Household Dimmer Switches and Lights???

[Mike F1]

Happy New Year you all!

Can someone explain to me why Dimmer Switches and certain lights play havoc on my Seduction?
I realize the Seduction creates a lot of gain... and just a little bit of "noise" can easily get amplified.
This buzz is noticeably audible when the volume of my system is turned past 1/2 way.

I have my entire system on one wall outlet and on a proper A/V power bar so I think I have no ground loops there.

If I turn off all the dimmer switch lights and CFL's in my house the "buzz" drastically reduces.
So, what are the dimmer switches and these lights actually doing to my household electrical system?
What is the theory?

With the Seduction out of the equation, the rest of my system (NAD CD player - 5670 Pre - Paramours) is very, very quiet.

Other than removing them (which the wife is not fond of) what can I do the mitigate this buzz emanating from my Seduction?

Regards

Mike

 

[Paul Joppa]

Dimmers and CFLs (and I presume LEDs) all generate a lot of RF noise, and since they are very price sensitive they rarely have good radiated-noise protection.

I know you can buy dimmers that are better protected; the cost is of course significantly higher because the appropriate shielding is as expensive as the rest of the dimmer.

You may be able to "harden" your preamp as well. Seduction already includes tube shields, of course. There are two further areas to pursue:

1) Better shielding. This could be as simple as better-shielded interconnects between turntable and preamp - if you're lucky. Otherwise, some kind of metal cage around the circuitry, such as the Hammond box (for which the four extra holes on the chassis plate are provided). I suppose the thread on the box was lost when Bottlehead got our own forum host.  :^(  There will be some increased heat from the lack of ventilation; I don't know how bad.

2) RFI filter at the first stage. This would be a tiny capacitor from grid to cathode, probably ceramic for good RF performance and maybe 100pF in value. This goes at the socket pins, after the 220 ohm grid stopper. I have not tried it so it's just theory right now! Note this will affect the cartridge as well; most carts have a range of recommended capacitance. Depending on where the RFI is being picked up, it's possible that a higher-capacitance cable from cart to preamp would have the same effect.

 

[Paul Birkeland]

I believe nearly all Lutron dimmers come with RFI suppression built in, but PJ is right, they do cost a lot!

 

[fullheadofnothing]

Also, just to be clear, you are using dimmable CFLs (i.e. not the bulbs that say "do not use in a dimmer" on their base) in fixtures designed for that, right? The last time I was in a room with CFLs on a dimmer, I didn't need a phonostage to hear buzzing!

 

[[email protected]]

Isn't  there a Hammond box that will further shield the seduction.  I recall looking in to that some time ago. 

 

[BigAl954]

As PJ said above, CFL and LED lighting generate enormous amounts of RF crud.
This will affect your WiFi at home ( try turning the lights off and compare signal strength and error rates etc)
Dimmers usually use triacs to control the voltage delivered to a bulb. Electronic dimmers for LED lighting often use more complex circuits that switch at high frequencies to achieve a cheap and compact build.
The cleanest sounding lighting is from low voltage DC lighting from a Battery supply (12V car battery for instance running a normal filament lamp)  I have used this in a Faraday cage for sensitive RF measurements and for noise measurements on condenser microphones and tape machine reproduce circuits.It's the RF equivalent of an anechoic chamber.

The crud put out by LED lighting is so bad that the FCC is investigating problems caused by the Ernst & Young building in LA for cell phone carriers. The crud basically wipes out cells.
See here http://www.pcworld.com/article/2095940/la-buildings-lights-interfere-with-cellular-network-fcc-says.html

Similar investigations are now occurring in Australia by the ACMA ( our FCC) because of interference to Digital TV and DAB+ reception ( DAB+ is our HD radio equivalent operating around 202 - 208 MHz using AAC+ encoding).

Dimmer wise, I use Tridonic electronic dimmers on halogen downlights in on-air studios with the dimmers mounted externally and long  low voltage cabling to the lamps. They are expensive, around $70 each ,but can drive 3 x 50w lamps each. This is quiet enough to not be picked up on our Neumann Large diaphragm condenser mics.

 

[Mike F1]

Thanks for the insight. Good stuff!

Are the dimmers actually radiating a electromagnetic field or are they causing a ripple on the ground? or a form of both?

An electrician friend of mine also recommended checking to polarity of all my plugs and switched in my house. I'm going to try that.
I'm also going to try a better shielded cables and a better power conditioner.

One more question, other than a "hammond box" is it possible to line the inside of the Seduction with some sort of shielding tape?

Thanks

Mike

 

[Paul Joppa]

It has been done. I would suggest woven screen or perforated metal as a better-ventilated option; make a 5-sided box where 4 sides lie against the inside of the wood base, and connect it electrically to the main chassis plate, preferably at many points