever.

in the test i purposely put the light right next to the mic- within a foot or so. given the size of the room, the light will always be within, say 5-6' from the light; maybe 8' ish feet at most, if i shuffle everything around. but the distance didn't seem to change anything in prior tests.

so here's my question: in which order should i try these next steps, and which is most likely to work? shuffling the beads around and some contact cleaner isn't a big deal, but the rest involve me ordering things and sourcing them from wherever and that'll take some more time and money. i don't want to go about it in a hamfisted way. and should i keep the ferrite beads i already have?
Old 28th November 2016
  #40
Deleted User
Guest
Quote:
Originally Posted by eor View Post
so get two shielded cat 5s, let them dangle, wrap them in electrical tape and copper foil and slap a bead on them? and then maybe wrap the whole thing in foil? that's... elaborate. not sure if a have a ohm meter around, but i'll check.


i tried to get two turns around the larger one but it didn't make the cable happy. i barely got it to close and it bit into the cable a bit. may not be the best course of action with these particular ones. maybe i should seek out larger ones.


so focus on putting on the side leading from the line lump to the power strip, and not from the dimmer to the line lump?


how close? the cables are pretty short, but i could maybe tape them so they stay near the dimmer. or should i but them between the light and the dimmer?


i hope its not cables because i just bought some from monoprice. i'd either have to find someone that makes cable using those specific connectors, or cut up the ones i have. and i'm not that great at soldering.


now deoxit d5 i do have. i'll give that a shot. the cables are brand new but the mic has been around forever.

in the test i purposely put the light right next to the mic- within a foot or so. given the size of the room, the light will always be within, say 5-6' from the light; maybe 8' ish feet at most, if i shuffle everything around. but the distance didn't seem to change anything in prior tests.

so here's my question: in which order should i try these next steps, and which is most likely to work? shuffling the beads around and some contact cleaner isn't a big deal, but the rest involve me ordering things and sourcing them from wherever and that'll take some more time and money. i don't want to go about it in a hamfisted way. and should i keep the ferrite beads i already have?
OK, forget the CAT5 for nom, You got me all wrong on that anyway, But sure clean that mic, and check your others, and put those bigger chokes, one on the PS cord close to the controller and one on the cord from the controller to the LED's and the small one's put all those by each big one.
Old 28th November 2016
  #41
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Richard Crowley's Avatar
We already discussed that a string of small ferrite chokes is NOT as effective as multiple turns through a larger choke.

Use your microphone as a "probe" to see where the interference is coming from.
Is it being radiated back down the mains power cord to the wall socket?
Is it coming from the power supply "line-lump" brick itself?
Is it coming from the wire between the power supply and the lamp?
Is it coming from the lamp itself?

Note that "hum" is generally used for quite low frequencies below 200Hz.
A high-frequency tone is more often referred to as a "whine" or "whistle".

Since your spectrum display shows that the tone (and apparently it's first harmonic/overtone) are well above the frequencies you and your guitar are making, you could use a notch filter to remove the fundamental and harmonics. Adobe Audition actually makes this quite easy. Of course, you should NOT have to resort to notch filtering on a regular basis, so you are correct that finding and resolving the root cause is the logical approach.

You could find a 15V old-school traditional linear power supply which would (presumably) NOT produce the noise you are picking up. Does the PITCH change with the dimmer control? Or only the amplitude?
Old 30th November 2016
  #42
Gear Addict
 

upon closer inspection, i noticed that my phantom powered mic picks up the buzz also, just nowhere near as much as the dynamic does. not sure what that changes, but its worth noting.

Quote:
Originally Posted by 2MuchStuff View Post
OK, forget the CAT5 for nom, You got me all wrong on that anyway, But sure clean that mic, and check your others, and put those bigger chokes, one on the PS cord close to the controller and one on the cord from the controller to the LED's and the small one's put all those by each big one.
the cleaning i can do. it seems like the next move here would be to source longer cables for the lights, so i can actually gets some wraps going. then maybe some of the giant donut kind of chokes.


Quote:
Originally Posted by Richard Crowley View Post
Use your microphone as a "probe" to see where the interference is coming from.
Is it being radiated back down the mains power cord to the wall socket?
Is it coming from the power supply "line-lump" brick itself?
Is it coming from the wire between the power supply and the lamp?
Is it coming from the lamp itself?

Note that "hum" is generally used for quite low frequencies below 200Hz.
A high-frequency tone is more often referred to as a "whine" or "whistle".

Since your spectrum display shows that the tone (and apparently it's first harmonic/overtone) are well above the frequencies you and your guitar are making, you could use a notch filter to remove the fundamental and harmonics. Adobe Audition actually makes this quite easy. Of course, you should NOT have to resort to notch filtering on a regular basis, so you are correct that finding and resolving the root cause is the logical approach.

