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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, Kijanki, for that detailed response. I will follow your advice and add the regular steel shields to the copper shields already in place. I will report back with the results.

I think you and Al must be right that the Cat6 cable has reduced system noise, and thereby reduced jitter. It's the only plausible theory that also explains the dramatic change in sound quality.

It's worth noting that whatever the jitter-inducing system noise was, it was not audible as a NOISE FLOOR, i.e. hiss, buzz, and other grunge audible when playing music. The system has been very "quiet." Because of that, I (falsely) believed that the system didn't suffer from any significant noise problem. But now I see that my reasoning was flawed. Apparently, not all detrimental noise is audible as a noise floor. I wish I'd known that!

Bryon
bryoncunningham OP
890 posts
 
Rodman - At your suggestion, I've been reading about the TI shield. It looks like a very interesting product. I think I will order some. Thanks.

Bryon
rodman99999
6,159 posts
 
A simple(but efficacious)solution. Happy listening!
kijanki's avatar
kijanki
4,428 posts
 
Bryoncunningham, Jitter creates sidebands to root frequency (like any modulation) at very low levels. In spite of low levels it is very audible because it is not harmonically related to root frequency. With music (many frequencies) it is basically a hash with amplitude proportional to sound level. When music stops noise stops as well. It can be detected only as a lack of clarity.
bryoncunningham OP
890 posts
 
My TI Shield arrived yesterday. I was thinking about placing it around the switching mode power supply in the G68. I think Kijanki warned me not to get magnetic materials too close to the power supply.

Anyone know how close is too close? And what would happen?

Thanks,
Bryon
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