Ferrite beads worth the effort?

[gunofason]

In the past, I've heard good things about using ferrite beads on cables to reduce EMI. Personally I've never used them but I've seen people use these on everything from single guitar cables to every wire on permanent installs. Is is really worth the effort or should I just consider moving the studio from under the high voltage powerline, and away from the cell phone towers (Just Kidding!)???

[ShamansDream]

You normally put ferrites on cables to keep from creating noise on other devices. This is usually only done on cables without shielding or unbalanced cables. These are normally power cables or things carrying significant current.

If you really feel the need to do this, use the clamp-on ferrites near the power source. LINK

[Matt Syson]

Hi
If you don't have a problem with picking up EMI then don't bother. If you have some kit that is sensitive and you have computers a plenty then it may be worth having a few clamp on types available 'in case'. If the studio is installed correctly there should be no problem unless you have a radio station or taxis next door.
Matt S

[gunofason]

Thanks for the replies folks! I really don't have current problems with EMI, it's more or less just a preventative maintenence issue. I might be doing some major wiring projects in the near future and was curious if I should go ahead and take the extra step to perfection!

Just out of curiousity, however, is the same true when your picking up radio stations though your guitar amp? Sometimes at live gigs, I'll pickup faint radio stations from time to time. Would ferrite beads help here or is this a myth as well? Thanks again!

[Matt Syson]

Hi
On your guitar amp it may well help to put a ferrite ring on the cable, perhaps both the guitar lead and the mains. A ring with space to get a couple or three turns through may be necessary. You could perhaps make up a short jack Male - female with a few turns through it to add at a gig if necessary. Whether it works enough is all down to individual circumstance.
Matt S

[ShamansDream]

If your amp is picking up radio station it means that the amp is not "immunne" to RF. This often signifies a poor design. It can come from the input line or from the speaker cables or even through the chassis. I would look for poor grounding or a problem with the source power. Chasing down the source can be a real bear. An AC line conditioner may be the most effective tool to combat this problem. If not, you have a proximity problem in which case short speaker cables and even dual amps are the only real solution. Try switching out amps in a location where you are having this problem.

If you are tying spare ground cables between equipment (which is a good idea for power systems) use a very heavy braided cable terminated very well (star washers). Ground cables depend on surface area to fight RF. Small ground cables (18-16awg) still have "resistance" to high frequncies. Any length of wire, regarless of termination, acts like an antenna.


When I have to deal with this kind of problem in my daily work, that being design of electronic enclosures, shielding the chassis and grounding are my first go-to and second, I evaluate the transformers being used in the circuits. Believe it or not, there are a world of differences in the new fangled transformer designs coming out today. Form factor is not everything. The old style transformers made with many shims of iron are much better to saturate the core than the one piece ferrite cores made for manufacturing ease and challanging form factors.