2. tech-talk
  3. 1328289757

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
bryoncunningham OP
890 posts
 
Thanks, Al. My Cat 5 cables are unshielded. I just ordered some shielded Cat 6.

Yesterday I received the materials to complete the DIY projects described in the OP. Hopefully there will be some results. I will report back.

bc
sarcher30
596 posts
 
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
bryoncunningham OP
890 posts
 
Thanks, Sarcher. Interested to hear if the Cat6 makes any difference.

I have an update...

I have installed 7 copper plates inside my preamp/dac. They are each 16 gauge, or .06", which is fairly thick. I grounded each plate to the chassis. I bolted 3 plates around the analog output stage, 3 plates around the power supply, and 1 large plate to the underside of the lid.

The results are surprisingly good. The noise floor dropped noticeably. The resolution increased slightly. The high frequencies got smoother. I can turn the volume up about 3dB with the same comfort level.

I've tried quite a few tweaks and mods, and this is one of the most audible. The results are much more obvious than when I recently added ERS cloth to the preamp/dac. Total cost for this mod: about $100 in copper from an online retailer, who also cut the plates to exact sizes.

Next up: I'm building a copper/aluminum enclosure for my reclocker. The enclosure will be grounded to a dedicated ground rod I just buried under the house...

...to be continued.

Bryon
sarcher30
596 posts
 
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's avatar
Ag insider logo xs@2x
almarg
9,670 posts
 
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?
I doubt that is necessary. As long as the shields are grounded at one end, I would think that should be sufficient. And I would expect that which end is grounded doesn't matter, since what you are trying to do is to prevent rfi from escaping from the cable.

In other situations, as you may realize, if the signal flow is unidirectional and only one end of the cable shield is grounded it is generally desirable for that to be the source end, so that rfi that may be picked up won't be conducted to the destination component. But that is not applicable in this situation, because rfi pickup is not the concern (and probably also because the link is bidirectional).

Regards,
-- Al
More to discover