Only put ferrites around cables or both conductors (High & Low).
Never around a single conductor carrying current. The ferrite will saturate.
Place the ferrite as near to the audio component end of the cable as practicable.
Never around a single conductor carrying current. The ferrite will saturate.
Place the ferrite as near to the audio component end of the cable as practicable.
Yes, agree it can saturate. Most HF conducted noise is common mode so clamping around both is very effective at quashing any residual noise.
Soft ferrites can work quite well when used to make common-mode chokes in AC line power conditioners.
Like this:
Like this:
Power conditioning, and seldom signal, unless it’s on the gates/drains of lateral mosfets, lol.
Usually choose a lower frequency material for this stuff.
Usually choose a lower frequency material for this stuff.
I'm planning on putting one on the AC input to a switch-mode power supply that I'm adding to a guitar pre-amp that I'm modding. It will help keep the noise from the power supply from polluting the AC going to the HV transformer.... FWIW, Cardas put them on all the Quadlink 5-C interconnect cables they made!
Would it be beneficial to put these on low voltage cables feeding DAC’s and a streamer from typical phone charger plugs and mains cables feeding a CD transport and amplifiers?
I haven’t put them on interconnect or speaker cables. The only ferrite clamp I currently use is just before a distribution block.
To be honest, I am not aware that there is a problem to start with and my high frequency hearing ain’t the best anymore but I figure a few well placed ferrites can’t do harm.
Thank you all for the replies.
I haven’t put them on interconnect or speaker cables. The only ferrite clamp I currently use is just before a distribution block.
To be honest, I am not aware that there is a problem to start with and my high frequency hearing ain’t the best anymore but I figure a few well placed ferrites can’t do harm.
Thank you all for the replies.
Put them as close as you can to the port. Essentially, below ~500 kHz, ferrites basically look like a short (mildly inductive, but that's generally negligible). At higher frequencies, they more or less look like resistors. In between they are more or less an inductor.
Rule #1: Every wire is an antenna, and every wire is a transmission line. Most RFI makes its way into an enclosure on cables entering and leaving the enclosure. That includes the AC power line, every input, and every output. The IEC line filter module (which you should be using!) keeps most RF from entering or leaving on the power cord. Ferrites are a powerful tool to deal with this. They also serve as a way to break RF ground loops.
You won't hear a difference (and certainly not an improvement - they're not the most linear things ever) from ferrites unless you've got an RFI problem. If everything in your system is working as expected, there's no need to start throwing ferrites at things. Usually modern equipment (especially well-designed equipment) won't need it. A 40-year-old phono preamplifier is a whole lot more likely to have issues than a modern DAC or class D amplifier.
For example, at my workplace RFI is a constant battle (plasma physics experiment). RF for plasma heating, 80 kV switching power supplies, RF excited ion sources, pulsed lasers, etc. It's always interesting to see that some equipment is almost bulletproof from an RFI perspective (I have never managed to take down anything made by Tektronix or HP/Agilent/Keysight from this), while others will fall over the moment even a tiny RF ground loop is created (cryogenic monitoring equipment seems to be quite prone to this). It's all about how well the I/O filtering is handled (and a little shielding, occasionally).
What kind of issues does it usually manifest? It ranges from audio-frequency noise (a lot of circuits work as AM demodulators even if that isn't their intended application), oddball system glitches, system resets / lockups and (in our lab at least), equipment failure. That said, it's very rare that I find a need to install ferrites on cables in an audio system.
As for ferrite saturation on current-carrying conductors: It depends on the ferrite and how much current is passing through said conductor.
Rule #1: Every wire is an antenna, and every wire is a transmission line. Most RFI makes its way into an enclosure on cables entering and leaving the enclosure. That includes the AC power line, every input, and every output. The IEC line filter module (which you should be using!) keeps most RF from entering or leaving on the power cord. Ferrites are a powerful tool to deal with this. They also serve as a way to break RF ground loops.
You won't hear a difference (and certainly not an improvement - they're not the most linear things ever) from ferrites unless you've got an RFI problem. If everything in your system is working as expected, there's no need to start throwing ferrites at things. Usually modern equipment (especially well-designed equipment) won't need it. A 40-year-old phono preamplifier is a whole lot more likely to have issues than a modern DAC or class D amplifier.
For example, at my workplace RFI is a constant battle (plasma physics experiment). RF for plasma heating, 80 kV switching power supplies, RF excited ion sources, pulsed lasers, etc. It's always interesting to see that some equipment is almost bulletproof from an RFI perspective (I have never managed to take down anything made by Tektronix or HP/Agilent/Keysight from this), while others will fall over the moment even a tiny RF ground loop is created (cryogenic monitoring equipment seems to be quite prone to this). It's all about how well the I/O filtering is handled (and a little shielding, occasionally).
