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
Bryon
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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- 113 posts total
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 |
Here are the results of my experiments with grounding
THE SETUP COMPUTER -> 50 shielded ethernet cable -> ETHERNET SWITCH -> 1 ethernet cable -> SONOS -> s/pdif cable -> RECLOCKER -> s/pdif cable -> MERIDIAN G68 -> analog interconnect -> PASS AMP THE EARTH GROUNDS computer: grounded to circuit #1 ethernet switch: NOT grounded Sonos: NOT grounded reclocker: NOT grounded Meridian G68: grounded to circuit #2 Pass amp: grounded to circuit #2 Other than the computer, all the above components are plugged into a single Shunyata power conditioner, which is itself plugged into circuit #2 (a dedicated line). THE EXPERIMENT I manipulated 2 variables. First variable: grounding vs. not grounding the ethernet switch. Second variable: using a shielded vs. unshielded ethernet cable for the 1 run between the ethernet switch and the Sonos. I tested 4 arrangements: 1. UNGROUNDED switch + UNSHIELDED cable 2. UNGROUNDED switch + SHIELDED cable 3. GROUNDED switch + UNSHIELDED cable 4. GROUNDED switch + SHIELDED cable I tested for continuity (from the ethernet switch to all other components), and I also did listening tests for each arrangement. Important point: For ALL arrangements, the 50 ethernet cable between the computer and the ethernet switch was SHIELDED. I only tested the shielded vs. unshielded ethernet cable for the 1 cable between the ethernet switch and the Sonos, which as you will see, changed both the continuity results and the listening results. THE CONTINUITY RESULTS 1. UNGROUNDED switch + UNSHIELDED cable Ethernet switch to Sonos input NO continuity Ethernet switch to Sonos output NO continuity Ethernet switch to reclocker input NO conitnuity Ethernet switch to reclocker output NO continuity Ethernet switch to Meridian G68 NO continuity Ethernet switch to Pass amp NO continuity 2. UNGROUNDED switch + SHIELDED cable Ethernet switch to Sonos input continuous Ethernet switch to Sonos output continuous Ethernet switch to reclocker input continuous Ethernet switch to reclocker output NO continuity Ethernet switch to Meridian G68 NO continuity Ethernet switch to Pass amp NO continuity 3. GROUNDED switch + UNSHIELDED cable Ethernet switch to Sonos input NO continuity Ethernet switch to Sonos output NO continuity Ethernet switch to reclocker input NO continuity Ethernet switch to reclocker output continuous Ethernet switch to Meridian G68 continuous Ethernet switch to Pass amp continuous 4. GROUNDED switch + SHIELDED cable Ethernet switch to Sonos input continuous Ethernet switch to Sonos output continuous Ethernet switch to reclocker input continuous Ethernet switch to reclocker output continuous Ethernet switch to Meridian G68 continuous Ethernet switch to Pass amp continuous THE LISTENING RESULTS 1. UNGROUNDED switch + UNSHIELDED cable Lacking pitch definition in bass. 2. UNGROUNDED switch + SHIELDED cable Lacking pitch definition in bass. Little or no perceptible difference from arrangement #1. 3. GROUNDED switch + UNSHIELDED cable Excellent. The best arrangement by a considerable margin. Very good pitch definition in bass. 4. GROUNDED switch + SHIELDED cable Better highs than arrangement #1 or #2, but like #1 and #2, still lacking pitch definition in bass. MY INTERPRETATION OF THE RESULTS I suspect that grounding the ethernet switch resulted in significant benefits because it grounded the shield for the 50 shielded ethernet cable running between the computer and the switch. I suspect that using a shielded ethernet cable between the ethernet switch and the Sonos resulted in poorer performance because, as you speculated Al, it defeated the galvanic isolation in the reclocker. It's worth pointing out that I did NOT hear a difference in the noise floor among ANY of the arrangements. I tested this by turning up the G68's volume to max and putting my ear to the tweeter. Because of this, I suspect that the main audible variation I heard pitch definition in bass was attributable to differences in jitter levels among the various grounding arrangements. I believe I have read that jitter can be audible as a lack of bass pitch definition. That could have been from Steve N., or some other source, Im not sure. This has been an informative experiment for me. For one thing, I didnt expect to hear a difference in bass response at all. Also, before the experiment, I would have guessed that arrangement #4 (grounded switch + shielded cable) would yield the best results, because I naively assumed that the more grounding/shielding the better. That was true only up to a point. Bryon |
- 113 posts total