Ferrite Core noise suppressors - Anybody use 'em?

Roypercy

Super Member
Hi all:

Parts Express sells these things cheap, that clamp onto your AC cord (or interconnect, I guess) and supposedly help with RF interference?

Useful cheap tweak, or snake oil?

Thanks for any insight

Roy
 
Roypercy said:
Hi all:parts Express sells these things cheap, that clamp onto your AC cord (or interconnect, I guess) and supposedly help with RF interference? Useful cheap tweak, or snake oil? Thanks for any insight
Roy
I get mine from PE too. I've found them to be useful on power cords. They do help supress EMI/RFI. Don't expect miracles from heaven, but every bit helps. Every guitar amp I build or refurbish gets one, as stage lights, etc. can be very noisy.
 
I have computer controlled shortwave (TenTec RX320) and use them on all leads (one at each end of lead) in and out of pc and radio. They do work. Not sure what you paid but Digikey has good prices also. Radio Shack thinks they are made of gold.
 
yep! i agree. i am a ham radio buff. i use them on my audio lines, balance audio input to the transmitter. rfi completly disapperaed. OH, AND, RADIO SHACK THINKS, EVERYTHING THEY SELL IS MADE OF GOLD.
 
Never used them but I did get some rfi in my mixer, so I stuck some ferrite beads right at the input transistors. Cured it a treat.

73 Bryan
 
I use them on power cords for digital source. I can't determine if they do a lot, but it seems a good idea considering all the other 'noisy' stuff that is on the same circuit. I notice that my current Tosh has a ballum just before the transformer, so I must be on the right track.
 
The technical name for such a core is a "balun," and YES, they do "work". What they do is basically prevent the wire they are put on from acting like an antenna. [Technically not 100 percent, but close enough to it.]

You'll notice many appliance cords have these "built-in" (molded over) by the manufacturer, in order to help the appliance meet certification standards for EMI interference/transmission.

It's not a bad idea to go around and put them on all appliance cords that don't already have them. That will reduce the amount/chances of general interference, probably lowering the "noise floor" of your audio gear in the area. Put them as close to the appliance end of the cord as you reasonably can, to minimize "antenna length".

Now if I could just figure out how to get these inside the motor of my ceiling fan.... :headscrat :D
 
if you're having actual RFI problems that you can identify as such,then i would take Arkay's advice and use them on the source of the noise..as for audio,i have tried them on both IC's and power cords,and they go nowhere near my stereo...can you say hi frequency filter?i have always found they sucked the life right out of the music,even on power cords!...depending on your gear and preferences this might be regarded as a good thing tho,so YMMV,to each his own and all that,they're certainly cheap enough to give a whirl and see
 
They don't make much difference with my current setup, but I've used them on power cables and interconnects with good results in the past.
 
The technical name for such a core is a "balun," and YES, they do "work". What they do is basically prevent the wire they are put on from acting like an antenna. [Technically not 100 percent, but close enough to it.] :headscrat :D

Not quite true... a "balun" (derived from "balanced" & "unbalanced") is actually a device - very often a transformer, sometimes with a ferrite core, to convert a balanced signal to unbalanced signal or vice-versa.

Ferrite beads are well known in the Amateur Radio (Ham) world for removing troublesome RF from audio signal lines in transmitters for example. They can be very effective in removing noise from power cables too - note that positioning is crucial for best effect.

Just my 3 ha'pence worth.
 
Arkay wrote:
The technical name for such a core is a "balun," and YES, they do "work". What they do is basically prevent the wire they are put on from acting like an antenna. [Technically not 100 percent, but close enough to it.]
Hyperion wrote:
Not quite true... a "balun" (derived from "balanced" & "unbalanced") is actually a device - very often a transformer, sometimes with a ferrite core, to convert a balanced signal to unbalanced signal or vice-versa.
These posts from our two good friends point to what IMHO is an example of how sometimes a very simple device quickly becomes the subject of a very complicated discussion of physics. When I attempted to dive into this stuff on the internet, the found that the subject became opaque after the first paragraph or so. That was when the maths started. [Sigh ... around the time mastodons had just left footprints, I taught myself up to the crib level and then .... poof!]

Anyway and regardless, I think something about both these posts is relevant to what we people do here in home audio. And yet we may ask the question: just how do these devices work ... if, when and where ...? I've tried, but right now I just don't have time to grit my way through stuff that I do not understand.

What I do know: baluns are used in antennae: if you construct a simple, dipole FM antenna, you can divorce/isolate the leader from the antenna such that the leader is not part of the radiating loop: ie the balanced antenna. This is a profound application. It must perforce translate into something that is commensurate with AC power supply because many audio appliances use a simple balun just before the power transformer. This may be a particularly sensitive issue in digital audio. It makes sense in every way!

One thing I wonder about is that the behavior of baluns are supposed to be in a responsive relationship to both current, voltage and impedance. As I interpret the subject, this is perhaps where the significance of balun implementation in audio really gets started. And, some of the negative comment regarding them may in fact have some basis in the the actual physics regarding their true nature. I for one would not use them on an IC without having understood a galaxy more than I have been able to fathom. I'm more likely to use them on an AC line — something I've done a lot in the past. Did it work? Well ... there was no epiphany, but then I was not conscious of an annoying noise floor either. Can you do an A/B test in respect to ferrous clamps? Hahahahaha .... Op. cit an endless discussion on A/B anything. Baluns ...? If you have the local tow truck service broadcasting on your system (such as I did 37 year ago) I'd be clamping my ass off. I did not know the existence of them then — too bad. Cheers ... Lorne
 
If you put these on power cords they will block a lot of hash from coming in or getting out through the power cord. The frequencies blocked are way above anything you can hear. Why this matters is the ultrasonic noise will use up the circuits capability and waste resources best used for the audio spectrum.

Thanks,
Ron-C
 
I got a couple of those things to clip on my Hammarlund's antenna feed and AC cord to try and eliminate the gawdawful thunder of RFI emitted by my PC/UPS. I noted about a .000000000002 dB reduction. The only way I can imagine those things would work is to cover every inch of every cable (signal and power) running to or from my shortwave rig and PC.
 
You guys know the specs for the popular TDK ZCAT series (and probably the likes of) shows these babies only yield impedance in reaction to frequencies between a minimum of 10MHz and a maximum of 500MHz - right?
 
Yep, that is where the noise lives from our digital gear that surrounds us all.

Thanks,
Ron-C
 
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