Is a dimmer noisy when it's turned OFF?

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.

Tonywinsc,

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.

Regards,
-- Al