You could find a 15V old-school traditional linear power supply which would (presumably) NOT produce the noise you are picking up. Does the PITCH change with the dimmer control? Or only the amplitude?
so grab the live mic and poke around to see where i get more and less buzz? neat idea. i'll give that a shot, too, it seems easy enough.

as for the dimmer, it does not change the pitch. that seems to be constant no matter what the variables are. its just the amplitude that varies, depending on the dimmer settings.
Old 14th December 2016
  #43
Here for the gear
 

I would either try another electronic dimmer that is designed for LED lamps like the ones from Lutron, or use an on and off mercury switch and dispense with the dimming. I used to run into the problem with halogen light fixtures that were not able to use line voltage but needed to have a transformer and the hum was from the transformer.

An alternative to get away from any 60 kHz power feed problems is to get DC powered LEDs which is what I did with my last installation. I ran them 15 feet to drivers modules that were sealed in boxes and powered by DC from a dimmable magnetic transformer I mounted in a crawlspace. Dimmer wall switch controls the AC feed to the magnetic transformer. The 8 Watt light modules are equivalent to more than a 150 Watt tungsten lamp in lumens.
Old 4 days ago
  #44
D2K
Gear Head
 

hi Eor,

this is a quite late reply considering its written in 2020. but nevertheless I hope it can be useful.

One day I have some unplanned spoken word recording session. As studio room was undergoing construction I decided to record in the control room without computer using 8trk field recorder. I connected EV RE20 and Sennheiser ME66.

I experienced what sounded like strong interference as a part of a signal. I went almost crazy because instantly I thought of new LED lighting and I was so right. Turning off and on LED switches turned off and on noise.
As thoughts were coming in a quick glimpses I first thought electrician must have made some mistakes with earthing, then I realize that 8trk field recorded does not have ground at its AC adapter. But anyway, it should not produce such a buzz. In short, I tried all control room outlets, jumped to studio room, tried all outlets there (but left the mics in control room) and buzzing was same at any outlet.

I was totally sure that if I use batteries that buzzing will disappear and that there is no point in trying that. Anyway, I gave a try to use batteries.
To my surprise, buzzing was exactly the same!
I could not believe, as having a theoretical buzz from EMI in mic is one thing, but to have it so strong was out of my understanding.
Please note that at this point little I knew that problem is NOT inside 8trk.

I started to move RE20 together with stand and I noticed that buzz is changing. Then I unarmed RE20 and it was crystal clear that buzz is completely gone. Sennheiser alone did not catch any buzz no matter which combination of LEDs I was turning on and off. Just a pure studio silence.

At this point I felt relief. I realized that electrical wiring of lighting is not a problem.
Next, I took the batteries out and connected with AC adapter again. No buzz with Sennheiser but buzz with RE20.

Next, I took the RE20 out into studio room but kept recorder in control room.
No buzz. Perfect silence. back to control room - buzz.

The same thing I tried at a later date with c414, Same result. Condensors are immune. I also have problem tracking Fender Jazz bass and Telecaster from control room. All loghts miust be off for highest snr.


SO, my question is: how you all girls and guys deal with LED in the studio room? We have all filament old school bulbs in studioroom. It is more and more hard to find them. Do you experience any problems and how do you deal with it?

THX!
Old 3 hours ago
  #45
Lives for gear
 
Richard Crowley's Avatar
It would be helpful to actually HEAR the noise people are talking about.
Many people use the word "hum" to refer to any kind of audio noise.
But, the proper use of the word "hum" is a continuous LOW frequency tone of 60Hz (North America) or 50 Hz (everywhere else on Earth).

LED lighting very frequently uses high-frequency switch-mode power-supplies (SMPS) to drop the high mains power down the the low voltage that LEDs take.
AND they frequently use high-frequency "chopping" for dimming control.
This creates the same kind of interference as old-school SCR theatrical lamp dimmers (although at a higher frequency).
The proper solution is to use filtering (typically a rather large inductor) in the power supply (or dimmer) circuit to limit the dVdT spikes that cause the interference.
Of course, end-user inhabitants of rooms where these LED lights are installed have no control over this and we have to deal with the interference as it exists.

This kind of interference is rather pernicious and finds its way into any vulnerable link in the audio chain.
Dynamic microphones (like the RE20) will likely be more sensitive to this kind of near-field EMI.
Although poorly shielded condenser mics could be affected, also.
Note that the EMI could also enter through connectors, cables, and the mic input stage.

Welcome to the era of energy-saving LED lighting, side-effects included at no extra charge.
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