Is a dimmer noisy when it's turned OFF?

Friends, my wife wants to add a rheostat to the dining room ceiling lamp. I know that dimmers are big sources of electrical noise, could will it have any effect on my listening room power when it's turned completely off? Just want to be sure.
A standard lamp dimmer adds no noise to the powerline when it is turned completely off.
Thanks, Elizabeth. Great to know.
Anyone know of any dimmers that are not noisy? I'm guessing no, but would be nice to add the flexibility to my listening room if it exists. Also, if there is such an animal, what types of bulbs lend themselves well to dimming without being noisy/buzzing? Would LEDs work well if they're dimmable? Not going the halogen route. Others?
I have halogens on dimmers, and yes they caused hell with my system when i had them "on". The level of buzz and hum introduced into the sound varied with the amount of dimming used. It was VERY audible. Lutron, and Leviton both make a nifty gadget called a "de-buzzing" coil. I believe it's called a coloital coil or something like that. Mounts anywhere, wires inline between the dimmer and the power source. My problem was solved! They run about $100 and are worth their weight in gold. Absolutely NO noise whatsoever no matter how high (or low) the lights are dimmed. (I have 800 watts of halogen bulbs on track lites to illuminate my art work, and not a peep out of lites or stereo.) Lamps Plus sells these "de-buzzing" coils. And NO, you should not get any noise in your sound system if the dimmers/bulbs are completely turned off. Only when they're on do the seem to cause problems. Good luck.
no need for dimmers if you use corner lighting. Ikea has paper column style standing lamps. they have switches that sit on the floor and just a step turns them on. place in the corners the shed low diffused light. they can also act as sound treatments in the corners as well. nice trick.

No , dimmers do not add noise when off . For that matter I haven't experienced any noise when they are on . I think it would take very sensitive equipment and a bats ear to hear any noise .
I agree with Tmsorosk, I have dimmers and hear nothing audible through the system.
Some dimmers do in fact make noise that's clearly audible in some systems. We went through 3 or 4 dimmers before stumbling on one that didn't make noise in ours.

Same with transformers (as for 12V lighting systems).

To assert that the phenomenon doesn't exist based on a single experience is no more valid than if I asserted that the phenomenon must always exist based on my single experience (which of course I don't). The varying experiences posted on this thread evidence the reality, which is YMMV.
I think the poster meant do dimmers make noise when switched off. They shouldn't make any electrical noise when switched off because the SCR circuitry should be depowered. Now, if the dimmer is only turned down to minimum and not actually switched off, that may be a different matter. The SCR circuitry would still be powered and might generate some RF noise. The typical household dimmer is a low cost appliance using a switching device that reduces the average voltage to the light bulb. That's why they do not usually work with fluorescent or LED type bulbs because they need a minimum voltage level to turn on. They generate gobs of RF noise just like when you break/make an electrical circuit. My old ARC SP-6b preamp that I had a couple of decades ago was sensitive to dimmer noise. I banned all dimmers from our house back then. Simple solution.
Oh, and also, you can dampen out the RF noise using an R/C circuit. (Resistor/Capacitor) that is the solution used on DC motors. DC motors use brushes that are rapidly making/breaking the electrical connection. A choke coil and capacitor kill the noise. All the DC motors in your car have that so your radio doesn't buzz and also not to interfere with other electronics.
I have DC hum in my preamp. I've had it in 3 preamps - all hummed (see this post preamp dc hum). I have a bunch of dimmers throughout the house and part of my trouble-shooting was to turn off every circuit at the main panel except my dedicated 20 amp main system line and still got DC hum in my preamp - grrr. Didn't hear it at one Seattle repair shop when they checked the preamp out. I got new transformer spec'ed similar to the one from the factory but have not tried swapping them yet. I also have a PS Audio Humbuster III on just the preamp and it helps, a little. Guess I will have to do the transformer swap sometime soon or move to another neighborhood (I live in one with a lot of high tech families in Redmond, WA).

My high gain Jasmine LP 2 mk II does not hum at all on the same circuit.
Another issue with dimmers that I have experienced specifically with LEDs is mechanical noise.

I have recently installed three dimmers, two for use with LED pot lights and one for ceiling lamp that uses standard style bulbs, but still LED.

