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Dimmer causing humming

 
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drice1234




Joined: 07 Oct 2006
Posts: 1309
Location: Allen, Texas


PostLink    Posted: Fri May 25, 2007 4:32 pm    Post subject: Dimmer causing humming Reply with quote


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I added 2 dimmers to my theater room which happens to be on the same 110v ac circuit that the power for my subwoofer is on. This is causing a hum through my subwoofer. Does anyone know of a filter that I can put inline with the power cord for my subwoofer? I am looking for the easy way out rather than redo the electrical either for the lighting or outlet.
Thanks
Dan
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Curt Palme
CRT Tech



Joined: 08 Mar 2006
Posts: 24296
Location: Langley, BC

TV/Projector: All of them!


PostLink    Posted: Fri May 25, 2007 4:40 pm    Post subject: Reply with quote

If these are the cheapie dimmers, spend more money on better ones. The SCR cheapie $4.00 ones create all sorts of noise. The more expensive ones have sero cross switching built in as well as noise suppression.
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drice1234




Joined: 07 Oct 2006
Posts: 1309
Location: Allen, Texas


PostLink    Posted: Fri May 25, 2007 4:47 pm    Post subject: Reply with quote

It was about a $35 dimmer. It has the 2 slide dimmers in one wall switch
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Curt Palme
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PostLink    Posted: Fri May 25, 2007 4:48 pm    Post subject: Reply with quote

You could try putting a choke inline with the AC line. I'd still try a couple of different brands of dimmers though.
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JustGreg




Joined: 07 Mar 2006
Posts: 3098
Location: Kenosha, WI


PostLink    Posted: Fri May 25, 2007 4:59 pm    Post subject: Reply with quote

This from the Lutron site:

WHAT IS RADIO FREQUENCY INTERFERENCE (RFI)?
RFI is a buzzing noise which may occur in some audio and radio equipment when solid-state dimmers are used nearby. Although every Lutron dimmer contains a filter to suppress RFI, additional filtering may be required in some applications. Typical examples of RFI-sensitive equipment are AM radios, stereo sound systems, broadcasting equipment, intercom systems, public address systems, and wireless telephones.

RFI can be transmitted in two ways:
Radiated
Conducted

Note: The suggestions in this application note will help minimize RFI: however, they do not guarantee that RFI will be completely eliminated.

Radiated RFI
Any sensitive equipment that is in close proximity to dimming equipment can pick up the RFI and generate noise into its system.

The following are three possible ways to minimize the radiated RFI:
Physically separate the RFI-sensitive equipment from the dimmer and its wiring.
Run dimmer wiring in its own metal conduit.
Use a lamp debuzzing coil (available from Lutron) to filter the RFI. See below for more information.
Conducted RFI
In some cases, RFI is conducted through the building wiring and directly into the AC power supply of the sensitive equipment.

To minimize the conducted RFI, follow these guidelines:

Feed sensitive equipment from a circuit without a dimmer on it.
Add a power-line filter to the sensitive equipment.
Add shielded wire for all microphones and input cables. Also, use low-impedance balanced microphone cables, which are less susceptible to interference than high-impedance types.
Make sure all the equipment is grounded. Connect all shields to the ground at one point. Ground lighting fixture metal housings properly.
Use a lamp debuzzing coil (available from Lutron) to filter the RFI.
Lamp Debuzzing Coils
Lamp debuzzing coils (LDCs) are the most effective way to reduce RFI. One LDC is required for each dimmer. Select the LDC according to the connected lighting load. The LDCs may be wired in series on either the line side or the load side of the dimmer. For maximum RFI suppression, keep the wiring between the LDC and the dimmer as short as possible.

Since the LDC itself make an audible buzz, mount in a location where the noise will not be objectionable (e.g., an electrical closet, a basement, or above a drop ceiling). LDCs are designed to easily mount onto a standard 4"x4" junction box. They are UL listed and thermally protected.

The following LDCs are available from Lutron:

Model # Rated Capacity:
LDC-10-TCP 600-1200W
LDC-16-TCP 1201-1920W

Note: For more details on LDCs, contact the Lutron Hotline and ask for Application Note #3.



