That's great news Spencer and i'm quite certain that this approach was FAR easier to impliment. Most everything that you've mentioned are known cures to known problems, so it's good to see that some of the old stand-by approaches still work as expected : )
Now get out of here and enjoy your system and all of the work that you've recently put into it : ) Sean
> |
Update for all:
The Faraday cage has been sidestepped.
I conquered the severe RFI by doing a number of things. The biggest impact was changing to a balanced junction box on my VPI TNT6-HR, allowing me to go XLR right from the tonearm output to the balanced phono stage input of my Atma-Sphere MP-3. The drop in RFI was immediate and undeniable.
Other steps that helped include placing ferrite rings on interconnects, moving the whole system away from the window facing the radio tower, shorting plugs in unused inputs(but never outputs!), moving to balanced cables from preamp to power amps.
Thanks to all for your advice. Hopefully, I won't ever need to build the Faraday cage. I had copper mesh all picked out and was ready to go. Glad I didn't do it. Cheers,
Spencer |
If you want it to work OPTIMALLY, you need to use thicker materials that are solid. The cage would also be attached to a low resistance Earth ground. Aluminum is FAR less desirable than steel and to a lesser extent, copper.
Using thinner materials that aren't solid i.e. metal screening, etc... that lack a low resistance path to Earth ground can also produce beneficial and highly usable results. How well you want it to work and how much you want to spend may dictate certain cost-cutting techniques to be implimented. Such are the design variables that any project / product encounters. Sean
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PS... Don't forget to address cabling coming in and going out of the device as these can act as EMI / RFI conduits also. |
Just found this thread, as yesterday I first ran into the idea of a faraday cage. I have just ordered some more Stillpoints ERS sheets, but I think a larger difference was made when I covered my audio magic power conditioner and placette preamp entirely in aluminum foil, with serious results for each. I think they are just plastic boxes without any metallic barrier on the inside to protect the bare wires on the inside. In that case, shielded cables has only done half the job, becuase inside the components everything is basically open. These "treatments" really allow ambient details and the correct timber of musical notes to appear, which were previously obscured. My guess is that AL foil is reflecting more of the airborne rfi, while the ERS sheets are better served on the inside of components to absob RFI from everything attatched to the cicuit boards or also around cables. I'm still trying to discover where the ERS sheets work best though, just got them a week ago. I may cover all my equipment with foil soon though unless I can find some metal cages of various sizes.Should I also cover the bottom of the walls of my room with foil along where the power lines run?
Any thoughts or recent revelations out there? |
Try going to Office Depot and look for the new style "mesh" office products (letterholders, wastecans, etc).. You may find what you need to cover whatever it is that you need to set up a field around your equipment. Stopping extranious waves is a matter of stopping whatever wavelength(s) is causing the interference. You may need to eventually try some copper shielding postioned or vectored within the wavepaths.
Remember, WL (wavelengths) are not only absorded, they also bounce. what you may stop, may richocette and enter from another angle.
Good Luck,
Tubby |
As Bgrazman points out the cage does not need to be a solid sheet of conductive material. A wire mesh with quite wide wire spacing works fine. Indeed, your metal car provides good protection from lightning strikes even though it has large openings for windows.
Also, as Jea48 points out, grounding is not necessary, although it might be a good idea if only for safety reasons. When I installed shielded 300 ohm twinlead wire from a roodtop FM antenna I was surprised to find that the shield, for which I had paid extra $, was left unconnected at both ends. Seemed like a waste, but it worked great for eliminating interference from passing auto trafic. |
Jea48 is right - no grounding needed. We do it in the lab all the time. All you need is a sheet of copper that encloses the unit. If you ever visit radio telescopes, you will see that they line the entire data room with copper foil. Also, bust open a cell phone and you will find the same.
Also, many new switching circuits have a sheet of ferrite polymer that simply sticks down on the surface of the PCB. Ferrite works better than copper at lower frequencies actually (e.g. 60Hz line frequency and multiples thereof) but both sandwiched together gets you even better supression (copper on the outside).
Arthur |
Three posts here speak of the Faraday cage needing to be earth grounded. I searched and searched the net a few months back to prove the case that the cage had to be grounded to reject RFI. The only thing I could find was that it did not... Example, CDP, DVD players, TVs, and radios. Two wire cord and plug no equipment earth ground. CDP and DVD players just a floating metal enclosure, a Faraday cage.
Jim |
Eldartford has it right from a physics point of view.
Practically speaking, we also used to use metal window screen material (stands up better & you can see through it). Then just run a wire to ground (if you use a water pipe, have to make sure that there is no plastic splice to break ground...for experimental purposes, we used to bury a piece of foil/screen about 1 foot deep & soak the ground with water).
good luck, |
If you do a search on ask.com or the like you'll find a lot of information on construction, resources, etc. But as was said before it is basically a box made of conductive material that is grounded separately from your components. They're used to protect devices from outside RFI/EMI getting in, or inside RFI/EMI getting out.
Cheers,
Tom |
I remember using one when I was a grad student doing open and closed cell patch clamping. Absolutely could not do without a cage, to much interference. I am sorry though, it was built when I got there. You might try contacting a university that has a neuroscience graduate program. Might even be able to higher a poor underpaid starving grad student to build one. |
Check out Verastarr.com for their "StarrDamp CS" sheets as one approach to reducing cabinet resonance while simultaneously shielding against RFI.
For interconnects, check out Zcable.com for their "Z-Sleeves". They have already designed and built what you want.
I use one surrounding the IC from turntable to phono RCA input, and one surrounding the older, fixed, power cord of my turntable, with resulting audible benefits as mentioned on the Zcable,com website.
If one places one of the tubular Z-Sleeves right in front of a squawking parrot, or Audiogon member like myself, furiously typing away, there is an immediate sweetening or mellowing of the noisy output from either one :>) |
To see if you really want to do this, wrap the thing in Reynolds Wrap (Aluminum foil) and ground the foil. If this makes no difference spend the money you save on good recordings. |
I would try to attract an African Grey Parrot to your cage as they are the "High end" in talking birds. Sorry I can't help with the Faraday cage, but I'm hoping to learn more on this post. I did look at your Funhouse though and I'll bet you have an exceptional sound. I especially like the rack you built to hold your system. |
Spencer,
Make sure you use the right kind of seed for the Faraday Parrot. If you don't you could attract an Amazon species and those suckers just yap all day.
Dean |