I installed the ceiling lamp dimmer first, using a Levitron brand dimmer and Sylvania brand bulbs. These bulbs buzzed, despite being labelled dimmable. The buzz was very audible and coming from bulb as well as the dimmer.

In the dimmer's literature it stated that it only worked for specific models of bulbs. I had on hand a Phillips bulb that was listed for use with dimmer. I swapped bulbs and voila no buzz from either the bulb or dimmer.

I was lucky with the pot lights, these weren't listed but only cause a buzz on occasion and hardly noticeably. I don't know the brand but are likely Chinese.

All this to say that dimmer noise is dependent at least in part to the type, model and brand of bulb used.

Also I have not heard any dimmer induced noise in my system since installing the dimmers.

Finally, to answer the OP, when switched off all noise stopped.

Tmsorosk expressly asserted that dimmers do not make noise even when on. See the post two above mine. The following poster seemed to agree. Sorry if it wasn't clear that I was responding to those comments.

I concur that (IME) dimmers do not make noise when turned off.
You guys are great. I will tell my wife that having a dimmer in the dining room is a BIG compromise but I am willing to make it. :-)
Tim (Tmsorosk) and Pops, in addition to verifying that your dimmers produce no audible noise through your systems (as you have done), you may also want to compare sonics between the situations where the dimmers are dimming say 50% or thereabouts, and when they are switched off.

See pages 36 and 37 of this paper by Bill Whitlock of Jensen Transformers, in which it is indicated that many commonly used dimmers generate "very strong" power line harmonics up to 70 kHz. It therefore seems conceivable that sonic effects may result from intermodulation of those harmonics with the audio signal, which would manifest as low level distortion rather than noise.

I can't cite relevant experience, though, as I have no dimmers in my house.

-- Al
Good recommendation Al, I have Lutron Maestro dimmers and do listen with them dimmed most of the time....maybe I have tin ears, LOL, but I do not hear any difference from all the way up, dimmed, or off.
...then there are dimmers that don't make noise (that you can hear), but kind of pixilate (make fuzzy) the sound of my system....actually, its the ceiling fan that does that. I searched many hours to find out what was wrong to find the problem.
Zero crossing dimmer is key. Cheap dimmers cause all kinds of noise. Here is what I learned posted in a non audiophile forum...

Good description. We also get that effect from leaving various appliances plugged in (microwave oven, television, etc.) even when they're switched "off". It's pretty low level, but for insanely critical listening we unplug as many as we conveniently can.
Wouldn't the key be to have lighting and dimmer on a separate circuit or even a different sub panel? I use dimmers in my home theater/listening room to great effect and notice no problems with noise. My components do run from a separate sub panel though. To me the right level of lighting can make all the difference, hard to control without dimmers.
Sonofjim, I my dimmers and have zero interference that I can detect.
06-05-13: Sonofjim
Wouldn't the key be to have lighting and dimmer on a separate circuit or even a different sub panel?
That certainly can't hurt, and certainly may be helpful. But I wouldn't count on it as being any kind of guarantee. There are too many variables involved that have essentially no predictability, including the possibility that radiated RFI may couple through the air to sensitive circuit points within the components and intermodulate with the audio signal, the run lengths and physical routing of the house wiring, the sensitivity of the particular components to distortion of the AC waveforms they receive, and of course the characteristics of the particular dimmers.

I mentioned earlier that I have no dimmers in my house. I do have, however, a floor-standing fluorescent lamp that has a built-in continuously variable dimmer (which is not in my listening room, and is almost always turned off). I just did an interesting experiment with it. I have a battery-powered portable transistor radio that can receive long-wave frequencies (below the AM broadcast band) down to about 140 kHz. I set it to that frequency, and to a volume control setting in the lower part of its range, and positioned it about 10 feet from the lamp. As I varied the setting of the dimmer on the lamp I heard nothing through the radio at most settings. However at a small range of settings corresponding to a moderate amount of dimming, the radio produced noise approaching the volume levels at which I would normally listen to radio stations on that set.

-- Al
Nothing wrong with correct long as they are variable transformers :)

this is IMO the only way to go if you must dim