HOW CAN I MINIMIZE RADIO FREQUENCY INTERFERENCE?
Radio Frequency Interference (RFI) occurs when solid-state dimmers emit noise that interferes with AM radios, audio equipment, etc. Every Lutron dimmer includes radio frequency interference suppression circuitry. Additional filtering may be required in some applications. In instances where interference does occur, Lutron recommends the following:
Ensure there is 6' (2m) between the dimmer and audio equipment
Place the dimmer on a separate circuit than the audio equipment
Run dimmer wiring in its own metal conduit
Use a lamp debuzzing coil to filter the RFI
Purchase an in-line filter for the audio equipment
Use an electronic low-voltage dimmer (requires a separate neutral wire) for incandescent loads.


I had the same problem when I installed Home Depot-esque toggle dimmers in a room adjacent to my HT. Not having any room for a dedicated breaker and feed (at the time) I yanked them out of the room and put in regular toggle switches.

Greg

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Greg

"Is it ignorance or apathy? Hey, I don't know and I don't care!" --Jimmy Buffett
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Joust




Joined: 05 May 2006
Posts: 2431
Location: Almonte, Ontario, Canada

TV/Projector: Marquee 8501LC


PostLink    Posted: Fri May 25, 2007 5:20 pm    Post subject: Reply with quote

You should also keep your audio on seperate breakers from your lighting.
Why make problems for yourself.
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drice1234




Joined: 07 Oct 2006
Posts: 1309
Location: Allen, Texas


PostLink    Posted: Fri May 25, 2007 5:24 pm    Post subject: Reply with quote

Quote:
You should also keep your audio on seperate breakers from your lighting.
Why make problems for yourself.


Do people post just to get their count up? I think my original post acknowledged the problem and made it clear that I was pursuing an easy solution before re-wiring. What does the above comment add to the discussion?
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CRT_Ben




Joined: 28 Aug 2006
Posts: 1684
Location: Northern Virginia


PostLink    Posted: Fri May 25, 2007 5:34 pm    Post subject: Reply with quote

drice1234 wrote:
Do people post just to get their count up? I think my original post acknowledged the problem and made it clear that I was pursuing an easy solution before re-wiring. What does the above comment add to the discussion?


Man, lighten up a bit! This is the intorwebs we're talking about here and people might not always read as carefully as they should...
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nuttall_chris




Joined: 08 Mar 2006
Posts: 832
Location: Ottawa, Ontario, Canada


PostLink    Posted: Fri May 25, 2007 5:36 pm    Post subject: Reply with quote

drice1234 wrote:
Quote:
You should also keep your audio on seperate breakers from your lighting.
Why make problems for yourself.


Do people post just to get their count up? I think my original post acknowledged the problem and made it clear that I was pursuing an easy solution before re-wiring. What does the above comment add to the discussion?


I agree that the post doesn't help you much but it is good info for anyone who has not yet wired their theatre.

Chris.
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Joust




Joined: 05 May 2006
Posts: 2431
Location: Almonte, Ontario, Canada

TV/Projector: Marquee 8501LC


PostLink    Posted: Fri May 25, 2007 5:38 pm    Post subject: Reply with quote

Its a valid recomendation. going for the Cheap way out will cause you lots of headaches and probably eventually cost you more money.
Why pick a fight you cannot win. The best you could hope for is to reduce the noise.

So in summary, I'll chalk up another post and stay out of your thread. Wink
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Person99




Joined: 09 Mar 2006
Posts: 4901
Location: Flower Mound, TX


PostLink    Posted: Fri May 25, 2007 6:13 pm    Post subject: Reply with quote

Joust wrote:


So in summary, I'll chalk up another post and stay out of your thread. Wink


myPosts++. Still way ahead of you lightweight.

Anyway, Dan. You might want to have an electrician look at it. Depending upon how easy to get to things, it might not cost that much to have the dedicated circuit run now.

I was super anal about this when they built my house so all the HT equipment is plugged into a dedicated circuit which goes to a sub-panel (which has no appliances on it). It really is worth it.

