Shielding components from EMI/RFI... Help please


A recent experiment with a product designed to reduce EMI/RFI left me curious about other ways to reduce EMI/RFI in my system. In the past ten days, I've stepped onto a slippery slope, at the bottom of which is surely some kind of insanity...

I've been experimenting with copper plates in an effort to absorb, deflect, diffract, and block EMI/RFI. I've tried copper plates under components, on top of components, and inside components.

This is the point where you tell me I don't know what I'm doing and I'm likely to short circuit something and/or electrocute myself. Consider me duly warned. This is also the point where you tell me to get some balanced interconnects, or at least to get some shielded interconnects for Chrissake. Consider me duly informed. Moving on...

I'm hoping you can help me make the most of this experiment, and help me avoid killing a component or myself. My strategy so far has been to:

1. Place copper plates at locations that generate a lot of EMI/RFI, e.g., components with switching mode power supplies or high frequency clocks. The system has a total of 3 SMPS and 3 clocks.

2. Place copper plates at locations that are vulnerable to EMI/RFI, e.g., under the amp, near the transformer.

3. Place copper plates inside noisy components -- in particular, my Meridian G68 preamp/processor. I've begun to build 2 partial Faraday cages, one for the SMPS, and one for the analog output stage.

4. Ground the copper plates either to the component chassis (when plates are used inside a component) or to an independent ground point (when plates are used above/below a component).

Has anyone tried this sort of thing?

Bryon
bryoncunningham
Thanks, Al. Everything you said makes sense. It's interesting that you took Dr. Johnson's course. It looks very interesting, although most of it would go way over my head.

Let me take this opportunity to say that, during this process, you've been an invaluable source of information, advice, and support. It is VERY appreciated!

I will now resume the rest of my life. My wife is expecting our first baby any day now, so I finished this experiment just in the nick of time! :-)

Bryon
I've been putting the finishing touches on reducing the effects of EMI/RFI by putting ferrites on things.

I've put some ferrites on power cords in the system (only on components whose performance is not affected by current draw).

I've also been wandering around the house, putting ferrites on things that dump RFI onto the power lines.

Question: Would it be effective, and is it safe, to put a ferrite on the GROUND WIRE of the system's dedicated AC line?

Bryon
Would it be effective, and is it safe, to put a ferrite on the GROUND WIRE of the system's dedicated AC line?
Hi Bryon,

I don't see any problem with that, although I have no idea as to whether or not it will provide a benefit. As you no doubt realize, what it will do is to raise the degree to which the the flow of currents that are at and above some frequency in the RF region is resisted. That should be no problem either under normal circumstances or under fault conditions that would require the breaker to trip.

Best,
-- Al
Update. Three things...

1. After further experiments with additional ERS cloth, placing it in every location I could think of, I have come to the conclusion that, in my system, to my ears, it is harmful more than helpful about 90% of the time. Some folks predicted I would say that. You were right. It has a tendency to make things sound strangely "muffled." I find that just as puzzling as my initial impression that, in my dac, it resulted in a slight improvement in sound quality. I have not yet removed it from the dac to see if my impression might have changed. That is certainly possible, especially in light of the extensive tweaks I've made to reduce RFI/EMI in the system since I initially installed the ERS.

2. I am happy to report that, with the loving support of my wife and timely medical intervention, I have overcome a three week addiction to ferrites. :-) There are now approximately 50 ferrites all over the house. I attached them to things that pollute the power lines, as well as to some of the cables in the system, including the ethernet cables. I did NOT attach them to the system's interconnects, speaker cables, or power cables. I must say, they really work, provided you don't put them in the wrong place.

3. Among my final experiments with ferrites was to create two RFI pigtails. They look like this. I attached one pigtail to the chassis ground of the Meridian G68 and a second pigtail to the signal ground of the amp (which was made easy because Pass includes a signal ground binding post on the rear of the amp, for reasons that are unclear to me). I have no idea whether the RFI pigtails make a difference. I probably should have posted this part in the thread on Magic. Perhaps someone can comment on whether the whole idea of an RFI pigtail is preposterous.

Bryon