Happy listening!
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
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
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- 115 posts total
Hey Sean - You can see a picture of some of the shields I added to the Meridian G68 here. I haven't taken a picture of the other enclosures yet. Bryon |
Follow up... I bought this ethernet switch to replace my Apple Airport and it works great. But when I got around to grounding it yesterday, I discovered that there is no obvious way to ground it. I thought there would be a grounding tab on the chassis, because a friend owns a slower version of the same switch and it DOES have a grounding tab. Does anyone know... Can I simply drill a hole in the chassis of the ethernet switch and attach a wire to some point on the system I know to be grounded? Or do the ethernet PORTS themselves have to shielded/grounded in order to pass the benefits of grounding on to the cables? Bryon P.S. The component immediately downstream from the ethernet switch is the Sonos, and it isn't grounded either. |
Hi Bryon, I'm not sure that connecting the chassis of the network switch to some ground would accomplish anything. And conceivably it could even be counter-productive, because it might create a ground path that would bypass the galvanic isolation that is provided in Steve's reclocker. One reason that it would tend not to accomplish anything is that the inductance of the ground wire would make it an ineffective conductor of high frequency (RF) energy, which is what you are attempting to dissipate in this case. Or do the ethernet PORTS themselves have to shielded/grounded in order to pass the benefits of grounding on to the cables?I don't think so, beyond the shielding and grounding provisions that appear to already be provided for the ports in the network switch and the Sonos. Presumably the shields of the ethernet cables are connected to the metallic shells of their plugs, which in turn contact the metallic shields of the mating connectors on the network switch, which in turn contact the metallic housing of the switch. A low impedance path will also exist from there to the chassis of the Sonos ZP90, through the shield of the ethernet cable connecting the switch to the Sonos. The Sonos appears to also use a shielded ethernet connector, based on a photo I found at the Sonos site. Presumably and hopefully whatever RF energy is picked up by the shields of the ethernet cables from the conductors they contain will be dissipated effectively in the metallic structures of the two components, and perhaps also further upstream. Those are my tentative thoughts, anyway. Perhaps Jim or Kijanki or one of the others who have been participating will comment further. Best, -- Al |
- 115 posts total