Sounds good! With respect to placement of the plate, if you haven't already done so it might be worth trying it positioned directly under the switch.
Best,
-- Al
Best,
-- Al
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
- ...
- 115 posts total
Yes, Al, the plate is directly under the switch. I placed it there to keep the braided ground strap as short as possible, to minimize any antenna effect. Out of curiosity, is there another reason why it should be directly under the switch? Also, I neglected to mention that I also changed another variable: I replaced the 1' unshielded ethernet cable between the switch and the Sonos with a SHIELDED version. So prior to this change, the configuration was... computer -> 50' shielded Cat6 cable -> ethernet switch (grounded to power conditioner/earth) -> 1' unshielded Cat6 cable -> Sonos -> reclocker... And my continuity results were... 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 So the break in continuity was due to (a) the galvanic isolation in the reclocker and (b) the UNSHIELDED ethernet cable between the switch and the Sonos. Now the configuration is... computer -> 50' shielded Cat6 cable -> ethernet switch (not grounded to power conditioner/earth, but grounded to the "grounding plate") -> 1' SHIELDED Cat6 cable -> Sonos -> reclocker... And the continuity results are the "OPPOSITE"... 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 So now the upstream half of the system (computer, ethernet switch, Sonos, reclocker input) is discontinuous from the downstream half (reclocker output, preamp, amp). In this new arrangement, the high frequencies are improved, which is consistent with my listening results from 3/3, where the presence of a SHIELDED ethernet cable between the switch and the Sonos produced the best high frequency results. At the time, I didn't go with a shielded ethernet cable between the switch and the Sonos because the bass was lacking pitch definition with that arrangement. But with the "grounding plate" for the switch in place, the bass pitch definition is excellent. My conclusions... 1. The variation in the bass was a function of grounding the ethernet switch to a sufficiently large chassis, which was originally provided by the power conditioner and is now provided by the grounding plate. The variation in the bass was NOT due to the presence or absence of EARTH grounding, as I originally believed. 2. The variation in the highs was a function of the presence or absence of shielding in the ethernet cable between the switch and the Sonos. I suspect that shielding that cable reduces noise, either... (a) noise transmitted from upstream components (computer, switch) through the ethernet cables, or... (b) noise transmitted from nearby components (amp, preamp, Sonos, reclocker) through the air, or... (c) noise transmitted from downstream components (preamp, amp, power conditioner) through the ground wire between the switch and the power conditioner (that ground wire is now gone, but it was present on 3/3, when I experienced the same variation in the high frequencies). Not sure which of these was the culprit. Bryon |
The plate is directly under the switch. I placed it there to keep the braided ground strap as short as possible, to minimize any antenna effect. Out of curiosity, is there another reason why it should be directly under the switch?Just my vague intuitive feeling that placing it there might enhance the effectiveness of the switch's internal ground plane, perhaps reducing the amount of digital noise generated within the switch that might end up coupling or radiating to points downstream. With regard to the well thought out summary you presented in your last post, my only comment is that it would seem to make sense that the best results were obtained via a configuration that does not provide any paths that bypass the reclocker and its galvanic isolation. As you noted, such a path previously existed, via the ground wire from the switch to the conditioner, and from there via power cords to the downstream components. Well done! Best, -- Al |
I agree that the current configuration seems to maximize the benefit of the reclocker's galvanic isolation. I have a follow up question for you, Al, about the dissipation of noise in an equipment's chassis... Is the dissipation potential of a chassis determined by its surface area, its mass, its material, its conductivity, its magnetism...? Several of the above? bc |
Is the dissipation potential of a chassis determined by its surface area, its mass, its material, its conductivity, its magnetism...? Several of the above?Excellent question, but I have no particular knowledge of what the answer might be. I suspect, however, that the answer will be a combination of those factors, and that the optimal combination will vary as a function of the frequency components of the noise. And unfortunately digitally-induced noise will typically have spectral components covering a huge range of frequencies. If you are feeling particularly ambitious at some point, I suspect that some good answers can be found in "Electromagnetic Compatibility Engineering", by the distinguished expert Henry W. Ott. Best, -- Al |
- 115 posts total