What kind of issues does it usually manifest? It ranges from audio-frequency noise (a lot of circuits work as AM demodulators even if that isn't their intended application), oddball system glitches, system resets / lockups and (in our lab at least), equipment failure. That said, it's very rare that I find a need to install ferrites on cables in an audio system.
As for ferrite saturation on current-carrying conductors: It depends on the ferrite and how much current is passing through said conductor.
could you add some more explanation about what happens / benefits when loop the wire through the ferrite.
Jim Brown a retired Audio Engineering Society interference expert is also a HAM radio operator.
The firsts part of this paper has tons of stuf that applies to audio systems.
"A Ham's Guide to RFI, Ferrites, Baluns, and Audio Interfacing"
http://www.audiosystemsgroup.com/RFI-Ham.pdf
Many other Jim Brown papers:
http://www.audiosystemsgroup.com/publish.htm
The firsts part of this paper has tons of stuf that applies to audio systems.
"A Ham's Guide to RFI, Ferrites, Baluns, and Audio Interfacing"
http://www.audiosystemsgroup.com/RFI-Ham.pdf
Many other Jim Brown papers:
http://www.audiosystemsgroup.com/publish.htm
Well stated, thank you. However, there is also a possible issue with ferrites and hysteresis noise/distortion. Bruno Putzeys has written about it: https://purifi-audio.com/blog/tech-notes-1/this-thing-we-have-about-hysteresis-distortion-3 Don't know for a fact if that's the cause of another issue, or maybe the physics is more like as described in the linked article at: https://www.diyaudio.com/community/threads/general-purpose-dac-clock-board.413001/post-7765137
Either way, IME ferrites can affect dac clocks in such a way that audio reproduction is adversely effected. The ferrite effect in a clock power may be easiest to observe as a degraded stereo illusion of sound stage, presumably due to loss of ITD timing accuracy (as little as a few microseconds can be audible for ITD lateral localization), and for reproduction of low level depth localization cues.
Repeating that story on every possible thread mentioning ferrites does not make it more credible. Show us measurements or controlled listening test results if you want it to be more than just a nice story.
The purpose of controls is to help assure what is actually being measured is what was intended to be measured. The purpose of controls has been satisfied in a blind (but not DBT) listening test. The test subjects could tell the difference between the ferrite and non-ferrite conditions by descriptive analysis of sound stage and other changes. The test subjects could describe how the ferrite condition audibly harmed sound stage, and do so without knowing it was the ferrite condition.
Thing is nobody cares about this type of evidence or bothers to remember that such things are reported not unfrequently in the forum. It is well known that humans tend to disregard new information that is disconfirming to their preexisting beliefs. And that is exactly what tends to happen. The skeptics ignore what evidence is presented and keep asking for evidence as though none was ever presented. When pressed they often try their darnedest to think up reasons to justify ignoring/disregarding the preponderance of blind test evidence out there.
That includes many situations where listeners have reported hearing changes they expected to be exactly the opposite of what was described as being heard. The skeptics tend to blame it on expectation bias even when the stated observer expectation should should have had the exact opposite effect.
Last edited:
Ferrites (along with virtually any magnetic material, including soft iron, mu metal, nickel, etc) have mediocre linearity at best due to their magnetic hysteresis. That's why we try to avoid ferrous alloys for speaker connectors, for example. This is a known, documented, measurable effect, and it's one of the (many) things that makes audio transformers quite difficult to design. Despite this, I've actually had pretty good success controlling parasitic oscillation with ferrite beads on the output of solid-state power amps, without too much measurable distortion. The amplifier in question still had no trouble meeting my standard (which is that 0.005% THD+N is good enough and any further improvement is only useful as an academic exercise).
It does not apply, however, to common-mode chokes (which is how clamp-on ferrites are generally used). When used common mode, they will have zero impact on the intended signals. The physics here is pretty easy to understand - the magnetizing force from the two conductors cancels. Even with very high-speed signals (pulse generator outputs with sub-nanosecond rise and fall times), common-mode ferrites generally have no impact on the normal (differential) signals.
This is an excellent paper on the topic. I like to send this to people whenever they start talking about fixing RFI problems with copper screen and foil tape. Another really good reference on this topic (and grounding, which is 80% of the battle) is "Noise Reduction in Electronic Systems" by Henry Ott. I think I paid like $15 for my copy on eBay.
Common mode chokes for differential signals, yes, agreed. Similar clamp-on chokes used on single-ended stereo signal cables is of course another matter. There the effects can be quite audible in some cases. Just mentioning it for people who may be using such cables. Had a cable that came that way with an old computer sound card (ferrite clamp around shielded cable with dual SE audio signals).
Last edited: