[django11]

I have a buzz in my little kitchen set up and I have figured out that it is caused by a dimmer that is on the same circuit as the amp.  Dimmer on= buzz on, dimmer off=buzz off.  I assume that no dimmer or a better dimmer would fix the problem.  Is there anything else that would do it?  A cheater plug?

[Speedskater]

All the interest in high efficiency lighting has spurred a lot of recent light dimmer development.  There have been low noise light dimmers for incandescent bulbs for decades.  Then the CFL & LED bulbs came along and they didn't like traditional dimmers.  The newest CFL & LED bulbs understand old-fashion dimmers but that won't help the  EMI/RFI noise,  as a mater of fact some of the new bulbs are rather good noise makers.
So if it's good old incandescent bulbs,  look for a replacement traditional dimmer that boasts low noise on the label.
If it's new CFL & LED bulbs, read all the fine print on both the bulb and the dimmer.

[Ethan Winer]

I have figured out that it is caused by a dimmer that is on the same circuit as the amp.  Dimmer on= buzz on, dimmer off=buzz off.

You can get buzzing from dimmers even when they're on different circuits. This article explains the cause and solution:

Hum and Buzz, Clicks and Pops

--Ethan

[srb]

I have seen (heard) the noise caused by cheap contractor grade dimmers greatly reduced and on occasion practically eliminated by replacing them with high quality (and comparatively expensive) Lutron dimmers.

Steve

[Speedskater]

And another "Light Dimmer" article from Rod Elliott,  but light dimmers have changed a lot since even September 2008.

http://sound.westhost.com/lamps/dimmers.html

[django11]

Thanks for the info guys!

I did try a Lutron dimmer:  same result. The model I tried is listed as having "superior Rfi suppression". 

 Lutron also has some info on RFI here :http://www.lutron.com/en-US/ResourceLibrary/360484.pdf

I thought I had a solution,they sell something called a Lamp Debuzzing Coil which is suppose to fix the problem however they note that "During normal operation, LDCs may make an audible buzz "  .

They also recommend using a "power line filter".  Is that mucho money?

[Speedskater]

Well I never heard of an "Lamp Debuzzing Coil" (LDC) before!  But Lutron has part numbers for them.
As for "power line filters",  there is no definition for them, so each brand can do different things.  But the price rang is about $20 to maybe $5000.

Jim Brown has some technical papers on "power line filters" and lots of other stuff.
http://www.audiosystemsgroup.com/publish.htm
http://www.audiosystemsgroup.com/PowerFilters.pdf

[django11]

I guess I was overly optimistic when I put "simple" in the thread starter...

[wakibaki]

You don't say what kind of lightbulb it is. Is it an incandescent or a CFL or even a halogen? I guess it's not a halogen since you mention replacing the dimmer with a Lutron, I see they have types for incandescent and CFL.

Have you tried a different lightbulb? It's not impossible that the bulb itself is the cause, particularly if it's a CFL, however a tiny spark in a poor connection can cause interference, without causing a visible problem with the bulb, although this is rare. Disturbing the bulb in the luminaire can sometimes stop such problems. Does the intensity change with the dimmer setting? 

You can go hunt for the source of the noise with a portable radio (AM). It may be going through the wiring or it may be airborne. If it's going through the wiring you may not be able to localize it.

Do you use the dimmer? Mostly in the kitchen I have the lights on or off, it's not mood lighting.

The ultimate fix, if no other cause can be found, is to get rid of the dimmer. Replace it with a common switch. You could have some supplementary lights if you want to vary the brightness.

w

[django11]

It is actually in my kitchen/dining/multifunction room.  So the dimmer does get used on the five incandescent light fixture over the table.  Buzz is loudest around a middling to low setting of the dimmer. 

I'll try the bulbs.  Not sure I have a portable AM radio...

I haven't checked for sure (I will) but I don't think that the amp and dimmer are on the same circuit.

Thanks for the input.

[srb]

Is it an incandescent or a CFL or even a halogen? I guess it's not a halogen since you mention replacing the dimmer with a Lutron, I see they have types for incandescent and CFL.

A halogen lamp is an incandescent bulb with the same simple resistance type load as a standard non-halogen bulb.  The halogen has longer life as the evaporating tungsten filament is deposited back on the filament via the "halogen cycle" instead of being deposited on the glass envelope.

Steve

[django11]

And halogen's can be dimmed as well.

I have another dac in now which doesn't seem as quite sensitive to the dimmer.  This one is powered by a wall wart and has a bit of a hum when the dimmer is off   .

Out of curiosity, the amp I am using is a vintage Rotel with a phono section.  It has a screw on the back for a ground.  Would it be of any use to ground it or would that just make an extra large antenna?

[Ericus Rex]

Grounding your phono ground wouldn't make a positive difference.  It could actually start ground loop hum in your system   

Hmmm, if you get hum with your other dac without using the dimmer it could be that you have an electrical problem in your house and the dimmer is just revealing that.  The fact that they are on different circuits also makes me suspicious of the wiring itself.  Have an electrician buddy?  (they're cheaper than non-buddy electricians; usually just the cost of a few beers)

[django11]

My house is 1950ish and I know for a fact that there are a few non code compliant things going on behind the walls.  I am fairly conversant with residential wiring, what type of "electrical problem" could cause a hum?

[HAL]

If there is any corrosion buildup between the house wiring, wall socket and plug contacts, it adds a non-linearlity to the circuit.  It can cause rectification issues and put DC on the line. 

If you have someone that can do it, try replacing the AC socket for the system.  While doing it make sure the copper wiring is cleaned before reattaching the connections.  Also see if the AC sockets have a third wire ground attached.  The small circuit checkers that plug into the socket will also check for that.

Other things like switching power supplies for PC's also dump noise on the AC line.

Try disconnecting all the switching power supplies in the house.  If it is quiet, add them back one at a time to see which might be adding to the buzz problem.

Just some thoughts.

[BPT]

look at thread 113220 for solution
Chris H.

[Speedskater]

My house is 1950ish and I know for a fact that there are a few non code compliant things going on behind the walls.  I am fairly conversant with residential wiring, what type of "electrical problem" could cause a hum?

What kind of wiring system do you have:
a] Romex® - Non-Metallic - multi-conductor plastic cable?
b] Metal conduit?
c] Plastic conduit?
d] old Knob & Tube?
e] other?

[django11]

I have made some progress thanks to your collective help .

So the offensive dimmer is on the same circuit as the system. 

I put the original dac back in the system.  It is usb powered so when I disconnected the wallwart for the other dac the hum dropped substantially.  There was another wallwart on the power bar and when I unplugged that one the hum was gone.

That still leaves me with the buzz when the dimmer is in use. I have another dimmer in the same room which is on a different circuit and that one has no effect on the system.  So I know that the buzz is wire borne.  The wiring is mordern plastic encased 2/14 with a ground.  No conduit.   Wall plugs are new.

I have another dimmer I will try and a switch as well...

[django11]

I was a bit premature on saying all the hum was gone.  When I went back into the kitchen there was a little hum that had returned.  So I tried Hal's suggestion of remove the power strip.  That did the trick for the hum.  I was quite pleased with that and figured I would try the dimmer because you never know:  the buzz is gone!  Yes!

Who would have guessed that the culprit was the power bar? 

Thanks to all and especially Hal.

[rollo]

Ah the Ole powerstrip buzz again. As a general suggestion use a standard switch in front of dimmer to cut all power to it if one must use a dimmer at all.
      BTW HAL is so old he knows all this stuff. I heard he roomed with Edison.


charles