Oh, and on the side, ditch the sliders! At least put a simple $30 Lutron IR controller on the main one, it is great to raise and lower the lights from your seat. Smile

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drice1234




Joined: 07 Oct 2006
Posts: 1309
Location: Allen, Texas


PostLink    Posted: Fri May 25, 2007 9:26 pm    Post subject: Reply with quote

I apologize to Joust. I should not post while at work and dealing with idiot customers. My irritation level is way to high. In my case running another circuit just for the audio is not an easy alternative. My HT is on the second floor with the breaker panel in the garage and no path to run new wires. I could steal a circuit and put a sub panel upstairs but I would still have to rewire a good part of my HT as most of the outlets and lights are on the same circuit. I am not a perfectionist. I can handle 95%. I will try to put a small UPS on the subwoofer to see if that helps.
Dan
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Person99




Joined: 09 Mar 2006
Posts: 4901
Location: Flower Mound, TX


PostLink    Posted: Fri May 25, 2007 9:40 pm    Post subject: Reply with quote

drice1234 wrote:
In my case running another circuit just for the audio is not an easy alternative. My HT is on the second floor with the breaker panel in the garage


Not to belabor the point, but that is how my house is and I could easily run another if I wanted. If they can go up to the attic for that, it is not that bad. But I won't push you too much further on it, I might get my head bit off. Smile

But another idea is one of those Panamax 2 SUB surge suppressors that have filtering.

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Dave

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drice1234




Joined: 07 Oct 2006
Posts: 1309
Location: Allen, Texas


PostLink    Posted: Fri May 25, 2007 9:49 pm    Post subject: Reply with quote

Thanks Dave, that is the kind of info that I was seeking. Just to let you know I cabled my house while it was being built. In order to get a cable from my garage to the upstairs attic would involve removing sheetrock. I wish I would have thought about this then. I do have a friend who is a master electrician. If I cannot resolve this problem in another way or if I do experience more electrical issues in the future I will use one of the existing circuits and put a sub panel in the upstairs attic.
Thanks
Dan
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Person99




Joined: 09 Mar 2006
Posts: 4901
Location: Flower Mound, TX


PostLink    Posted: Fri May 25, 2007 10:03 pm    Post subject: Reply with quote

Here is the datasheet on the one I was talking about:
http://www.panamax.com/Literature/PDF/M2SUB_Data%20sheet.pdf

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Curt Palme
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Joined: 08 Mar 2006
Posts: 24296
Location: Langley, BC

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PostLink    Posted: Fri May 25, 2007 10:28 pm    Post subject: Reply with quote

I'm curious. Does the sub hum without the audio cables disconnected? If so, it's RFI going right into the sub amp itself. If not, you might be able to install a ground lift transformer in the RCA connector line.
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JustGreg




Joined: 07 Mar 2006
Posts: 3098
Location: Kenosha, WI


PostLink    Posted: Sat May 26, 2007 1:20 am    Post subject: Reply with quote

Curt Palme wrote:
I'm curious. Does the sub hum without the audio cables disconnected? If so, it's RFI going right into the sub amp itself. If not, you might be able to install a ground lift transformer in the RCA connector line.

Does anybody have a simple schematic for building that kind of filter? Curt? I know Gary is hard at work on ps's, perhaps he'll take it on for members with unique arrangements where pulling or creating dedicated "clean" lines isn't possible.
I'm sure something like that already exists but I think one of us could do it for alot less money. And we'd be taking care of "one of our own".
Just a thought.

EDIT:OK...I just read the thread for Gary's isolator/filter...owie that's a "charged" topic. I guess there isn't a "simple" schematic but Mike spent alot of personal time over at AVS working through the long and complex Marquee Maint thread just for the love of it. He didn't sell a thing at that time. It just seems to me that collectively producing a DIY appliance being discussed here (I hate to call it a product) seems doable.

All that's required is teamwork, without remuneration being the motivating factor. There's enough brain power here to make it happen. Sadly I'm starting to see us heading down the AVS road in that opinions, participation, and free expression, are being backseated to "somebody's product".

Greg

My apologies to you Dan for taking your thread off target.

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"Is it ignorance or apathy? Hey, I don't know and I don't care!" --Jimmy Buffett
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jask




Joined: 17 Mar 2006
Posts: 10164
Location: kamloops BC


PostLink    Posted: Mon Jun 04, 2007 1:38 am    Post subject: Reply with quote

Here is a link that has a 2Kw design for audio use.
http://myweb.tiscali.co.uk/nuukspot/decdun/mainsconditioner.html
is this the sort of thing you had in mind Greg?
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