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

Showing 13 responses by sarcher30

Just build a faraday cage around your whole room;). Run all your cables through copper pipe. Your cell phone won't work anymore but who needs distractions?
Nice room. Warm and inviting.

I once wrapped the umbilical cords of my preamp with aluminum foil then teflon tape over that. It was cheap and did lower the noise floor. When I moved I decided to remove the foil and listen again. The sound improved quite a bit without it. The sound was more open and airy. Sure the noise floor was higher but not much.

So I suggest once you get used to the change remove it and revaluate its benefits. You may be surprised with the results.
That is an interesting observation about digital interconnects. I have a Linn DS which uses an ethernet connection from a NAS in a different room. I wonder if your theory would apply in my situation? I'm not sure if ethernet cables benefit from more shielding? Guess I could search the net to see what pops up.
Almarg, that makes sense. Thanks for the info.

Bc, I found some sheilded cat6 cable online. It was cheap enough I decided to give it a shot anyway. I have to run my ethernet fairly close to some power cords because my house is not prewired with it. I'm using some cat5 I made myself now. I know it is not sheilded. I think if your ethernet cable is sheilded it will say so on the jacket.

Sean
I am guessing that consumer equipment is unlikely to have sheilded jacks if most ethernet cables are unsheilded? Oh well. They only set me back $25 with shipping.
Bc, I should get my cat6 tomorrow. I will report back if I hear any change. I have my doubts though. Please let us know how your projects work out.

P.S. I like your real room. Nice and tidy. If not for the speakers you would not know an audiophile lived there.

Sean
I installed my shielded cat6 today. I think it made a slight improvement but it could just be my imagination. I had to reboot my NAS and Linn DS afterward. It takes a long time for the NAS to reboot so it makes it difficult to do a proper A/B comparison. It looks like the Linn DS ethernet port has metal tabs on the sides so I think it is shielded. I don't know if they connected the port to ground though. My NAS also seems to have a shielded port. The only thing in the chain without shielded ports is the router. So I plugged in both ethernet cords next to each other and then wedged in a scew between the metal shields on the RJ45 plugs to tie their shields together. Does anybody think that will work?
Almarg, I have heard of interconnects with the shield only connected on one end. I was not sure if that arrangement would work in this application.

Thanks again.

Sean
Sounds like you made some worthwhile improvements. Your conclusions seem to support the idea of separates. I have separates in my system and some even have separate power supplies. I'm a believer.

It is interesting that with some careful shielding some integrated solutions can be improved. Makes you wonder why you don't see shielding like you have done in more high end integrated designs.
Almarg, I've always wondered about the code to use only one ground rod as well. I have never heard an explanation. Usually people say you can't do it but never explain why. I will have to read that paper you linked to.
Well I read the Whitlock paper and it explains it quite nicely. Thanks for the link.
Jim, Interesting article. Do you think it would be worth while to have a second ground rod installed? It seems that even an eight foot ground rod would be difficult to install without drilling a hole first.

Sean