Radio-Magnetic Shielding

Factual Questions
1
      • So my new digital/MIDI drums won’t work plugged into my soundcard, and I have found that for many MIDI instruments this is fairly common: they often work 100% with other MIDI instruments and modules, and even with external PC/MIDI interfaces, but not with internal soundcards that have MIDI connections directly on the card.
  • So I want to add electrical shielding between the PCI cards. I have seen this problem mentioned many places (people often note how their cordless or cell phones won’t work near their computers when the computer’s case is open), but I have not found any products specifically to reduce it. Ideally I would be able to get some wire screen mesh (say 3/16" square) covered in no-conductive insulation, and mount a sheet of that between each pair of cards and run a ground wire off it. I don’t know anything like that though, I plan to explore the home warehouse stores today. If I can’t find that, I will make a wire device rather like the letter “E”, except with more horizontal pieces, if you will. Looping the wire would be easier, but it will resonate more IIRC.
    ???
  • Whatever I use has to allow air to circulate between the cards, so I can’t use anything solid like aluminum foil. Any suggestions?
    ~
2

If you do go with a mesh, you need to make sure that it’s fine enough. You’ll need to determine the frequency of the radio noise, get the wavelength from that, and then make the grid spacing smaller than the wavelength.

3

<opened this thread expecting to hear about some new weapon on Star Trek>

4

First, any screen mesh that you get will have small enough spacing for RF shielding.

Second, why do you believe that shielding will fix the problem?

5
      • Well, I tried using aluminum foil after all, on both sides of the soundcard. I covered the foil with scotch tape and attached a grounding wire, run to the PC case. The soundcard does seem to sound a bit more crisp & clear, but the difference is minor at best. The MIDI drums still don’t work at all.
  • I am guessing: the drums don’t work when connected to the PC, but the keyboard controller works when connected to the PC (with the same cable), and the drums respond when connected to my midi controller keyboard. I don’t have anything else to connect the drums to, to verify that they’re sending.
    …
    While looking online for info on my particular situation, I found a lot of other people with the same problem, with different hardware: people who had some MIDI instrument that worked fine with other MIDI instruments or modules, but that didn’t work when connected to their PC. The most common solution given was to get an external USB MIDI adaptor. I found no common piece of hardware or instrument brand represented, except for internal soundcards.

The problem is irritated by the fact that “nothing can be done quickly”. I only have the one single-line MIDI/gameport cable to try; I’d buy another and try it, but there’s nowhere near that I can just drive to and grab one off the store shelf; everything I need I have to get mail-order. There’s local music/instrument and electronics stores, but they don’t carry any MIDI/PC interface equipment at all–because the music stores don’t sell computers, and the electronics stores don’t sell musical instruments. And neither of them knows anything about hooking the two devices together.
~

6

I bought a MIDI to game port cable two weeks ago at a PC store called Micro Center.

But I’m suspicious of the idea that shielding is the problem. It sounds to me like a compatibility of the MIDI instruments supported with each system, or how they’re encoded, or something like that. Not that I know a lot about MIDI, but I do know a fair amount about grounding and shielding.

7

Try adding some clamp-on Ferrite Cores to the cables at the ends near the PC. This blocks some of the computer’s high frequency electrical noise so it doesn’t run along the cables and make your equipment confused.

I think Radio SHack stores sell these.